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Rear Inside Tire Cupping/Alignment/Shocks/Weight?

Chisel_86

Drag Racing Champion
When I bought my car over 2 years ago ('10 GTI) it had tread cupping on the inside rear tires. I bought new ones, got an alignment, and new rear shocks (Bilstein B4). I've rotated the tires a couple times since then and they are showing the same cupping as before with about 30k on the tires. Is this a general problem on these cars?

I'm considering adjusting the alignment with less camber to see if it helps. Maybe -0.75/-1.00 instead of -1.3/-2.3.

People say it can also be due to bad shocks. I feel like mine should still be good after only 30k...

Another thing I was thinking about is wheel weight. Mine are the Detroits which are notoriously heavy for factory alloys, and I'm wondering if the OE shocks have a hard time dampening the weight, and thus causing excessive bounce even though the wheels/tires always balanced well...

I hate the fact that my tires are wearing out in less than two years. Tread depth is still ok at 5 and 6/32nds.

Here's my alignment readout.
 

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kec789

Ready to race!
I was coming here to post a similar question. I bought my 2017 SE new, and had to replace my OEM tires early due to road noise, which was caused by the rears cupping. No accidents, no tracking, nada.

Had an alignment done and it barely needed any adjustment. I drive a lot due to my commute and a year later had to buy another set due to noise coming from cupping.

I've since bought three or four new sets of tires due to cupping and no one can see anything wrong, including a VW dealership who looked at it first.

When I had new brakes and rotors done last April I had my independent VW shop go through everything and they also said all looked great. I even had another alignment done, and this one needed even less adjustment than the previous one.

I am STILL getting rear cupping and I'm tired of buying new tires every year. Yes, I drive a LOT, but still. I tried a more frequent rotation, but that didn't seem to provide THAT much more times in between new tires.

So, anyone got any idea how to resolve this? The first couple of sets were not the most expensive, but they weren't cheap either. It didn't make much, if any, difference in how fast they started cupping. I'm now down to buying whatever since I drive 90% of the time on a nice freeway with little traffic. No, they aren't the cheapest, but I'm also not spending $150-200 a tire just to replace them a year later. I just did it again today and it made me sick how much tread was left on all of them.

If someone could point me in the right direction, that'd be great.
 

Chisel_86

Drag Racing Champion
So, anyone got any idea how to resolve this? The first couple of sets were not the most expensive, but they weren't cheap either. It didn't make much, if any, difference in how fast they started cupping. I'm now down to buying whatever since I drive 90% of the time on a nice freeway with little traffic. No, they aren't the cheapest, but I'm also not spending $150-200 a tire just to replace them a year later. I just did it again today and it made me sick how much tread was left on all of them.

If someone could point me in the right direction, that'd be great.

Wow, that really stinks! I feel your pain.

I've since read that keeping the rear tires inflated to 35psi MAX seemed to help for some, compared to the factory spec which is 38psi I believe.

I really want to know if adjusting the camber closer to zero will help since it's the cheapest and easiest solution.
 

Thumper

Autocross Champion
I've since read that keeping the rear tires inflated to 35psi MAX seemed to help for some, compared to the factory spec which is 38psi I believe.

I really want to know if adjusting the camber closer to zero will help since it's the cheapest and easiest solution.

Odd, normally underinflating makes cupping worse. The problem with going to zero camber (or closer to it) is that the suspension is designed to work where they engineered it to with the rest of the car. Negative camber is designed for more control at high speeds. The car tends to "lift" at higher speeds, taking weight off the suspension and changing the camber. The camber setting at rest is designed usually to equal zero or close to zero camber at highway speeds. Kind of like they give you the cold tire pressure understanding it will be 2-3psi higher while driving.

If you move the camber to zero at highway speeds it will be POSITIVE which will then move the contact patch closer to the outside of the tire and consequently give less even traction, not a good thing at 65mph. You could definitely move the camber closer to the positive side of the factory specification range, like you said about -1.0. Every car and driving conditions are different that's why they give ranges, but I would stay within that range for street driving.
 

Chisel_86

Drag Racing Champion
I believe the cupping is due to excessive bounce in my case, which is odd because I replaced the shocks in an effort to solve the problem. Obviously it did not.
I think with a lower tire pressure the tire won't want to bounce as much and may stay in more constant contact with the road surface.

As for the alignment, I fully understand the reason for a negative camber setting. I'm thinking to adjust it to half of what factory states and go from there. I don't believe that negative camber is as important for highway speeds as it is for heavy cornering so I think I'm ok there. I'd say 75% of my drive time is highway and roughly 0% track day.
 

Chisel_86

Drag Racing Champion
Came back to post an update, kinda.

The lower pressure in the rear did not seem to change the wear pattern on the rear tires. I've since rotated the worst tires back to the rear for my driving sanity. I can still hear the hum/roar of the cupping, but it's not nearly as bad as when those cupped tires were on the front. Now all of my tires are cupped to some degree.

I have yet to change my alignment settings, but I'm planning on inspecting some bushings and upper shock mounts next.
 
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