Rear wheel wearing faster than the others

[idosubaru]

2002 OBW H6 with rear VLSD. Rear passengers side tire is wearing noticeably faster than the rest.

 

No torque bind, no noises, car runs and drives fine.

 

The VLSD units are sealed right so if the LSD if failing fluid change does nothing right?

[Suzam]

Is it even wear across the tread? I would doubt the LSD is at fault. If it failed you would most likely have greater symptoms.

Edited October 31, 2010 by Suzam

[flight_of_pain]

What type of wear? Incorrect toe will cause the rears to eat themselves in a hurry.

[idosubaru]

Had an alignment earlier this year.

 

It appears to be relatively even wear across the tire.

[flight_of_pain]

Had an alignment earlier this year.

 

It appears to be relatively even wear across the tire.

 

Does it pull when braking? How are the brake pads on that side, similar pad wear to the other side?

 

As far as alignments go: I can take my legacy in every six months and it will be out of whack.

[idosubaru]

Does it pull when braking? How are the brake pads on that side, similar pad wear to the other side?

nah, everything works fine, i've replaced both rear and front pads.

 

I can take my legacy in every six months and it will be out of whack.

that's bizarre, i wouldn't trust the mechanic, i guess yours or your driving is just different. guy i knew that worked in the alignment field said it's a waste, cars don't "loose alignment" for no reason - how often are the doors, windows, and hood and trunk and all sorts of other parts that have alignment in them ever get aligned. never had uneven tire wire on the dozens i've owned and never paid for an alignment, except on this car. maybe that's my problem, i went and got an alignment!

 

tempted to get this one aligned again and see the spec's, ask them to be mindful of it. can something be wrong that they won't pick up? could the tire be straight /aligned but still wear unevenly - doesn't seem like it right?

[nipper]

http://www.procarcare.com/includes/content/resourcecenter/encyclopedia/ch25/25readtirewear.html

 

Any of those?

[Fairtax4me]

Assuming all 4 tires are of the same brand and style, did you check the treadwear speed and weight ratings on each tire to make sure they are all the same?

[idosubaru]

http://www.procarcare.com/includes/content/resourcecenter/encyclopedia/ch25/25readtirewear.html

 

Any of those?

definitely none of those - it looks like normal wear, there's nothing odd about the tire tread, looks perfectly fine by itself. the tread is getting lower faster than the rest, by a good margin apparently.

 

bad memory tells me the last set of wheels/tires did the same thing, but i'm not sure. i have multiple matching sets of tires/wheels and multiple subarus and swap between winter treads, etc so hard to keep track sometime.

 

cars101 seemed did not definitely seem to mention that the H6 VDC models got the VLSD rear diff, so i'm not even sure i have VLSD or not.

[nipper]

hrmmm .. is your rear diff bad?

 

Rear wheel bearings all check out?

 

How is the rear strut?

 

How much weight are you carrying in your car, and how often is the mother in law there

 

Are all the rear end bushings good?

[hankosolder2]

Two thoughts: Perhaps the static alignment is good, but a bad bushing (or some such thing) is causing the wheel to sharply toe in or out under power or braking. I'd think you'd feel it acting squirrely, but who knows?

 

Does this car have VDC? Assuming it works like the other traction/stability controls out there, it can brake on an individual wheel. Say you're whipping around right hand turns and the car wants to plow the front (understeer) due to being nose heavy (even worse with the H6.) The stability control is going to apply the right rear wheel to help the car pivot around that axis and in doing so might be causing some add'l tire wear to the right rear. Do you push the car hard in turns?

 

Nathan

[Manarius]

I had someone tell me once that the right rear tire in an AWD system is going to be the one that wears the most.

 

I didn't really get an explanation, but maybe this is semi-normal behavior?

[nipper]

I had someone tell me once that the right rear tire in an AWD system is going to be the one that wears the most.

 

I didn't really get an explanation, but maybe this is semi-normal behavior?

 

 

Nope, that goes back to the old wives tail that the right wheel transmits all the power to the ground.

[idosubaru]

no spirited driving, though lots of twisty and bad roads around these mountains so a bad bushing sounds worth a look. they seem to fail so rarely though hard to imagine on a 2002.

 

no noises or other issues so i'd imagine the rear diff and strut are fine as far as i can tell.

 

struts can cause wear like that?

 

we carry no weight as a daily driver, maybe 200-300 pounds in the back when we travel.

 

yes this car has VDC, rarely activates though as it has a little VDC light in the dash and makes a sound when it does activate.

[hankosolder2]

You mentioned that you have multiple vehicles and sets of tires. Is there any possibility that at some point sets were mixed up, or a more worn full size spare of the same make and model was swapped on and perhaps you forgot about it?

 

Furthermore, is it possible that another driver of the car nailed a pothole or a curb and replaced the tire with a good (but more worn) used one of the same make and model without you knowing?

 

I'm not suggesting that you're senile or anything...it's just such an unusual problem that it's worth considering all the unusual possibilities.

 

Nathan

[1982gl4]

In Vt we change rear bushings in Subarus all the time. I have even been doing ones in 05-06 cars. Got to love those NE roads, I would say it's worth a look.

-SB

[idosubaru]

In Vt we change rear bushings in Subarus all the time. I have even been doing ones in 05-06 cars. Got to love those NE roads, I would say it's worth a look.

-SB

Nice hit! Thanks, do you know which bushings and how do you know when they're bad? Is it obvious or does it take some "testing"? The only bad bushings I've seen have always been pretty much completely shot...even missing. Not sure if there's an in-between so to speak?

 

You mentioned that you have multiple vehicles and sets of tires. Is there any possibility that at some point sets were mixed up, o

no, not a fleet, only my wife and i drive them and all of my wheels are different. OBW, Legacy, Forester XT Turbo, WRX, so no swapping possible.

[1982gl4]

Usually the rear trailing arm bushings are the ones that go bad. They are the ones that the lower arms on the rear suspension mount to towards the front of the car if that makes any sense. Usually you can see some cracking, but they can be a pain to see due to the location, and you have to press them in and out when you change them (At least here we have a lot of rust). The dealer here charges outrageous amounts to do them because they must drop the rear suspension out which you don't really have to do. It makes the bushings a lot easier, but makes the time for the job go way up.

 

This is a little different suspension setup than you have. I don't believe yours has a toe link. I work on so many of these It's hard to keep which ones have which parts strait. This is the closest/best pic I can find.

 

 

The bushing is where the trailing arm (lower control arm as they call it in the pic) closest to the toe link mounts to the body. I see these wear a lot faster than most other bushings on newer Subarus. Again a little different suspension, but hopefully it gives you an idea of a probable cause or a place to look!

 

-SB

[idosubaru]

Usually the rear trailing arm bushings are the ones that go bad. They are the ones that the lower arms on the rear suspension mount to towards the front of the car if that makes any sense. Usually you can see some cracking, but they can be a pain to see due to the location,

 

Great, thanks for the first hand feedback SB i'll be looking at those then.

Edited November 3, 2010 by grossgary

[idosubaru]

*** "success"? *** The lower control arm on the bad side is 1/8" shorter than the other side.

 

Looks like they should be the same. And the sway bar end link was replaced at one point. I bought this car wrecked and rebuilt the front end, it had been run off road at a high rate of speed, so this isn't a huge surprise.

 

I have two questions:

 

1. would 1/8" shorter cause uneven tire wear?

 

If yes:

 

2. how did the alignment shop miss this? could it "pass" alignment but still be wrong, doesn't seem like it.

 

So - next step is replace that control arm and see if it fixes it.

 

None of the bushings are obviously bad - there's some minor cracking but nothing obvious. Like you mentioned some are really hard to see because they're recessed under brackets or bolts, couldn't really tell visually. Prying and pulling yielded no noticeable play.

[Fairtax4me]

I wouldn't think that little difference would cause an issue, but... new sway bar link? Could the sway bar be bent? That might place more "weight" on the tire.

I would imagine it would have to be a significant bend to cause that, but it might be worth a shot to disconnect both ends and see if either side wants to hang down away from the end links.

[idosubaru]

but it might be worth a shot to disconnect both ends and see if either side wants to hang down away from the end links.

yeah hotdog that's a great idea! nothing looks out of the ordinary, i was inspecting it.

 

hope it's not super-loaded and hard to reassemble? guess it shouldn't be that big of a deal, just a couple bolts.

[nipper]

I dont remember, does subaru use the rear alighnment to help with the steering (passive angle change through suspension axis). If there is a bushing out of wack, it can be causing tire scrub.

[idosubaru]

no clue nip.

 

CRACK! i mistyped earlier, the LONGER control arm is the side that is wearing fast.

 

it also has an impact mark on it - like a lip of the metal is bent up. but how could a control arm "be too long"?

 

it has a curve in it so maybe it got "pushed up" around the curve and lengthened the effective length i was measuring?

 

on the bad side that's wearing - the front control arm - points forward and in front of the hub, has a bushing that doesn't look good. isn't broken, no give when i yanked on it, but the bushing is cracked and "sticking out" past the lip of the bore it's pressed into.

 

if the MOOG is a replacement part - then the sway bar end link was replaced on one side, but not the same side that is wearing faster.

[Fairtax4me]

I dont remember, does subaru use the rear alighnment to help with the steering (passive angle change through suspension axis). If there is a bushing out of wack, it can be causing tire scrub.

I wouldn't think they would go that far for a Legacy. Maybe on something more performance oriented like the Impreza WRX/STi. But what do I know?

 

hope it's not super-loaded and hard to reassemble? guess it shouldn't be that big of a deal, just a couple bolts.

As long as both wheels are off the ground there should be no load on the sway bar. If there is... something is wrong.

Honestly, I wouldn't bet too much on bushings. Both of the trailing arm bushings on my car are about shot and I have no abnormal wear that I can tell on the rear wheels.

Of course this is also an entirely different suspension... but rubber bushings don't tend to fail one at a time.

Edited November 4, 2010 by Fairtax4me