Rear Neg camber wear, or tire failure?

[LateFan]

I've searched and read a few threads about inside tire wear in the back with excessive negative camber.

My son's car has completely worn out the inside of the right rear snow tire. He just swapped out summer tires and found this weird wear.

H&R sport springs, not that low. All new bushings in rear suspension recently. Altimax Arctic snows on stock bottle caps. Two winters of use. Front ones look almost new. Left rear shows some inside wear, a bit of cupping. Right rear is shot, but only in two distinct places. My neighborhood tire shop says he thinks it's tread separation - could be too much stress and heat on the inside, could be manufacturing fault. I don't know.

Left-Right, directional snows. Right shows a bit more wear here but not bad...


But spin it a bit and it's completely bald. This happened at two spots, not 180º apart but random. Tire man thinks it's separating and the bulging spots are wearing down fast.




I wouldn't think sport springs would be causing excessive camber wear. Do you think this was the suspension's fault? We don't want to ruin a new set of summer tires.

Possible clue (?) - he did take a long trip (over 1000 mi) loaded down with teammates, gear, and 7 bikes on the car. D'ya suppose the back was squished down, wacky camber?

This is how it sat right after we mounted the new wheels and summer tires. H&R Sport springs and E90 drop hats in front.
I hardly see any negative camber, but it's not loaded down.


Thanks for your experience and opinions here -

[varg]

It's probable that worn trailing arm and subframe bushings have compromised your rear end alignment enough to wear one tire more than the other. I'd check that whether the tire itself is the problem or not.

[LateFan]

Brand new bushings. Rebuilt rear suspension a year ago.


Can you check the rear alignment on an E30? An arm bent and too much toe out or something weird?

[SkiFree]

An arm bent

Given fresh bushings ...... that's my guess, exacerbated by the over-loaded road trip. It may be mild enough not to make much difference when not under load. I see it every once in a while. More common on the z3m coupes (given all their rubber).

[LateFan]

Where do you usually find bends? Is it in the legs of the arm, or the mounting points of the subframe?

Can an alignment shop check the rear as-is and give you camber and toe numbers? Do they do it at resting height? Because the camber will go more negative as the suspension is loaded, correct?

[SkiFree]

Where do you usually find bends? Is it in the legs of the arm, or the mounting points of the subframe?

Typically, it will be a twisting of the legs.

Can an alignment shop check the rear as-is and give you camber and toe numbers? Do they do it at resting height? Because the camber will go more negative as the suspension is loaded, correct?

Yes, yes, and yes.

If the one trailing arm is bent, it's numbers will obviously differentiate from the other side. If it doesn't, it could be that that side was just massively overloaded during the trip.

[LateFan]

Good info - thanks very much.

And if it's hard to visually see any bend, how do you trust that someone will send you a straight used one? They may not even known it's bent.

[SkiFree]

Good info - thanks very much.

And if it's hard to visually see any bend, how do you trust that someone will send you a straight used one? They may not even known it's bent.

Unfortunately there's no good way to tell visually, short of having a jig setup.

[rommaster2]

Just throwing this in here if it were all the way around I would suspect it to be a suspension component the fact its not all the way around the tire leads me to side with the tire guy that its a separating tire.

Only way to know if the suspensions messed up though is to measure the alignment. Camber is a fairly slow wear angle though and with tire rotations id hazard to say you would need extreme camber to notice wear. Toe is the more likely culprit if its suspension based. I base this off of 8 and a half years in the tire industry as well as the fact my car has noticeable rear negative camber and my tires have no camber wear from once a year rotations.

[LateFan]

Thanks - good insight.

We're scheduled for a rear alignment measurement soon. I've run several sets of these General Altimax Arctic snow tires on a couple of cars and they did fine. Continental owns General and those are a former euro (Gislaved?) snow tire relabeled as a General. Could be a bad tire - I'm kind of surprised he didn't notice any vibration. Looking for the receipt - I'm thinking it was Tire Rack.

[LateFan]

Just ran across the pics from when we rebuilt the rear suspension a couple of years ago. Not that they show anything revealing to me, but here are the better ones...





And those are the same snow tires when they were nearly new.

[LateFan]

Snow has melted, made it to the alignment shop.

Camber Rear -

Left: -2.79º
Right: -2.68 (so a hair over the spec max of -2.33, but it's lowered on ET15 wheels)


Toe Rear -

Left: .42
Right: .61 (spec range is .09 to .22)

Total: 1.03

Thrust Angle: .10

[LateFan]

^^ bump..

Do those toe numbers cause any alarm? Or is that just the result of a bit of lowering?

Thanks -

[PacificExposure]

Is there any discernible tire wobble? Maybe the wheel hub itself is tweaked or wheel not mounted flush, which wouldn't show up on a static alignment. That's the only reason I could think of that would result in the wear you experienced.

[LateFan]

No hub wobble, tracks nice and straight. Alignment / tire guy thinks it was just bad snow tires. May have been triggered by heavy load, improper inflation, & heat??

But I've had that same General Altimax / Gislaved snow on three different cars - first time we've had any problems.

I just don't have any experience with rear alignment to know if an additional .2 to .4º is a significant number.