Unusual tread wear
04-20-2018, 03:40 PM
#16
Also need to account for the "M0" Mercedes spec tire being a slightly different compound than the "Nx" Porsche spec or generic global spec Cup 2 tire. It might be more susceptible to wear on the outer tread blocks because it uses a softer compound to provide the grip, balance, and performance Mercedes wanted on whichever car that is the OE tire for.
04-20-2018, 04:45 PM
#17
Rennlist Member
Were these tires new? Same thing happened to a friend of mine this past weekend. They were very new and outer edges were corded after 2 days. Rest of treads looked good.
04-20-2018, 05:00 PM
#18
That looks like typical track day cording on outer edges due to insufficient negative camber. Could be a little chunking too. I highly doubt any warranty claim is going to be honored.
-Mike
-Mike
04-20-2018, 05:10 PM
#19
Rennlist Member
Thread Starter
Mike, this is outside edge cording with -2 negative camber. Confirmed alignment today. He doesn’t do DE just Autocross and really doesn’t drive the car much. It sits at his business in a garage between events. In central Florida roads are flat and straight, so no weekend mountain road driving. I am much harder on my tires and never experienced this, so I was at a loss to explain it at 500 miles.
04-20-2018, 05:14 PM
#20
Rennlist Member
Thread Starter
These were new tires with 3 autocrosses on them. I guess this happens. I didn’t notice them were M0! I hope the replacements are N spec. Thanks for catching that.
04-20-2018, 05:31 PM
#21
Rennlist Member
Was that at RTR's event at Jefferson? I was just about to comment about that tire until I saw your post (I was the RTR Safety Guy that had to tell him he couldn't keep running it). Worst part of the job...
04-20-2018, 05:34 PM
#22
I've seen wear like this at our car control school with street cars with aggressive drivers. The autocross surface could have something to do with it as well. Still would be very surprised a warranty claim would be honored here.
-Mike
04-20-2018, 06:05 PM
#23
Rennlist Member
Thread Starter
It looks like -2 isn't enough. Tire temps across the face of the tire with a pyrometer right after a performance run would tell a lot. Someone watching the outer tires closely on the outside of a corner could determine if the outer edges are tucking under.
I've seen wear like this at our car control school with street cars with aggressive drivers. The autocross surface could have something to do with it as well. Still would be very surprised a warranty claim would be honored here.
-Mike
I've seen wear like this at our car control school with street cars with aggressive drivers. The autocross surface could have something to do with it as well. Still would be very surprised a warranty claim would be honored here.
-Mike
Thanks. Not expecting a warranty claim but don’t want to repeat the result. I have a pyrometer and can ask someone to check the temps and wear at the event next week. He is a fast, aggressive driver but so am I. I just didn’t think a Cayman’s setup would be that much different from the GT3. I guess bad assumption, we will need to test and measure this set more closely.
04-20-2018, 07:35 PM
#26
Easy enough to see by going to the Michelin site. Otherwise you're SOL if you want to run that tire.
Apples and oranges. Rear suspension is totally different. So is weight distribution.
Apples and oranges. Rear suspension is totally different. So is weight distribution.
04-20-2018, 10:18 PM
#27
Not familiar with the specific suspension here, but one thing to be on the look out for is making sure the ride height/suspension geometry always results is *more* negative camber as the suspension is loaded up. The top of the knuckle should be closer to the center line than the bottom as the suspension is compressed.
On E36 M3s it is possible to set the front suspension too low. If set too low, the outer portion of the lower control arm pulls inward as the suspension compresses if the inner ball joint is lower than the outer ball joint at the knuckle. With the suspension set proper, the lower control arm slopes downward from the inner ball joint to the outer ball joint and never passes parallel to the ground at full compression. Thus, as the suspension compresses, the lower ball joint on the knuckle is pushed out giving more negative camber.
The height error I'm referring to could be out in the weeds, but this sort of thing can cause the dynamic negative camber magnitude to be a lot less than the static camber measured at alignment.
-Mike
On E36 M3s it is possible to set the front suspension too low. If set too low, the outer portion of the lower control arm pulls inward as the suspension compresses if the inner ball joint is lower than the outer ball joint at the knuckle. With the suspension set proper, the lower control arm slopes downward from the inner ball joint to the outer ball joint and never passes parallel to the ground at full compression. Thus, as the suspension compresses, the lower ball joint on the knuckle is pushed out giving more negative camber.
The height error I'm referring to could be out in the weeds, but this sort of thing can cause the dynamic negative camber magnitude to be a lot less than the static camber measured at alignment.
-Mike
04-21-2018, 06:57 AM
#28
Rennlist Member
Thread Starter
I am also not too familiar with the Cayman suspension. My wife has a Boxster so I can educate myself. I believe he added eibach lowering springs and set the camber at -2, which doesn’t seem too radical and I am guessing the set up is pretty common. I will take a look at it next week.
04-21-2018, 10:26 AM
#30
For autox you need more air pressure in the rear to get the car to rotate and not dig in, which is giving you what you have right there. I would try that first before messing with alignment. Plus, it's easy 
Gary
Gary