Tires: Michelin cups. Bike 2011 GXR 750 Can someone advise....if the track temp is cold do you INCREASE or Decrease tire pressure? Thanks,
ya just wanna see 25psi on the rear/34 or so on the front right off the track. This doesn't change if it's hot or cold outside, but you may need to start with more psi to GET them to 25psi hot-off-track. (rear tire psi). Compound is more of an issue when it's cold.. as with almost any brand, you would THINK you wanna run a soft compound in the cold, but the problem with that, is the tire cold-tears. The surface gets hotter than it does further into the tire, and it gets the dreaded feathered look from cold-tear. medium or harder rears actually will work better depending on the track, in cooler temps.
I was running hard compound Pirelli tires in the cold and soft Pirelli tires in the heat in 2007, glad you guys finally caught on :up:
Greg, Thanks for the info....so typically I start with the Front at 30 psi and the Rear at 22 psi. So lets say I come off the track and the temps are ABOVE 34 psi and 25 psi? Do you decrease or increase tire pressure? Versus you come of the track and the tire pressures are BELOW 34 and 25 psi? In addition how long do you have to take these readings? 30 seconds or 5 minutes? As you know it takes a few minutes to come off the track including the cool down lap!!! Thanks Craig
don't go slow on a cool down lap.. (why do people do that anyway??) sooner the better. The michelin rear is the lightest of all the tires, and the thinnest. It looses heat pretty fast, so check ASAP. Ideally, we check on hot pit road.. if it's above the ideal psi when you check hot off track, take air OUT to the desired psi ..
Just curious, does anyone have a general idea how much pressure a 25 psi rear tire can lose in the 3-4 minutes it takes to get back to your pit? I know it will vary depending on ambient temp so lets say its 70 degrees and sunny with low wind.
At that temp, very little. I'd say a fraction of a PSI. As Greg mentioned, the carcass is what retains the heat and keeps the pressure up, so you're not going to get much of a decrease from just coming off the track and the very outermost surface of the tire cooling a few degrees. If that ambient is significant cooler than that, you may want to try and get it checked sooner. Again, like he mentioned, having someone waiting on hot pit with a gauge.
I think you guys may be making things way more complicated than is needed. The more the tire flexes the more heat it will generate, therefore the lower the pressure the hotter the tire will get. However, "hotter" or "colder" is not what you should be worried about when it comes to the tires. How much grip and how long it lasts is what's important. These things are achieved using proper suspension and chassis settings, not tire pressures. Every tire has an ideal operating range in terms of temperature and pressure. Either find it yourself or ask the tire guy what he recommends. Then using tire warmers get your tires up to operating temperature and set the pressures. That's it. Focus the rest of your time and energy on finding good lines and settings. disclaimer; this is my personal experience from teams that I have worked with. It worked great at every track and in varied conditions. Your results may vary, this post was intended as helpful and in no way signals my desire to argue. Good luck.
I agree for the most part but pressure/temperature is important for tire life which is something I've been having trouble with lately. I'm quite happy with traction/handling but seem to be getting what I thought was cold tearing and ended up going in the wrong direction with pressure (down). The reason I asked about hot pit vs. pit pressures is to see if I was overlooking something. As I'm sure you know race tire wear can be very sensitive to a small change in pressure. I've been running Michelin slicks for a couple of years now and never had issues until later last year. I've always aimed for 34f/25r hot off track, I may try bumping that up slightly to see what happens. BTW, I'm talking rear tire only. Front tire is literally perfect, smooth edge to edge and seems to last forever.
are u suggesting that tire pressure in no way affects grip or longevity? i agree that using warmers to set a recommended "warmer" pressures is a great starting point. but in my opinion and my experience, deviating from whats recommended is not always a bad thing.
the michelin cup tire seemed to like 25psi hot off the track (rear tire). that's that. tire vendors would give a "recommended" psi to start with, that for some was fine, and others not so fine. This further varies on the track you are at, the ambient temp, track surface temp, etc. So yea, checking hot psi off the track can be a pretty darn big deal for some riders. Set it and forget it will get you a ballpark, most of the time..
Once again, my post was meant as helpful information based on my personal experiences from working with and learning from several people who know a lot more than me on respectable pro-level teams. If anyone should find it objectionable, please, feel free to disregard any or all of the information. There are many ways of achieving the same thing in any situation. Some are better than others. Often times, people will reject a new way of doing something simply because they've never done it that way before or because it runs counter to what someone, somewhere, once told them. In racing there is only one person who can win the race and that person has obviously done something different, something a little bit better, than everyone else. In my opinion, based on my experience, achieving the highest levels of grip for the longest time is best done through good chassis set up and riding technique rather than tire pressure. The more "known good" constants a person can have the easier it will become to effectively isolate and fix problems. The more variables the more confusing the situation. Set the tires at the correct pressure at the correct temperature (known good constant) and if there are any grip or wear issues see if adjusting suspension, chassis, and/ or technique will fix it. Now compare lap times.
