Front end vibration when braking.

[Thunder-71]

Car developed a front end vibration when I brake, not terrible but quite noticeable. I figured warped front discs so I replaced them with new Brembo made in Italy (only discs I could find with 2 years warranty AND not made in China). The vibration is still there. No vibration while cruising even at high speeds and no whining noise to suspect bearing. I am puzzled. What the heck else can it be? Bearings? Front Struts? Any of you had this? Any ideas?

[Dmitry at Pelican Parts]

Have you looked at the control arm bushings?

[v2rocket_aka944]

Rotors don't really warp under typical usage - what is oft-described as warped rotors is really uneven pad deposits on the metal surface.
Basically...you hit the brakes really hard at some point, perhaps repeatedly, and then came to a stop and held the brake pedal, squeezing the rotors with the pads.
Because everything is so hot, the pad material leaves a sort of fingerprint on the rotor in that spot.
When you come off the brakes the pads are basically still riding the discs but there might be a fraction of a millimeter clearance sometimes so you don't feel each time that fingerprint rubs the pads. But when you hit the pedal, the pads squeeze and have to "jump" over that fingerprint a little bit with causes the steering wheel shake and vibration.

Resurface the rotors and maybe scuff the pad friction surface up a little and should be good...
And re-examine (or pay attention to) your braking and stopping habits, people who get repeated "warped rotors" are doing the same process (hard braking and then extended hot stop) habitually.

As far as rotors...regardless of where they are made (most will be China now) if you buy them from a good place like here on Pelican or your local auto store the quality will be fine. It's just a chunk of cast-iron that happens to be the right shape and have holes in the right place for your car.

[Thunder-71]

Originally Posted by Dmitry at Pelican Parts

Have you looked at the control arm bushings?

No but I will, Thanks.

[Thunder-71]

Originally Posted by v2rocket_aka944

Rotors don't really warp under typical usage - what is oft-described as warped rotors is really uneven pad deposits on the metal surface.
Basically...you hit the brakes really hard at some point, perhaps repeatedly, and then came to a stop and held the brake pedal, squeezing the rotors with the pads.
Because everything is so hot, the pad material leaves a sort of fingerprint on the rotor in that spot.
When you come off the brakes the pads are basically still riding the discs but there might be a fraction of a millimeter clearance sometimes so you don't feel each time that fingerprint rubs the pads. But when you hit the pedal, the pads squeeze and have to "jump" over that fingerprint a little bit with causes the steering wheel shake and vibration.

Resurface the rotors and maybe scuff the pad friction surface up a little and should be good...
And re-examine (or pay attention to) your braking and stopping habits, people who get repeated "warped rotors" are doing the same process (hard braking and then extended hot stop) habitually.

As far as rotors...regardless of where they are made (most will be China now) if you buy them from a good place like here on Pelican or your local auto store the quality will be fine. It's just a chunk of cast-iron that happens to be the right shape and have holes in the right place for your car.

I understand the braking habits on which you are right, the rotors are smooth no heat marks, no deposits. Still I installed brand new rotors and the vibration is still there.

[v2rocket_aka944]

Hmm..
Perhaps the slide pins on the caliper are sticking and the caliper is getting "cocked" rather than applying the "passive side pad" evenly.

[Slam]

When was the last time your front wheel bearings were adjusted? If they're loose/sloppy/worn out then they can cause what you're describing. Adjustment is pretty easy, and Google is your friend, but try not to get too caught up in the whole pre-load vs no pre-load debate. You'll go mad wondering if you got it right...

Cheers!

[944fan]

I had the same issue for a long time. What helped was to replace my whole front suspension, it was about time anyway. All my front was tired and worn out. Plus good alignment and balancing on all tires.

[944fan]

Dont buy from ebay parts because are cheap unless you are looking for trouble. I learn that the hard way especially when you work on suspension or any part of the car. Pelican parts super good prices and proven track on the parts.

[944fan]

By the way if you want life time warranty on any german car on almost 90% of parts go *******.com . Between pelican and fcp i set up my car super nice and no problems

[roobarb]

Originally Posted by Thunder-71

I understand the braking habits on which you are right, the rotors are smooth no heat marks, no deposits. Still I installed brand new rotors and the vibration is still there.

Did you manage to solve the issue? I have the same problem and my discs and pads look great

[Thunder-71]

Originally Posted by roobarb

Did you manage to solve the issue? I have the same problem and my discs and pads look great

I have not solved it yet and truthfully I am not sure how to. It has to be front suspension like control arm bushings, Dmitri suggests to check them, how do I do that? or tie rod ends. Another Pelican asks if bearings are adjusted, yes they are properly adjusted, another asks if bearings are worn but if they are shouldn't they be noisy? I 'll see if I can figure it out and let you know. Any ideas will be appreciated especially what is the best way to check the control arm bushings. My 1984 has the serviceable steel control arms.

[PaulHunt]

I would seriously take a look at the wheel bearings. Had the same issue with my Yukon, thought it was the brakes but it turned out to be the hub and bearings.

[roobarb]

Originally Posted by PaulHunt

I would seriously take a look at the wheel bearings. Had the same issue with my Yukon, thought it was the brakes but it turned out to be the hub and bearings.

I noticed a little play in the front wheel hub When the car was raised. Shot a video of it and will upload here (couldn't get it to upload from my phone). Is there supposed to be any play at all? I feel like I should adjust according to the last step in this pelicanparts tech article. Same procedure as on a -85 N/A?
http://www.pelicanparts.com/techarticles/Porsche_944_Turbo/88-SUSPEN-Front_Wheel_Bearing_Replacement/88-SUSPEN-Front_Wheel_Bearing_Replacement.htm

Here's video. Look at the rim, you'll see the movement
https://www.youtube.com/watch?v=yyHfTNg78nQ&feature=youtu.be

[roobarb]

Update: Tightened the big "nut" a little, and it eliminated almost all vibrations in the steering wheel when braking. So this was the issue on my car. Quick and easy fix!

[PaulHunt]

There shouldn't be any play. Got the same problem with a newer Yukon. You can feel it when you hit potholes and bumps.. Just don't want to shell out the 500 to fix right now.