Tire pressure different on tire vs car

[bullwinkle]

Plus, if you inflate the tire to 51 psi it will over inflate when it heats up, while driving. 1 psi per 10 deg F.

Yes-but that’s not actually a problem-the 35 is a COLD inflation pressure. The tires will increase in pressure while driving & heating up, they could possibly even make 50 PSI after an extended high speed hot weather run. Won’t hurt them a bit! I try to adjust PSI to load & driving conditions, go up a little higher if fully loaded & a long run.

 

[berniedd]

There is no tire you can buy where the maximum PSI rating is under 50. They do this because idiots overinflate tires way higher than they need to be because they "think it looks too low"

I just looked, the maximum PSI rating on my CRV's 225/65/R17 Japan-made Bridgestone Dueler tires is 44 psi. These tires have a 102T rating. At that 44 psi, sidewall info for the max load it can carry is 1874 lbs. It also says on the sidewall that maximum inflation pressure used to seat the tire bead on the rim is not to exceed 40 psi. The Honda owner's manual says recommended tire inflation pressure is on the door jamb. The door jamb label says 30 psi. The car's curb weight is 3488 lbs and maximum permissible vehicle weight is 4563 lbs. So if we were to assume 50/50 weight distribution front and rear, that would be a maximum 1140 lbs load allowed for each front tire, at the recommended 30 psi.

I understand that the 30 psi is usually a compromise between ride comfort and handling. So I put 33 psi in my tires. Makes for slightly better handling, better tire wear resistance, and easily perceived less effort to turn the wheels when cornering at very slow speeds. The tires are original to the car, and now have 44,000 miles on them. The remaining tread on 'em is about half of what they were when new and is equal in thickness across one shoulder to the center, to the other shoulder. .

 

[CapriRacer]

It's there any kind of reference or formula available to derive an approximate and appropriate pressure when changing tire sizes given the factory size and pressure?

There is. They are called load tables and you can find a set of them here: TirePressure.org

Just match the loads and you can get the pressure.

Word of warning: Ride and handling is controlled by more than just inflation pressure and varies widely between makes/models. However load carrying capacity is more or less a Law of Physics kind of thing and is almost exclusively tied to inflation pressure - meaning that the pressure is way, way more important and you'll have to choose the exact make/model to suit your desires, and not use inflation pressure to fix a bad decision.

 

[CapriRacer]

Yes-but that’s not actually a problem-the 35 is a COLD inflation pressure. The tires will increase in pressure while driving & heating up, they could possibly even make 50 PSI after an extended high speed hot weather run. Won’t hurt them a bit! I try to adjust PSI to load & driving conditions, go up a little higher if fully loaded & a long run.

Ah ..... Mmmmmm ....... Not exactly.

Normal pressure build up is 10%, so a 35 psi inflation only increases to 38.5 psi - normally. To increase 15 psi a tire would have to increase - hold on, I'm going to do the math - 160°F. That would result in severe damage to the tire.

 

[SHOZ]

The tire pressure that counts is the cold pressure. What the pressure ends up with as it heats up is only of race driver consequence.

 

[USA]

The pressure in the door label was set by the builders of the car. I have never had a problem using their
numbers.

 

[Jetronic]

Recently replaced tires on 08 Mustang with the recommended tire size. Decal inside door states 35psi, tire states 51 psi. Im clueless. When I checked pressure tire dealer had filled 35, I increased to 45 (just could not bring myself to do over 50psi )

51 psi is what you need to put in the tyre if it has to carry it's maximum load. What's on the decal should be the minimum for the actual load.

 

[350Rocket]

The recommendation on the door, was put there to match the tires installed at the time of manufacture. That being said, his new tires do not have the same pressure ratings as the tire they put on the car in 2008. The manufacturer of his new tires say what it can it be inflated to. New tread design and capacity determine what you can inflate them to. New tires may look low on pressure if inflated to what the door label says, and may feel like they drag, going around corners. Filling to max capacity probably will make for a rough bumpy ride, if not needed. And no I've never seen a tire brand and type written on a sticker, that's why you can't assume every tire ever installed on that car has the same inflation requirement. I hope that clears this up for you.,,

As others are saying...this is wrong. Follow the door placard which tells you the correct pressure for this specific vehicle. Not the maximum pressure allowed for the tires themselves which has nothing to do with recommended pressure.
Only reason to change it is if you do like I did and go from standard or p metric tires to a heavier load range like D or E then you want higher pressure because it's not the same load range as what the truck came with. But this is typically a truck thing, not a passenger car issue.

 

[350Rocket]

So if the door label said to run them at 35 psi, then whats the sense of buying tires rated to 51 psi?. Plus not understanding how the tires will perform BETTER carrying max loadsm with higher pressure, is extremely uninformed on your part. Glad I could help you understand that.,,

You are the one that needs some education on this subject.

 

[SHOZ]

Tire wear is what I go by. My Hyundais tire wear are the first to agree with with the door sticker.