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I purchased a new set of Michelin Pilot Sport 4S from the dealer back in April for my 991.2 C2S. Since then, I've put about 4K miles on the car, and two track days at Watkins Glen, which was about a month ago. After the event, I noticed excessive shoulder wear, but not any chunking (I did not inspect them thoroughly at that point.) Today my car is at my indy mechanic for a tech inspection as I have another track event scheduled for next weekend. After seeing the tires, my indy said he could not pass the car's tech inspection due to chunking on the driver's side front tire.
When the tires were installed back in April, the dealer performed an alignment per Porsche spec. In hindsight, I learned the car could have benefited from applying additional negative camber (was at -0.45, post alignment). Regardless, my indy mechanic feels that the factory spec alignment should not have caused the chunking. A year ago, I drove the same car, at the same track, for two days, on Pirelli P Zeros. No chunking occurred.
The Porsche dealer I purchased the tires from told me trying to file a claim would be fruitless, since he stated, "a free replacement would only be honored due to road hazards, and the wear is normal for tracking a car,." I said, "after two track days?" I then went on to explain how this is a very popular tire at the track, superior to the Pirelli. Further, although I've used the same tires while tracking a different car (E92 M3), using the same set over multiple events, I had never experienced this. I understand that there are more variables to consider (type of car, speed, alignment, etc) as it relates to comparing wear from one set to the next, but I'm still very surprised at the chunking.
Last week I had another alignment performed, after talking with Tom at DSC since I have their controller. I conveyed his specs to the tech, so I feel more confident that the alignment is dialed in.
Now I'm trying to figure out my next move. Purchase two more 4S tires, and hope the additional camber applied from the recent alignment will prevent future chunking, or?
the PS4S is not a track tire. if you start putting actual HPDE loads on them they will start to delaminate (in chunks). this is worsened considerably by sliding.
I've destroyed tires during one track day in the past prior to dialing in more negative camber and getting another set of rims with MPSC tires. Also, don't forget to upgrade brake pads and fluids or that's a future post.
I've destroyed tires during one track day in the past prior to dialing in more negative camber and getting another set of rims with MPSC tires. Also, don't forget to upgrade brake pads and fluids or that's a future post.
Do you recall how much negarive camber you're running up front?
Do you recall how much negarive camber you're running up front?
That was a previous car (GT3) with way more negative camber than you can dial in on a stock 991.2. R-compound tires need plenty of negative camber, but that will shorten the life of street tires (inner shoulders wear much quicker). That's the tradeoff if you want to do track days and push hard.
Yup, both the PS4S and cup2's will start "chunking" or delaminating if they're pushed too hard without enough camber, or if their pressures aren't monitored closely. Tires should start cold at 28-29psi and warm up to 33-34 max. I gradually bleed off air after every seession to get to 33-34 hot pressure. There's a long thread about this on Rennlist already. I got 5 track days out of my last front set (with OE alignment). I've since changed my alignment to the max spec on OE C2S suspension (-1.4 camber front, -2.1 camber rear) and my PS4S look great after 3 track days.
Pics attached: of delaminating from OE alignment and not checking pressures
: max alignment specs
: new PS4S after 3 track days
the PS4S is not a track tire. if you start putting actual HPDE loads on them they will start to delaminate (in chunks). this is worsened considerably by sliding.
What he said also you really need way more negative camber otherwise the outside of the tire is under too much load and wears too much. I would switch to cup 2s and max out the camber. Either way you are going to be running through tires it’s just a matter if you are wearing out the inside or outside edge
+1 on seeing MPS4S chunking after 1-2 days at the track. I run Cup 2s at the track for the 911, and personally chunked the MPSS on my other car, and have seen this on other 911s running the MPS4S. Couldn't tell you camber/psi they were running though.
PS4S are terrible on track. More camber is needed if you are going to track no matter the tire. Cup 2's are a better dual purpose tire.
Just repeating what other have said to reinforce the point. Lol.
PS4S are terrible on track. More camber is needed if you are going to track no matter the tire. Cup 2's are a better dual purpose tire.
Just repeating what other have said to reinforce the point. Lol.
PS4S are really not that bad for the track, only a few seconds slower depending on the track. The n-spec version has cup2 compound on the shoulders, and they have a 30k mile tread wear guarantee (or 15k mile in our case since staggered fitment). They also have deeper tread and can handle a similar amount of heat cycles. No doubt Cup2 are better, but they are more expensive and don’t last as long. It also depends on how much power you have and how track oriented your brake pads are.
In addition to what's been stated, it also depends on what run group you're in or how hard you pushed it. A green student would have been fine, higher run groups or pushing it when they're cold, too high pressure etc. not so much.
PS4S are really not that bad for the track, only a few seconds slower depending on the track. The n-spec version has cup2 compound on the shoulders, and they have a 30k mile tread wear guarantee (or 15k mile in our case since staggered fitment). They also have deeper tread and can handle a similar amount of heat cycles. No doubt Cup2 are better, but they are more expensive and don’t last as long. It also depends on how much power you have and how track oriented your brake pads are.
I'd say that's a fair statement if you are new to the track. I do remember liking the PS4S's until I got faster and started to chunk them. A good track alignment and cup2's will last longer than you would think if not pushed to the limit every corner. I tried a set of the Cup2 R's and those were great for about 5 hot laps, then they fell off fast. The cup2's are a great in between once you get to that point. After that it's slicks and and a cup car! LOL!
Temp and pressure management are a huge factor that would destroy a tire quickly.
FWIW my OEM P Zero held up fine at the track but needed a ton of air bled after each session to keep hot temps at 35. At a track day at Area 27, there were many cars that toasted new sets of PS4S, but none were even checking tire pressures
Using Cup 2 tires, they too needed to have air let out each session to keep pressures at 34-35. The grip did drop off after 5-6 laps, but stayed steady in feel for another 5 laps. I am not exceeding the ability of the car/tires/brakes and just having fun.
PS4S are terrible on track. More camber is needed if you are going to track no matter the tire. Cup 2's are a better dual purpose tire.
Just repeating what other have said to reinforce the point. Lol.
07-27-2023, 01:30 PM
Michelin Pilot Sport 4S Chunking - Normal?
