Tire Pressure Question

[mnetwork]

No one will give me a straight answer on this question.. I recently got rims and tires. I went up size therefore making my sidewall shorter.. Logic tells me that I would need more tire pressure because the area inside the tire has gone down from the stock tires. When I call the tire place to ask them, they tell me just follow the sticker on the car.

I don't know what to do... I am running 225/45ZR-17 tires.

 

[99gst_racer]

There's alot more involved with recommended tire pressure than just taking only area into account.

But, you're thinking way too hard. The manufacturer recommended pressure rating is printed on the sidewall.

 

[TKW#13]

There's alot more involved with recommended tire pressure than just taking only area into account.

But, you're thinking way too hard. The manufacturer recommended pressure rating is printed on the sidewall.

The tire is stamped with the maximum air pressure under loaded conditions. If the tire is stamped at 44 psi that is the max. air the tire can handle and it also gives you the weight carrying capacity. Which does not mean you run the tire at that pressure, if you ran them that high you will wear out the center of the tire. I have 235/45r17 and I run anywhere from 38-42 psi. because of my driving habits (aggressive).

 

[Gregory]

A smaller volume inside the tire does not mean you need more air. Yes, pressure is inversely related to volume in a closed system, but that only means that as your volume gets smaller, you need to put in less air to obtain the desired pressure, and the tire will obtain the same rigidity. Your tire is a fixed size, so just put in what is recommended on the sidewall (or a few lbs less than the max). Remember, your pressure goes up when you drive because the air in the tire is heated from the warm tires.

I'm a little confused to why you think you need to put in more air though. Am I misinterpreting your question?

TKW, what are you referring to by max psi under 'loaded conditions?' The pressure will remain the same whether the tire is mounted on a car or sitting in the shop. Or do you mean when the tire is warm and being driven hard?

Hope this helps.

 

[Eclipse98_RS]

I think what he means "Under loaded conditions" is when the tire is inflated and on the car. The tire is under a load from the car. With a normal R rated tire 35 PSI is fine. With a Z rated tire you can go higher. I used to have Z rated tires on my old RS and ran them at 36 PSI. Just dont over/under inflate them and you should be ok. Logic would tell me 38-39 PSI should be ok to run on those tires.

 

[mnetwork]

I think what he means "Under loaded conditions" is when the tire is inflated and on the car. The tire is under a load from the car. With a normal R rated tire 35 PSI is fine. With a Z rated tire you can go higher. I used to have Z rated tires on my old RS and ran them at 36 PSI. Just dont over/under inflate them and you should be ok. Logic would tell me 38-39 PSI should be ok to run on those tires.

That`s both exactly what I meant and exactly what I`m doing. I currently have the tires filled with 38 psi. Anyone else think this is a good idea for these tires?

 

[oldman420]

a good rule of thumb is to take your max rated tire pressure and decrease 5psi from there. Then after this you can play with it, little more psi for the more aggressive driver. when it comes down to it it really depends on presonal preferance.

 

[DGajre777]

I run 225/45 17 (ZR rated) tires at 36 psi on all 4 on my AWD.

 

[1sickgst]

So, I'm rolling on 205/40ZR17's and it says the max psi is 50 under load. What psi is recommended for these. Take note this is just daily driving. Thanks.

 

[Talonracn50]

I only run about 30psi in mine, but then again, I am not a spirited driver all of the time. I would think that 38-40psi would make the sidewall really hard and not absorb as much of the potholes around here!