Any recommendations for (cold) tire pressures for the OEM Michelins on track? Thanks in advance.

I found a 38psi front and 40psi rear (hot) to work pretty well. I started with 30f/36r cold and both came up about 6 degrees after a session. but this change will depend on suspension settings, track temps, etc..

Not sure what you should start off with but I wouldn't go below 40 Front/ 38 Rear when hot. Cheers -JJ

I just finished two days at Lime Rock and started with OEM recommended pressure for both front and back. After a few session I check how far over onto the sidewall I was going and it looked perfect. There were two other CS's on stock tires there and they were also running OEM pressures and their tire wear was on the money as well. I checked again on my second to last run on the second day and it still looked great. I was curious about tire pressure but from they way I learned, how the tire is wearing is most important and you adust tire pressure if needed to correct for proper tire wear. Most high performance tires have some kind of an indicator on the top of the side wall to show you where you should be wearing to.
There was a new Carrera in the pits beside me and the owner was asking me about tire pressure for his car, we looked at his tires and found the right side wearing perfect but the left side was wearing about a half inch onto the side walls. As I'm not an expert at this, I suggested he talk to someone with more experiance but it looked to me like he needed more air pressure in the left side tires. Lime Rock is a tight, short track with mostly right handers and his left side tires were getting more of a workout. Make sense?? Anyway three of us CS owners with varing ability found the stock pressures to be fine, for Lime Rock anyway. Temps were in the 60's and sunny both days.

This comes up fairly often so if you look around using the search tool you will find a lot of good and well researched information about this subject.

I haven't found "THE" setting yet. I've only gotten two track days in the Cayman so far. (Hey, it's only got 1,700 miles - give me a little time!) My results were pretty similar. When tire temps got hotter than what you've listed, I found the car squiming around quite a bit.

Some advise on Tire Pressures and how to do it.

I think I posted the process we use at MantisSport last year, but this is important for performance, safety and tire life. So here it is again.

Cold temperatures are totally unimportant on track, they are your start point only. Measure pressures HOT and bleed them down (or take them up) to your recommended HOT pressures. (Michelins Sport Cups should be at approx 36lb.).

You will rarely find two identical days or tracks so we do this after every session. We then measure the cold temps the next morning, before one side of the car is exposed to the heat of the sun, and record this as our start point. When we do this the cold pressures are all over the place, every corner is different. I use this information to calculate the starting pressures for each tire prior to qualifying. Then I measure the pressures after qualifying (in pit lane) and adjust as nessessary for the race. Some weekends I will have 4-5 cars running, every one of them will be different.

Do not make the mistake of setting your pressures based on an other driver or another track. The track, driver and cars are all different. Tire pressures are only relevent to one car, one driver and one track on that day. With practice and experience you will become very good at getting close, but you will never be perfect. Check them yourself, HOT. Make sure you are right that day. Your car and your tires will thank you.

Stan Carmichael
MantisSport

Stan,

Thanks for sharing your valuable experience on this important topic

So for street tires which have recommended cold pressures, do you shoot for hot pressures that are a few pounds higher than the cold ones given? Thanks.

not really...you shoot for a hot pressure that works best with your particular setup and preferences. Your goal is to minimize tirewall deflection and maintain maximum contact patch (usually...for dry conditions at least). The only way to get to this number is to use a pyrometer and test....taking into consideration your other suspension settings, car weights, speeds, ambient conditions, and the course. And you can usually start with the tire makers recomendations as a range to target.

I think you will find with the PS2's the avagerage cold-to-hot delta will be about 4-6psi. So set your colds accordingly and bleed down to your hots after your first session. And they tend to work best in the recomeded ranges...at least for those who recomended them your ideal numbers might be different.

dw

__________________

Atlas Gray Cayman S

I find 37F, 40R hot is good for most tracks with 18" PS2s.

Just a quick warning - if it is cold weather, the tyre won't come up to temperature as quickly. Therefore, if you start with "standard" cold pressures, you could end up damaging the tyre with excessive rollover - I did. Now when it is cold I either put a bit more air in, or go gently for longer, until the tyre gets up to temp.

A couple of points in direct answer to your questions.

Beware of starting your cold pressures too low on cool mornings, you will create more heat than you should by allowing the tire to flex excessively. If you are unsure set your pressures 2-4 lb below optimum and bleed them down after the first run. You don't want to risk overheating the tire, it will loose grip rapidly.

My experience with PS2's, like most street tires, are that they work best at around 40lb hot. Spindoc, aim for between 38 and 40 lbs. hot on all four corners. Personally I want to see all four at the same pressure.

Willr, if you are happy with 37 F and 40 R you are battling a set-up issue. You should be more equal front to rear, we ran PS2's at Targa this year and 40 hot all around worked great with the stock suspension on. Like DW said earlier in this string 4-6 lbs below optimum is where you want to start. We ran about 36 cold to get to the target of 40 lb hot.

I don't like to see excessive tire pressures difference on the rear vs. the front, like DW said the idea is to maximise the contact patch while providing the maximum stability in the sidewall and carcass. The only reason you would change that front to rear is if the suspension isn't working correctly. Ultimately we all want the maximum contact patch we can get on all corners of the car.

Stan

Good advice, Stan.

In my case I found setting front = rear pressure tended to make the car a little too snappy. Lower front pressure stabilised it a bit.