PCA SDR

I just purchased a set of RA-1's and had then delivered shaved. After they got here I began to wonder about heat cycling. My Azenis 615 seemed to last longer (wear better) when I had them heat cycled. Would this also play with the Toyo's?

Second question on my 911SC what cold tire pressures should I start at and what hot pressures work best for AX?

The consensus is that they do not benefit from heat cycling:
http://www.specmiatawest.com/garage/toyora1_care.shtml

Hot pressures depend on car, driver, and track. I found 37# hot to work well for me, but I have seen everything from 28 to 44 on the internet. Also, they appear to have a very wide range of pressures where the temps across the tire look good per a pyrometer. I can say that if they feel "greasy", then they are too high and should be lowered 3-5#.

Ron, what Kris said.

Start with somewhere around 32# cold if it's a normal warm SD day and work on where the pressures go when hot. If it's hotter than normal, start a couple pounds lower. Work for hot pressures around 36#+ but nothing over 42#. You will have to work backwards to find the right cold starting pressure for your car. There is no magic - just time and patience. RA-1's are extreamly forgiving and have a very wide performance curve. Three or four PSI off and you will still be within 95% of the tire.

Ron:

I run RA-1's, but since we're in the same class, I'm no telling you my secrets!

JUST KIDDING! The best pressures seem to be around 37 to 39 front (hot) and 38 to 40 rear (again, hot). Depending on how your car handles (under or over-steer) you can adjust the grip front to rear accordingly with pressures. Since I have a bit of oversteer, I run the fronts lower to dial-in a tad of understeer as compensation. Remember: our individual car's suspensions are set-up differently .

The Toyo website indicated pressures between 37 and 40 (hot) to be "optimum."

FWIW: I start mine at 32 cold-front and 34 cold-rear.

See you the 23rd?

Dan Chambers wrote:Since I have a bit of oversteer, I run the fronts lower to dial-in a tad of understeer as compensation.

This seems backwards to me: a little less pressure should increase grip at that end?

I'm with you Chris it seems as though those # should be reversed.

My understanding is the "general" rule is let air out to get a bit more grip, in actuality, if you have the tires set optimally, both adding and removing air reduce grip so it doesn't matter. However, the very general rule does often work, take some air out of the end that needs more grip as a starting place. If it helps, great, if not, do something else, like add air

Guess that's why I'm almost the slowest in PSS

Jad wrote:My understanding is the "general" rule is let air out to get a bit more grip, in actuality, if you have the tires set optimally, both adding and removing air reduce grip so it doesn't matter. However, the very general rule does often work, take some air out of the end that needs more grip as a starting place. If it helps, great, if not, do something else, like add air

I agree that the optimum contact patch is compromised by either too low or too high of pressures.

The effective spring rate, however, only goes one way: a lower pressure give a lower effective spring rate, which theoretically should increase grip at that end.

All that being said, I have been fairly unsuccessful in changing the balance of the car via air pressure alone. Changing spring rates and sway bars is much more effective, in my experience.

kurquhart wrote:

Jad wrote:My understanding is the "general" rule is let air out to get a bit more grip, in actuality, if you have the tires set optimally, both adding and removing air reduce grip so it doesn't matter. However, the very general rule does often work, take some air out of the end that needs more grip as a starting place. If it helps, great, if not, do something else, like add air

I agree that the optimum contact patch is compromised by either too low or too high of pressures.

The effective spring rate, however, only goes one way: a lower pressure give a lower effective spring rate, which theoretically should increase grip at that end.

All that being said, I have been fairly unsuccessful in changing the balance of the car via air pressure alone. Changing spring rates and sway bars is much more effective, in my experience.

FWIT: I'm talking about "micro-managing" my grip. Kris, your logic is right, but as Jad indicates, any adjustment off the "prime" inflation cuvrve works. Since it is faster and easier to release air pressure directly after a driving session (and while the tire is still hot) that is the path I often choose. Increasing air would be the better way to go, most likely.

I've been running RA-1s for the past three years at much lower pressures than the rest of the spec boys with great satisfaction. Others have experimented with the lower pressures are happy too. I don't run shaved however. What Jad said makes sense, but so much has to do with individual car set up. My inexperienced opinion.

Thanks everyone,

Now I have to drive the car with different tires and different sizes then I'm use to and try to get better times. It's the driver not the car that's slow. At least that's the cheaper option.

Ron