DSR

I have never run any of my cars on the track, but would like to try it for some fun. My concern is tire side wall height. After a past experience in my '64 Chevelle which had upgraded suspension and handled well for a '64. example no body roll on corners. It had Good Year Eagle GT tires 235x70x15's.
After making a high speed run 100+mph on a set of 12 to 14 tight turns I lost exactly 20psi from all 4 tires I had max tire pressure of 45psi and only 25psi after the run. My guess is the tall side walls were folding over and letting air out. This scared the **** out me, and I never pushed that car so hard again.
Now I have a '65 Corvette with the suspension upgrades and 205x?x15 tires, 15" rims with a 26" tall tire. I would think larger rims would help, but is there a rule of thumb for tire side wall height for cars running on the track?

Dave

Gary2KC5

Dave,
The general rule of thumb is to make sure you are using tires designed for lateral loads generated from driving at speed on a race track. They aren't expressed in side wall height but rather in the actuall tire size which is wheel diameter (15), tread width (235), and % of side wall height to tread width (70%).

you want a low profile tire with a small % of wide tread. a good stiff side wall is prefered too.

If you could view a picture of your tires in a corner it would scare the **** out of you again. The reason for the loss of air pressure is that you were actually pulling the tire from the wheel. a picture, of your tires in a turn, would look something like a diagonal line verses a vertical line. the tread, on the ground) would be about 6" pulled away from the wheel (at the bead).

DSR

Gary: Thanks, so a set of tires made for racing with a shorter, stiffer side wall would be a whole lot safer. If I wanted to keep my same tire height of 26" (as I have a 3.70 rear end gear) What rim size would I be looking for 18" or 20"?
Dave

c4cruiser

The problem with tires for a Mid-year car is not so much the overall size but how they will fit in the wheelwells. A friend used to have a 65 with 225/7-15's and the rear tires had about a 1/4" clearance between the sidewall and the upper part of the wheel well lip. Hard cornering would cause occasional scraping.

While a wide tire (wide section width/short sidewall) would be the best bet for track use, any tire like that with a 26" diameter is most likely not going to fit very well in the wheel wells. A 275/40-17 tire will be about 25 1/2" to 26" high, but the tread will be close to 10" wide. This tire would mount on a 17" rim that would typically be 9 1/2" wide (late C4 stuff).

A late C3 aluminum wheel with a 255/50-16 tire may also work. These can be installed with adapters and not cause a lot of interference between the suspension and body. That tire is very close to 26" tall and there are high-performance tires that are available in that size. The Kumho Escta MX is available in that size and is a very good tire for occasional track use.

In addition, the mid-year cars had different suspension dimensions and later wide wheels with lots of negative offset will hit the suspension components, especially the control arms. Decrease the offset and the tire sticks way out from the body.


To keep such tires from rubbing, you would have to greatly increase the stiffness of the suspension (shocks and/or springs) or radius the wheelwells.

DSR

Cruiser: Thanks for your input. That gives me some direction while kicking around the idea of a extra set of wheels & tires for the car.
Dave