Wrong Tire info on Door Jam? + My first Tank Results

The door jam tells you the manufacturer's recommendation for the specified tire size. The tire marking tells you the tire manufacturer's maximum cold pressure rating of the tire. Both are important, though the tire manufacturer's rating should be taken as a stronger predictor of adverse consequence (e.g., unusual wear).

 

Throughout this & other chat rooms, you'll find lengthy discussions about tire pressure for this car. You'll find a few different schools of thought.
Your tires & door jamb are consistent with others.
When inflating the tires, I default to the manufacturer's spec of 35psi, since an engineer in the ivory tower at Toyota chose that.
On any car, the tires SHOULD be rated for higher pressure than the car requires. It's a built in safety cushion. 44psi compromises vehicle handling.
Having said that, watch this thread for reactions to my rationale.

 

Hearing Toyota state that you should set your tires at 35psi is kind of like when you first buy, say, a olympus digital camera. In the manual it states that you should only use olympus brand batteries and storage devices for your own saftey.

I feel, like in the stated case above, the companies are just doing a bit of CYA (cover your behind), plus helping out some friends in the tire industry at the same time. While the olympus example stated above brings in direct $$ to olympus, it's also a CYA move designed to blame someone else (namely you) if you do absolutely anything that's not within their guidlines.

I've owned digital cameras for 5 years now, never had battery problems when using third party batteries. Do I take a slight risk? Possibly, but I like to believe that most companies don't design cheap products that continue to be faulty at the result of losing customers and sales - rather, I think most companies prefer to make the cheapest yet most durable product available to the consumer to have an edge over their competitors. While tires can be a bit of a different argument, as they directly relate to my saftey, I promise you that Toyota's reasoning for putting 35 was two fold - a little help to the tire companies, and it's a CYA. I also promise you that most third party tire companies wouldn't advertise a "max pressure" that could very easily explode or blowout - there's give in there too, and the max pressure stated on the tires is within safe standards tested heavily by each company.

-m.

 

amen, a lot!
my first car had high-speed rated 2-ply tires that wore off 1/3 of their tread in 10k miles. i re-shod the car with radials and sold the car at 42k miles with the same tires on it.
and remember the old silky-smooth ride Cadillacs? the factory-recommended psi's were in the mid-to-low 20's, though that wore the tires out like crazy....

also note that it was not too many years ago that the tire jockey's, when "seating" a new set of rubber on the wheels, would run them up to 60-70 psi for several seconds, then drop them back to spec. you never saw headlines about "hundreds of tires exploding" come from that.... because they didn't. a new tire can probalby handle 20 psi cold overpressure, but that's not any reason to DRIVE the car at those psi's...

i will be experimenting with tire pressures and will report in the future.

 

Tire pressures are chosen primarily to satisfy the ride and handling engineer. In reality, few agree with this chosen pressure, but the R&H group will not buy off on the car if their number is not used.

To determine if the pressure you use is "safe" one must evaluate the wear pattern and contact patch. Basically, if the outsides of the tire wear more than the middle, the tire is under pressure. If the middle wears more than the outsides, the tire is over pressure. The mass the specific wheel/tire carries affect this, as does tire pressure. Thus, most front wheel drive vehicles have higher front pressures than rears.

The MINIMUM safe operating pressure measured cold is the pressures on the tire placard. The highest safe operating pressure cold is either the maximum rated tire pressure on the sidewall, or the lesser pressure which results in even tire wear and thus maximizes the contact patch area. Many feel the higher pressures improve ride and handling by reducing side wall deflection and offering a firmer, more precise feel to the road. Others say this results in a rough ride. It is up to you. Just stay above the minimum and below the maximum and monitor your tire wear patterns. Depending on how many people or how much cargo you carry, you may need to tweak the pressures a few psi to generate ideal wear patterns.

 

ok here is evidence that "overinflating" tires will cause handling issues.

when a tire is overinflated it creates a curved profile to the ground. just as a stomach bulges when full the tire will do the same thing.

this results in less tire contacting the road which in turn reduces the coefficient of friction which may lead to skiding and loss of control.

that said, realize that as someone mentioned, the guidelines set by tire and vehicle manufacturers are just that, guidelines.

another word for guidelines is hints, suggestions, etc. so the "max" pressure is the maximum safe pressure under the severest conditions one can reasonably expect.

now foregoing the the "disaster movie plot" scenario, you can under optimum conditions inflate your tires to double the PSI maximum and get away with it. but those are optimum conditions which are as rare as maximum safe conditions.

so all this boils down to the fact that tire pressure that is anywhere in the stated range is for all intensive purposes, just fine.

This info was taken from a conversation i had with my brother who was the manager of a major retail tire store in the Pacific Northwest.

he also said that the stated max can be exceeded easily with no danger at all. the reason?

with all the lawyers in this country, those warning labels are to please them more than anyone else. he also said that the only thing you need to be concern about is the rating of high performance tires. the higher the speed rating, the less likely the tires will be in compliance.

 

When I first got my Chevy Avalanche I hung out at the ChevyAvalancheFanClub.com site a lot. The boys there recommended 38PSI vs Cehvy's recommended 32 for better mpg.

And when you're getting 13-18mpg every little bit helps.

Fred

 

Advance Auto Parts says:

http://www.advanceautoparts.com/howtos_tip...r20030101gm.htm

Simple Fuel Mileage Tips

Most vehicle manufacturers recommend tire inflation pressures that are a compromise of comfort and safety. In the vehicles owners manual are listed a range of tire inflation pressures usually to compensate for loaded and unloaded conditions. One of the most important changes you can make is to keep your tires inflated at the highest recommended level. If the manual gives only a single inflation pressure, read the information on the sidewall of your tires concerning maximum safe inflation pressure and add 3-5 pounds of air making certain not to exceed the stated maximum inflation pressure noted on the tire. Keep a close eye on your tires for uneven tire wear. Greater tread wear in the center means too much pressure. If this happens, rotate the tires and slightly reduce air pressure.

 

Thank you.

 

This was completely true for the old bias belted/bias ply tires. Modern radials are structured in such a way that the tread does not lift towards or away from the ground so drastically like the old bias tires did. The result is that they will keep far more of the thread on the ground over a wide range of inflation pressures.

For proof, go look at the Michelin site at the pictures of tires running over glass plates. The best one is when they run a tire over the glass plate with water flooding the ground. They show that higher pressures keep the tire flatter on the ground and resist aquaplaning much better than lower pressures. I can't find the link but I posted a link to tirerack.com on a different thread that showed the Michelin demonstration.

As for why the tire pressures are lower on the manufacturers plate than what some owners recommend, (as others here have said - I'm just joining my voice in to the choir- the manufacturer is primarily concerned with all around compromise leaning towards soft ride. Over the years the pressures have gotten higher but the tires are essentially the same radial with (predominantly) steel belts, yet the manufacturers have steadily raised pressures from around 20Lbs to 35lbs. Why? C.A.F.E. (corporate average fuel economy) to increase their fleet's average fuel economy, and to reduce the likelyhood of lawsuits due to blowouts (remember Firestone and all the SUV blowouts, the first thing they said was to increase pressure - not lower it).

There are other benefits to higher pressures, due to the tire not wriggling around so much and getting excessively hot (especially with a lower speed rating on the tire like on our stock tires) but this is a much smaller piece of the puzzle, ao I'll just leave it at that.


As for the original question regarding the 60LB maximum vs. the tire sidewall listed limit of 44lbs (both cold). Please do not exceed the sidewall pressure, unless you talk to the tire manufacturer. All modern tires actually do hold up to a lot higher pressure than what is listed on the sidewall, because the tire gets hotter and the hot expanding air inside the tire increases the pressure. since we have no consistent way of checking hot pressures, the manufacturers use cold pressures and add a rather significant pressure margin. Since even the highest pressure XL rated tires only go to about 50Lbs or so, the 60Lbs limit is well above any tire that we would use (today).