[rohrt]

Advertisement on the radio had a pop quiz about where to find the proper tire pressure reading for your vehicle. The correct answer according to them was the door jamb.

This seems a bit counter intuitive to me. Since you change tires on a car with different sizes and brands who would know better what pressure should be then the the tire manufacture themselves.

So since that apparently is not the correct answer. Is the tire pressure related to the vehicle weight?

[salem1912]

I think tires only show the Max air pressure you should run. Door jamb is what they recomend.

[chipster]

Originally Posted by salem1912

I think tires only show the Max air pressure you should run. Door jamb is what they recomend.

Correct answer.

[hada76]

go by tire info. yes max press is for max load

[David Jones]

And the door jamb is for the oem tires.
They have no control over what you install later on.

[b-man]

Door jamb pressure is what I would consider to be the minimum tire pressure you should run.

The sidewall max pressure is as high as you'd ever need to go, but almost never would you want to.

I always bump the pressure higher than the door jamb pressure by 4 to 10 psi depending on the load or if taking a long freeway trip, also keeping ride quality in mind.

Increasing tire pressure to enhance fuel economy is helpful but you reach the point of diminishing returns after about 40 psi.

[Chris65LeMans]

Remember that if you're using the door jamb sticker from an older car like my LeMans, the recommended pressure will refer to the original bias plys. That recommendation has no value for modern radial tires - in this case, ignoring the door jamb and following the tire recommendation is the way to go.

[Bob Rutledge]

Most tires today show 44PSI. I generally run 38 PSI and get even tire wear. So, my answer is the tire not jamb.

[The Champ]

Chris

I agree that the bias ply number is pretty much irrelevant (unless you are running bias ply reproduction tires).

But once again - the inflation on the tire is the MAX pressure. That number is irrelevant to what pressure you should run under normal conditions.

For most of us, a tire pressure reading of somewhere around 35 PSI (plus or minus 10%) is a decent rule of thumb for most of our cars with radial tires. Adjust to your own preference as needed - but do not exceed the MAX pressure on the sidewall.

[rohrt]

Thanks for the replies. All good info.

My daily driver has 32psi in the jamb and 44 on the tire if I recall correctly.

I will have to check a few tire but I thought the tires gave a range, like 40-44 max. So it makes sense that would be the max pressure.

I will have to look at the jamb again and see if it says anywhere that the psi given is a minimum value.

[NBF823]

Door jamb for sure - two cars can use the same tire, but have very different weight distribution.

[mechanickeith]

Remember a while back a major big 3 company had issues with blowouts on their SUV's?? The big 3 mfr had a much lower pressure on the door jam than what was recommended by the tire maker. This was done soley for ride comfort. Funny how the change to a different tire by them also had a raised pressure sticker for the door jam. Same as what was on the new tire.
I always go with whats on the sidewall. If its 44 max, I usually set them no lower than 40. I gained 2 mpg running at 40 instead of the 32 that was recommended. No noticable change in tire longjevity either.

[A.J.]

Inside of fuel door on my Audi and doorjamb on the VW

[Fatty's Garage]

I remember from a suspension design course I took in college that you should always use the pressure on the jamb. That's what the engineers designed and tuned the suspension too. I've also been told that by a BF Goodrich design engineer.

[goatwgn]

Originally Posted by Chris65LeMans

Remember that if you're using the door jamb sticker from an older car like my LeMans, the recommended pressure will refer to the original bias plys. That recommendation has no value for modern radial tires - in this case, ignoring the door jamb and following the tire recommendation is the way to go.

X2. Although the "door jamb" sticker on my '66 Tempest Custom wagon is in the glovebox.

[b-man]

Originally Posted by Fatty's Garage

I remember from a suspension design course I took in college that you should always use the pressure on the jamb. That's what the engineers designed and tuned the suspension too. I've also been told that by a BF Goodrich design engineer.

Doesn't really apply when running radial tires on cars originaly spec'd with bias, or when running non-stock wheel and tire sizes.

Otherwise I have to agree.

[Will]

Running the pressure higher than necessary reduces straight-line traction and will wear the centers of the tires out before the shoulders.

Higher pressures do tend to sharpen steering response and aid in ultimate handling (where you're pushing the car to it's limits) as well as potentially improve mileage a little bit due to decreased rolling resistance. When I was autocrossing regularly the guys who were running on their regular street tires would pump the tires up to whatever the max on the sidewall was during the event, then lower back down afterwards.

The very best way to figure out what inflation pressure you need is to use a pyrometer to measure the temp across the tread of the tire after driving for awhile. You want the temp as even as possible across the tread. Of course, most of us don't have one of those so there are other ways to figure out your optimal inflation.

Put a chalk stripe across the tread then drive around the block. If there is still chalk showing out near the shoulders your pressure is too high. If it's all completely gone, you might be too low, add a couple psi and try again. You want just a little chalk showing right at the edge of the tire tread.

[pontiacs-r-us]

Very good info Will,& good explanation.I think you have use a little of your own judgement as well...The auto manufacture did engineer the car,& not the tire manufactures.I never run tire max listed on sidewall.That is a general psi that shouldn't be exceeded.Always seems to harsh of a ride,& almost always wears center of tire.Also remember this can be a safety issue as well.I have been very curious as to why on my G8 it lists 36 psi front,& 39psi rear?Because of IRS? Never seen recommended psi higher for rear tires.After all engine weight is most always greater than cargo weight. Any Incite on this anyone???Thanks,KD


Sent from my iPod touch using Tapatalk

[GT182]

Just my .

Back in the 97 when I put a new set of Cooper Discoverer A/Ts on my Jeep GC, I asked the dealer what his thoughts were in tire pressure. He said that tho 32 is "recommended", you can increase up to the max if you wish. But he didn't recommend the max tire pressure unless you were carrying a whole bunch of extra weight. Going up from 32 to 38#s is what he recommended as the high point if you wanted to run extra air. It also decreases the rolling resistance a bit to help get better gas mileage. But it also affects stopping on wet, snowy, or icy roads; and to use caution when stopping on sharp corners. And at 38#s it doesn't hurt tire wear all that much. He ran his cars and pick up that way and said everything was normal.

So I went with what he said. My front Coopers lasted about 40,500 miles and the centers wore normally. Outside tread wear as bad but that was due to the front 4WD hubs going bad. If that hadn't of happened I could have gotten more mile out of them. I replaced the front Coopers in 2013. Still running them on the rear as of now but they need replacing before winter sets in.... close to 49,000 on the rears.