Cupping on interior shoulders of rear tires

[ochy38]

Hi everyone, my GF has been putting a lot of highway miles on her '07 yaris 3 door recently, and I noticed a lot of road noise from the rear of the car. Got down and looked today and the tires are beginning to cup quite a bit on both rear's on the inside walls. I did a quick check on the fronts, they looked fine but I should look again. What could be the problem here? The car has about 120Kmi on it.

[TOUGEghost]

Lack of tire rotation.

[UberSilver]

Shot shocks., bad bearings(less likely).

[ochy38]

Originally Posted by UberSilver

Shot shocks., bad bearings(less likely).

I pushed on the car and it didn't keep bouncing, but I suppose with 120K the shocks are about due. It doesn't sound to me like the bearings are going on the car, kind of noisy but I relate that more to the cupping of the tires.

[Flipper_1938]

Originally Posted by TOUGEghost

Lack of tire rotation.

X2

[CoryM]

If it is just the inside edges that are wearing, it's probably toe wear. Blown rear shocks will make for cupping across the entire tread, worse in the middle.
What tire are they? Some tires are very prone to cupping/noise just by design.

[ochy38]

Originally Posted by CoryM

If it is just the inside edges that are wearing, it's probably toe wear. Blown rear shocks will make for cupping across the entire tread, worse in the middle.
What tire are they? Some tires are very prone to cupping/noise just by design.

The tires are plane jane Bridgestone Insignias. I didn't think there was a rear toe adjustment on this car.. is there a bushing or something that could cause the toe to go out of spec? Seems to be happening pretty evenly on both tires. I'll take a closer look after work today but memory tells me that the wear starts at about center of the tire and gets worse the closer you get to the inside shoulder

Originally Posted by TOUGEghost

Lack of tire rotation.

What would cause this? Wheel bearing? something else?

[TOUGEghost]

Rotation as in removing the wheels and tires and rotating them to a different position on the vehicle. This is done to prevent uneven tread wear and prolong the life of the tires.

[ochy38]

Originally Posted by TOUGEghost

Rotation as in removing the wheels and tires and rotating them to a different position on the vehicle. This is done to prevent uneven tread wear and prolong the life of the tires.

Ah, understood. She is definately overdue for a rotation, but (and maybe I'm wrong) I would assume cupping would point to a suspension issue, I was under the impression that rotating just allowed all four tires to wear evenly in relation to eachother.

[ochy38]

Originally Posted by TOUGEghost

Rotation as in removing the wheels and tires and rotating them to a different position on the vehicle. This is done to prevent uneven tread wear and prolong the life of the tires.

I just looked into the rotation issue some more. Definately thinking thats the problem, its been at least 1.5 years since she rotated the tires. I've been a amateur-ly working on cars for the last 5-6 years and never heard about that one. I just assumed rotating allowed all four tires to wear evenly in relation to each other. Thanks for the info.

[why?]

Originally Posted by ochy38

I just looked into the rotation issue some more. Definately thinking thats the problem, its been at least 1.5 years since she rotated the tires. I've been a amateur-ly working on cars for the last 5-6 years and never heard about that one. I just assumed rotating allowed all four tires to wear evenly in relation to each other. Thanks for the info.

just do some research before rotating them anything but front to back. Nowadays even a lot of cheap tires will almost disintegrate if you try to put them on the other side of the car. Something about handling characteristics making it not possible or something like that.

[CoryM]

The rear suspension of the Yaris should make for flat tire wear. You should not see any cupping from the rear at all. The idea is to take the tires from the front of the car (where they get worked hard doing steering and camber changes) and put them on the rear so they can become smooth again. Chances are you have some toe-in on the rear axle (from pothole or curb bump most likely). It is possible that it is from lack of rotation, but it is unlikely IMO. I would suggest getting your alignment checked. Do a google image search for "toe wear" and compare to what you have.

Cheers.

[Viperoni]

The cause of cupping can be a tough one to determine, but i'd go with worn shocks and negative camber, or negative camber and toe in.