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Discussion Starter #1
I installed new StopTech rotors (plain, no drill no slot) and Project Mu pads in summer 2015. I did indeed bed them at the time. Somewhere around early 2017 I started getting funny behavior in traffic where the car would start to vibrate after a few stops and brake performance would drop, so I "fixed" this by "bedding" the brakes: I got off the highway and did a few heavy stops, it went back to normal. Eventually this stopped happening.

Somewhere near the end of the year, I started getting persistent vibrations when driving over 70, especially when stopping from highway speeds. I assumed that the previous problem had warped a rotor, so I replaced the passenger side with a cheapo from Advance Auto. Nothing changed. A few weeks later, I got a flat tire, so I replaced all 4 wheels and tires. Nothing changed. Instead of throwing more parts at it, I ordered a dial indicator: all 4 rotors are within 0.001" of runout. I did a rotation of the new wheels and tires, it still vibrates the same. I jiggled the front wheels, no bearing play that I could notice. None of the wear surfaces are worn out of spec. It vibrates too much for me to feel comfortable bedding them again.


TL:DR; Rotors are within 0.001" runout, no bearing play, tried with 3 different wheels/tires per side.

I figure it's probably still a rotor, bearing, or suspension bushing somewhere. I just have no idea how to isolate it. Help?
 

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This doesnt make alot of sense. You have a vibration at 70mph and a vibration while braking. That could also be 2 different vibrations. You also replaced a RF rotor for the brake vibration, why? I dont understand why you wouldnt do brakes in pairs. You also got a flat tire and decided on replacing all 4 wheels and tires....why all 4 for just a simple flat?? I think there is alot of info missing here that may lead to different conclusions.



For the brake vibration concern, when braking at highway speeds do you feel any feedback/shimmy in the steering wheel or do you feed more of a brake pedal pulsation?
Also did you check to make sure your rotors are not at the min spec?
 

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Discussion Starter #3
I'm thinking they're the same vibration because they're perfectly in phase when braking down from highway speeds to a stop.

I replaced the RF rotor but not the LF because I was on a road trip and just happened to have a friend in South Carolina with a garage, but his local parts stores only had one rotor, so I felt for which wheel had the worst feel and swapped that one: an educated wild guess.

Replaced all 4 wheels because it was time for winter tires anyways. It was December and I made my way down in Florida at that point, my tire got attacked by a gator, so I shipped my winter tires back from Massachusetts for a safe drive home.

Rotors are 1.20" and 1.19" front, 0.77" and 0.79" on the back. Wear limits are 1.1" and 0.71", pads have at least 60% left on them.

I feel the vibration mostly in the steering wheel, not so much the pedal. I also feel a bit in the seat, I hear my seat belts rattling in the back.

I did try to do some "bedding" last night, I know that's a favorite fix for all these types of issues. The car did prefer pulling to the left when the brakes heated up, and the vibrations got EXTREMELY bad when the brakes were hot, even at 30mph. After a 5 minute cool down, everything felt like it originally did, maybe slightly less chunky feeling.

I feel like that's leading me to believe it's either a bearing or rotor on the driver side
 

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I'm thinking they're the same vibration because they're perfectly in phase when braking down from highway speeds to a stop.

I replaced the RF rotor but not the LF because I was on a road trip and just happened to have a friend in South Carolina with a garage, but his local parts stores only had one rotor, so I felt for which wheel had the worst feel and swapped that one: an educated wild guess.

Replaced all 4 wheels because it was time for winter tires anyways. It was December and I made my way down in Florida at that point, my tire got attacked by a gator, so I shipped my winter tires back from Massachusetts for a safe drive home.

Rotors are 1.20" and 1.19" front, 0.77" and 0.79" on the back. Wear limits are 1.1" and 0.71", pads have at least 60% left on them.

I feel the vibration mostly in the steering wheel, not so much the pedal. I also feel a bit in the seat, I hear my seat belts rattling in the back.

I did try to do some "bedding" last night, I know that's a favorite fix for all these types of issues. The car did prefer pulling to the left when the brakes heated up, and the vibrations got EXTREMELY bad when the brakes were hot, even at 30mph. After a 5 minute cool down, everything felt like it originally did, maybe slightly less chunky feeling.

I feel like that's leading me to believe it's either a bearing or rotor on the driver side

If you are feeling a vibration in the steering wheel when applying the brakes at highway speed after they have gotten hot, i would recommend replacing front brakes complete, pads and rotors. Alot of time brakes can warp and even develop grooves on the inner and outer face of the rotors that can cause vibrations will braking.



Some will say to have the rotors resurfaced and you'll be good to go. I dont always find that to be the case. I have cut rotors myself for vibration complaints and i tend to find that the grooving will come back eventually. I just recommend replacing the brakes.



BTW a gator attacked your tire!?! :eek:
 

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Check your bushings in your lower A-Arms. I had this behavior in a BMW. I just started to get it and mine are worn.
 

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Check your bushings in your lower A-Arms. I had this behavior in a BMW. I just started to get it and mine are worn.

What kind of bmw? I've never seen bad bushing or joints in lower control arms cause a vibration will driving or while braking. If anything, it would be more of a noise.
 

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In BMWs the thrust bushing is common to wear to cause these issues. Now normally it only happens at higher speeds like a slight vibration when brakes applied 50+ mph. It feels like warped rotors.

I now have a slight wobble when I apply brakes 50+mph, just like the thrust bushing in a BMW. The rear most control arm bushing is in a similar location and performs a similar function.

Does the vibration dissapear at lower speeds? At under 45 mph my car feels fine.
 

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In BMWs the thrust bushing is common to wear to cause these issues. Now normally it only happens at higher speeds like a slight vibration when brakes applied 50+ mph. It feels like warped rotors.

I now have a slight wobble when I apply brakes 50+mph, just like the thrust bushing in a BMW. The rear most control arm bushing is in a similar location and performs a similar function.

Does the vibration dissapear at lower speeds? At under 45 mph my car feels fine.

Not to get off topic here but i think you may a bit misinformed. Thrust arm bushings only job is to absorb forward movement "thrust" When they go bad, they tend to leak or even show signs of cracking and stress cracking on the rubber side of the bushings. Normally you can feel that they are bad by simply driving at a very low speed and just hitting the brakes real hard. You will hear and feel a very loud thump. If you are standing on the outside you may even be able to see the front wheels even move forward a bit after the brakes have been applied. Obviously that all goes out the window if the bushings is completely collapsed and popped out lol. Maybe what you may have experienced was an issue with a ball joint on a lower control arm or something along the lines of excessive play in the suspension due to worn components. You also cant rule out a bad bearing hub or impact damage. I have seen bad bearings and hubs causing brakes to warp due to uneven rotation while driving and braking .



I've been replacing thrust arm bushings for years on E60-G12 and so on. I've never replaced them for a vibration or a brake vibration. Them causing suspension noise is a different story :)
 

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Discussion Starter #10
FYI folks, the actual problem was probably a defective rotor. There was a chunk missing out of the back side of the rotor, which would explain why it was true when I measured it but still pulsated.

The pulsations already caused the other rotors to wear unevenly, so it looks like all new rotors for me.

It also may or may not have caused some side effects with my power steering, which is now drinking fluid. My own fault for letting it vibrate this long.
 
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