Shuddering Problem While Braking

[Subaru_Nation555]

I drive a 1994 Legacy SS with 121,000 miles on it and recently I have been having a problem with the steering wheel vibrating and suddering when braking and crusing at 60ish mph. The problem happens when braking anywere from 20-80mph and at speeds of 55-65mph. There is a little vibration from the brake pedal but mostly from the steering wheel. Its the worst under moderate pedal pressure-if you slam on the brakes the problem is much less evident. On the highway it's really bad and sometimes makes the CD player skip. Today I had all four wheels alignded and balanced but that made no noticable difference. I was thinking it was one of a couple of factors:

alignment-but that didnt help, the problem was really only under braking.

suspension-I recenlty had GR-2s installed in the front. Possible something is worn or loose?

ball joints-the guy at the tire store suggested that this might be a problem but I dont really know anything about ball joints

warped rotors or varaible thickness-I have had warped rotors and this just dosn't feel the same-rotors have about 15K and pads have about 1K miles on them. Pads are EBC Greenstuff and rotors are Brembo OEM replacements

bent wheels-The stock 15" wheels are original and have been through alot, possible that they are bent?

Any other thoughts or suggestions would be appreciated. Thanks.

[evolutionmovement]

Flat spot, badly imbalanced, ball joints, or bent wheels. They shouldn't have done an alignment if you had bad ball joints.

Steve

[professor]

warped rotors usually feel the same no matter the speed or pedal pressure. bent wheels will rock you when they find a resonant speed.

your problem really sounds like ball joints or tie rod wear, either one will allow the hub to judder badly especially under light braking, ball joints being more likely. look for ripped boots.

if you place the front end on jack stands you should be able to investigate the play with your bare hands, you can see the movement at the worn joint by grabbing and torqueing the tires

you will need to check the alignment again after replacing the ball joints

[Subaru_Nation555]

I placed the front up on stands and twisted the wheels back and fourth. It didn't seem like there was any excess play but I not 100% sure what to look for. If it is the ball joints that are worn and need to be replaced, what might they cost. I was kinda hoping it was the wheels-I want an excuss to to upgrade to some WRX rims

[evolutionmovement]

You need to shake the wheel up and down for the ball joints. Back and forth will tell you if you have a tie rod issue. You should not be able to move the wheel in the vertical direction at all and only with effort side to side. Any slop is a problem. I wouldn't worry about needing a new control arm, though, if you wore out a ball joint that bad, you'd have picked it up easily even shaking it side to side.

Steve

[Subaru_Nation555]

I tried moving the wheel up and down and there was no movement at all. Its strange because the problem is less evident now then it was a couple of days ago. Hopefully I will be getting some new wheels and tires soon and maybe WRX brakes. Thanks for your help.

[vrg3]

I'm thinking it probably is the front brake rotors. You generate a lot more heat when braking at highway speeds than at low speeds, and that tends to bring out the problems of disc thickness variation. Very hard braking can sometimes even it out some too.

If you're planning on putting on a pair of WRX front brakes anyway, then you may as well see if that resolves this problem.

Did you bed these EBC pads in well when you installed them?

[evolutionmovement]

Good point, Vikash, my car shook from bad brakes even when not on the brakes (but much worse when I was). I was pissed as I swapped my bent wheels out before I did the brakes and was hoping the wheels would've cured the shaking.

Steve

[Subaru_Nation555]

Did you bed these EBC pads in well when you installed them?

Prob not as well as I could have, but they were fine for the first couple hundred miles. As of now the brakes are nowhere near where I want them to be. I should have just waited to upgrade to WRX ones.

[jmaziarz]

I have a very similar problem with my 93 Legacy L. I have replaced the tires, rotors and pads but the problem persists. Just to add a bit more detail I also find that:

1) The speedometer needle wobbles at speeds < 40 mph
2) The car steering wheel vibrates at all speeds (the faster the speed the greater the period of vibration)
3) When coming to a stop, the car "bounces" (I don't know how best to describe it other than it is like I were bobbing my head to music)
4) The vibration can be felt slightly in the break pedal also

[LedJetta]

this happened all the time with my 91 wagon, that thing ATE rotors.

[evolutionmovement]

So did mine until I got my rotors cryo-treated.

Steve

[tris91ricer]

My rotors are actually loose on the wheel, I found out. They shudder and shake at just about any speed, but I've been meaning to replace a buncha things, anyhow. Tie rods and Ball joints it is!

[evolutionmovement]

If the rotor is loose then your wheels are loose!

Steve

[tris91ricer]

Uh-oh.. Well, I'mma borrow a torque wrench then.. They were tight after I put new pads on, but they seem to have this habit of loosening up... hmmm..

[evolutionmovement]

Torque spec is like 65 or something, but I use 90 or so. Also if you don't have the right lug nuts for the wheel seat angle then they won't hold right either.

Steve