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Hard pulls from a stop while turning right or left and spinning the tires will do this. Same thing when taking off and turning on wet roads causing the rears to spin. The wear can be worse on summer tires in cold weather too. Or cold weather on summer tires taking off ramps at speed.
This is the first set of MP4S tires I've seen wear out. Up until now I've had no data on wear patterns for this tire.
So a quick anecdotal observation ...
Earlier this week I had the opportunity to run some hundreds of miles of spirited roadway. During a fairly quick stretch of open sight turns I was over inflated. This created a lot of bouncing that was the same as I've experienced with the older MPSS design.
But there was a major difference with the new design ... on initial turn in all I got was slip as the car continued in a straight line. Trying to stay linear on my steering inputs I would eventually get a harsh bite with the tires and the car would harshly grab the pavement and jerk into the turn. It was like catching an edge when skiing. Quite annoying, if I may say so.
Before heading back to the coast through many miles of tighter turns I dropped 5 psi in each tire, resulting in cold pressures the next day of 34 front and 39 rear (ambient temperature in the garage of 60F). The car returned to the joyous beast I know and love!!!
Hypothesis ... The MP4S tire has harder compound in the center with less grip. The edges are progressively softer. The extreme sides are very soft for maximum grip and, under proper inflation, safety (indicated by the forces placed on the tires in the tight turns after the inflation was lowered). The extreme sides are also most prone to wear.
The above could help explain the wear only occurring on the extreme edge, but I just checked pictures of my first worn out rears (MPSS) and although the cords were exposed the wear half an inch in was still minimal (but the wear pattern in the OP's case is extreme nonetheless).
As the Philly Bruce would say ... anyhoo ...
I vote for an alignment by a tire specialist who can assess driving style with expectations of tire life. Someone who will discuss this with you before he decides on the correct settings for you.
And yes, lowering the car changes the alignment adjusting ramps as the suspension compresses affecting optimal unloaded settings. And yes, spacers affect the leverage to push on the suspension. All of those modifications need to be compensated for when deciding what is best.
And by the end of the day, with a lowered car, it may be these tires did the best they could and you simply need to crawl under the car to inspect them more frequently ... once a wear pattern establishes it can't be reversed and it will proceed exponentially.
I had the same issue. Took it to a friend of mine who owns some tire shops.
The alignment was a little off - which pissed me off cuz the local stealership had done it.
Decided to have it aligned properly but at the less-toe extreme of spec. Has worked well.
@wayne - I was running 34 front 39 rears as well. I spoke to Wells at S-Car-Go and he said to bring it by but im going to speak to your guy at Dependable too. As a side note, the tire dealer did say that there were less than 10 sets nationwide of the PS4S, which typically means a refresh is imminent.
There's really nothing for the inside edge of that tire to rub on back there other than a brake cooling scoop or the coil spring or inner fender, .........
Here are pictures with a wheel installed and you can see there's nothing really in that wear area.
Petza - you proved my supposition wrong :-) But thanks for the pic's that great data, this is why this is such a great forum!
Wanted to give a quick update on this. I took it over to S-Car-Go today and Pat walked me through the alignment. He said the alignment was decent and the tire wear was "normal". I just let them go too long. He did find my fronts where out of balance. These had been a problem since I bought the tires. I had to take them back to the tire dealer twice and they still didnt get them right. I think I just got immune to it but he noticed immediately.
See the setup he gave me below. I took it for a quick spin and it felt like the 997 equivalent of shredding turns in fresh powder. Epic.
The for everyone's input.
Ps - pro tip for the day. I saw Pat use some amazing cleaner to instantly get the tire weight adhesive off. He said it was called "Cosmoline Remover". He said he started using it when repairing 996 convertible tops he uses it on everything. Doesn't effect paint.
ignore the tire pressure numbers. the machine was acting up. always some new eye candy in the shop. they just put a 4.0 in this.
I bet the car handles much better now. You actually had the front wheels toed out before which makes for a wandering feeling in turns. With just a little bit of toe in, it should track through corners much better now. I still think you have more toe and camber at the rear than you need unless you'll really be pushing the handling. With those settings, I estimate new rears at 12-13k miles. You'd get significantly better tire wear at the rear (like 50% more) if you used setting more like what's on the front, and bet you couldn't tell much of any handling difference, but drive it for a while this way and see how the wear looks and how it feels. I like they way they were able to get both sides just about dead even with a 0.0 thrust angle - that's good stuff.
I took it over to S-Car-Go today and Pat walked me through the alignment. He said the alignment was decent and the tire wear was "normal".
Surprised to hear that tech call your wear "normal". I never saw anything like it and as you saw in several previous responses from others, some said it must be due to rubbing against something rather than regular wear, suggesting again a wear pattern not "normally" seen.
Hey TheBruce: I assume your reference to "fresh powder" was meant to be in the context of skiing and not driving, no? I just need to make sure before I do something stupid this winter, LOL . Bruce
Normal? I dunno about that. When I purchased my car used, I wore through the rears in a flash with the inside ring down to the cords.... got an alignment, done. I asked them to take the negative camber in the rear out. Never had that happen in 6 years and 100K miles since. Most said it was not the negative camber that did it, but improper toe. I believe it was the negative camber Porsche specs for safety. Just look at the car sit... those rear wheels have negative camber. They gave you -1.7... that may be "normal" but that is going wear the interior rings down. Let the arguments continue.......
11-16-2018, 10:51 AM
