02 OBW H6 auto 180k miles.

 

the rear tire has scalloping/cupping on the outside edge. it has done it with different tires/wheels so i don't think those are to blame.

 

seems to not do it in the winter (my winter tires are fine) and i drive more miles in the winter on this car (use it exclusively in the winter). but in the summer it seems to escalate quickly.

 

is the strut the most probable cause?

been reading a lot and that seems to be the most common cause, but have never seen this before myself.

I would think the strut is the probable cause. It is the most likely suspension component that is allowing the road wheel to excessively hop up and down.

 

You might also want to see if the road wheel is bent. Have a tire shop balance the tire/wheel, and ask the shop if the wheel is possibly bent. With the road wheel off, look up into the open wheel well to see if there are any oil stains on the strut, as a bad strut will leak out its oil at a bad seal.

thanks, maybe i'll try to visually inspect that strut again, got nothing the first time just looking from underneath (tire still on). struts are harder to inspect on these.

 

a bad strut could possibly cause scalloping but no other symptoms? seems like there would be other performance related issues but i guess i could see where that's not the case too.

 

You might also want to see if the road wheel is bent. Have a tire shop balance the tire/wheel, and ask the shop if the wheel is possibly bent.

it has done it with different tires/wheels so i don't think those are to blame.

What brand tire is it? I've seen this same wear problem with cheap tires and fixed it with better quality tires. My daughter's Corolla had terrible scalloping on the rear Pep Boys tires so we had the alignment checked and it was in spec. Replacing the Cornell tires with Michelins solved the problem.

 

Not saying that this is your problem but it's one possible cause.

The set on there now are directional bridgestone tires. I've had it happen to another set too, forget which. memory suggests it's not tires - cause i swap wheels/tires across multiple Subarus (i own a bunch) and it only does it on this car - but we do drive it a lot and it was most noticeable once the tires were well warn (old).

 

It's happened with a few different tires....now you got me wondering if maybe the 2 (or more?) different times were cheap or old tires? quit confusing me!

Edited July 4, 201114 yr by grossgary

pulled the wheel - strut is dry as the desert.

bounce test - push down on bumper - does the same as every other car, so it passes that test.

but i've read they can fail/wear internally.

 

i think i'm ready to guess strut....but sort of don't want to throw parts at it either, i don't have much experience with failed struts.

Edited July 4, 201114 yr by grossgary

I just posted about a nasty steering wheel shake. The tire came from the rear of the car where the strut and spring have 230K on. This was the only strut on my car this old and the only tire with the exact problem as you have. Its the strut

I just posted about a nasty steering wheel shake. The tire came from the rear of the car where the strut and spring have 230K on. This was the only strut on my car this old and the only tire with the exact problem as you have. Its the strut

oh yeah! thanks! your tire was cupped on the outer edge too? you posted on here, i must have missed it - i'll try to find it.

 

$54 shipped to my door for a new KYB GR-2 makes this an easy decision, just ordered it.

oh yeah! thanks! your tire was cupped on the outer edge too? you posted on here, i must have missed it - i'll try to find it.

 

$54 shipped to my door for a new KYB GR-2 makes this an easy decision, just ordered it.

 

You will love the KYB GR-2 struts. I have put them on several cars over the years, and they have all served me well. The last ones I put on a VW Jetta. I found it very helpful to use a bottle jack to lift and hold in place the entire strut assembly, so it can be bolted at the top hat.

thanks roost. this is my first ever new strut replacement!

so really - the ride quality is noticeable for daily drivers like me?

The set on there now are directional bridgestone tires. I've had it happen to another set too, forget which. memory suggests it's not tires - cause i swap wheels/tires across multiple Subarus (i own a bunch) and it only does it on this car - but we do drive it a lot and it was most noticeable once the tires were well warn (old).

 

It's happened with a few different tires....now you got me wondering if maybe the 2 (or more?) different times were cheap or old tires? quit confusing me!

 

It's probably not cheap tires based on what you just told me. I've only seen this happen to re-branded tires made by Goodyear and Kelley, some Nittos and some older Goodyears. Even in those cases damper wear may have been a factor but the better quality tires handled the "skipping" without shedding chunks of rubber.

 

AFAIK struts and shocks can lose much of their compression and rebound damping even when full of oil. The piston, rings and cylinder wall wear out and much of the oil bypasses the damping orifices by leaking around the worn sealing rings. This is especially true for the first inch of travel where the shocks spend most of their time. They still pass the old "bounce test" but can't maintain good tire to pavement contact which results in the tire skipping or bouncing along the pavement tearing out little chunks of rubber causing scalloping or cupping.

 

New struts should fix it for ya!

thanks SF, appreciate more feedback. ordered and hopefully it fixes it.

i know we are all a bunch of tight fisted, penny pinchers around here, but - shocks and struts are supposed to be replaced every 50K.

 

yeah, i know, who does that?

 

as already mentioned, they do wear out internally - might not show any signs of leaking but they do wear out.

 

gary, hope your new struts solve your problem - more than likely will.

i know we are all a bunch of tight fisted, penny pinchers around here, but - shocks and struts are supposed to be replaced every 50K.

50k, really? i am surprised at how few (one or none) strut failures i've had. i've had to replace strut mounts and broken springs, but never the struts i don't think. it's about time.

50k, really? i am surprised at how few (one or none) strut failures i've had. i've had to replace strut mounts and broken springs, but never the struts i don't think. it's about time.

 

well, lets just say that is the "recommended" interval very few folks ever do them that often (myself included) but there ya go.

when i got my 90 leg wagon it had blown air struts - got a set of used coilovers and slapped those on, then later swapped in some new struts as the used ones were pretty used up - that was pretty close to 50K ago - really dont plan on changing them again any time soon unless it starts showing problems like you are describing.

What Bridgestone's are you running? The Grids and Potenzas are absolutely terrible for scalloping. I would put them right up there with Fuzions unfortunately. I would say it's more than likely the tires, or air pressures. I'm sure some people may beg to differ, but directional tires do not cooperate on subaru's. The only set I have not seen wear funny was my own Goodyear Eagle GTHR's. Otherwise, almost every set of directional's that comes through the shop wear's stupid. I've had much better luck, and terrific wear out of real cheap tires like Ironman, Starfire, and Hercules. For so much less money, they are quiet, perform very well for a daily driver, even in weather, and wear good their whole lifespan. Just my 2 cents

What Bridgestone's are you running? The Grids and Potenzas are absolutely terrible for scalloping.

i think they are grids, nice guess crazy head!

I've seen a few, haha, I have really had zero luck with those tires. I'm not saying the problem couldn't be rooted elsewhere. But every set of those tires I've seen come through is all scalloped up.

actually it wasn't a grid, it was potenza's. but either way, one you mentioned. i have two other sets of old wheels/tires sitting that i think are scalloped too - i'll check thsoe when i get home and see if that's true/what brand they are.