Shudder when braking

[94jedi]

Hey all, I finally have some money set aside for maintenance as well as the time to drop off my car at my local Indy shop. Ever since I bought my car last October, it's had a slight shudder when hitting the brakes. It's only for a second or so, and smoothes out completely as you continue braking. The shudder feels "worse" the faster you're going. The suspension is original and the car just hit 100k mi . Could this be fcabs? After some research, that seems to be the consensus culprit. The front brakes were fairly new when I bought the car with about 91k on it. I've only put 10k mi on the car while I've owned it. Another question - this may or may not be related but the car vibrates a bit and it seems to correlate with speed. At 80mph, it's very noticeable. Obviously I avoid those higher speeds. Any thoughts guys? Thanks!

[Newjack]

Hey all, I finally have some money set aside for maintenance as well as the time to drop off my car at my local Indy shop. Ever since I bought my car last October, it's had a slight shudder when hitting the brakes. It's only for a second or so, and smoothes out completely as you continue braking. The shudder feels "worse" the faster you're going. The suspension is original and the car just hit 100k mi . Could this be fcabs? After some research, that seems to be the consensus culprit. The front brakes were fairly new when I bought the car with about 91k on it. I've only put 10k mi on the car while I've owned it. Another question - this may or may not be related but the car vibrates a bit and it seems to correlate with speed. At 80mph, it's very noticeable. Obviously I avoid those higher speeds. Any thoughts guys? Thanks!

It could be FCABs which are easy and fairly inexpensive to replace. Could be a warped rotor causing the shuddering, but if it stops shuddering by braking a little bit then I doubt its rotors. Maybe the brakes weren't bedded properly?

Shuddering at highway speed is almost certainly an alignment/wheel weight issue. Have an alignment done and get your wheels balanced, hopefully none of them are bent.

[slater]

if the shuddering stops, it is not a rotor - however, when the shuddering commences, do you back off the brakes, or apply more pressure?

FCABs could cause it, really bad RTABs could potentially cause it. bad tie rods/ends could cause it. any other issues with your car?

peter

[slater]

Shuddering at highway speed is almost certainly an alignment/wheel weight issue. Have an alignment done and get your wheels balanced, hopefully none of them are bent.

bent wheels or a wheel weight issue would be apparent before even touching the brake pedal. look elsewhere.

peter

[Newjack]

bent wheels or a wheel weight issue would be apparent before even touching the brake pedal. look elsewhere.

peter
I was referring to OP's second issue with vibrations that increase as speed increases. This could very well be an alignment/bent wheel issue.

I had vibrations at highway speed when I bought my car. The pervious owner broke the passenger rear wheel hitting a pothole and replaced it with an OEM style 135. He never had an alignment done after putting on the new wheel.

When I got new tires and got an alignment the vibrations stopped completely and the car is incredibly smooth at all speeds.

[slater]

doh. didn't even see the second issue. derrrrrrrrrrrrr.

[SoarinZHP]

Could be steering guibo?

[BCS_ZHP]

FCAB check - jack up one front side, get the wheel off the ground, grab the wheel at the 3 & 9 o'clock positions, try to shake/wobble it. If you hear clunking or excessive play, it's the FCABs, replace as soon as you can. Next grab your wheel at the 12 & 6 o'clock positions, again try to shake/wobble it. If excessive play then you have worn out ball joints and they should be replaced.

And do the check on both front sides, the passenger side nearest the shoulder and potholes tends to experience the most abuse/wear.
Bruce

[94jedi]

Thanks for the input guys. I'm thinking is suspension related, although today I noticed that I could feel it in the brake pedal when applying pressure and it did feel like it followed the rotation of the rotors. I'm not sure what it is, just hoping it doesn't cost me $2k to fix lol

[94jedi]

I'm doing the car off at the shop on Friday morning and they'll have it all week while I'm in vacay.

[94jedi]

So as we all figured, the FCABs are completely shot so I'll have the shop replace those with z4 units. Also figured it was time for some 100k mile stuff: trans fluid, and diff fluid service. Also had the VCG done as well. My mechanic says the cooling components are in good shape so I'll hold off on that for a bit. So that's about $800+ worth of maintenance... Yikes...time to get back into DIY lol

[Smilez]

Everything you mention can be done at home if you have the time. When my bushings were going out i started to feel a vibration at around 80mph, then they went to hell quick.Maybe three 3 weeks later i couldn't drive pass 70mph without vibration. I replaced them in Meyle HD and haven't needed to do them since.

[94jedi]

Everything you mention can be done at home if you have the time. When my bushings were going out i started to feel a vibration at around 80mph, then they went to hell quick.Maybe three 3 weeks later i couldn't drive pass 70mph without vibration. I replaced them in Meyle HD and haven't needed to do them since.

Yep, I figured that. Unfortunately DIY was not an option at this time since I'm in the middle of moving from MD to NC and don't have a garage. To add to that, I've just returned from a 1 week vacay so unfortunately, I'm short on time as well. Once I get settled into my new home, I'll have a garage again and access to my tools. For now, I'll have to take the sting of indy shop prices. What I'm not sure about is the selection of FCABs. I really wanted to go with powerflex polys but everyone seemed to be high on the Z4 or Meyle HD's. I went w/ the Z4's thinking it would be a slight performance improvement over the Meyle HDs.

[slater]

glad you got it sorted.

enjoy the new garage, get it organized and then use it for that cooling system stuff. :)

peter

[94jedi]

Got the car back, brake shudder is completely gone. It still doesn't ride perfectly smooth so tire balance and alignment is going to happen in the near future. I have a bad feeling that I have a bent rim or two though. For those of you that have replaced 135's, did you go with oem or reps?

[Vas]

Usually go with aftermarket wheels like apex, vmr and other brands.

[94jedi]

Gotcha. Thanks for the input. Some csl reps might look nice. I also like the bbs lm look... But I'm on an "Alzor" budget lol. Wonder if those are decent?