Front end vibration while braking at low speeds.... even after new rotors/pads

[TheSubaruJunkie]

So I've had this real annoying vibration in the brake pedal and steering wheel as I come to a stop from about 45. If I brake from 70 i dont feel much until i get down to 45 and then the front of the car shakes violently until probably 15mph, where i can still feel alittle pulsating in the brake pedal.

 

This has been an ongoing problem for a while, and of course I always thought of warped rotors. Last weekend I put brand new rotors and pads on, and still... same thing. Almost no change at all.

 

There are no problems at all when accelerating, or cruising. The car is smooth with no vibration at all... until i need to slow down or come to a stop.

 

Kinda stumped here.

-Brian

 

p.s.

Its a 1993 Legacy Turbo Wagon

[elmwood22]

Have you tried balancing the tires?

[McDave]

Have you tried balancing the tires?

Yeah, does it shake even when coasting down without using the brakes?

[TheSubaruJunkie]

There are no problems at all when accelerating, or cruising. The car is smooth with no vibration at all... until i need to slow down or come to a stop.

 

 

No problems while coasting. If I take my foot off the pedal while braking, the vibration disapears... I can coast down from 35 to 0 just as smooth as I can accelerate from 0 to 60.

 

Yes, I had new tires installed the day after I put all new suspension on the car. Full alignment as well. That was about 5 months ago.

[yohy]

Just a thought. If you over torque the lug nuts you have the chance to warp the rotors, especially true if an impact wrench was used. I would back off on the lug nuts, then re-torque to proper specs.

[McDave]

Must get caffeine before posting in the morning.

 

Did you clean the rotors before installing them, and keep them clean during assembly?

 

Since you say it is better with the new brakes, but not fixed, there is a chance the new rotors could have runout. I do have to resurface even new rotors from time to time. Do you know someone with a dial indicator that can measure runout with the rotors mounted on the car?

 

Also if you live in the rust belt or do offroading, there could be a build-up of rust or dirt on the hub mounting surface. This would show up when checking the rotor too, so remove the rotor and check the hub surface for debris and runout next.

 

Are you getting any bearing noise?

[TheSubaruJunkie]

Must get caffeine before posting in the morning.

 

Did you clean the rotors before installing them, and keep them clean during assembly?

 

Since you say it is better with the new brakes, but not fixed, there is a chance the new rotors could have runout. I do have to resurface even new rotors from time to time. Do you know someone with a dial indicator that can measure runout with the rotors mounted on the car?

 

Also if you live in the rust belt or do offroading, there could be a build-up of rust or dirt on the hub mounting surface. This would show up when checking the rotor too, so remove the rotor and check the hub surface for debris and runout next.

 

Are you getting any bearing noise?

 

All good points. I didnt think to check for any debris on the hubface when I installed the rotors. But that would make sence.

 

I did clean the rotors with brake parts cleaner before installing. I even had a buddy handle them when installing cause my hands were filthy.

 

I know for a fact I did not overtorque the lugs. I may have to pull everything to check the hubs though

[OB99W]

No problems while coasting. If I take my foot off the pedal while braking, the vibration disapears... I can coast down from 35 to 0 just as smooth as I can accelerate from 0 to 60.

That makes it very unlikely wheel balance or other tire issues have anything to do with the problem.

 

 

Yes, I had new tires installed the day after I put all new suspension on the car. Full alignment as well.

Please define "all new suspension". Exactly what was changed?

 

 

That was about 5 months ago.

Was the problem there before that time?

 

I agree that any dirt/rust between the hub and rotor will lead to rotor runout. You can feel as little as 0.001" of runout, and 0.002" is really too much.

[McDave]

I may have to pull everything to check the hubs though

If/when you do get to this point, go ahead and take the rotors to someone that has a brake lathe (preferably the parts store you bought them from) and have them chuck up the rotors onto their lathe and have them checked for runout. If there's more than a couple thousandths runout, then I would return the rotors(s) rather than resurface it/them.

[TheSubaruJunkie]

That makes it very unlikely wheel balance or other tire issues have anything to do with the problem.

Yup, my thoughts exactly

 

 

Please define "all new suspension". Exactly what was changed?

New struts and springs at all four corners.

 

 

Was the problem there before that time?

 

Yes.

[OB99W]

New struts and springs at all four corners.

Okay. I asked because slight brake surface irregularities can lead to significant vibrations when you throw in some front end looseness. If the problem is still there once you've verified that significant rotor runout isn't a problem, make sure that ball joints, tie rod ends, etc., don't have excessive play.