I am going to putnam park next weekend and the stock tire pressures 36/44 seem quite high. I am running michelin pilot sports. Thanks for any suggestions.

 

Speaking from the wealth of experience of only one track day a couple weeks back... .... I experienced brake fade and tire instability after about 3-4 laps in to an approx 10 lap session (2.7? mile laps at TWS). I was on stock tires at stock pressure when cold (Pirellis). On the last session Dan from Vivid advised me to drop the pressures all round by about 5psi, I did that and there was a significant improvement in the tires holding out the whole session. I had been checking pressures coming in after a session and noticed up to a 10psi increase of stock, but 7-9 more typical!

If you have time to get more apt brake pads and brake fluid before the event I'd recommend that (what I am doing for sure) also. Have fun and be safe!

 

Same limits...I droped all pressure on my contis to 28 in front and 32 in the back.....normal is 36/44 for me. Off the track after a run it was 38/46..... VIR.

And I was not driving it as hard as some others on this board....this is on the last runs as I had improved a lot by day 3.

No fade...Castrol SRF.


JB

 

best way to get optimal tire pressure for the track are to use a contact pyrometer. Measure the inner, middle and outer 1/3's of the tread after a couple of hot laps. You want to achieve even temps across the tread. If the middle is hotter then bleed off a couple # of air. If the middle is cooler you know to add some air. If the outer block is much hotter then you need to add negative camber.

 

Plan is to take it easy this time and then get the michelin PSCs for the next one around (hopefully midohio). Thanks

 

Muker -

I'm guessing that you don't have a tire pyrometer handy.

I'd recommend that you try the pressures recommended above to start. Chalk the sides of the tires before you go out to see how far they are rolling over. (Just use cheap sidewalk chalk for kids.) Decreasing pressure will make the wear more toward the sidewall, and increasing the pressure will make it go the other way.

I have a lot of miles at Putnam Park. I always swap tires left to right at mid-day and the end of the day. Unfortunately, you can't do that, since the Pilot sports are directional. There are 8 RHTs and 2 LHTs. Please watch your left side tires closely for wear. If you drive the car hard at all, you can wear them out in a weekend easy.

Hope you have nice weather. I'll be there in 2 weeks.

Jon

 

Are these HOT or COLD tire pressure readings? If they are cold readings, you'll be into the 50's when they heat up and you'll have no grip. On stock tires, I used to (pre-child), drop my temps to 36/44 hot. Now I just drive to work with my r-compounds!

 

I used to use my R compounds alot until I noticed that they kept going flat. Now I just change out between my 19 for street and 18 for mexico.

 

I've spent a lot of time at the track in various cars, AND, I own a pyro-meter, and a 966TT that I have had at the track on street tyres a couple of times....

I found that 34 front/38 rear HOT gave pretty optimum surface tyre temps as measured with the pyrometer. I also felt these pressures gave the highest grip levels (as much as you can on damn street tyres at the track anyway - only about 2 good laps in them before they turn into ice-skates). This was running Michelin Pilot Sports (not Cups).

Cheers,

Beej

 

what air pressure is normal for street use with 19" tires cold pressure..?

thanks

 

I have Michelin PS2's on my car and called Michelin to find out what pressures they recommend for the track. They told me to start at 26 front to 28 rear psi cold, and try to keep the hot temps between 36 front, 38 rear. This has worked well for me. I ran an entire season last year and have had excellent wear. I would still be using the rears this year if I hadn't gotten a flat that resisted a couple of repairs. The fronts will be used again this season.

 

I usually start 28front/32rear cold pressures and check hot pressures. I try to keep the pressure under 35 hot. As far as brake fade, I have seen it more if PSM is working overtime. So either drive more smoothly or turn off PSM.