Recommended Tire Pressure

Recommended Tire Pressure

Hey everyone,

I got 205/50/17 Sumitomo tires with my new ICW 17" rims for my 04 corolla s. I was never given the recommended tire pressure for the tires... just on the sidewall it gives the maximum 40 psi, but that's definitely not the recommended. How would I go about finding out what the recommended air pressure for these tires are?

I know that according to the owners manual, the stock 195/65/15 tires' recommended pressure was 30 psi.

If anyone can steer me in the right direction, I'd appreciate it!

Thanks!

Stick to the recommended 30 PSI. More pressure has a negative effect on ride and handling, and will cause uneven wear.

28.5 psi is probably about right. Your tires are 5% wider than stock, so the pressure should be 5% lower than stock. For tires, the contact area times the pressure equals the weight supported by the tire. The weight of the car hasn't changed, but you want a larger contact area with a wider tire, so you have to decrease the pressure to get it.

Kumho Escta Supra 712 (215/50-16)

What do you think the pressure should be in those? No one has really been able to tell me...

oxymoron is correct... 28 psi should be about right for 215/60-16's.

Oxymoron,

What are you basing this information on? :?:

Macaddict

An engineering degree :wink:

It's basic physics:

Force = pressure x area

The force on the tires is the weight of the car. The force isn't going to change when you change tires.

With a wider tire you want a larger area in contact with the road, so the pressure has to drop. If the tire is 5% wider, the pressure should be decreased by 5%. If you put on a wider tire and inflate to 30 psi, the edges of the tire won't have much weight on them and you'll get excessive wear at the center of the tire.

I tend to disagree with you. I believe that a wider tire has an inherently wider section width. I do not believe that you need to drop the tire pressure to achieve this width. Of course, if you put the same tires on a much heavier car, you might need to put more pressure on them to keep them 'straight' and to not have the tires riding the sidewall.

Additionally, I do not think the tire weight raitings would change much from a 195/65 to a 205/60 for example.

Also, with a lower sidewall ratio, I would think that you would need, at least, to have the minimum recommended tire pressure to keep the sidewalls strong enough to help during cornering.

Please tell me what you think...

MacAddict

I disagree with you. I can only think of one other way to explain it. Have you ever seen road racing bicycles. They have 3/4 inch tires and require pressures of 125 psi typically. Mountain bikes with much wider tires only require 30-40 psi. Both tires are supporting basically the same weight. The mountain bike tires require less pressure to support the weight (force) because they are wider (larger contact area).

I have a question - I don't need an answer, just answer it for yourself. The spare tire is 125/70/16 and the recommended inflation pressure is 60 psi. Why?

That makes sense. Thanks for explaining it.

MacAddict

I noticed that when I inflated my tires from 30 psi to 38 psi, my car hydroplaned more. I take it this is because there is less tire touching the road?

something like that...

the tire contact patch is smaller, and so there is less time for the tread to push the water out of the way

How about for 215/40/18??

On my winter tires, Vredestein Wintrac - 195.65R15 on 15" stock wheels: I run 29-32 PSI- depending of the weather and temperature.

On my previous summer tires, Yokohama AVS-es100 - 205.60R15 on 15" stock wheels: I used run them between 33-36 PSI - depending on the external temperature (hot summer day or cold spring day) and car usage (hwy, long trip, city driving, etc...).

For my new Conti Extreme Contact - 225.45R17 on 17" Kazera KZ-U - I plan to inflate them between 32-35 PSI maybe a little bit more.

Tire pressure is sensitive to external temperature, car usage and driving style. I think eveyone shloud found it's own preference. But you should, at least, inflate your tires at Toyota recommandation (see your owners manual or in your glovebox, I think it's 30PSI).

W~

Optimum tire pressure is a function of several things including driving style and objective (e.g. racing is quite different from highway cruising). The general theme is to shoot for no more tread contact than is required. The bicycle example in this thread is a good illustration: street competition tires are very small and hard in order to minimize rolling friction. Trail running requires a lot more flexibility to absorb uneven contact surfaces and avoid sharp shocks to the balance.

The best guide to how well your tire is working is temperature (more flex creates more internal friction which generates more heat). As an example, we track 8 or more spot temperature readings on each race tire (with temperature probes and a Palm Pilot) and adjust pressure and wheel geometry for uniform readings across the contact surface. It's significant to be aware that front wheel drive cars heat up front tires quickly when driven hard... heat builds and adhesion deteriorates quickly so that the first few laps will typically be the fastest.

On my street LE, I run BridgestonePortenza 195x65 R15's on 6.5" rims at 36-40 psi (higher in front). I scrapped the stock tires for these mainly for wet performance which I consider the most critical street "drive time". My "rule of thumb" adjustment for highway use is to feel the tires for uniform temperature at each rest stop. If a tire seems hotter than the others, I add a few pounds of air. If I keep the front and rear tires pretty close and rotate front to read @ 10,000 miles I tend to get uniform wear across the tread surface and the occasional "40 mpg" tank.

Works for me