View Full Version : Tire Pressure & Mileage
Had a slow leak in a rear tire on my Thunderbird. I noticed my instant mileage went down proportionally with the amount of under inflation in the tire. When the tires are inflated correctly I get around 30 mpg but 10 pounds under inflation on one tire drops me to around 22 mpg.
I've known a low tire burns more gas but I didn't realize how much until now.
raymeketa
12-28-2011, 03:10
My Toyota Avalon Limited has built in sensors that turn on a warning light when pressure in any tire drops by 2 or 3 pounds. I get an average of 33 MPG highway keeping the pressure at maximum recommendation. I've never tried it at any less pressure.
John Kepler
12-28-2011, 06:41
My Toyota Avalon Limited has built in sensors that turn on a warning light when pressure in any tire drops by 2 or 3 pounds. I get an average of 33 MPG highway keeping the pressure at maximum recommendation. I've never tried it at any less pressure.
Yeah......those "wonderful" little tire pressure sensors (Toyota ain't the only one that has'um!) that make your tires VERY difficult to work on, fail frequently, and cost somewhere between $70 and $120 a pop to replace! All to replace a $2 tire pressure gauge and 30 seconds of time! Ain't "progress" wonderful!
High Plaines Doug r
12-28-2011, 07:49
I run three cars with the tire pressure at 40-44 psi (the rated max on the sidewall) One is a 1999 Cadillac Seville, next is a 2001 Isuzu Trooper and the latest is a 2011 Toyota Corolla. Tire wear is really good and even from inside to outside but I rotate religiously. Ride can be a little harsh. I record my mileage and gas-ups each fill. Mileage has improved maybe .2-.5 mpg over the recommended pressure. I have deflated to 28-32 psi during the winter months for better traction. My impression is that max tire pressure improves mileage but not much.
Ask for a tire gauge at the place you buy tires. If they don't give you one for free; you are doing it wrong.
Mike Josephic
12-28-2011, 08:57
Don't inflate your tires to the MAX INFLATION level imprinted on the tire.
This is not a safe practice. This is the maximum safe inflation level for that
particular tire -- but not necessairly the one correct for YOUR CAR. Incorrect
inflation effects tire life, handling, increased blow-out or tire damage possibilities,
etc.
Read the owners manual or look at the sticker on you door or glove box
that gives the factory recommended inflation for YOUR CAR. They give a range,
usually a "normal load" and a "full load". Pick one that best suits your needs.
Also, please take into account now that we're heading into colder winter temperatures
that you lose air pressure as the temps go down. In other words, you will need to add
a few pounds of air pressure to comphensate for this. Check at least monthly.
Mike
Ditto on the "Don't inflate your tires to the MAX INFLATION level".
Our local Quick Lube place had a habit of doing that and I finally started telling them to leave the tires alone. The last time the wife went there for a lube she overheard a phone conversation between the manager and an irate customer. Seems the customer had a blow-out as he left the store and entered the freeway. The tire shop where he sent the car found his tires grossly over-inflated.
That "MAX" number on the tire means the MAX inflation before the tire heats up from driving or loading.
Inflating to the max rating is not " gross OVERinflation " Yes, many cars have a different rating from what's on the tire. No, it is not going to cause a blowout as soon as you start driving. Look at the Ford exploders that had so many blowouts and rollovers, that was due to what? under inflation! Leave your tires anywhere from the manufacturers suggestion (excluding Ford Exploders) and the max rating on the tire. Never ever trust a tire shop. They do not hire mechanical engineers to check tire pressures. I have no idea how many times I have picked up my truck to find it had 4 sloppy flat tires on it and goober was so proud because he caught my dangerously "over inflated tires" Yep, he put them all at 32PSI right where ALL cars should have their pressure set. I bumped them all back up to 42 on a 44max and no longer feel like I am driving on a marshmallow road. Same crap on my moms van. Some other goober set her tires to 32. They actually looked almost flat. If you hit a bumb the thing wallowed all over the road like the S.S. Minnow. Bumped up to 40 and it rides like a van instead of a shrimp boat.
Round tires roll easier, more pressure keeps them more round. That flat spot on the bottom kills mileage.
JB White
12-29-2011, 07:47
I do the same with my Lincoln. Adjust the pressures between the door label and the sidewall max. I get much better handling and the mpg average is a few gallons higher.
The Grand Am has the pressure sensors and I'm ready to discombooberate that entire system along with the 'change oil' idiot lights.
John Kepler
12-29-2011, 09:34
"Discombooberate" it? Lotsa luck! Obamy and his Gang made it a "critical system", and your ECM computer will go ape-$hit if you do much of anything to it. And here you thought you actually owned your car!
Yeah......those "wonderful" little tire pressure sensors (Toyota ain't the only one that has'um!) that make your tires VERY difficult to work on, fail frequently, and cost somewhere between $70 and $120 a pop to replace! All to replace a $2 tire pressure gauge and 30 seconds of time! Ain't "progress" wonderful!
Came out of the VA Hospital last month, got in my Toyota Highlander, drove a few feet until I realized that my right front tire was completely flat. The "low pressure" tire sensor did not pick this up.
You are absolutely right, So much for progress!!
Came out of the VA Hospital last month, got in my Toyota Highlander, drove a few feet until I realized that my right front tire was completely flat. The "low pressure" tire sensor did not pick this up.
You are absolutely right, So much for progress!!
It's a low pressure sensor, not a NO PRESSURE sensor...LOL
M1Riflenut
12-29-2011, 02:34
TPS systems are nothing but a pain in the ass. Like John posted above, they can make a simple tire change an expensive proposition if bubba at the local tire shop does'nt know what he's doing. They also make "altering" your tire psi a thing of the past as each wheel position has a preprogrammed pressure. You can still run different psi's but that annoying light will stay on, and depending on the make/model it may effect how it runs. Some vehicles use different sensors for the front and rear and run different psi front to rear. Try rotating your tires on one of those. On some you can, on others (older early systems) the sensor(mounted in the wheel) has to stay at that wheel position. Some brands/models(mainly vans and pu's) also have them inside the spare tire and if that goes low, which can happen just from sitting over time, it will turn the light on too. Fancy metal or chrome valve caps? not anymore. Most of these useless devices use the valve stem as the antenna and mounting a steel cap on them can screw up the signal it puts out and guess what.....the light comes on. Also, many of them are aluminum and a steel valve cap will corrode to the end of the stem and when you try to take it off, threads go bye bye or it just breaks off. We've also had lots of them break off during the winter when they get hit in deep snow/ice. Brass and rubber stems at least bend, cold aluminum just cracks or breaks off. Yep, another useless device to suck a little more cash from the consumer. Bout as usefull as wipers on headlights.
Inflating to the max rating is not " gross OVERinflation " Yes, many cars have a different rating from what's on the tire. No, it is not going to cause a blowout as soon as you start driving. Look at the Ford exploders that had so many blowouts and rollovers, that was due to what? under inflation! Leave your tires anywhere from the manufacturers suggestion (excluding Ford Exploders) and the max rating on the tire. Never ever trust a tire shop. They do not hire mechanical engineers to check tire pressures. I have no idea how many times I have picked up my truck to find it had 4 sloppy flat tires on it and goober was so proud because he caught my dangerously "over inflated tires" Yep, he put them all at 32PSI right where ALL cars should have their pressure set. I bumped them all back up to 42 on a 44max and no longer feel like I am driving on a marshmallow road. Same crap on my moms van. Some other goober set her tires to 32. They actually looked almost flat. If you hit a bumb the thing wallowed all over the road like the S.S. Minnow. Bumped up to 40 and it rides like a van instead of a shrimp boat.
Round tires roll easier, more pressure keeps them more round. That flat spot on the bottom kills mileage.
You might know a lot about something but you don't know **** about cars, tires, handling or data analysis.
That "flat spot" on the bottom of your tire is called the "contact patch" and is all that grips the road surface during acceleration in any direction. Those few square centimeters transfer power to the road and provide the friction necessary to turn and brake. Over-inflation reduces the size of that contact patch. Set your tire pressure to the recommended and add a couple of pounds to it but not to near the maximum. As far as data analysis goes, let's say you are getting 30 MPG and pumping the tires up to near the maximum gets you 30.5 MPG. That's a whopping 1.6% increase in mileage. Phew, you're really saving now, eh? On the other hand, you are causing excessive tire wear, excessive suspension wear and decreased handling and braking performance to say nothing of the harsh ride and increased road noise. If your vehicle is handling like a banana boat, change out the crappy stock shock absorbers, keep the suspension aligned (all four wheels on an independent rear suspension chassis) and use the proper size and speed rating tires. Oh yes, keep them properly inflated. These things will have a better effect on your gas milage than over-inflation. Your life and the lives of your passengers are riding on those four little contact patches.
Russ, who was a factory-certified, state-licensed auto service tech and has well over 1.5 million miles of driving as a non-professional
John Kepler
12-31-2011, 03:47
"Never attempt to teach a pig to dance. It wastes your time and annoys the pig!" S.L. Clemens
Don't attempt to educate an individual that has already made up his mind and has NO desire to be confused by any facts. As an old race car crew chief, mechanical engineer, and ASE Certified Auto Mechanic, I can show him just how much difference half-a-pound of air-pressure can make in the performance of a car.....but he already knows more than I do based on how his mini-van "wallows".....all I had was 128 channel on-board computer telemetry, suspension load-sensors, lateral accelerometers, pyrometers, and precision time-sequencers good to the millisecond to tell me what the car was doing! Actually, as any tire engineer will tell you, the BEST (only) way to set effective tire pressures on a given suspension is with a pyrometer.......3 readings (5 is better) across the entire tread....a higher reading in the center of the tread tells you you're over-inflated. Our shop deals with very high-end cars (Porsche, BMW) and we set ALL performance car TP's with the pyrometer. Data is ever so much more subjective and equivocal than "feelings"! For some folks, "anecdote" and "impression" alloyed with pure whimsy and wishful thinking are always better than science and engineering!
"If you can't express it with numbers, it's an opinion, not a fact!" Dr. D.F. Lowe, PE
"No engineer has EVER gotten into trouble by over-estimating the depth of human stupidity!" Dr. T.J. O'Keefe, PE
"If a little is good, a lot must be better!" Dicky Bunnel's Law
(Dicky exited this veil of tears on July 23, 1974 at age 19 while attempting to empirically prove his Law! He additionally proved the rectitude of the statement, "A little knowledge is dangerous!")
JB White
12-31-2011, 10:43
"Discombooberate" it? Lotsa luck! Obamy and his Gang made it a "critical system", and your ECM computer will go ape-$hit if you do much of anything to it. And here you thought you actually owned your car!
It figures. That's why it hasn't been done yet but I'm getting annoyed at having to open the fuse panel and reset things. I rarely drive the Pontiac but I have to hear the complaints. I may have to black out those idiot lights instead. I keep a gauge in my cars so I don't need a mindless light to tell me I'm wrong and I don't need it to tell me to change my oil a month after I've already done that.
As far as tire pressures are concerned, passenger vehicles aren't exactly blueprinted like a race car. The manufacturer sets recommendations based on several factors including an average of data based upon the tire brands offered from the factory. Replace those tires with a brand having a different tread pattern, rubber compound, sidewall construction etc. and that label on the door is more of a suggested range than an actual recomendation.
If I adhered to the factory label as a rule and set my tire pressures accordingly, I get slippage when accelerating on wet or snowy pavement, tire chatter when making a quick turn, and feel a sense of funky handling when transitioning from concrete to asphalt.
John, you may be more educated than I when it comes to the math but I know how my car handles and responds to me. I've worked as a dealership mechanic, road tested customers vehicles, raced at the hobby level, and have driven the highways and backroads roads in 2/3's of the US and Canada. I'm still a race fan and am aware of the footprint, oversteer, understeer and have a constant mental image of those things as I drive. I'm not a soccer mom.
When I adjust my tire pressures to my liking across the front and again across the back it's due to experience with those tires and that vehicle. I've worn down quite a few sets of tires in my time and have never experienced uneven tread wear due to inflation. I've had some scalloping evidence due to worn mechanicals but not enough to trash a set before the repair work was done.
Put me into the stubborn class if you wish but that's how I do it and will continue to do it until my vehicle and tire combo tells me to change.
mike24d20
12-31-2011, 11:25
Plus one on what JB wrote. I drive a truck 100% of the time now.. When I bought it, it had p-rated tires on an I haul heavy loads. Upgraded too LT truck tires an if I inflated too the door sticker ( 32 psi ) just where in heck would I be? Stuck along side a road or upside down in a ditch with blown tires. I have seen tires go from nylon too steel basaed tires, an weird numbers on the side, man what a headache when trying too buy tires. But one true thing I have learned is each tire brand is different on the way it will handel an that lil sticker is not 100% correct. I also live 10 miles from the nearest paved road on a dirt an rock filled mud track.
John Kepler
12-31-2011, 01:12
Now, where did I say that the OEM recommendations were Holy Writ and the only way to go? That would be nonsense if you're a "performance driver" and check your tire pressures more than once a year. But then, so is running tires at a hefty percentage of the maximum tire pressure too (guys like the one poster do nothing but help our "bottom line"......the ultimate result of such foolishness is a busted tread belt and a new set of skins....the "stupid tax" for such shenanigans is me recommending the most expensive tires we sell!) What I said is quite the opposite....run the pressures that fit your vehicle condition and the projected use. A tire pyrometer will let you do that definitively, and far better than a pressure gauge alone. A completely adequate pyrometer can be purchased at Harbor Freight for around $50.....one hell of a lot less than replacing a single tire! No guesswork, no supposition, no "maybe yes, maybe no", just hard data. Or don't....my mark-up on quality tires is 40% and I'm the cheapest shop in town!
In my younger more careless days I used to let tire presssure get into the 20s before doing anything about it. After I got interested in mileage and started tracking it, I would notice a drop of maybe a mile or two per gal with pressure a few psi under spec
RCNixon.
That "flat spot" on the bottom of your tire is called the "contact patch" and is all that grips the road surface during acceleration in any direction. Those few square centimeters transfer power to the road and provide the friction necessary to turn and brake. Over-inflation reduces the size of that contact patch. Set your tire pressure to the recommended and add a couple of pounds to it but not to near the maximum. And add a couple pounds? Yep, thats the kind of scientific answer I would expect from a state certified expert. So, you suggest exceeding the recommendations then bash me as an ignorant moron for saying the same thing?
As far as data analysis goes, let's say you are getting 30 MPG and pumping the tires up to near the maximum gets you 30.5 MPG. That's a whopping 1.6% increase in mileage. Phew, you're really saving now, eh? On the other hand, you are causing excessive tire wear, excessive suspension wear and decreased handling and braking performance to say nothing of the harsh ride and increased road noise.............Your life and the lives of your passengers are riding on those four little contact patches.
I could give a $#@% less about gaining .5mpg it is losing 2-3MPG and having poor handling due to soft tires that I am worried about.
I know exactly what a contact patch is and I also know what a sidewall is. The sidewall should not be part of the contact patch. The lives of my passengers are also riding on those sidewalls and in the case of the Ford exploders the sidewall proved much more important than the contact patch.
Don't attempt to educate an individual that has already made up his mind and has NO desire to confused by any facts. As an old race car crew chief, mechanical engineer, and ASE Certified Auto Mechanic, I can show him just how much difference half-a-pound of air-pressure can make in the performance of a car.....but he already knows more than I do based on how his mini-van "wallows".....all I had was 128 channel on-board computer telemetry, suspension load-sensors, lateral accelerometers, pyrometers, and precision time-sequencers good to the millisecond to tell me what the car was doing!
If you would like to take a ride in my moms van I can show you what a difference 8lbs of pressure makes. It's the difference between a barely controllable boat and a vehicle that isn't unpleasant to drive and actually drives like it should. But hey, you are the expert so without ever seeing the vehicle or the tires much less driving it, you can tell me how assuredly stupid I am for believing that it rides better, handles better and gets better mileage at 40PSI than the door panel recommended 32PSI. I don't need a computer to tell me the difference between white knuckles because the thing is all over the road and being able to relax because I have control of the vehicle.
Ofcourse, I'm just some guy who "might know a lot about something but you don't know **** about cars, tires, handling or data analysis." and is tired of getting cars back from "experts" who drop the pressure ten PSI to "fix" the problem so the vehicle handles like crap and wallows all over the road. But then again, I don't go to a tire shop very often since I miraculously don't go through tires constantly despite your assertions that I am ruining my tires.
You can say I am stubborn all you want but the truth is, I would change my tire pressures if I was seeing the problems you experts say I must surely be having. I would also change my pressure if the handling and ride were better at the lower pressures you assert are "correct"
JDBoardman
01-04-2012, 08:46
To Mr. Kepler: I agree that the best way to set the proper tire pressure for the use you put your car to and the way you drive it is to use a tire contact pyrometer. Once the readings are uniform across the contact patch, the pressure is proper.
To Guamsst: In general, I also agree with your statements that higher than "factory suggested" pressure is better. As a prime example, the Chevy Corvair recommended a significantly lower pressure in the front tires than in the back tires, which made the car handle like a pig. The car understeered terribly - but this was in response to Ralph Nader's "Unsafe at Any Speed" that said the Corvair was an unsafe design because it had terminal oversteer. The factory recommended pressure is, at best, a compromise between ride comfort (too soft a tire pressure) and acceptable handling (too harsh a ride).
My experience is empirical - back in the day when I was closed course racing, I learned early on that what worked for street tires of one brand didn't necessarily work for another brand, and racing tires required a much different pressure than did street tires. And slicks differed from each other depending on the compound. As John Kepler says, "if you can't express it with numbers, it is an opinion, not a fact". Unfortunately, "facts" can also lead you off into the weeds sometimes too.
RCNixon.
And add a couple pounds? Yep, thats the kind of scientific answer I would expect from a state certified expert. So, you suggest exceeding the recommendations then bash me as an ignorant moron for saying the same thing?
I could give a $#@% less about gaining .5mpg it is losing 2-3MPG and having poor handling due to soft tires that I am worried about.
I know exactly what a contact patch is and I also know what a sidewall is. The sidewall should not be part of the contact patch. The lives of my passengers are also riding on those sidewalls and in the case of the Ford exploders the sidewall proved much more important than the contact patch.
If you would like to take a ride in my moms van I can show you what a difference 8lbs of pressure makes. It's the difference between a barely controllable boat and a vehicle that isn't unpleasant to drive and actually drives like it should. But hey, you are the expert so without ever seeing the vehicle or the tires much less driving it, you can tell me how assuredly stupid I am for believing that it rides better, handles better and gets better mileage at 40PSI than the door panel recommended 32PSI. I don't need a computer to tell me the difference between white knuckles because the thing is all over the road and being able to relax because I have control of the vehicle.
Ofcourse, I'm just some guy who "might know a lot about something but you don't know **** about cars, tires, handling or data analysis." and is tired of getting cars back from "experts" who drop the pressure ten PSI to "fix" the problem so the vehicle handles like crap and wallows all over the road. But then again, I don't go to a tire shop very often since I miraculously don't go through tires constantly despite your assertions that I am ruining my tires.
You can say I am stubborn all you want but the truth is, I would change my tire pressures if I was seeing the problems you experts say I must surely be having. I would also change my pressure if the handling and ride were better at the lower pressures you assert are "correct"
Nope, you are advocating pumping the tires up to the maximum as noted on the sidewall. I am advocating adding three or four PSI to the recommendation in the manual or door frame. There's a big difference. Ignorant moron was never mentioned. Lack of real knowledge and experience was.
I agree that the tires should not be running on the sidewalls. Anyone who would say that it is OK is stupid. If you are measuring the pressure and it is at the manufacturer's recommendation and the sidewalls are on the ground, there is more wrong there than the recommendation. Have you checked your gauge against a good, working one? Even with twenty-five PSI, I have not seen many tires running on the sidewalls. Buy or borrow a Moroso, Draeger or the like and check your guage against that. If you are seeing thirty or thirty-two PSI and the sidewall is dragging, as I said before, something is wrong. If your guage is reading that low, who knows how much pressure is really in the tires after you are finished with them.
I and John are basing our not-so-humble opinions on tens of thousands of hours working on hundreds if not thousands of cars of all kinds from soccer-mom vans to high-performance vehicles. Oh yeah, that and our engineering degrees. Check your instrument against a know-good standard and then report back. Of course, all of the design engineers and tire engineers just may be wrong and you are right.
Have you ridden the car with the tech driving with the tires set to recommendation? How are the shock absorbers and the suspension bushings?
Again, I re-iterate, it is very hard for me to believe that at thirty-two PSI, the tires are running on the sidewalls. What the heck is in that thing? Sandbags? Is it up-armored?
Russ
John Kepler
01-08-2012, 05:32
In general, I also agree with your statements that higher than "factory suggested" pressure is better. As a prime example, the Chevy Corvair recommended a significantly lower pressure in the front tires than in the back tires, which made the car handle like a pig. The car understeered terribly - but this was in response to Ralph Nader's "Unsafe at Any Speed" that said the Corvair was an unsafe design because it had terminal oversteer.
Mr. Boardman: Not quite! As a collector/owner/driver of Corvairs (1965 Corsa 140 Coupe, 1967 Monza 110 Convertible (one of 2109 flop-tops made that year), 1969 Monza 110 Coupe (one of 1547 made that last year)) as well as a restorer, and as a CORSA (Corvair Society of America) member for a lot of years, that isn't QUITE what happened! The GM tire pressure recommendation for the Corvair pre-dated Nader's book by several years. No, Ed Cole designed a car that was a radical departure from the typical "GM Floating Power" motiff of the 1950's and replaced it with a very precise, neutral handling Europeanesque performance suspension. As with any performance set-up, the Corvair, particularly the Early (60-64) with the swing-axle rear suspension (before anyone jumps, most cars that had independent rear suspension in the late '50's/early 60's were swing-axles.....Mercedes, Porsche, Volkswagen, Triumph/Standard just to name a few......Ford had a swing-axle FRONT suspension in pick-ups and vans into the late 90's!) had a minor amount of TTO (trailing throttle over-steer). As a 60's car went, the Corvair's TTO was fairly mild.....NOTHING like the "Porsche 911 Surprise" which was a near instantanious transition from neutral/slight understeer to "terminal over-steer" as the rear-end went into business for itself.! The early Corvair's TTO, like any performance car, was cancelled by a small application of power, something the 'Vair had gobs of.. The Late Model Corvair with the semi-trailing link rear suspension has none of the TTO that the Early did and handles with delightful precision right to the limits of the tires and the rest of the suspension......Bilsteins, a mix of Delrin and polyurethane bushings from Corvair Underground, and a set of Pirelli's can move that point to the "you've got to be kidding me!" levels that have just surprised the hell outta more than one Kid and his Rice Rocket" with the $600 Flow-Master exhaust. With a moderate amount of work, the Late Corvair more than earns it's 1960's moniker....."The Poor-Man's Porsche!"
Once Ed Cole delivered his little gem.....the rest of GM started pecking at it. The very first item was that European inspired neutral handling. In the GM model, cars were built to travel in straight lines, so GM's had so damn much under-steer (push) and Ackerman built into'um that you could roll the tires off of'um trying to get them to corner. In an effort to get the neutral handling Corvair to "drive more like a GM", and over the rather loud kicking and screaming of their OEM tire suppliers, principally Goodyear, they lowered the recommended front tire pressures to 12-14 psi, while jacking the rear pressures to over 30....a big number back in the old bias-ply tire era. This ridiculously bad mix of recommended tire pressures DID give the poor long suffering Vair a modicum of GM desired understeer....but at the cost of dismal handling and an exacerbation of TTO to the point it was noticeable to even the most obtuse driver.....and generally scared the bejezus out of'um due to it's all but unknown nature in virtually all US built cars, and led directly to the Naderites screaming about suspension tuck and other non-existent suspension design defects. FWIW, a 1962 Mercedes 300 SEL had one hell of a lot bigger, nastier handling problems (TONS of TTO plus suspension tuck at very high cornering loads) with it's "Precision German Engineering" than the 62 Corvair did even with GM's stupid tire pressure recommendations! On fairly ordinary radials, I run Earlies at 26 front and 30 rear, lates at 30 and 32 for openers.
FWIW, in 1972, the NHTSA agreed that the Corvair, ALL Corvairs, were free of any of the suspension design defects that Ralph Nader insisted were there and GM knew about, ending a series of Nader-inspired lawsuits in the favor of the Defendant (GM)....and completely meaningless. Don Yenko and those that had to race against his freakin' Corvair-based Stingers could have told them that!
Oh.....anyone doubting just how fast a Corvair can be is cordially invited to try your luck against my '65 Not-Exactly-Stock Corsa 140 with a comparable displacement mill (2.7 l...I can't generate the torque or straight-away speed that a big old V-8 can.....though the game changes considerably at the first turn!). Bring money......loser buys the first round<BG>!
Nope, you are advocating pumping the tires up to the maximum as noted on the sidewall. I am advocating adding three or four PSI to the recommendation in the manual or door frame. There's a big difference. Ignorant moron was never mentioned. Lack of real knowledge and experience was.
I agree that the tires should not be running on the sidewalls. Anyone who would say that it is OK is stupid. If you are measuring the pressure and it is at the manufacturer's recommendation and the sidewalls are on the ground, there is more wrong there than the recommendation. Have you checked your gauge against a good, working one? Even with twenty-five PSI, I have not seen many tires running on the sidewalls. Buy or borrow a Moroso, Draeger or the like and check your guage against that. If you are seeing thirty or thirty-two PSI and the sidewall is dragging, as I said before, something is wrong. If your guage is reading that low, who knows how much pressure is really in the tires after you are finished with them.
I and John are basing our not-so-humble opinions on tens of thousands of hours working on hundreds if not thousands of cars of all kinds from soccer-mom vans to high-performance vehicles. Oh yeah, that and our engineering degrees. Check your instrument against a know-good standard and then report back. Of course, all of the design engineers and tire engineers just may be wrong and you are right.
Have you ridden the car with the tech driving with the tires set to recommendation? How are the shock absorbers and the suspension bushings?
Again, I re-iterate, it is very hard for me to believe that at thirty-two PSI, the tires are running on the sidewalls. What the heck is in that thing? Sandbags? Is it up-armored?
Russ
Well, considering the door jam says 41psi I would be running at max or 1 PSI over with the stock tires on my truck so you are actually advocating running max pressure in this case atleast. My point is that you can't suggest running more than recommended then tell me I'm doing it wrong when I do the same. Ofcourse, that is for the standard tires which the truck didn't come with in the first place so it would only matter to those who blindly follow the door sticker or manual. I'll go off the max on the tire itself as a guide before using the guidance for the wrong size, style and brand of tire on the door.
As to the van, It is a full size van, don't know what it weighs but it's heavy, none of that matters though as the "tire pros" left the tires 10-12psi below max. It wasn't riding on the sidewalls full time but there was a little wear on the edge of the sidewall and as you know, that ain't right. I guess the way I worded it made it sound like the sidewalls were flat on the ground but that wasn't what I meant. 40psi was real good. 42 was great so I didn't bother with the 44PSI max as there didn't seem to be any benefit left in more pressure at that point. When I drove it at first I thought the problem was a soft suspension on a tall heavy vehicle. After I drove it on a back country highway I realized it just wasn't right. Stopped for gas, checked the tires and thought the first one had a leak because it was so low. All 4 had the exact same pressure. Turns out, when she bought it a few days before the guy had it serviced and they rotated and checked the tires. Anyways, bumped them up and it no longer felt like the same vehicle. No, you guys never said "moron" but there was plenty of talk of how the tires would explode and kill everyone and the tread would wear off after a hundred miles and....etc.
Part of my problem with not trusting the "experts" is how often they are wrong because they make assumptions and feel they must be right because they are "experts". Case in point, my ex wife was a "mechanic" by job description and supposedly very competent. I stopped letting her work on my truck after she qouted the torque specs for the front wheel bearings off the top of her head. The correct torque for my truck is "finger tight". When I asked her where she got that number she said that was "standard". Not everyone is a self proclaimed expert with nothing to base it on. But, just like with firearms there are plenty enough floating around and I tend to trust personal experience when I am getting the desired results from what I am doing.
JB White
01-09-2012, 07:16
There are torque specs for wheel bearings??? Kidding of course but I never knew any mechanic that could tell you what those specs were because nobody used them. The bearings were preloaded and backed off by feel.
In the 70's when I was in the dealerships the numbers on the valve cover decals were all guidelines as well. Timing advance, plug gap etc. were all numbers based on a fleet average. I recall a factory rep on site telling me to set a customers engine to factory numbers exactly and it ran like crap. The Sunscope readings were all over the place. He then gave me a range of numbers compiled by mechanics in the field. Within those ranges I was able to tune and balance that engine better than it had ever run before. In regard to adjustment, nothing on that engine was set to factory spec. Not even the plug gaps.
Too bad for customers at that time that all warranty work had to be set to those numbers specified. Of course we cheated to make them happy. Several of the cheats were illegal but they worked. The EPA swat teams never showed up. ;)
John Sukey
01-09-2012, 08:38
Mr Kepler, brought back memories of my corvair. Had a Holley 4 barrel carb. Nader's garbage about tuck under was ridiculous since the VW bug had exactly the same type of rear end. There was a fix for that "tuck under" by adding a sway bar, which I also had installed.
There are torque specs for wheel bearings??? Kidding of course but I never knew any mechanic that could tell you what those specs were because nobody used them. The bearings were preloaded and backed off by feel.
Yep, I believe on my Dodge it is 12-14lbs then loosen and retighten to "finger tight" by the book Had I left it to her, she would have set them to, I believe 18lbs was her suggestion, and left them that way.
JB White
01-09-2012, 10:08
Yep, I believe on my Dodge it is 12-14lbs then loosen and retighten to "finger tight" by the book Had I left it to her, she would have set them to, I believe 18lbs was her suggestion, and left them that way.
When we did it it was done differently. The preload was set and the rotation was checked as it was backed off to a certain amount of runout by checking top to bottom. If we went too far, the nut was snugged again before backing off to where the feel and rotation felt right. It would take a lot longer to type it all than it would be to show you in under a minute.
Things were probably a lot different back then than they are now. We still packed (regreased) the bearing by hand. Goop was our friend. :)
Vern Humphrey
01-09-2012, 10:49
Yeah......those "wonderful" little tire pressure sensors (Toyota ain't the only one that has'um!) that make your tires VERY difficult to work on, fail frequently, and cost somewhere between $70 and $120 a pop to replace! All to replace a $2 tire pressure gauge and 30 seconds of time! Ain't "progress" wonderful!
And they nag the $hit out of you!
I had to put the spare on, which doesn't have the sensor, and the warning light and bell nearly deove me crazy until I got the main tire re-mounted.
John Kepler
01-09-2012, 11:01
If you want to get perfectly anal, you actually set bearing lash with a dial indicator, not torque on the nut. If you talk to Timkin or Hyatt, it's 1.0-1.5 thousandths. Rule of thumb: tighten until the bearing locks-up and back off 1/4 turn....or buy a dial indicator and surface block! All of which is a complete arcane and perfectly useless hunk of information.....cars today ALL use modular bearing/hub assemblies that fail 10 times more often than the old "you set'um" tapered roller bearing days and cost $350-$450 to replace instead of $10! Like I said before....ain't "progress" wonderful!
Well, considering the door jam says 41psi I would be running at max or 1 PSI over with the stock tires on my truck so you are actually advocating running max pressure in this case atleast. My point is that you can't suggest running more than recommended then tell me I'm doing it wrong when I do the same. Ofcourse, that is for the standard tires which the truck didn't come with in the first place so it would only matter to those who blindly follow the door sticker or manual. I'll go off the max on the tire itself as a guide before using the guidance for the wrong size, style and brand of tire on the door.
As to the van, It is a full size van, don't know what it weighs but it's heavy, none of that matters though as the "tire pros" left the tires 10-12psi below max. It wasn't riding on the sidewalls full time but there was a little wear on the edge of the sidewall and as you know, that ain't right. I guess the way I worded it made it sound like the sidewalls were flat on the ground but that wasn't what I meant. 40psi was real good. 42 was great so I didn't bother with the 44PSI max as there didn't seem to be any benefit left in more pressure at that point. When I drove it at first I thought the problem was a soft suspension on a tall heavy vehicle. After I drove it on a back country highway I realized it just wasn't right. Stopped for gas, checked the tires and thought the first one had a leak because it was so low. All 4 had the exact same pressure. Turns out, when she bought it a few days before the guy had it serviced and they rotated and checked the tires. Anyways, bumped them up and it no longer felt like the same vehicle. No, you guys never said "moron" but there was plenty of talk of how the tires would explode and kill everyone and the tread would wear off after a hundred miles and....etc.
Part of my problem with not trusting the "experts" is how often they are wrong because they make assumptions and feel they must be right because they are "experts". Case in point, my ex wife was a "mechanic" by job description and supposedly very competent. I stopped letting her work on my truck after she qouted the torque specs for the front wheel bearings off the top of her head. The correct torque for my truck is "finger tight". When I asked her where she got that number she said that was "standard". Not everyone is a self proclaimed expert with nothing to base it on. But, just like with firearms there are plenty enough floating around and I tend to trust personal experience when I am getting the desired results from what I am doing.
Ah HA! Two vital pieces of information revealed by "questioning to the void" (Kepner-Trego troubleshooting protocol). First: the door jamb and (hopefully) the owner's manual show that the correct pressure is 41 PSI. Second: it is a full-size van. You should be running the correct-sized and correct load and speed range tires. Then, by all means, set the inflation to the recommended to start. As you have found, setting the pressure up a bit will result in better handling and increased fuel mileage. You should still stay below the maximum for the tire. If the max is too near the recommendation, perhaps you need a higher load-rated tire. Check with the manufacturer or the owner's manual to get the correct size, load rating and speed rating. As an example, I picked out tires for my Saturn L300. The service writer would not sell me the tires or mount them, either. I had picked out "S" rated tires and the book calls for a "H" speed rating. Who knew the Saturn needed 130 MPH tires? She wouldn't sell or sevice the wrong tires because of liability concerns. Mrs. Nixon's T-Bird requires "H" rated tires.
I still think you should check your guage. I was at the doc today and I took my own advice. I brought my blood pressure machine to the appointment to check it against the Doc's good mercury manometer. Lo and behold, my machine grades on the curve, reading about ten points high on both readings. Now I know.
So, the take-aways? Get ALL the information needed, set the pressure per the manual, select the correct tires for the vehicle and check your measuring equipment for calibration.
Believe it or not, I'm not trying to belittle you or be argumentitive. I have some expertise I want to share that may help you with a problem you are having.
Russ
There are torque spec. for lug nuts also but when was the last time you saw any on do that. :icon_scratch::icon_scratch: Good old air gun with a “universal socket” ha,ha, to round the nuts off. :eek::eek::eek:
Lordy! More information about tires than NASA knows about tiles. How the heck can you figure out what pressure your tires should have when the information is printing in rubber, in tiny little numbers that you need a magnifying glass to read- upside down(if the sun is just right).
John Kepler
01-10-2012, 02:34
There are torque spec. for lug nuts also but when was the last time you saw any on do that. :icon_scratch::icon_scratch: Good old air gun with a “universal socket” ha,ha, to round the nuts off. :eek::eek::eek:
If you come to our shop.....every time a tire is mounted! Just because you see an impact gun being used doesn't mean the wheel isn't being torqued correctly! We use torque-limiting extensions on our impact guns that have been calibrated against "The Gold Standard", my Dad's old Pratt & Whitney beam-deflection torque wrench.....and they're good enough for government work! On new cars with "throw-away" brake rotors, failure to correctly torque wheels leads to warped rotors almost immediately.
If you come to our shop.....every time a tire is mounted! Just because you see an impact gun being used doesn't mean the wheel isn't being torqued correctly! We use torque-limiting extensions on our impact guns .......
Must be nice, Nothing like getting a flat and there you are on the side of the road standing on the tire tool and hopping up and down and the nut won't break loose because they used the good ol impact gun.
cars today ALL use modular bearing/hub assemblies that fail 10 times more often than the old "you set'um" tapered roller bearing days and cost $350-$450 to replace instead of $10! Like I said before....ain't "progress" wonderful!
One of the reasons I am still driving a 98 Ram is that so much of it is similar to something from 1970. It's one of those vehicles that has the new stuff where it's and improvement and the old stuff where it was unnecessary to change it. When I look under the hood I can atleast tell which piece is the motor and don't have to look past the flux capacitor find the dipstick for the tranny.
First: the door jamb and (hopefully) the owner's manual show that the correct pressure is 41 PSI.
Second: it is a full-size van. You should be running the correct-sized and correct load and speed range tires. Then, by all means, set the inflation to the recommended to start.
I still think you should check your guage. I was at the doc today and I took my own advice. I brought my blood pressure machine to the appointment to check it against the Doc's good mercury manometer. Lo and behold, my machine grades on the curve, reading about ten points high on both readings. Now I know.
Russ
The 41PSI in the door was on my pickup. Which does not have the tires listed in the door due to it being a low production model with unusual tire size. I was just making the point that you can't always go by the info on the vehicle even though you normally can.
I didn't even bother on the van as it is used and no longer has the stock tires. So, I went with the tire max as a guide.
as to the tire guage, I keep multiple el cheapo gauges on hand and alternate between them. I know they are not 100% reliable so if i have any doubt I toss them or atleast check them against another gauge. I'd keep a better gauge on hand but I have a tendency to lose any small items I spend good money on.
Not directed at you, but I just want to say one more time, I do not advocate actually exceeding the Max tire pressure.
As long as we are talking about gauges and air pressure, I might as well throw in a couple of good shade tree mechanic stories. In highschool my buddy had an 80 something Monte Carlo. I sold him the 350 out of my Van and he swapped it for the godawful diesel in the Monte. Later on, he put a set of air shocks on the back to bump up the rear a bit. He came over one day and was complaining that he had an air leak in his air shocks and couldn't find it. He said every time he got to wherever he was going and checked the pressure he had lost 2PSI. Then he said it didn't matter how long the drive, it was always 2PSI. I told him to check it again and he did, 2PSI down. So I told him to check it again right away, and again it was 2PSI down. At this point I started laughing and told him he was letting out 2PSI every time he checked it. He checked it 4 more times and lost 8PSI....LOL He wasn't happy to find out he had spent 3 days checking for a leak he was actually creating himself.
When he put the engine in he had to do allot of Bubbafication to swap from Diesel to Gas. Most of it was minor stuff related to location of accessories and wires. One problem was the throttle cable which had to be run to the opposite side of the engine. So, to keep it out of the way he zip tied it to this long brace that ran along the firewall. It worked perfectly for a while. Then one day while driving home it started to rain. All of a sudden the car surged forward and took off on it's own then it just as quickly slowed down and coasted. Then without warning it took off on it's own again but quickly began to coast once more. It was at this point he figure out what that brace on the firewall was for. It was actually the arm that connected one windshield wiper to the other and every time the wipers moved it would pull the throttle cable. He said once he got the wipers set to the right speed he averaged about 55 give or take a few...LOL
John Kepler
01-10-2012, 05:57
Must be nice, Nothing like getting a flat and there you are on the side of the road standing on the tire tool and hopping up and down and the nut won't break loose because they used the good ol impact gun.
One of the reasons I am still driving a 98 Ram is that so much of it is similar to something from 1970. It's one of those vehicles that has the new stuff where it's and improvement and the old stuff where it was unnecessary to change it. When I look under the hood I can atleast tell which piece is the motor and don't have to look past the flux capacitor find the dipstick for the tranny.
You need to improve your reading comprehension skills. I said we use TORQUE-LIMITING EXTENSIONS. We tighten lugs to the EXACT factory torque specification.....no more, no less, we also apply anti-seize to all lugs and hubs. If you can't get'um off, you probably shouldn't be out without a keeper. Oh, and MOST new automatic transmissions do NOT have dip-sticks, and require a transmission machine to service.
mike24d20
01-10-2012, 11:30
Must be nice too have all the fancy dodads that a tire shop has or even yet a modern guarge. But us po foke who do not own such have only lug wrenches an lil ole pocket air presure gages for use. An I have been along side of a road jumping on a 4-way too losen a air empact torqued lug nut.
John Kepler
01-11-2012, 03:12
Must be nice too have all the fancy dodads that a tire shop has or even yet a modern guarge. But us po foke who do not own such have only lug wrenches an lil ole pocket air presure gages for use. An I have been along side of a road jumping on a 4-way too losen a air empact torqued lug nut.
Then either this happened a while ago, or you desperately need to find a different shop! Times have changed, and the days of a shop just hammering lugs on with an impact until the moron behind it gets bored enough to stop just causing a bit of cussing on the side of the road ended decades ago! Alloy wheels and "weight reducing" light-weight (CHEAP!) brake rotors do NOT take kindly to over-torquing!
The very first tool my Dad bought me (Poppa was an old Navy aircraft mechanic as well as an engineer) was a beam-deflection torque wrench....I've still got it, still use it to re-assemble engines even though it has been joined by several other. more "user-friendly" types. I've been using it to check wheel-torques since I was in my early teens. My Dad also made sure I knew all about anti-seize compounds (Navy term: "toad $hit"). A torque wrench, anti-seize compounds judiciously applied, and the knowledge to use both means that unlike you'all apparently......I have NEVER had a problem changing a flat. Look, Sears will sell tools to anyone without regard to race, color, creed, sex, national origin, or economic status so I really wouldn't go there if I were you......if you ain't got the proper tools to maintain your car to the point that you can change a wheel.....that's your choice.....and you have, in my opinion, chosen poorly! Investing in correct, functional tools is the cheapest money any individual can spend! Every tool I own has paid me back at least 5 times it's original cost.....some several times that! Hell, yesterday I drove 400 miles to purchase and pick-up $1000-worth of new fairly specialized shop tools......one of the three items bought paid for the lot as soon as we got it back to the shop!
No, you need to improve your reading comprehension skills. I said it must be nice in reference to your use of a torque limiting extension. I referenced the nuts being over torqued by the proverbial "THEY" using an impact gun (wrench).
Oh, and MOST new automatic transmissions do NOT have dip-sticks, and require a transmission machine to service.
Thats the sort of nonsense I am talking about. What's wrong with being able to check your fluids at home without paying a kings ransom to a dealer for a simple check?
And finally John, you need to get out more. Just because you do things correctly does not mean most others do. If you were to go to a random sampling of tire shops and watch them work your eyes would be open and your head would be aching. Oddly enough, some of the best tire service I ever had was by some guys on Guam who had a van on the side of the road with a trailer for their equipment and generator. There was allot they couldn't do but they covered the basics quick, cheap and correctly.
John Kepler
01-12-2012, 05:53
Thats the sort of nonsense I am talking about. What's wrong with being able to check your fluids at home without paying a kings ransom to a dealer for a simple check?
You want the "official" explanation, or reality?
"Official Explanation": Modern trannys use a variety of different working fluids, not Dex/Merc 3 or Mercon 5 and certainly not something you can buy cheap at Wally World! If you include a dip-stick, that implies that Goober has to look at it, more than likely misreading, and then dumping something (cheap) in it if the stick that he's misreading says it needs, without really looking to see what flavor of juice it's supposed to take! This in turn, leads to said tranny expensively expiring on the Extended Warranty the Marketing guys insisted they had to have without doing that pesky math to calculate how much that was going to cost. The solution was to get Goober the hell outta the "Charlie-Foxtrot" loop by eliminating the dip-stick and the temptation to (mis) use it all together. What Goober can't access, Goober can't screw up....and no engineer has ever gotten into trouble by over-estimating the depth of human stupidity.
Reality: While the "Official" position DOES make a great deal of sense if you're a manufacturer....the "other" reality is that that freakin' dip-stick is an expensive pain in the ass! It's a "loose part" that requires a $100/hour UAW member to screw into the vehicle rather than having a "cheap" multi-million dollar robot do it, and the fool thing is unique to each model you dump the tranny in, adding to the already disproportionate cost of an item that is an expensive PITA going in. Like modular bearings, it's great if you're building the car.....not so much if you're buying/maintaining it!!
're
And finally John, you need to get out more. Just because you do things correctly does not mean most others do. If you were to go to a random sampling of tire shops and watch them work your eyes would be open and your head would be aching.
Yeah I do......and the reason I can't is for the reasons you've stated. We should rename our shop "The Last Resort"! I'd kill to have "first crack" at most of the work we do! No, cars usually come to us AFTER Bubba has had at them! In the two years my son and I have had the shop open, I have seen gross incompitence bordering on (and sometimes exceeding) criminal negligence, out and out fraud, and profound ignorance treated like it's a virtue! I have a GMC 4x4 pick-up in the shop right now with a busted tranny and transfer case because some moron convinced the owner that his "transfer case needed service" (a lie.....there's no PM on the TC) and proceeded to use the wrong fluid (New Process, like the rest of Chrysler went to a proprietary synthetic in 2002.....Bubba filled it with Dex III!). The TC handgrenaded with the wrong fluid and busted the tranny like a dry stick in the process.....three Large to repair! We have already been deposed in 3 lawsuits against some of the perpetrators of this "maintenance-induced destruction". So no.....you aren't telling me anything I don't already know
No, cars usually come to us AFTER Bubba has had at them! In the two years my son and I have had the shop open, I have seen gross incompitence bordering on (and sometimes exceeding) criminal negligence, out and out fraud, and profound ignorance treated like it's a virtue!
I bought my truck "New" on Guam in Jun99. It was 2yrs old already but still "New" it was built in Jun97 or atleast that's the most recent date I've found on any parts. Anyways, 2yrs and 75 miles of being transferred from one dealer to another and sitting in the hot sun all day left it with allot of squeeks and I took it to the local dealership who basically replaced the whole front end under warranty because as they said "If we miss something it may be month's before we get the parts in". Well, a while later I took it back for something else, I think to have the gas gauge reset as it read almost empty but was EMPTY. I am hard on brakes and tires. Speed limit was a max of 45 on Guam. I averaged 75. When I had them reset the gas guage they did a run through of the truck and when I came to pick it up the mechanic pulled me aside and said "Hey bro, we saw you had your brakes done, We was wonderin who did your brakes." At this point I replayed everything in my head and was trying to figure out what I could have screwed up. When I told him I did it myself in the front yard, he shook his head in dissapointment. This really had me worried so I asked him what was wrong. He laughed and said "Nothin bro, they're good. We just been looking for a shop to do brake work who won't F- it all up" He then went through the laundry list of problems he had seen on brake jobs. Most of what they saw seemed as if the person who did the work was drunk or high.
To keep it simple now, I just burn my brakes down to nothing then replace the rotors along with the pads instead of trying to have them turned to save a few bucks. I just get tired of hearing that they won't turn my rotors due to heat damage....hah...crybabies....LOL In reality, it is just cheaper to replace the rotors than pay someone else to do the work.
You and my local mechanic would have had a field day with my truck last time I had it worked on. He tried to politely point out all the stupid things I had done under the hood. When I explained the conditions I was facing trying to get parts and ship it back from England he saw that I was more desperate than stupid. After explaining that we had to splice in a coil off a British sedan just to get it to the shipping yard after the factory coil cracked and got water in it, he laughed and said he originally wasn't sure he even wanted to know why there was a bubba'd up coil connection spliced into the factory coil wires. Nothing like getting your truck in from the dock and having to ask where the nearest parts store is, so you can start fixing all the stuff you rigged up overseas. In the end I am sure he was happy I authorized him to fix or replace about $400 worth of little stuff. I let him know that I agreed that as long as he had to pull the heads off a 12yo truck with over 100k on it I would rather spend the money on gaskets hoses bolts and doodads now than pay to have them replaced later when they weren't easy to get to or already off.
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