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Those pressures are WAAAY TOO LOW. I run 33/36 hot. If the higher pressures aren't working right for you, that means you aren't getting enough heat into the tire and that running lower pressures is generating the heat for you instead. Not ideal.
If the tires still don't grip, it's because you aren't driving hard enough to get sufficient heat into the tires. You are better off with Cup2s if that is the case because they don't require as much heat.
Max, I always swap tires side to side after a track day. Otherwise, that rear tire outer edge gets toasted quickly. I'm surprised that doesn't happen to you with the cup2s as well. Tire life between the cup2 and dunlops should be the same because of the rear outer edge wear. The real advantage of the dunlops is that the tires are just as fast as they were on day one until that rear outer edge cords, and once you are up to temp, the performance never drops. I would agree with you that the very first session is a throw away session. It takes forever to get the tires up to temp on the first session. After that, though, it should only take 2 laps to get up to speed. My PB laps have been as quick as lap 2 or as late as lap 11.
As a few of you here know - we put these tyres through hell and back in Tarmac Rally’s. We started with a 991.1 GT3 on MPSC N0 for 2 years and tried the Dunlop Race 1 in a back to back GP circuit test (new for new) tyre test with a tyre deal on the table with Dunlop if we went with it. The Dunlop Race 1 was an inferior tyre in terms of tyre wear and lap time. We stayed with the MPSC and over time realised that the lower the pressure the faster we went .... until we were peeling the tyre off the rim and finding punctures - so found a happy medium.
In 2018 we moved up to a 991.1 GT3 RS on MPSC N1 tyres initially. My first impression was how much harder it was to get the tyres up to operating pressures/temps with the 265/325 combination compared to the 245/305. (I actually suspect the RS is probably over-tyred for the weight and power of the car). You need to put a lot more energy into these tyres to get them up to operating temperature - this means sliding it about initially which some may not like.
We soon got to test the “new” Dunlop Race 2 back to back again with the MPSC N1. Initially there wasn’t a great deal of difference between the two tyres. We were running MPSC type pressures on the Dunlop because it seemed logical. Over time we started increasing the pressures on the Dunlop and the performance just got better.
After doing a lot of race miles on the MPSC N1’s the best lateral g’s we ever saw was 1.68g. The Dunlop Race 2 has shown us low 1.8g over the same course and the stage times have proved faster.
The Dunlop definitely slides a little earlier (where the MPSC starts squealing) which might not be to everyone’s liking, but it is very consistent and controllable on the move.
I do admit here I have much appreciated support from Dunlop, but if the tyre was slower than the MPSC then I would not use it - I need ever tenth I can find racing the guys I’m mixing it with.
I have not used or tested the MPSC N2 or R compound, but from what I can understand the N2 is actually harder than the N1 and the R would not make the distance we are required to race on the controlled tyre numbers of our rules.
The truth is they are all awesome tyres - I’m just arguing feel, number of consecutive laps and tenths around a track.
Here is an example of some of the torture we put these tyres through..
As a few of you here know - we put these tyres through hell and back in Tarmac Rally’s. We started with a 991.1 GT3 on MPSC N0 for 2 years and tried the Dunlop Race 1 in a back to back GP circuit test (new for new) tyre test with a tyre deal on the table with Dunlop if we went with it. The Dunlop Race 1 was an inferior tyre in terms of tyre wear and lap time. We stayed with the MPSC and over time realised that the lower the pressure the faster we went .... until we were peeling the tyre off the rim and finding punctures - so found a happy medium.
In 2018 we moved up to a 991.1 GT3 RS on MPSC N1 tyres initially. My first impression was how much harder it was to get the tyres up to operating pressures/temps with the 265/325 combination compared to the 245/305. (I actually suspect the RS is probably over-tyred for the weight and power of the car). You need to put a lot more energy into these tyres to get them up to operating temperature - this means sliding it about initially which some may not like.
We soon got to test the “new” Dunlop Race 2 back to back again with the MPSC N1. Initially there wasn’t a great deal of difference between the two tyres. We were running MPSC type pressures on the Dunlop because it seemed logical. Over time we started increasing the pressures on the Dunlop and the performance just got better.
After doing a lot of race miles on the MPSC N1’s the best lateral g’s we ever saw was 1.68g. The Dunlop Race 2 has shown us low 1.8g over the same course and the stage times have proved faster.
The Dunlop definitely slides a little earlier (where the MPSC starts squealing) which might not be to everyone’s liking, but it is very consistent and controllable on the move.
I do admit here I have much appreciated support from Dunlop, but if the tyre was slower than the MPSC then I would not use it - I need ever tenth I can find racing the guys I’m mixing it with.
I have not used or tested the MPSC N2 or R compound, but from what I can understand the N2 is actually harder than the N1 and the R would not make the distance we are required to race on the controlled tyre numbers of our rules.
The truth is they are all awesome tyres - I’m just arguing feel, number of consecutive laps and tenths around a track.
Damn, those blind and narrow turns are scary! I can see why you would need a good navigator with these type of races. Impressive, and thanks for sharing your thoughts as well.
Originally Posted by JustinS
Michelin, all day.
Great post. That convinced me. Ok, we're all throwing away our dunlops and moving back to cup2, people.
I'll give Dunlops another try with higher pressures (37 hot rear?) and slower warm-up (two laps instead of one). Not sure if I should try going to more aggressive camber too (-2.4 now)
I'll give Dunlops another try with higher pressures (37 hot rear?) and slower warm-up (two laps instead of one). Not sure if I should try going to more aggressive camber too (-2.4 now)
LOL, 7 minutes sums it up nicely, Max.
Slower warmup should help. The tires are terrible when they are cold and it takes time to put heat into them, which is why the first session takes patience. I don't line up front on first session. I hang back, let the temps build up, and by the end of the session the car is flying. After that, it only takes 2 laps to warm up (outlap plus one). First session start dead cold at 27/28 first session. I bleed the pressures down to 32/34 after the first session and after that, I never touch the pressures again. Pressures will go up to 34/36 the next session, but no matter how hot it is or how hard you drive, it won't go higher than that. The mistake is to keep bleeding out pressures. You will chase your tail doing that.
Pressures will go up to 34/36 the next session, but no matter how hot it is or how hard you drive, it won't go higher than that. The mistake is to keep bleeding out pressures. You will chase your tail doing that.
The MPSC is heading south at 36 psi and cooked at 38 psi.
But for me the remarkable thing about the Dunlop is it’s consistency after many heat cycles.
As a few of you here know - we put these tyres through hell and back in Tarmac Rally’s. We started with a 991.1 GT3 on MPSC N0 for 2 years and tried the Dunlop Race 1 in a back to back GP circuit test (new for new) tyre test with a tyre deal on the table with Dunlop if we went with it. The Dunlop Race 1 was an inferior tyre in terms of tyre wear and lap time. We stayed with the MPSC and over time realised that the lower the pressure the faster we went .... until we were peeling the tyre off the rim and finding punctures - so found a happy medium.
In 2018 we moved up to a 991.1 GT3 RS on MPSC N1 tyres initially. My first impression was how much harder it was to get the tyres up to operating pressures/temps with the 265/325 combination compared to the 245/305. (I actually suspect the RS is probably over-tyred for the weight and power of the car). You need to put a lot more energy into these tyres to get them up to operating temperature - this means sliding it about initially which some may not like.
We soon got to test the “new” Dunlop Race 2 back to back again with the MPSC N1. Initially there wasn’t a great deal of difference between the two tyres. We were running MPSC type pressures on the Dunlop because it seemed logical. Over time we started increasing the pressures on the Dunlop and the performance just got better.
After doing a lot of race miles on the MPSC N1’s the best lateral g’s we ever saw was 1.68g. The Dunlop Race 2 has shown us low 1.8g over the same course and the stage times have proved faster.
The Dunlop definitely slides a little earlier (where the MPSC starts squealing) which might not be to everyone’s liking, but it is very consistent and controllable on the move.
I do admit here I have much appreciated support from Dunlop, but if the tyre was slower than the MPSC then I would not use it - I need ever tenth I can find racing the guys I’m mixing it with.
I have not used or tested the MPSC N2 or R compound, but from what I can understand the N2 is actually harder than the N1 and the R would not make the distance we are required to race on the controlled tyre numbers of our rules.
The truth is they are all awesome tyres - I’m just arguing feel, number of consecutive laps and tenths around a track.
Thanks for the info. What tire pressures do you run with the dunlops and what rear camber/toe do you use? Do you still have some premature outer edge wear?
Thanks for the info. What tire pressures do you run with the dunlops and what rear camber/toe do you use? Do you still have some premature outer edge wear?
Very similar to what Joe said - but I tend to run the same pressure front and rear 34/34 psi hot. (That will equate to about 24/26 cold, so I tend to start the day with about 29/30 bowing that I will bleed about 5 psi off in total on the first 2 runs - then stop.)
Having said that, these tyres still hang in there at 38 and 39 psi!
Camber I run is about 2.5 neg front, 2 neg rear. Zero toe front, 2-3mm toe in rear, front sway soft, rear sway med. (note - I’m on KW Competition suspension)
This is in line with what you will read in many of the track set up threads here - not rocket surgery.
Tyre wear is awesome - no outer edge wear to be concerned about.
But changes in rake should have a negligible effect on front to rear weight distribution...
I suspect you’re just changing the suspension geometry operating point when you raise the rear or lower the front, changing the dynamic behavior (e.g., camber change vs compression).
Very close. Changing rake barely moves weight distribution. It does move aero noticeably (which is why Red Bull uses it) but for our street cars it will be tough to notice. The big effect you can feel instantly is the change in roll center height (RCH) and hence roll axis.
The strut front suspension in our cars in particular is very sensitive to ride height. Lower it and you drop RCH much faster than you lower the car- a few centimeters drop will put RCH below ground level. This makes it easier for the front suspension to roll over, meaning the rear does more of the work resisting body roll in a corner. The net result being that the front is more lightly loaded and sticks better while more heavily loaded rear oversteers more as you lower the front of the car. Raising the rear does the same, though it is less obvious as with multi-link RCH and ride height are not as closely coupled.
Learning a lot re tires as I have tried all but the new MPSC2 N2s here, good stuff...
I'll give Dunlops another try with higher pressures (37 hot rear?) and slower warm-up (two laps instead of one). Not sure if I should try going to more aggressive camber too (-2.4 now)
Try less camber front. More camber won’t help, just flip rears side to side.
Slower warmup should help. The tires are terrible when they are cold and it takes time to put heat into them, which is why the first session takes patience. I don't line up front on first session. I hang back, let the temps build up, and by the end of the session the car is flying. After that, it only takes 2 laps to warm up (outlap plus one). First session start dead cold at 27/28 first session. I bleed the pressures down to 32/34 after the first session and after that, I never touch the pressures again. Pressures will go up to 34/36 the next session, but no matter how hot it is or how hard you drive, it won't go higher than that. The mistake is to keep bleeding out pressures. You will chase your tail doing that.
Exactly, except for Dunlops I will try 26PSI all around. Just because the TPS will only “take” at that pressure.
The rears will still go over 36 but like Joe said bleed them to 32-34 and leave them alone for the rest of the day and in hot climates you will have a better tire the rest of the day compared to the Michelin’s.
With Michelin’s I have to start lower, or you will have to pit on the first session.
Either way, with both brands the first session is partially lost.
Ok, you guys just convinced me to change my tire order on the 991.2RS from Mich’s to Dunlops. I had a bad experience with the Dunlops that came from factory on my 991.2 gt3, but after reading this, could have been because I was running the pressure too low? Or, is this specifically an RS discussion (does the same apply for gt3)? The Dunlops on my 991.2gt3 looked like one of the inner bands got hot and folded over into the band of tread next to it; it looked like that uneven inside band tread wear the front gt4’s had issue with. This was also with completely oem alignment. I got an alignment, some camber and Mich’s and had better wear this time around on the gt3. However, the car I’m replacing tires for currently is a 991.2-3rs. You guys seem so unanimously supportive of the Dunlop 2’s vs the Mich 2’s, I’m gonna take a leap of faith and assume my last experience with Dun’s on my gt3 was either user-error or difference between gt3/Dunlop and rs/Dunlop combination.
I'm cross-posting to this thread in order to get as much coverage from the brain trust as possible. See this thread for details (https://rennlist.com/forums/991-gt3-...ace-2-a-3.html). Thanks in advance for thoughts, opinions, etc.
08-03-2019, 05:13 AM
