Does tire size affect tire pressure?

[ARB1977]

Hey guys im courious, im sure this is a scientific question but hey were BITOG 'ers right. Does a tire size effect tire pressure? Lets say your running a passenger car tire compaired to a 54" tire would running a bigger tire really need more pressure or could you run lets say 32 psi and be safe? I guess in this this case does size matter?

 

[BuickGN]

It totally depends on the manufacturer. I've had two same sized tires for the TL. One spec'd 33psi and the other 45psi. Light truck tires sometimes say 60psi on the sidewall while the exact same brand and size (two co-workers of mine) only "passenger" insetead of LT call for 35psi. I know this isn't any help.

 

[Eddie]

There is a load vs pressure curve for each size tire. Yes, the size of the tire does affect the required pressure at a given load. I have seen the P vs L plots for tires but, I do not at the present remember where to find them.

 

[JHZR2]

It is dependent upon the tire construction, but Id venture to guess that a larger quantity of lower pressure air very well could hold as much load as a smaller quanity of higher pressure air. It would be a function of the whole tire system together.

Again, a non-answer...

 

[CapriRacer]

Hopefully, this will answer everyone's questions and correct a couple of misconceptions.

http://www.geocities.com/barrystiretech/loadtables.html

 

[rpn453]

Just like a bicycle tire, you usually need higher pressure to run a narrower tire under the same load.

 

[1sttruck]

With truck tires most seem to pay attention to 'load index', like 120, but 'load range', like E, is important for considering side deflection in tires. Maximum tire pressure seems to vary more with load range than load index. Tire pressure requirements also seems to vary a lot with load and speed on truck tires, something that a lot of people seem to disregard as most seem to only focus on comfort.

 

[1sttruck]

As an example for my 3/4 ton pickup I run stock size 265/70-17, load range E, with the the front / rear tire pressures for a light load being 50 / 40 psi, for a heavy load are 60 / 70, one needs to add 10 psi for sustained speeds over 65 mph, and the tires aren't rated for sustained speeds over something like 85 mph. Since I find myself on the freeway often with up to a medium load I run 65 psi front and rear and will add more for heavy loads. This is more important in the summer in order to keep tire temps under control. For off road one may need to decrease tire pressure, but I do so more for ice than off road conditions in order to get a bit larger contact patch.