Michelin PS2 vs Cup Tire Data Interesting
08-15-2005, 04:59 PM
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Michelin PS2 vs Cup Tire Data Interesting
I had the opportunity (was forced) to try my PS2’s as a result of cutting my rear Cup tire so I got to compare some tire data. Here are the conditions: Gingerman Raceway, different front size tires 265-35-18 on the Cups and 235-40/18 for PS2’s, 315-30/18 rear for both, newer tread Cups, very low tread PS2’s, the cup wheels (Fikse) were wider than the PS2 wheels (I-forged), the Cups were at good pressures, the PS2’s were a few pounds too low, inducing push that slowed the lap, tire temps were around 180F on the inside with too little camber up front, too much in the rear. Here are the data charts showing lat and long g’s. The darker colors are the Cups. The lap time for the Cups was 1:32.1, for the PS2’s 1:33.3 again, sub optimal pressures and a lot of push.
As you can see, the max lat and long g loads on the tires are about the same! Yes, the R’s were pretty new and the PS2’s were pretty shaved but dang, the Cups have more rubber and they’re R compound! Quite surprising but consistent with my butt meter and I believe I can get comparable lap times with either tire. The tires drive differently. The cups are quicker to respond and want less slip angle than the PS2’s. The PS2’s squeal louder but are more confidence inspiring because you can throw the car around more and it’s easier to catch as the car response is slower. The cups and PSM really cause problems under heavy trail braking but the PS2’s are not as troublesome (although it still sucks). The cups take longer to heat up or grip less when cold. I am thinking of not running the Cups anymore.
As you can see, the max lat and long g loads on the tires are about the same! Yes, the R’s were pretty new and the PS2’s were pretty shaved but dang, the Cups have more rubber and they’re R compound! Quite surprising but consistent with my butt meter and I believe I can get comparable lap times with either tire. The tires drive differently. The cups are quicker to respond and want less slip angle than the PS2’s. The PS2’s squeal louder but are more confidence inspiring because you can throw the car around more and it’s easier to catch as the car response is slower. The cups and PSM really cause problems under heavy trail braking but the PS2’s are not as troublesome (although it still sucks). The cups take longer to heat up or grip less when cold. I am thinking of not running the Cups anymore.
08-15-2005, 07:06 PM
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A couple things to consider:
Your 'performance window' is only a few percent wide. That means that a 1 or 2 second difference means a great deal.
180 degrees isn't nearly hot enough for the Cups. The cups need about 25 degrees more temp on the inside for decent camber.
For 265 you need a 10 inch wheel. For 315 you need a 12. The Cups need to have a trapezoidal cross section with the wider base at the wheel, not at the tread. This is really critical.
These 2 laps don't look comparable driving wise. Big difference in sections 4 thru 6.
I'd be very surprised if the PS2's last even half as long as the Cups on the track.
Chris Cervelli
Premier Motorsports
Your 'performance window' is only a few percent wide. That means that a 1 or 2 second difference means a great deal.
180 degrees isn't nearly hot enough for the Cups. The cups need about 25 degrees more temp on the inside for decent camber.
For 265 you need a 10 inch wheel. For 315 you need a 12. The Cups need to have a trapezoidal cross section with the wider base at the wheel, not at the tread. This is really critical.
These 2 laps don't look comparable driving wise. Big difference in sections 4 thru 6.
I'd be very surprised if the PS2's last even half as long as the Cups on the track.
Chris Cervelli
Premier Motorsports
08-15-2005, 07:23 PM
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Very interesting. Here's a couple graphs of mine from a couple years ago comparing Michelin Pilot Sports (street tire) and Pirelli PZero Corsas (DOT R-compound) at Thunderhill. The PS's were 245/40/18 & 275/35/18 and the Corsas were 235/40/18 & 265/35/18. Laptime were 2:10.8 for PS and 2:07.6 for Corsas.
Track map (3.0 mile):
Speed vs. distance plot:
Lat acc vs. distance plot:
Not huge differences in lat acc but able to accelerate a little earlier here and there. A tenth here, a tenth there and it adds up to a 3 sec/lap difference.
Track map (3.0 mile):
Speed vs. distance plot:
Lat acc vs. distance plot:
Not huge differences in lat acc but able to accelerate a little earlier here and there. A tenth here, a tenth there and it adds up to a 3 sec/lap difference.
08-15-2005, 11:46 PM
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Chris:
My IR sensor is way on the inside of the front left tire. I am quite confident they are getting up to temp as I can cook them if I really push hard (for me sloppy) for a few laps. I plan to move the sensor to get better data. As I said, I cannot get enough camber in the front of my car (only -1.4 degrees) so I am roasting the outsides and ruining tires early. I will post a new thread on fixing that issue.
My Fikse's are 10 or 10.5 up front and 12 rear.
I was faster through 4-6 on the PS2's (due to traffic on the Cup lap), and as I said, I had a big push problem on the PS2's and couldn't adjust pressure at the track as the valve is recessed and I forgot my extender that night.
The bottom line for me is I expected to see at least a 0.1 lat g difference. I am not sure that there is any. Now, my inconsistent driving sure doesn't help looking at the data, but maybe it is a small enough difference that simply adds up to a 1-2 second advantage. If that's the case, OK, but I expected to see a bigger difference in the g numbers.
Dennis: Were those the stock PS ribs or were they PS2's? There is a very big difference. Otherwise, your data is what I expected and you can clearly see higher grip data on your charts, not on mine.
My IR sensor is way on the inside of the front left tire. I am quite confident they are getting up to temp as I can cook them if I really push hard (for me sloppy) for a few laps. I plan to move the sensor to get better data. As I said, I cannot get enough camber in the front of my car (only -1.4 degrees) so I am roasting the outsides and ruining tires early. I will post a new thread on fixing that issue.
My Fikse's are 10 or 10.5 up front and 12 rear.
I was faster through 4-6 on the PS2's (due to traffic on the Cup lap), and as I said, I had a big push problem on the PS2's and couldn't adjust pressure at the track as the valve is recessed and I forgot my extender that night.
The bottom line for me is I expected to see at least a 0.1 lat g difference. I am not sure that there is any. Now, my inconsistent driving sure doesn't help looking at the data, but maybe it is a small enough difference that simply adds up to a 1-2 second advantage. If that's the case, OK, but I expected to see a bigger difference in the g numbers.
Dennis: Were those the stock PS ribs or were they PS2's? There is a very big difference. Otherwise, your data is what I expected and you can clearly see higher grip data on your charts, not on mine.
08-16-2005, 06:19 PM
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Not Sport ribs or PS2, they were the plain ole Pilot Sports. I don't have data from when I ran Pilot Sport Cups, but they were another couple tenths faster per lap than the Corsas. Cups had a much quicker breakaway than the Corsas though.
