OT: Wacky WRX tire wear, So much for those wear bars! Options

[bondo]

I had noticed the rear tires on the WRX (Julie's daily driver) were getting near the wear bars. The fronts were not quite there yet. We decide that new tires are due in the near future, but haven't gotten around to getting them.

So last weekend we drive to Riverside and back (approx 450 miles). On the way down I notice a bit of vibration around 75 mph. Knowing new tires are due, I figure it's that and assume it will go away when we get new tires. On the way back, it's a little worse. Then it starts to really rumble arould 70 mph, but only on very slight right turns (a gradual lane change on a straight part of the freeway does it, but tighter turns don't)

So when we get gas (about 10 miles from home) I decide to take a close look at the front end. I thought maybe a bearing or suspension component was bad, as the wear bars are all unworn all the way across on both front tires. When I grab the tire to do the "tech inspection" wheel wiggle, I cut my pinkie on something sharp. So then I turn the wheel all the way to the left (I'm looking at the left front tire) so I can see the inside edge.. and it's showing belts! I did the same on the other front wheel and it has the same problem, but to a lesser degree.

Now I know bad camber can cause uneven wear.. bit the wheel looks straight. I checked it with a framing square, and the top is only about 3/16" in from the bottom on the left side, and maybe 1/8" on the right. I have driven cars with much worse camber problems and they didn't wear THIS unevenly. The car stracks straight, and doesn't get bad gas mileage (25 mph on the highway, good for a WRX), so I don't think it's a toe problem. We have been known to take corners fast, but in my experience that wears the outside edge of the tire, not the inside. Maybe the all wheel drive somhow factors into this?

Ok, enough text, time for some pics.

First pic: Wear bars all the way across (It's nearly impossible to see this wear with the wheel pointed straight)

[bondo]

Second (and last) pic: Tire from the top, showing the worn profile. (It looks like somebody took a beltsander to it at a 30 degree angle) Anyone have any ideas what cause this?

[mightyohm]

Just out of curiosity how do the rears look?

I am not riding in that car with you again.

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[Jeroen]

is the tire rubbing somewhere on the chassis or suspension?
maybe on full lock?

this doesn't look like a camber or toe problem to me
(the wear on the rest of the tire is very nice and even)

[qa1142]

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

Check for rubbing on swaybar, inner fender, etc while wife is at full lock and full power going up Pikes Peak

[bondo]

Hehe. Rears are worn evenly, just down to the wear bars. No odd wear onthe rears at all.

The only signs of rubbing is a little bit of the plastic fener liner, but where it rubs is on the actual sisewall, like where the letters are.

[Kostamojen]

Very odd, ive never had wear quite like that with my Impreza...

Are there any mods to the suspension or wheels/tires, or is it stock?

First thing I would do right after you get new tires is get an alignment. However, DONT get a stock alignment, and try to get some adjustable rear camber bolts on the car before you get the alignment (without them, Imprezas do not have a way of adjusting rear camber, its a good thing to have). Try for even Toe all around, with ~.75 to -1 degree of camber up front, and ~-.5 in the back (With it even of course to the other side, but the general idea is just slightly more front camber than rear camber). Thats the setup I've had for my car and I get ideal tire wear.

Also, what tire pressure have you been running? With that kind of excessive wear on the outside of the tread it looks indicative of not enough tire pressure. FYI, the "recomended" tire pressure on the WRX is not ideal with even the stock tires, about 5psi too low all around.

[bondo]

I think the suspensions is stock. It does have a salvage title though, so things could be bent. The wheels are definitely stock. I checked the pressure.. 25 psi.. too low. But why didn't the outside wear too? Any suggestion of where to get those rear camber bolts? What are the full reccomended alignment specs (caster, toe, etc.) for a street car?

[Kostamojen]

QUOTE (bondo @ Aug 15 2005, 06:28 PM)

I think the suspensions is stock. It does have a salvage title though, so things could be bent. The wheels are definitely stock. I checked the pressure.. 25 psi.. too low. But why didn't the outside wear too? Any suggestion of where to get those rear camber bolts? What are the full reccomended alignment specs (caster, toe, etc.) for a street car?

Hmm, salvage title... Check the frame and the control links/arms to see if anything looks odd.

Heres a good price for camber bolts, and a local shop (IE cheaper shipping) http://www.mpjperformance.com/cgi-local/mi...Code=SUBSUSMISC

If the tire pressure is too low AND the alignment is off, it could mean alot of the tire is riding on the inside... The inside of the front tire is usually the first place to wear out anyway with Subarus.

Heres a short list of different alignment recomendations: http://www.ravensblade-impreza.com/techdoc...lign/align.html

If you want to know what other folks have done, read a few threads on nasioc's suspension forum, TONS of info there: http://forums.nasioc.com/forums/forumdisplay.php?f=32 (Note, the tire forum is seperate from the suspension forum: http://forums.nasioc.com/forums/forumdisplay.php?f=88 )

[bondo]

Cool, thanks!