Ray G

I would agree with that. My CS felt "lighter" compared to my CGT too, but the CGT was much much faster and has a lot more grip in corners. Btw, I'm on my 3rd set of tires on my CGT

The CGT is very stable compared to my other track toys too (CS, GT3, misc 911s, etc.). Even at 150mph+, you can feel the downforce helping you.

Regarding tire temps, the cold pressure is irrelevant; it is the hot temps that count. I found hot temps around 39 or 40psi was about right. Much more than that and they would lose grip. I like to use the on-board pressure monitor while tracking, so I know when my tires are up to temp.

MANUAL

Ray,

If you did not have the on-board pressure monitor, would you be able to tell if the tires are overheating, i.e., as they overheat do they lose their grip progressively or suddenly?

And your car still exhibits understeer in certain corners and has the anti-sway bar on the middle setting, correct?

Ray G

The grip lessens gradually as the pressure & temps go up (beyond a certain point), and yes I think I would notice that. I've been on track in 97 degrees, and I just keep my pressures in the 39-40 degree range, and it was okay. But late in a session, it can get a little greasy in hot weather (like any car). This is just my seat of the pants accessment. I didn't use a pyrometer on the tires.

I only get understeering in sharp corners, and then only when the tires are cold or too hot. I still have the sway bars set to the factory setting. Sometimes a little less pressure (say 37psi) in the fronts would help, but I think it's more a function of tire heat.

One word of warning: Beware of cold tires! I spun in my CGT once while pulling out onto the track after the car sat for several hours. It's really easy to put a little too much throttle down too soon, and I don't even think I did that. (note T/C was on in that instance.) I think it was a lateral skid that started the spin.

MANUAL

Thank you for the warning. The weather eye one needs to have when driving this car, T/C on or off and tires too cold or too hot, appears substantial and similar to that needed for an AP1 S2000.

I read that due to the Caparo Freestream T1's weight, the tires do not warm up quickly enough on the street. So the engineers have commissioned a bespoke tire compound.

On a marginal note, CNN has reported a first-time skydiver slipped from her tandem harness during a jump Saturday and fell to her death. After reading a little about the incident on dropzone.com, spinning a supercar on cold tires appears relatively less risky. LOL.

Ray G

The OE CGT tires are Michelin street tires at the end of the day, so they don't have any real ugly behaviors when too cold or too hot. I've driven my GT3 with Michelin PS Cup tires that never got hot enough for grip in 35 degree weather. It's not that bad on the CGT.

MANUAL

As the tires wear, they will take longer to reach optimum temperature due to decreased tread-squirm right? So, assuming same ambient temperature, to decrease the warm-up time needed, should cold tire pressure be slightly increased?

thusly

FWIW - I drove the CS again on the track yesterday; Pirelli Corsa System tires were very much a disappointment. In my earlier writing, the first CS track day was fabulous - the Pirellis were sticky, grippy surprisingly good. The second day was similar, but a little less grip. Yesterday was the third day (I ran only half the sessions) and from the get go, the tires were slippery. I first thought it was the track, and thought that some heat in the tires and the track would help. It didn't. I should have signed up for the drifting contest for my last run.

Big disappointment; I hadn't experienced tires that dropped off so dramatically over a pretty short period. It was even more disappointing after I did a few laps with a guy in a Challenge car and slicks. A friend's GT-3 with pretty worn MPSCs were amazingly sticky, with pretty gradual wear (and greater slip) near the end of their lives.

Anyone experience pretty consistent performance over time on the track with the MPS2s on the CGT?

Ray G

The MPS tires do last a long time at track days. I've been very pleased. I've replaced all my CGT tires twice, mostly because the tires had too many heat cycles, and had gotten hard. They still had plenty of tread left. Even then, the grip did not drop off too badly.

The MPS Cup tires are even better, when you can get heat into them. Just wonderful. But, they can't be fitted to a CGT without changing wheels.

I hated the Pirelli Corsa tires on my CS - I went through several sets, and they got slippery after only 1 or 2 track days. They were a big disappointment.

W8MM

Thanks, Ray.

Good information. I'm scheduled to be the pace car for a Porsche club race at Putnam Park in July. It's good to know that I can expect consistent performance from the MPS tires.

Ray G

Nobody seemed to answer this, so here's my opinion: I have not noticed the tires taking longer to heat up when they are worn. However long it takes, the important point is that once they are up to temperature, pit and check your pressures (or keep an eye on the TPMS). I usually get up to temp by 3 or 4 laps. You should maintain the hot psi to be constant. If you want to get fancy, use a contact-type pyrometer and check for uneven temps across the tire width. (low temp in middle: under-inflated, high temp in middle: over-inflated).

The tire temps (and psi) will rise based a number of factors, such as ambient temp, and how inflated the tire is to begin with. For example, if you have really low cold pressures to start with, it will flex the side wall more and heat up faster. This is usually not a good way to do it, because it wears your tires out faster.

W8MM

I find watching the TPMS display quite entertaining while driving around my (neighbor)hood as well as while on the track.

The tires seem to gain a few PSI just from being driven in a straight line. One might be tempted to explain this by speculating that the acceleration forces are responsible, since it takes unnatural restraint to not exercise the motor. However, I find that all four tires increase by the same margin even when merely tooling down the road.

Interesting, no?

Ray G

Yes, I noticed that too. The CGT tires seem to change PSI a lot - that is, warm up quickly, and by a larger margin than my other cars. The TPMS is a great tool.

MANUAL

Ray,

Thank you for your opinion.

If it usually takes 3 or 4 laps to get up to temp., to what top speed do you limit the car on the longest straight as the tires are warming up? Once up to temp., what is your top speed on the straight?

Ray G

It's not strictly the top speed that I limit, so much as the speed in corners and braking, because the tires are not as sticky when cold. I run at maybe 75% of my usual rate the first lap, 85% the second lap, and so on until I can see the psi coming up into range. Of course, you always have your butt to tell you when things aren't gripping well enough.

MANUAL

Your method seems similar to mine. I have used this method for years in street driving and, recently, go-kart track driving without major consequences. I have had plenty of close calls but none where I sat up and thought seriously about tire temperature.

Assuming an a) linear warm-up time and b) proportional temp./grip ratio:

if your tires usually take 3 or 4 laps to warm up to maximum grip, you usually run the first lap at 75% with a tire warmed to 25-33%, correct? On the second lap, 85% accompanied with a tire warmed to 50-67%, correct? And so on until you see the psi coming up into range. Unless these estimates are miscalculated, is it wise to run a CGT at a pace starting at 75%?