WilliamG
Hinge Fanatic
I wonder what causes the change? If there's no perceivable wear at 5k miles, what is changing? So bizarre.
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2021 Plaid - Here we go again! SSDD and tires...
- Thread starter Dameon
- Start date
Yeah, I struggled with the same thought. Why is it so well hidden and then BOOM... delam. All I could come up with is that things are happening inside the tire, under the top layer... belts, steel, tying the tread to the sidewall are breaking until, at some point, the stress is too great and it breaks which tears the rubber in the manner you see in a failed tire.
WilliamG
Hinge Fanatic
But wouldn’t that then rule out any alignment? I mean, if it’s alignment the wear should be on the outside, no? I’m not an expert in these things, but I do like to ask questions!
lolachampcar
Well-Known Member
All the previous S had significant rear negative camber and inner shoulder wear. Some of the new cars have the problem (mine does not - getting 30K without swapping versus 20k with swapping). This makes me think the issue we are seeing now is in alignment and not un-correctable geometry.
If there was an issue with excessive negative rear camber on the first gen S (I had a 2015 P90DL), I never saw it. That car ate tires like nobody's business... the wear was VERY even though (should be a thread I started related to this "issue" around here somewhere). I was glad to get more than 10K from a set of rear tires. The factory Michelin's were good for 10-12K, but I found that Falken's would get me another 2-3K with no perceivable performance or sound considerations. They were less expensive too.
What do you mean "swapping"? Rotating? Swapping side-to-side? Swapping between 21" and 19"?
lolachampcar
Well-Known Member
Muzzman1
Active Member
I have 25k on mine at this point. I have not bother rotating for the last 10k since they are dead even all around. Only have another 5-7k left on them.
Okay, I found some time to install the shims last week... what a major PITA! The biggest problem was fitting the shims between the upper arm and the rear sub-frame. Despite what the instructions say, they don't simply "roll in from rear to front". Maybe my car has some very early production differences that the later cars didn't, but there is an obvious obstruction that would completely prohibit access from rear to front. In the end, the only way they would even fit was to install them upside down. it is conceivable that the "gripping arc" could hit the axles on major compression, but that seems unlikely. I'll keep an eye on "ding marks" on the axle just to make sure. Also, I had to have my wife hang from a 6' cheater bar wedged under the bottom shock mount to even get a millimeter of space to slide the shims in from front to back, Yes, I had the opposite side tire on the ground to offload the sway bar tension.
All this hassle was after my (incorrect) assumption that I had a 16mm socket. I have several complete sets of sockets from different manufacturers (Kobalt, Craftsman, etc.) and none of them include a 16mm. 20mm and 22mm are also above the normal range of most box wrench sets. I had those from other projects. Anyway, I had to run to Lowe's to get a Kobalt 16mm socket... they only had one deep, impact, socket left in the drawer.
Could be mental, but I don't think it is, there is a distinct ride and sound difference after installing the shims. We'll see what the tires do now. Could be worse. Who knows.
n2mb_racing
Active Member
5/8" is almost exactly 16mm. Off by 100 µm, so likely good enough.
I considered 5/8" as it seemed to fit "okay", but decided just to buy a 16mm. 80ft/lbs on an "okay" fitting socket bothered me.
just to be clear, 5/8" is ever so slightly smaller than 16mm. 15.875 mm vs 16. That's really within the tolerances of any manufacturer machining these things, but if anything is going to fit more snugly around a 16mm bolt, it'll be the 5/8".
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