Wildly Uneven Tire wear

Had a nail in the front right tire. Took car to tire shop to repair left front tire and rotate/balance all tires. Shop called back saying rear tires were "chewed up" and recommended against rotation. Returned balanced and repaired tires to original position. Decided to see what was going on. Tire shop was correct. Left rear tire had very strange wear on inside of it. Now please note that the "Get Alignment" answer is not much use. Left rear camber is -1.2 deg., right rear is -1.5 deg. Left rear Toe is -0.10 deg. right rear is +0.12 deg. Rear Cross camber is 0.3 deg. Rear Toe is 0.02. The tires are Goodyear Regatta 2 with wear rating of 560 and have 33000 miles. (Note, later versions of the Regatta 2 had wear rating improved to 680.)

Now for the mysterious (to me) part. The severe wear is on only one spot on the inside edge of the tire. The rest of the tire has uneven wear, but to a much lesser degree. The other rear tire has some uneven wear, but nothing close to the bad spot shown. Will be replacing very, very soon, but would like any feedback of what would cause the wear to home into one specific spot.

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Tire psi has been 38 psi, although lately I have increased this to 42/40. Note that the wear is entirely on the inside edge and the tire looks good on the outside. There has been no rotation of these tire since a flat caused the front tires to be replaced early. There has been no skidding (at least with me driving) and the ABS makes it rather hard to do that.

The tire is definitely out of balance now. Contacting Goodyear may be justified, but it's only a tire and 30k miles is not insignificant. The end result could be Goodyear gives me one good tire....which I really don't want just one good tire. The true focus is to see if there is something really strange with the car that could do this.

In the end I like "voting" with my wallet, like most other Prius owners. Since I will keep a car for 150,000 miles or more, I have proven that wear ratings are key to having 2 sets of high end tires or 6 set of stock/OEM tires. Guess which is cheaper....and generates far less waste.

One last note. When looking at the front and rear tires, the front tires looked really good and symmetrical.
The real surprise was the wear rating was significantly higher (680) on the front, than the rear tires. (Why the change?) The biggest limitation with the 2001 Prius is the rims are 14 inches so really high end wear ratings (e.g. Michelin Hydroedges) are not made in this size.

Tire psi has been 38 psi, although lately I have increased this to 42/40. Note that the wear is entirely on the inside edge and the tire looks good on the outside. There has been no rotation of these tire since a flat caused the front tires to be replaced early. There has been no skidding (at least with me driving) and the ABS makes it rather hard to do that.

The tire is definitely out of balance now. Contacting Goodyear may be justified, but it's only a tire and 30k miles is not insignificant. The end result could be Goodyear gives me one good tire....which I really don't want just one good tire. The true focus is to see if there is something really strange with the car that could do this.

In the end I like "voting" with my wallet, like most other Prius owners. Since I will keep a car for 150,000 miles or more, I have proven that wear ratings are key to having 2 sets of high end tires or 6 set of stock/OEM tires. Guess which is cheaper....and generates far less waste.

One last note. When looking at the front and rear tires, the front tires looked really good and symmetrical.
The real surprise was the wear rating was significantly higher (680) on the front, than the rear tires. (Why the change?) The biggest limitation with the 2001 Prius is the rims are 14 inches so really high end wear ratings (e.g. Michelin Hydroedges) are not made in this size.

 

<div class='quotetop'>QUOTE(dogfriend @ Aug 22 2007, 02:08 PM) [snapback]500449[/snapback]</div>

Thanks greatlly for the info. The 2001 Service manual does not call this out of spec, but this is because the combined toe is what is specified at 0.1 +/- 0.33 degrees. The shop alignment machine also called this in spec. However, you may have better info than I am using. Let me know since I am listening. A resulting thrust angle of 0.1 degrees does not appear to be causing this very localized problem......but if it is then I do not want to exclude it yet either. I will be posting what I have found out shortly that may be interesting.....for those few who care about strange tire wear.

 

Here is what a lot of reading has uncovered about the strange tire wear that appears to match the wear I am seeing. First let me point out that bus drivers, truck drivers (who use LOTS of tires), and motorcycle drivers seem to know the most about this specific problem of uneven wear. Quick Summary:

VERY IMPORTANT-It is much more common on undriven tires then the driven tires. (i.e. more common on Prius rear tires.)
VERY IMPORTANT-It is greatly accelerated by unbalanced tires. Specifically, as the uneven wear starts, it soon accelerates as the tire starts to unbalance to an even greater degree.
VERY IMPORTANT-If the suspension does not dampen the oscillations (i.e. bad shocks), then the oscillations will be much worse, and the problem will occur often and fast.

NOT SO IMPORTANT-Rotating tires distributes the wear, but does not "prevent" this effect. (Rotating is very important for most other wear mechanisms, so don't misinterpret this statement.)
NOT SO IMPORTANT-Bad alignment usually causes bad, but even wear.

STRANGE FACT-There is a much higher susceptability to this uneven wear with tires that have an "aggressive" tread design. Aggressive appears to describe deep and jagged tread patterns.

Bottom line is to 1) Keep tires balanced periodically, especially the rear tires, 2) An unbalanced tire's initial sign may be noise prior to the car vibrating, 3) Pay attention to wear ratings. The higher the wear rating the less wear between rotations, 4) Feel your tires (very slowly), just looking failed for me.

[Thanks to priusenvy and others who responded. All replys appreciated.]