What causes tire wear like this?

[rturbo 930]

I have a nasty shake at highway speeds. Noticeable at 65, threatening to shake the car apart at 85. Nothing seems loose if I jack up the car and try to wiggle the wheel back and forth. Front right has a bend in the rim, but both tires are worn like this. The tire on the bent rim is worn more than the other side. I know a bent rim can cause a vibration, and I'll be fixing that, and the tires being worn like this I'm sure is contributing also, but how did they get this way to begin with? Sort of a butterfly effect from the bent rim, or something loose in the steering that isn't obvious from wiggling the wheel? Bad alignment? I don't think I've seen a tire worn this way before.

[roguetoaster]

If it is not a mechanical fault with the car, which seems unlikely, then it is probably a belt or tread separation in the carcass of the tire. They can be very hard to spot and present in very strange ways.

[rturbo 930]

If it is not a mechanical fault with the car, which seems unlikely, then it is probably a belt or tread separation in the carcass of the tire. They can be very hard to spot and present in very strange ways.

In both front tires though? Or is the problem in the one tire and resultant shaking causing the other tire to wear the same way?

[ehrawn]

[Northern]

My Discovery has scalloping on the rear tires from a sloppy balljoint and worn bushing - any play in your front suspension?

[rturbo 930]

My Discovery has scalloping on the rear tires from a sloppy balljoint and worn bushing - any play in your front suspension?

Shouldn't be, although I haven't gone over it thoroughly, just a basic check. Although it was 10+ years ago now, I replaced almost everything in the front suspension, including control arms, bushings, Z3 rack, tie rods, springs and shocks. Only thing left that I can think of is wheel bearings, and I thought one of them was bad since I have a noise that sounds like it's coming from that corner, but didn't feel any play when I checked it. I'll probably take a closer look at it. I don't put a ton of miles on the car so I would think the parts I replaced should still be in good shape with 40k miles on them at the most.

From the link ehrawn posted, I suspect my bent wheel is causing a vibration, and that's the source, but not sure.

[AWDBOB]

Shouldn't be, although I haven't gone over it thoroughly, just a basic check. Although it was 10+ years ago now, I replaced almost everything in the front suspension, including control arms, bushings, Z3 rack, tie rods, springs and shocks. Only thing left that I can think of is wheel bearings, and I thought one of them was bad since I have a noise that sounds like it's coming from that corner, but didn't feel any play when I checked it. I'll probably take a closer look at it. I don't put a ton of miles on the car so I would think the parts I replaced should still be in good shape with 40k miles on them at the most.

From the link ehrawn posted, I suspect my bent wheel is causing a vibration, and that's the source, but not sure.

On two E30s that received new control arms but didn't get driven much, I've had the ball joints seize up but not show any play. May be worth popping the boots off to check condition/make sure they move freely.

Also I misdiagnosed ball joint play recently because I only shook the wheel from the side.

Jack the car up slightly and put a long pry bar under the front wheel and move it up/down while looking at the ball joint. I had one fail that had vertical play that didn't show via shaking the wheel from the side.

May not be your situation since it's on both sides, but worth checking.

[rturbo 930]

Appreciate the input - I'll check that next time I have it in the air.

I think I may have the explanation for the uneven wear though. I noticed this a few days ago. I think the scalloped effect is simply due to how the tire is made. It's on both sides, and it has a specific pattern that follows the pattern of the tread. The spots where it's worn down to the cords are pretty much perfectly between the diagonal grooves in the tire. If someone has an alternate explanation, I'm open to ideas.

The second thing I noticed is that the one tire is bald all the way around except in one area, that happens to be right after the bend in the rim (marked with red arrow), as if the tire is bouncing in that spot, and therefore not wearing as much in that area. Again, alternate theories welcome.