PSS treadlife and dropoff

Pete_vB · 03-14-2013, 10:24 AM

I replaced my rear Michelin Pilot Super Sports earlier this week with another set. They lasted just over 10k miles of mixed use, mainly street with some autocross. A few notes:

The fresh replacement tires are much, much stickier than the ones I just took off. Huge difference in the amount of throttle the car will take while cornering. It's clear the old tires had heat-cycled out or hardened.

There was noticeable chucking on the inside of the rears from autocrossing last weekend (see photo, top of the picture). This didn't happen with the tires were fresh, but perhaps when the tires got older and harder they become more susceptible to this.

The fronts are lasting more than twice as long as the rears- there is still lots of tread depth left. I know this is largely because I drive with DSC off, and I suspect the rears don't wear very well while sliding.

Overall I'm again very impressed with the PSS when new, but I'm not impressed with how much grip it lost towards the end of life. I suspect performance was very compromised over the second half of the tires life, especially wet/ damp grip. That suggests the amount of life the rears were providing great performance was perhaps only ~6k miles, making the listed 300 tread wear rating misleading.

Unfortunately I had to replace the tires on short notice due to a cut in the tread, so I didn't get a chance to test the 30,000 mile tread wear warranty.

Sorry, thought I put this in wheel and tire, please move.

RimasRS · 03-14-2013, 12:07 PM

interesting that inner side is much more healthy.. How much camber you are running any mods?

Thanks for review...

Pete_vB · 03-14-2013, 05:03 PM

Quote:

Originally Posted by RimasRS

interesting that inner side is much more healthy.. How much camber you are running any mods?

Thanks for review...

All stock, it's the inside that's fried, and ~2 degrees camber. I could do less, but I'm burning the tread off due to wheelspin, sure I'd be slower with less camber.

Kgolf31 · 03-14-2013, 05:25 PM

Quote:

Originally Posted by Pete_vB

All stock, it's the inside that's fried, and ~2 degrees camber. I could do less, but I'm burning the tread off due to wheelspin, sure I'd be slower with less camber.

Toe effects power down more than camber.

If you're going to do some autocrossing I'd suggest a higher performance tire, just IMO.

Pete_vB · 03-14-2013, 05:40 PM

Quote:

Originally Posted by Kgolf31

Toe effects power down more than camber.

If you're going to do some autocrossing I'd suggest a higher performance tire, just IMO.

I do have another set of wheels and tires with AX rubber on them. I just don't always swap- these do pretty well when they are fresh, better than most believe.

Toe is pretty minimal. I just like to drive this car sideways too much is the real issue.

CarJunkie · 03-14-2013, 10:43 PM

Having autocrossed 3 times on the stock PS2's last year, (as well as some very spirited canyon drives) I think I can say I had similar results. My third day of autocross was very disappointing because there was so little grip. Heat cycles seemed to be the most likely reason.

Pete_vB · 03-18-2013, 11:48 AM

So I did a little research and gave this some thought. I also autocrossed the car again this last weekend with the half-warn front PSS and fresh rears.

First, with this tire setup it drives like a completely different car. Rather than being easy to provoke throttle on oversteer, it actually takes some effort, much more than I've ever experienced in this car before. This tells me that even at over half tread depth the front PSSs have lost a fair bit of grip. The car actually feels very fast with this setup, letting you get on the power very early, but time is definitely being lost to mild understeer in sharp corners.

In hindsight I guess I shouldn't be too surprised that the PSS go off with age:

1. I know the PSS compound shares a lot with the MPSC, and that tire is well known for "going off" with heat cycles.
2. Thinner rubber grips less. While this seems counter-intuitive, especially to guys that shave their street tires to go racing, but really that's done to reduce heat buildup and tread-block squirm. If those are not issues, then tire with more rubber will be stickier.

See this quote from dunlop racing tires:
"Heat Cycles is not an issue with Dunlop racing tires as it would be with other brands. The more important factor is how much tread is left on the tire. Stable fact: thicker rubber has more grip and develops more heat, thinner rubber has less grip and runs cooler. After each session you have less grip. As the tire wears out, you have less and less grip. It could be slight or it could be large."

Based on this, two things occur to me:
a) Next time I need to plan on replacing the rear tires much sooner, far before the wear bars, to maintain decent performance and overall car balance, even if I'm not driving in the wet.
b) I don't think I'd ever recommend anyone change the front tires on the 1M without changing the rear, even if they are the same type of tire, unless they are simply not pushing the car. I think it would likely be a recipe for oversteer.

HP Autosport · 03-19-2013, 02:01 AM

You have likely heat cycled the rear PSS out. As you heat cycle the tires from autocross or track days, the rubber compound gets harder and harder and grip reduced.

There is a reason why race teams will usually use a fresh set of tires for practice, qualifying and race.

In our Time Attack days each heat cycle hardens the rubber compound enough to add lap times by couple tenth of a second. Having or not having a fresh set of tires for the timed laps usually means winning or losing in our class.

yemski · 04-04-2013, 03:23 PM

I have started to notice this too with my PSS. When I first got them the grip was phenomenal. Now after approx 11 months, I can break traction pretty easily in dry conditions with the tires warmed up. There is still well over 5 mm tread depth left but most of the tread grooves in the center are worn out. These tires were never tracked either.

FDM68 · 04-05-2013, 08:24 PM

One thing to mote is the PSS's actually use an all season rubber for the inside 2/3 of the tire. This rubber will harden quicker than the outside third. The PSS was developed as a street performance tire. I have them an d love the street ability but would run a diff tire for SOLO/AutoX events.

03-14-2013, 10:24 AM	#1
Pete_vB Captain 118 Rep 898 Posts Drives: '69 GT3, GT4, 1M, 912 Join Date: Nov 2010 Location: SF Bay Area, Shenzhen, Oman iTrader: (0)	PSS treadlife and dropoff I replaced my rear Michelin Pilot Super Sports earlier this week with another set. They lasted just over 10k miles of mixed use, mainly street with some autocross. A few notes: The fresh replacement tires are much, much stickier than the ones I just took off. Huge difference in the amount of throttle the car will take while cornering. It's clear the old tires had heat-cycled out or hardened. There was noticeable chucking on the inside of the rears from autocrossing last weekend (see photo, top of the picture). This didn't happen with the tires were fresh, but perhaps when the tires got older and harder they become more susceptible to this. The fronts are lasting more than twice as long as the rears- there is still lots of tread depth left. I know this is largely because I drive with DSC off, and I suspect the rears don't wear very well while sliding. Overall I'm again very impressed with the PSS when new, but I'm not impressed with how much grip it lost towards the end of life. I suspect performance was very compromised over the second half of the tires life, especially wet/ damp grip. That suggests the amount of life the rears were providing great performance was perhaps only ~6k miles, making the listed 300 tread wear rating misleading. Unfortunately I had to replace the tires on short notice due to a cut in the tread, so I didn't get a chance to test the 30,000 mile tread wear warranty. Sorry, thought I put this in wheel and tire, please move. __________________ 1M, GT4, 1969 Porsche 911 w/ 997 GT3 Cup Motor (435hp & 2,100 lbs)
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03-14-2013, 12:07 PM	#2
RimasRS Colonel 85 Rep 2,438 Posts Drives: BMW X3 SD Join Date: Sep 2010 Location: Europe iTrader: (0)	interesting that inner side is much more healthy.. How much camber you are running any mods? Thanks for review...
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03-14-2013, 10:43 PM	#6
CarJunkie Colonel 2617 Rep 2,819 Posts Drives: e82 1M, f87 M2cs Join Date: Nov 2011 Location: Tri-Cities, Washington iTrader: (1) Garage List 2020 M2cs [0.00] 2011 BMW 1M [0.00]	Having autocrossed 3 times on the stock PS2's last year, (as well as some very spirited canyon drives) I think I can say I had similar results. My third day of autocross was very disappointing because there was so little grip. Heat cycles seemed to be the most likely reason.
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03-18-2013, 11:48 AM	#7
Pete_vB Captain 118 Rep 898 Posts Drives: '69 GT3, GT4, 1M, 912 Join Date: Nov 2010 Location: SF Bay Area, Shenzhen, Oman iTrader: (0)	So I did a little research and gave this some thought. I also autocrossed the car again this last weekend with the half-warn front PSS and fresh rears. First, with this tire setup it drives like a completely different car. Rather than being easy to provoke throttle on oversteer, it actually takes some effort, much more than I've ever experienced in this car before. This tells me that even at over half tread depth the front PSSs have lost a fair bit of grip. The car actually feels very fast with this setup, letting you get on the power very early, but time is definitely being lost to mild understeer in sharp corners. In hindsight I guess I shouldn't be too surprised that the PSS go off with age: 1. I know the PSS compound shares a lot with the MPSC, and that tire is well known for "going off" with heat cycles. 2. Thinner rubber grips less. While this seems counter-intuitive, especially to guys that shave their street tires to go racing, but really that's done to reduce heat buildup and tread-block squirm. If those are not issues, then tire with more rubber will be stickier. See this quote from dunlop racing tires: "Heat Cycles is not an issue with Dunlop racing tires as it would be with other brands. The more important factor is how much tread is left on the tire. Stable fact: thicker rubber has more grip and develops more heat, thinner rubber has less grip and runs cooler. After each session you have less grip. As the tire wears out, you have less and less grip. It could be slight or it could be large." Based on this, two things occur to me: a) Next time I need to plan on replacing the rear tires much sooner, far before the wear bars, to maintain decent performance and overall car balance, even if I'm not driving in the wet. b) I don't think I'd ever recommend anyone change the front tires on the 1M without changing the rear, even if they are the same type of tire, unless they are simply not pushing the car. I think it would likely be a recipe for oversteer. __________________ 1M, GT4, 1969 Porsche 911 w/ 997 GT3 Cup Motor (435hp & 2,100 lbs)
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03-19-2013, 02:01 AM	#8
HP Autosport Supreme Allied Commander 3815 Rep 54,307 Posts Drives: F80 M3 Join Date: Mar 2007 Location: Santa Barbara, AP, Brembo, GIAC, Koni, Ohlins, Performance Friction, www.hpautosport.com iTrader: (36)	You have likely heat cycled the rear PSS out. As you heat cycle the tires from autocross or track days, the rubber compound gets harder and harder and grip reduced. There is a reason why race teams will usually use a fresh set of tires for practice, qualifying and race. In our Time Attack days each heat cycle hardens the rubber compound enough to add lap times by couple tenth of a second. Having or not having a fresh set of tires for the timed laps usually means winning or losing in our class.
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04-04-2013, 03:23 PM	#9
yemski Lieutenant 34 Rep 491 Posts Drives: 2011 1M Join Date: Oct 2006 Location: Bay Area iTrader: (2) Garage List 2011 1M Coupe [0.00]	I have started to notice this too with my PSS. When I first got them the grip was phenomenal. Now after approx 11 months, I can break traction pretty easily in dry conditions with the tires warmed up. There is still well over 5 mm tread depth left but most of the tread grooves in the center are worn out. These tires were never tracked either.
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04-05-2013, 08:24 PM	#10
FDM68 Captain 33 Rep 761 Posts Drives: 11' 135i Join Date: May 2010 Location: Georgia (hearts still in Germany) iTrader: (0)	One thing to mote is the PSS's actually use an all season rubber for the inside 2/3 of the tire. This rubber will harden quicker than the outside third. The PSS was developed as a street performance tire. I have them an d love the street ability but would run a diff tire for SOLO/AutoX events.
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