Vibration after AP Racing BBK install.

[RADRACR]

Installed this April. I'm noticing a vibration (steering wheel) during braking as of late. I performed the initial bedding procedure after install, and only street driving ever since. Not tracked yet.

Right before the car comes to a complete stop, it feels like a section of a rotor is "stickier" than the rest of the rotor, causing a "jerky" stop. This is the best I can describe it.

Do I need to re-bed or does this sound like something more serious? Crossing fingers as this kit cost a small fortune.

[fullerra]

What pads are you using?
I don't necessarily think it would be from the kit itself. A song as the calipers are firmly bolted on there should be no vibration. The two possibilities I can think of are a worn front suspension bushing and/or a slight warping of the rotor that hasn't heated evenly. (happened to me the first session of a cold track day, but went away mid session).

[NickyC]

Probably a warped rotor.

[GuidoK]

Originally Posted by fullerra

A song as the calipers are firmly bolted on there should be no vibration.

It is possible for a caliper to vibrate/cause vibrations when it is firmly bolted to the suspension.
The m3/135i bmw performance calipers have 2 little weights bolted to them specificly to counter possible vibrations:


There are people who remove them and don't experience vibrations, so the need for them is questionable, but they are there against possible vibrations. The new m3/m5 etc calipers don't have those weights.

However I think it is more likely that something else is wrong, like a warped rotor. That might be difficult to measure on a floating rotor. (fixed is easy).
Maybe unscrew the rotor itself and put it in a lathe and measure? (still you have to align the clamp, so the warping can become non measureable.)
Maybe with a knive edge ruler? Or the standard way with a dial like you do on fixed rotors?

[inTgr8r]

With only street driven, I highly doubt that it's a warped rotor.
Much more like ly to be pad deposit.

Have you had the pads frozen to the rotors after getting wet?

[RADRACR]

Originally Posted by inTgr8r

Have you had the pads frozen to the rotors after getting wet?

How would I know? I don't recall anything abnormal.

Can spraying the rotors at a car wash warp them? Obviously it's a no-no on super hot rotors, but even on daily-drive-temperature?

Today I did some "street bedding" while I was out but it didn't make much difference.

What sort of specialty shop would I need to find to diagnose a warped rotor?

If it's pad deposits, how to fix?

[Beedub]

theirs definitely not warped.... ignore any comments that suggest so....

i would guess raised deposits from washing?? the AP rotors seem to really oxidise quickly when wet and left standing...

on a side note i have never experienced what your talking about and have had my rotors glowing on numerous occasions, when you did the install did you follow the instructions and measure run out and shim the calliper correctly, this is a key part of the install.

[RADRACR]

I did not properly check run-out during install, but if it was run-out wouldn't I have noticed immediately instead of months later? I did shim the calipers.

[GuidoK]

Have you already had the rotors off the car? That's where you have to start

Inspect the inner&outer side for rust or deposit.
Inspect the mounting flange for debris/rust (although if there was any debris there you should have noticed from the beginning)

If they're clean, measure the warp in the rotors.
Do you have a floating or fixed disc in front?

[Beedub]

another word of advice i always go for a alittle drive after washing to remove the rotor rust and blow out any standing water in the cars settle spots. good practice if you don't do this imo.

[RADRACR]

I'm looking for path of least resistance for diagnosing and/or solving my issue.

Sounds like my first step is to get a run-out tool. If it looks good, will new pads solve the issue? Or does debris effect the rotor as well?

[exdos]

Have you lost any balancing weights off your front wheels?

[RADRACR]

Originally Posted by exdos

Have you lost any balancing weights off your front wheels?

Good call. I have noticed vibration in the steering wheel during cruising. Would off-balance tires have a dramatic effect during braking? I feel it more in the steering wheel than the brake pedal.

But that doesn't explain the "surging" at very slow speed right before complete stop... or does it?

[exdos]

For any vibration felt through the steering wheel my first port of call would always be to check that the wheels are bolted on properly and the wheels are properly balanced to within 5gms at least. Once you've ruled those things out you can then delve deeper.

[Beedub]

Originally Posted by aestheticstorm

Good call. I have noticed vibration in the steering wheel during cruising. Would off-balance tires have a dramatic effect during braking? I feel it more in the steering wheel than the brake pedal.

But that doesn't explain the "surging" at very slow speed right before complete stop... or does it?

no but the type of surge you indicate something rocking or loose and your feeling it due to the low speed application.??? plausible? is everything Tqed up to spec.?

[The HACK]

Slotted rotors?

[RADRACR]

Originally Posted by The HACK

Slotted rotors?

Yes

[The HACK]

Originally Posted by aestheticstorm

Yes

Check and see if there's any weird wear patterns trailing each slot. If there is, swap to a new set of pads.

I don't know how to explain it. It's not the rotors per se, but some how with slotted rotors, sometimes it creates a weird wear patter on the pads (because the slots attempt to scrape away a thin layer every time you brake) that causes it to catch the lips of the slots and create a weird vibrating sensation when braking.

if changing pads don't help, you can take a small grinder and grind off or smooth out the trailing edge on each slot just a little bit. Some heavy braking and re-bedding usually fixes it for me.

[RADRACR]

Thanks for the troubleshooting guys. My next steps will be:

1) Check tire balance.
2) If pass, check run-out.
3) If pass, try new pads.
4) If pass, modify the slots.

I'll report back.

[RADRACR]

Well, my brake debacle has come to an end. For now. I will never buy an international part again. Unfortunately, I waited 6 months to install. Then this problem happened just over 6 months later. So I was technically out of warranty. Heaven forbid I get a break.

First, the runaround: I called AP Racing UK, who directed me to call Stillen, who directed me to call AP Racing UK, who directed me to call Essex, who directed me to call AP Racing UK, who directed me to call Stillen, who directed me to call M0dbargains (where I purchased), who didn't care at this point. So I gave up.

Stillen was the most ridiculous of the bunch. The UK-built kits are another brand as far as they're concerned. They won't touch them. I asked if they resurfaced discs. He said yes. I asked if he'll do mine. He said no, because I'm not a customer. "What difference does it make where a disc was purchased?" "Resurfacing is something we don't like doing." Huh?

After several hours of research about how resurfacing a disc is done and who does it, I finally found a small outfit in Michigan. So I got that done and got brand new pads and the vibration is gone. Since I never drove the car hard since install, I'm convinced that the rotors were bad out of the box, and it took some driving to make the runout worse until I noticed.


BEFORE





AFTER

[3002 tii]

You don't need to go to a specialty shop to turn/resurface rotors. A lot of garages should do that. My guess is you had pad deposit (driving in cold or wet and brakes never fully warming up to optimal temps) OR uneven pad wear caused by slotted rotors.

[RADRACR]

My research indicated that you don't want to cut, turn, or use whatever standard equipment you'll find at garages, especially on slotted discs. The best method is Blanchard grinding or similar. This gives you:

• truer parallelism
• less material removed from the disc
• crosshatch for more even pad bedding

Also, I've been driving for 18 years with lesser brakes in areas of the US with extreme seasonal changes and never had dramatically fucked up brakes like this. I refuse to believe that somehow driving in dry Idaho summertime left such deposits. And Beedub never had this problem with the same kit.