Tire Pressure

[Corky]

Hey Guys,

What tire pressure are you guy's running in your 225R70 15's. My sticker on the door say's 20 psi, but that was for the original F70-15's. Are the radials different? Any guidence would be appreciated. Thanks, Corky

[Tom B.]

Re: Tire Pressure

Corky,

Most of the maximum recommended tire pressures for radials I've found on the outer sidewall of the tire. I've been using 32psi for a 35psi max in the 215/R7015's that I have on my 68. TBarr #24014

[Duke W.]

Re: Tire Pressure

I agree with Tom. If you want the best handling and steering response run them at the maximum placarded COLD pressure, which is probably 35 psi (cold) front and rear. If you want improved ride quality drop the pressure, but I wouldn't go below 28. In the sixties recommended pressures for the bias ply tires were low for good ride quality. In the seventies, tires pressures went up because of radial tires and the energy crisis and CAFE (corporate average fuel economy). Higher pressures reduce rolling resistance, which improves fuel economy. Back when I installed 6.70-15 Michelin X radials on my SWC in 1964 (long before maximun cold pressures were placarded on the sidewalls) I ended up running them at 45 psi cold. They worked great!

Duke

[Joe L.]

Re: Tire Pressure

Corky------

Automotive manufacturers' tire pressure recommendations are established based upon the best pressure considering a COMBINATION of factors. Among those factors is RIDE QUALITY. For the VAST MAJORITY of folks, they want them to be happy with the RIDE QUALITY so that, when the time comes, they'll come back and buy another car of the same brand. Consequently, RIDE QUALITY is HEAVILY WEIGHTED in the "formula" which the manufacturer uses to determine recommended tire pressure settings.

I never use these, though. I always set my pressure at or very near the maximum tire pressure shown on the sidewall of the particular tire which you are using. That provides the best fuel economy, tire wear, and, in my opinion, all-around performance. For drag racing, though, you might want to lower the pressure in the rear tires considerably. Of course, the extra traction might break the relatively weak Corvette differential, but you will get a better "bite" off-the-line. My last drag race was in 1967, so I don't often find the need to lower my rear tire pressure. I learned my lesson then.

[Tom Freeman]

Re: Tire Pressure - uneven ware??

Won't running the pressure at or near the max on the side wall lead to uneven tire wear, wearing out the center tread first because the tire is running only on the center threads?

tom...

[Joe L.]

Re: Tire Pressure - uneven ware??

Tom-----

I've been running my tires this way for many years. And, yes, there sometimes is a slightly greater wear seen on the center treads than the outside. I have always found the difference to be MINIMAL, though. And, most important, the OVERALL tire wear is greatly reduced, so the differential tread wear is moot. I usually get 50,000-60,000 miles on my Goodyear Eagle STs on my 69. My 92 with about 37,000 miles on its ORIGINAL GSCs still look great; probaly good for at least another 10,000, or so. Someone once told me that I'd NEVER get more than 25,000 miles on the GSCs.

[Duke W.]

Re: Tire Pressure - uneven ware??

Tom - If your tires show center wear because of high pressure, then you should go around corners faster to even out the wear.

Duke

[Jerry Clark]

Re: Tire Pressure

Hi Corky:

I run my 225s at 28 - 30, qutie a bit lower than the others here, I find the wear pattern even and the ride much improved over the higher pressure. It is all in what you are looking to obtain, comfort, wear or handling. Good Luck.

jerry

[Jeff]

Better protection, too

I always run, at least, max cold pressure. I like a stiff ride, have never owned anything but trucks or Corvettes (nothing with more than 2 doors or automatic, either) and always buy the Z51 and one ton models so a few more pounds of air doesn't deteriorate my ride.

I never notice any uneven tread wear even above max pressure. But one of the very real world benefits of higher tire pressure is the increased ability of the tire (and rim combo) to protect itself from road hazards. If you've ever seen those videos depicting the dynamics of a tire/rim combo hitting a pothole, you'll know what I mean. The rim actually deforms, considerably, not just the tire!

Tire wear throughout the recommended ranges, even at the bottom is usually pretty even (but not necessarily maximium). The only odd wear I have noticed is with 10ply tires the sidewalls won't flex enough to allow the tread to sit flat at the lower pressures. As a result, the outsides wear quickly and choppily as the center tread is sucked down but not too many folks run 10 plys on their Corvettes. The supple sidewalls of passenger car tires, especially radials, seem to allow the tread to sit substantially flat at any pressure within the recommended range.

JP