n192da

-Wheels have been mounted and balanced. Twice, to be sure.
-Tires/wheels were road balanced(matched?).
-Got an alightment job done

On the freeway, at 75mph, you can feel the steering wheel vibrating a bit. It seems to have gotten worse over the last 3,000 miles--in fact, I'm positive of this. I noticed over the last 1,000 miles or so, if I brake fairly firmly from freeway speeds (70-80mph) the steering wheel REALLY vibrates; and it's VERY unnerving depending on how hard I brake.

I ordered a new set of tires and they just came in. I'm going to get them installed tomorrow.

I was told by a tire guy that the tires I have are *cupped*, or have uneven wear. (I bought them used from an i-clubber in a wheel/tire deal).

Would uneven wear cause this type of shimmying with the steering wheel? Could it be anything else?

I mean, I'm pretty sure the tires are the problem, but I thought I'd throw my situation out to you guys to see what you thought. I don't want to spend several hundred dollars going in the wrong direction.



Also, a few other things:
- the car has never been wrecked, let alone driven abusively or off-road.
- this "problem" has been a problem ever since I installed the used tires/wheels.

Thanks guys!

Mikkito

How are your rotors?

n192da

Explain.

psoper

one of your front rotors is warped I'd bet....perhaps something got overtorqued on the changeover?

Calsoldier

iTrader: (6)

I'd say it's actually the wheels being out of balance by improper tire wear. I've had that a bunch of times when my suspension was out of alignement causing uneven wear and the shaking you're describing.

Oleg

n192da

AGH!!

Well then,

1) I don't feel the shimmy-thing on the brake pedal. Would that matter?

2) Would bad rotors cause steering wheel vibration on the freeway, under NO braking? (just crusing)

yayitzian

iTrader: (4)

no but if your rotors are warped and you try to brake, it will shimmy and vibrate. mine are warped right now.

n192da

Aw crap.

What causes this rotor warping? The car only has 46k miles on it.

EDIT: also, would the steering wheel shake be different when the car is cold, versus after you've been driving (braking) alot? It seems to be less prominent if the car is cold. I could verify this tomorrow to be sure.

EDIT EDIT: alsoooo... if it's a problem with uneven tire wear (cupping, problem with the tread/carcass), would it get worse as you heat the tire up? (as opposed to cold tires).

Flanders

iTrader: (6)

Have you hit any curbs or anything else in the last few months?

It does not seem like there is an easy answer for this one. If you have been going to the same tire shop the whole time try another, maybe a shop that is recomended on this site.

Have the new shop balance and rotate, if you go to a place that does more than tires have them check your rotors.

Ned

1fastGC

iTrader: (3)

warped rotors.. time to change it

1WRXNFX

Agree, check your rotors, maby need new, maby can resurface.

Wingless Wonder

iTrader: (7)

StopTech white paper on rotor warpage.

I don't know if the brakes or your tires are the actual problem but I don't ever have my rotors turned. If they have excessive runout that I can feel during hard braking due to wear or pad material buildup, I will just replace them with either another set of DBA 650 slotted series or the DBA 5010 SL (slotted) with an aluminum hat for some weight savings. There are several manufacturers that produce rotors that meet or exceed OEM specs. Don't go with bargain basement brands for high-performance use.

I don't like to have rotors turned because it reduces rotor mass that helps dissipate the enormous amount of heat under hard braking. That's why the factory specifies a minimal thickness to OEM rotors. I also think that even for street use, a turned rotor might not be up to the task of extended downhill grades under certain conditions.

--
0==WW==0
"…axles of evil…" - george w. bush

RussB

iTrader: (2)

i had that problem with my wrx. i had the rotors turned and it fixed the problem... for a little while. like the stoptech article that WW linked, they started to act up again. replacement fixed the problem for good.

NYImpreza

rotors can warp due to extended periods of breaking, like going down a hill. They heat up and the force from the cailpers can "bend" or warp the rotors. they then cool leaving them slightly out of trueness. This might be what's happening

n192da

Well, actually it's funny you guys mention that.

In those last 3,000 miles I've ridden across the Siskiyou Summit (elev. ~4500 ft) at least a half a dozen times. Needless to say, there's some periods of heavy braking, as I tend to run at a quick pace through the mountains (hey, it's fun!)

But, uh... wow, that's WEAK if the stock rotors can't handle some mountain driving.

WEAK WEAK WEAK

This sounds like a flaw to me. How the hell do you guys who do trackdays/autocross days not fry your rotors?


EDIT: so it sounds like it's definately not a tire problem, now. Hmm.

How much for new rotors (I don't need top of the line performance stuff, just something that works like the OEM did (or didn't, as it was)).

How much for turning?

EDIT EDIT: how hard is it to do the turning myself? Is there a HOW-TO on this?