Tire wear mystery

Its gonna be moderately critical on AWD cars like Soobs to keep all 4 tires the same model AND very near each other in total wear. Often, vibration is tire/wheel related and older tires may have some bubble/tire seperation beginning. A car may begin 'cupping' or have other odd tire wear if shocks are failing or a wheel is out of balance as resonant 'bouncing' can occur. Its POSSIBLE someone put the the worn tires on one side to try to decrease strain on the center diff since tire wear was uneven. I'd expect getting 4 new tires, with a good wheel inspection/balancing - coupled with a good wheel alignment, to alleviate most of the problems you mention. Also, try to inflate the tires to at least the manual or 'door' specs - most folks prefer to add 2-3-4 lbs above those pressures.

Carl

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Carl

This may seem like a stupid question, but how do you tell that your shocks are failing on a Subaru? I'm used to driving a Windstar and a

1987 Chevrolet Celebrity, and the Outback, um, handles a little differently. When I push down the bumper looking for bounce, it just doesn't go anywhere, and on the road it handles so much tighter than the sloppy jalopies I'm used to, that I'm afraid Outback "this is terrible" might still seem really good to me.

If somebody did that, was it reasonable, or boneheaded? Sounds like the sort of thing I would do...

If I put it off until the bad tires finish wearing themselves out, am I damaging the car?

Adam:

To begin with, were the worn out tires moved from their original location?

If they were, that could explain why only one side. On the other hand, if they were not, a weird wear pattern on only one side of the vehicle would lead me to believe that the car has a camber problem on that side. Was the car banged sideways against the sidewalk/curb?

When you say that the right front tire is showing the same problem after the 600 miles, I believe that you really need a 4 wheel alignment. Find what are the angles your car requires and make sure the alignment is left within those specs. I have found that some shops have different specs for some vehicles than those recommened by the manufacturer. I always go for the manufacturer's. You can do the wheel alignment even before you replace the tires as long as there are not major diferences between them.

As long as the depth of the tread is about the same, you should not have any problem letting the 4 tires wear out before replacing them.

I recently had a similar problem with 2 Toyo Proxes TPT tires. In my case, the rear tires had the center bead worn out normally but both sides of each tire showed cupping, flat spots, etc, as if you had stumped on the brake without having ABS (but remember that the center bead does not have any defects). Inspection of the suspension, alignment, brake system, wheel bearings etc found not problems at all. Taking the tires to the tire dealer promted the guy to say that it was either a strut or alignment problem. Sooo... I moved the tires to the front and I am (well, the wife is) tolerating the noise until I need to replace the 4 tires. By the way, these tires require higher pressure than specified in the rear and lower pressure in the front as indicaded but the groove depths.

Adam Aulick wrote:

It has been my experience tire wear you described is caused by worn shocks/struts. Running oddball size tires will eventually have you looking at a $1k transmission repair bill. And the really painful thing is all the problems that caused this repair bill will still need to be addressed.

I don't know anything about the past, but there's no damage evident in wheel appearance or vehicle handling at any rate. If somebody did move them, that makes the whole thing a lot less strange. Perhaps the tires wore unevenly front/back, somebody got to the point where two tires were no good and two almost no good, replaced the no good just to sell the car, and swapped the others out to one side to avoid problems with the center diff. That explanation just leaves me with some problem, hopefully as mundane as alignment, causing patchy wear in front.

You mean not major differences between the old tires and the new ones I'll put on, or major difference between the tread wear on the older/newer tires currently on the car? Either way the answer is they're pretty different.

It's not. The left side is worn down much more than the right. Sigh.

Not stupid - I also have never 'really' been able to spot bad shocks on smallish cars. One of my daughter's had a Toy Camry that was VERY bouncy when driven - blown shocks. Same with another Daughter's Maxima. But how to tell when they are - um - on the way out? I dunno. maybe someone will chime in. Offhand, if those 125K miles were 90% highway, you may be OK for another 50-75K - who knows? If it's tight and not bouncy now, just start saving for struts.

The THEORY is the open diffs on each axle will prevent the center diff from responding to slippage. I wouldn't rely on it though.

Do the car AND YOURSELF a favor - put good, SAFE tires on the car.

I guess you got the answer by now, new tires with proper alignment.

Good luck!

Adam Aulick wrote:

I had way too much tire wear on a pretty new Outback a year ago. A dealer agreed and aligned them. Wouldn't speculate how it happened. I happened to talk to someone else waiting for their car to be serviced later at a different dealership and they said they had the same problem. I asked that service manager what might be causing it and he thought it could be the way cars are tied down on the transport trucks when they are delivered.

Hi,

At that mileage, if the shocks (struts) are original, they'd be my first target for eliminating the "cupping." As explained by others, your tires are "bouncing" along the road, and after the wear begins, it tends to accentuate this wear pattern.

Shock mfrs suggest replacement at 50k miles. My experience is like others in that smaller cars don't always respond to the "driveway bounce" test, but I've yet to have any go over 100k miles w/o being "gone."

After that, suggest four matched tires, careful alignment, a couple of PSI over door sticker, and careful observation for further problems. At that mileage, it's not impossible other suspension bits may be worn, especially if they've been trying to do the job the shocks should do!

Rick