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I've run 26 cold on SP2s in my GT3 in the first session of the day (70-80F). It's just a bit too low, takes most of the first 25min session to get them up to spec.
I too would suggest 28ish on the first session then drop some on the first break. I aim to run 33/35 hot.
Also have side muffler delete for context.
Besides temp, the driver, rear side muffler delete and ceramic rotors make a difference in cold start PSI.
Depending on what kind of pace you're running, I'd recommend doing a cooldown lap after 2-4 hot laps and then going again. Trying long stints at pace on cup2's will overheat them (not pressure!) and give you that greasy feeling and speed up the wear.
3-4 laps in mild and medium ambient temps, 2-3 hot laps in hot weather before doing a cooldown lap.
This is a continual common issue. and talking point on all the threads about pressure. To understand, ex. you have a trailer, towing something, take the pressure out of the tire, and it will bake, and then catch on fire if you drive long enough. So you have high pressures on trailers to stop the tire from baking. Too high, and it will cup do to surface issues and wear.
Race tires, or perfromance tires have to balance, surface area, contact patch, pressure, temp and time. Sprints may get away with less pressure or shorter tire expectations. Endurance would be the opposite. Everyone is trying to find the happy medium, while going faster, its impossible, either swap tires, control speeds, or change to a tire thats more compatible to the conditions. hence, qualifying tires are softer, and shed agressivly, have different compounds and cannot withstand long amounts of heat. Thats why you have soft, med, hard etc on race tires. these performance tires (cup 2 ex) are mulit compound, they are designed to give an overall balance, so you have to manage speed, time and temp for the tire, or you need to have a lot of tires and wheels. So best answer, run at 80% keep the tire temp in range by slowing your speed or add pressure and extend the life of the tire, as best as possible, become a better driver by hitting better lines, carrying more corner speed with less transition, and stop trying to race the clock. Its DE, its not a race, your not suppose to run these tires are race speed, they are not designed to product record breaking lap times. they are designed for hobby driving. They are road tires. These are not race cars either,
Depending on what kind of pace you're running, I'd recommend doing a cooldown lap after 2-4 hot laps and then going again. Trying long stints at pace on cup2's will overheat them (not pressure!) and give you that greasy feeling and speed up the wear.
3-4 laps in mild and medium ambient temps, 2-3 hot laps in hot weather before doing a cooldown lap.
those who keep aksing, need help understanding pressure, to manage tire life. If you cool down the tire, and run a few laps on and a few laps off, you can run all day long, but this is not what some are doing.lol so either raise the pressure, to keep the tire from baking or continue to bake tires. especially these types of street tires.
thanks for advice and tips here. this was really frustrating day especially since its first time on a track this year! so i think i baked my tires and don't want to risk a 105dB day at Laguna Seca on this set so will be buying new set. I don't have a tire pyrometer. Im tempted to try the track connect psc2's. anyone give them a try and whats your evaluation? Dougr743 I don't trailer. I used to long time ago but with street cars like the gt3 i think the appeal is just drive to the track have fun and drive home without all the fuss. I wouldn't mess with tire warmers. I'll just use michelin's recommended cold pressure to start and adjust once after 4 laps and try to keep to it.
On the PSC2's looking on tirerack i noticed only the N1's for sale. where do you all get N2's? the track connect tires don't appear to have a Porsche specific designation.
What would you personally start at, cold, on a hot day at Thunderhill if car has side deletes and PCCBs?
Higher then with steel and side mufflers.
You have to go out and bleed, but bleed when they are good and hot, not completely cooked.
Dunlops Sport Maxx 2 take the abuse of continuing hard laps much better then the MPSC2 N2, but they need an extra lap to be fast, not so much an issue as with the Michelin’s either as you can afford to start higher.
I dont know what every tire rec is but a cup 2 would be in the 190* degrees, cold base would be around 26 ft 28/29 rear. Then see. If you are checking 3 or so points on the tire, and its colder than the low recomendation, then you bleed air ONLY when the tire is totally cold, you dont bleed hot tires. so you want to be about 170 to 200 degrees, and never run below 29ilb totally hot.
So check temp cold, before you leave your house, check pressure, pull of highway, asap check temp and pressure, The tire should be cold and then check tire and pressure, make adjustment, then check same process after you get off the track. Add air if too hot, but not unitl the tire is back at cold temp, Or remove if you are below optimal temp.
I bleed hot tires at the track... How to get the right pressure if not? I was also at a few McLaren & Porsche camps and they also did. I personally start at 26-28psi and like to run them at 32F and 32-34R at track temp.
If I run them at 28-30psi cold they usually goto like 36-40psi hot so I've started with lower cold pressures.
I've found great wear and temps on the inner, middle and outer tire running these 32f and 32-34r.
I bleed hot tires at the track... How to get the right pressure if not? I was also at a few McLaren & Porsche camps and they also did. I personally start at 26-28psi and like to run them at 32F and 32-34R at track temp.
If I run them at 28-30psi cold they usually goto like 36-40psi hot so I've started with lower cold pressures.
I've found great wear and temps on the inner, middle and outer tire running these 32f and 32-34r.
How hot is the tire? If the tire is 190 degrees at 39lbs, and you lower it, you will heat the tire past is working temp. after about 200 degrees, its starts to lose grip, then as it rises, it bakes, getting greasy. If the tire is below 170, drop pressure to raise temp. Pressure is the control for temp. Its the temp of the tire that gives it grip, not pressure, if you run too low, the tire will role or fail. delaminate.
Ex you set front at 29 cold, rear 32, go out, for 20 min, really hot day, hot tarmac, hot everythig, the tires are 210 degrees, Do you plan on making them hotter? Think about it, Baking is just like baking, would you turn up the heat? Its a balance of heat to get to proper pressure. hence tire warmers set at 175 degrees are the tires optimum temp to perform, then you set the tire to 30lbs at 175, and if you come in at 38 lbs, but temp is 175, dont touch it. Its correct. if you come in a 210 degrees etc etc, you are going to have to have more pressure at cold to keep the heat down. Continually lowering the pressure will bake the tire.
Cold PSI innthe door is often a good indicator for hot temps on the track.
MPSC2 like to be 30-32 hot.
This means starting 22-24 on a cold day..
So to be a bit on the safe side and to keep the TPMS happy, start at 26 and bleed down to 32 after a few laps.
This isn’t sound advice as:
(1). These are street tires - if you use 22 24 cold you could get serious tire damage, particularly to the side walls along with the potential for delamination
(2) all - start at 29 front and 33 rear for an RS this is the placard pressure found on the door frame (use the placard pressures as the starting point in any car with PSC2).
(3) do a series of warm up laps at moderate pace - warming your tires, quickest way to do this is hard braking into corners
(4) come in and reduce pressures to 29 front - 33 rear
(5) continue to monitor pressures - optimum front is 29-32 front, optimum rear is ~33. Again going below 33 in the rears is putting the sidewalls at risk.
(6) camber - for optimal wear on 265/325 section tires with RAS ensure the front wheels are set to -0.5 more than the rear. -2 front -1.5 rear is a good all round combination.
I really want to help, I mean it, My DOT Race tires (ex on motorcycle) would need more air to keep temps lower, My full superbike slick, needed less. also have different recomended hot temps, Soft, med, hard compounds build heat and hold heat in different ways, some wick faster than others. When people complain about greasy tires, not sheding and the car sliding all over the place, its usually because the tire is way too hot! As the tire wears, as the day go's on and as you put more laps, miles etc on the tires. they are going to go away, but you should feel that change. So can see it on the tire. Cold track days, tire temps fall, the tarmac is cold, you go out with high temp, with warmers, come in cold and tires tear. We take out air to keep temps higher. We dont add pressure and make them worse. So just take temps across the middle 2/3rs of the tire, not side wall or edges. I think groundhog is correct on min pressure on street tires, I believe michelin has a 29 psi limit hot. So once you go below 29psi hot, you will or could damage the tire.
I basically do what groundhog suggested... No matter what I gotta decrease the pressure. If I start at 32psi cold they will be up near 40psi hot and that is absolutely garbage pressure, slipping all.over the place. Once I get down to 32f and 32-34r it feels golden. I likely will try and keep the rears at 34psi for safety.
Likewise, I don't suggest deflating a hot tire, I don't ever have back to back runs. There's usually 30-60min between runs, so just before I adjust pressure. I measure temps though asap after a run and obviously record my starting temps to know how much to drop or add.
I basically do what groundhog suggested... No matter what I gotta decrease the pressure. If I start at 32psi cold they will be up near 40psi hot and that is absolutely garbage pressure, slipping all.over the place. Once I get down to 32f and 32-34r it feels golden. I likely will try and keep the rears at 34psi for safety.
Likewise, I don't suggest deflating a hot tire, I don't ever have back to back runs. There's usually 30-60min between runs, so just before I adjust pressure. I measure temps though asap after a run and obviously record my starting temps to know how much to drop or add.
Any advice to do things better please share.
What is the temp of the tire when you are at 40psi? Check next time, they may be cool, not to temp.
Temps are the key to getting longer life, and less fade out of the tire. get warmers and you never drop temp, the tire does not cycle and you get so much more out of the tire and the day. Its cycles that kill the tire, also heat, but overheated and cycled is a terrible combo. With all the money spent on these cars, if you really want to be a track rat, get a trailer, a set of warmers and buy a few sets of wheels.
Peter what might help them is this, do you look for a specific PSI rise in your tire pressure? Or do you look for a certain lap that the tires develop good grip?
I'm assuming no Chicken hawk warmers.
Guys I'm new to the 991 RS but race open wheel and Shifter Karts about 6 track days a month.
BTW here is what to low a pressure will do to your sidewall.
05-25-2020, 02:29 PM
