Seeking advice re BBK and brake vibration on circuit

[timbo_3101]

Hello fellow racers,

I am enquiring as to whether any of you E9x M3 racers experience brake vibration on circuit, from any cause ... whether it is extreme temperatures distorting hardware, brake deposits, or rotors warping, etc.

Having attended 15 events in my 1M (KW Clubsport, Michelin PSC+, and Pagid Yellow RS19 with performance fluid and braided lines), I am still having vibration with moderate braking. This is my third set of OEM front rotors, and my options are to pursue race-grade rotors or a full BBK upgrade.

I am hoping that the greater experience on this M3 forum will be able to shed some light on my problem

Thanks,
Timbo

[BimmerRob08]

There are a lot of fella's on here that run BBK's and track them regularly and you'll get a lot of good feedback from them. Also many run OEM with upgraded pads, lines, fluid as you do and from my experience with OEM is that depending on hard you are on them at the track, you'll experience such problems as you are talking about. I experienced pad-transfer material onto the rotors at Nurburgring but that eventually wore off after a few hundred miles of normal street driving (cooler temperatures than tracking obviously) then my rotors were back to normal with ZERO vibrations. I know a South West region racer with a E92 M3 that races with OEM and upgraded pads, lines, fluid, and never has problems and he holds records and so I'm sure he's not easy on his brakes.

3 rotors though, wow! We're they actually warped or what? Many believe OEM rotors won't warp. I'm not sure as I've not seen this happen but I guess its a possibility.

If your gonna go BBK, you'll experience much better brake thermal performance and consistency and you will still probably have to swap out pads from track to street and do proper brake run in procedures to keep them optimal. That's what I've done with my APs.

Good luck!

[timbo_3101]

Thanks BimmerRob08.

Yes, three sets of front rotors and one set of rear rotors before 10000km. (This vehicle has been set up for circuit racing, and is rarely driven on public roads.)

The vibration occurs tends to occur above 150km/h, not on warm up laps, and returns later on during sessions. Hence my feeling that it is related to extreme temperature.

I have read that there are many owners have experienced problems with OEM components on track, but trying to ascertain how susceptible BBK systems are to this, given that both E9x and 1M are (front) heavy vehicles.

[BimmerRob08]

Originally Posted by timbo_3101

Thanks BimmerRob08.

Yes, three sets of front rotors and one set of rear rotors before 10000km. (This vehicle has been set up for circuit racing, and is rarely driven on public roads.)

The vibration occurs tends to occur above 150km/h, not on warm up laps, and returns later on during sessions. Hence my feeling that it is related to extreme temperature.

I have read that there are many owners have experienced problems with OEM components on track, but trying to ascertain how susceptible BBK systems are to this, given that both E9x and 1M are (front) heavy vehicles.

Unfortunately I can't give any smart feedback on how these OEM brakes would perform at the stress level your car is put through, my track experience was at the novice level but hard braking is hard braking, it's the just the entering speed that might be a bit slower but I think none the less, dozens of laps would for sure manifest other problems that I just didn't get to experience with my OEM brakes at the time. So kinda comparing apples and oranges here. But I would guess that form what I experienced with m OEM set up, if I had the chance to run it for as many laps and as hard, I'm sure they'll perform well below standards for track use. Already it was noticeable at my level of track experience.

But I will say again that my buddy John that competes with his M3 runs OEM rotors and calipers, everything else is upgraded of course and he runs strong at many events. Sure is puzzling that some people will experience all sorts of problems, others can push the OEM rotors and their fine. And I doubt it's a question of how hard you, him or others are pushing the car. At some point between street driving and track driving there has to be that threshold where OEM brakes do great and start to perform poorly, that's just my thinking though.

[mlhj83]

I have 40k miles of relatively hard driving and 10+ track days on my OEM rotors - no problems. I have run both M Performance Sport Pads and PFC08.

You have to lay down a layer of pad material before each track event - known as bedding-in - otherwise you'll get brake judder. I would say drive around normally, and brake normally until the RS19s clean off the uneven deposits, as race pads are at their most abrasive when cool. Once your brakes are smooth again, then proceed to bedding-in your brakes prior to each event.

You cannot proceed to brake hard repeatedly at the track without laying down an even layer of pad material first.

[BimmerRob08]

Originally Posted by mlhj83

I have 40k miles of relatively hard driving and 10+ track days on my OEM rotors - no problems. I have run both M Performance Sport Pads and PFC08.

You have to lay down a layer of pad material before each track event - known as bedding-in - otherwise you'll get brake judder. I would say drive around normally, and brake normally until the RS19s clean off the uneven deposits, as race pads are at their most abrasive when cool. Once your brakes are smooth again, then proceed to bedding-in your brakes prior to each event.

You cannot proceed to brake hard repeatedly at the track without laying down an even layer of pad material first.

At the time I did not do the bedding in procedure with my OEM brakes which probably would have made the difference. But I have done so with AP BBK as you described exactly but still I have wheel-wobble vibration under braking. But bedding in is the proper thing to do.

[mlhj83]

Originally Posted by BimmerRob08

At the time I did not do the bedding in procedure with my OEM brakes which probably would have made the difference. But I have done so with AP BBK as you described exactly but still I have wheel-wobble vibration under braking. But bedding in is the proper thing to do.

From your other thread, I guess we have already established the cause of your vibration as being down to your AP Discs having too much runout in their fully assembled state.

[dogbone]

When I first started tracking my M3, it had a blower, but the rest of the car was 100% stock. The car had 14k miles on it---no hard braking prior to tracking. On the first day, after the first warm up lap, the brakes would shake/vibrate/judder, and they would shake worse as the day wore on, and as I kept going to more track events, they would shake even more. An instructor who drove my car, agreed that something was not right.

I decided to buy a used AP Racing kit. Due to a long story that I won't get into, I received the front part of the kit first, so I put the fronts on, leaving the rear stock for the time being. ALL of the vibration disappeared instantly. I have never had another peep of shaking since. Now the car has all four corners with AP, and I use Cobalt Friction brake pads and Castrol SRF fluid and the car stops like a monster.

I did the labor of replacing the front rotor rings myself when the first rotor set wore out. They're still as bombproof as ever.

The plain and simple fact is that the AP Racing BBK has been THE MOST reliable mod on my car. Between AP, Castrol SRF and Cobalt Friction (XR2 front, XR3 rear), braking is simply something I do and NEVER EVER worry about. The pedal feel never ever changes----no matter 50 degrees, 105 degrees, first lap, 10th lap, Street tire, Hoosier R6, bumpy track like Buttonwillow, smooth track like Laguna Seca, beginning of day, end of day......the brakes simply do not care. They just work. That's a great peace of mind.

[BimmerRob08]

Originally Posted by dogbone

When I first started tracking my M3, it had a blower, but the rest of the car was 100% stock. The car had 14k miles on it---no hard braking prior to tracking. On the first day, after the first warm up lap, the brakes would shake/vibrate/judder, and they would shake worse as the day wore on, and as I kept going to more track events, they would shake even more. An instructor who drove my car, agreed that something was not right.

I decided to buy a used AP Racing kit. Due to a long story that I won't get into, I received the front part of the kit first, so I put the fronts on, leaving the rear stock for the time being. ALL of the vibration disappeared instantly. I have never had another peep of shaking since. Now the car has all four corners with AP, and I use Cobalt Friction brake pads and Castrol SRF fluid and the car stops like a monster.

I did the labor of replacing the front rotor rings myself when the first rotor set wore out. They're still as bombproof as ever.

The plain and simple fact is that the AP Racing BBK has been THE MOST reliable mod on my car. Between AP, Castrol SRF and Cobalt Friction (XR2 front, XR3 rear), braking is simply something I do and NEVER EVER worry about. The pedal feel never ever changes----no matter 50 degrees, 105 degrees, first lap, 10th lap, Street tire, Hoosier R6, bumpy track like Buttonwillow, smooth track like Laguna Seca, beginning of day, end of day......the brakes simply do not care. They just work. That's a great peace of mind.

This is exactly what boggles my mind. Its expected the OEM brakes when not upgraded with pads/fluid/lines will be the weakest link but the AP's are such great brakes. Maybe I was the unlucky guy to get a defective kit?? Or its something else. Just gonna have to wait till I get them off.

Originally Posted by mlhj83

From your other thread, I guess we have already established the cause of your vibration as being down to your AP Discs having too much runout in their fully assembled state.

Yes thank you, but until I swop my OEM brakes back on I (we) can't be sure its the BBK. I hope it is in a way so at least I found the problem but then again I hope its not the BBK because they are good brakes and have a hell of a good reputation but well, we'll see I guess in a few months.

[timbo_3101]

Thanks all for your input.

Originally Posted by dogbone

When I first started tracking my M3, it had a blower, but the rest of the car was 100% stock. The car had 14k miles on it---no hard braking prior to tracking. On the first day, after the first warm up lap, the brakes would shake/vibrate/judder, and they would shake worse as the day wore on, and as I kept going to more track events, they would shake even more. An instructor who drove my car, agreed that something was not right.

I decided to buy a used AP Racing kit. Due to a long story that I won't get into, I received the front part of the kit first, so I put the fronts on, leaving the rear stock for the time being. ALL of the vibration disappeared instantly. I have never had another peep of shaking since. Now the car has all four corners with AP, and I use Cobalt Friction brake pads and Castrol SRF fluid and the car stops like a monster.

I did the labor of replacing the front rotor rings myself when the first rotor set wore out. They're still as bombproof as ever.

The plain and simple fact is that the AP Racing BBK has been THE MOST reliable mod on my car. Between AP, Castrol SRF and Cobalt Friction (XR2 front, XR3 rear), braking is simply something I do and NEVER EVER worry about. The pedal feel never ever changes----no matter 50 degrees, 105 degrees, first lap, 10th lap, Street tire, Hoosier R6, bumpy track like Buttonwillow, smooth track like Laguna Seca, beginning of day, end of day......the brakes simply do not care. They just work. That's a great peace of mind.

Haha, thanks dogbone for this clarification - regarding front BBK, and racing on hot summer days. I am also seeking this peace of mind. Do you think the initial vibration on your first event was just heat/expansion of OEM components?

[dogbone]

Originally Posted by timbo_3101

Do you think the initial vibration on your first event was just heat/expansion of OEM components?

Yeah, I think so. Around town, the brakes would not vibrate or shake in any way. But once they heated up, it was shake city right away----not one single shake-free lap after the warmup lap. Once the blower was on the car, it was a bit tough to run into a dealership and ask for warranty on the rotors......I've heard that dealers will warranty the rotors once, as a courtesy. But in my case, I didn't think it was realistic.

The AP kit for me has completely solved ANY issue regarding braking---in every way. And I always stress this point when talking to people about brakes----don't mess around with brake fluids. Get Castrol SRF and don't mess around. Just last weekend at Laguna Seca, there was a guy with an E90 M3, AP Kit, Endless Pads, and.....Motul......and he was complaining that his brake pedal was getting mushy. Endless are good pads. But Laguna Seca is a sneaky track. It's so smooth and nice, that you don't realize how much you're pounding your brakes. But you DO work your brakes over very hard at that track. His Motul just wasn't holding up and he was boiling the fluid-----LAME. People say, "oh SRF is way too expensive...." No it's not. You can find it online for $56 liter, and it lasts a LONG time-----way longer than Motul. People say they change Motul every 6 track events to keep the pedal feel consistent. I can go 20 with SRF. So the cost more than evens out. It might even be cheaper to run SRF in the long run. And seriously----someone drops $6k+ on a BBK and now they're looking to save $50 on brake fluid???

I know I'm preaching here, but people like to fight me on this one. I will tell you this. There's three of us guys locally here who track and have AP kits E90 M3's. Two of us have SRF, the third has some other fluid. The two of us that have SRF never talk about the brake pedal feel. It's always consistent. The third guy, talks about the pedal getting a little soft, but it recovers pretty quickly......WHO WANTS THAT!!?????

[timbo_3101]

Thanks again, dogbone - am grateful for your collective E90 racing experiences

I never made warranty claims for rotors either given that my vehicle is exclusively for circuits. If I proceed to BBK (as opposed to merely using performance rotors), I will have to decide which kit to fit ie ST or AP, and then hope there are no more mechanical issues!

[JEllis]

Just out of curiosity how many miles are on your M3? If it has high miles and or has seen a lot of track use, its possible some of your front bushing are going. Only mention this as a slim possibility given that you appear to only get the vibration during braking.

I have Brembo GTs, 380mm, no vibrations felt during a hard track day.

[dogbone]

Originally Posted by timbo_3101

Thanks again, dogbone - am grateful for your collective E90 racing experiences

I never made warranty claims for rotors either given that my vehicle is exclusively for circuits. If I proceed to BBK (as opposed to merely using performance rotors), I will have to decide which kit to fit ie ST or AP, and then hope there are no more mechanical issues!

Sure man! One thing that might sway you in your decision making process is that, as you get faster and more aggressive, the pads in the stock calipers start to wear out pretty fast----they're just not very large. There's a member on this forum with an E90 M3 who was burning through a set of Endless ME-20 front pads in his stock calipers/stock rotors in less than 2 full track days!! He justified the switch to a BBK because while the initial jump in is expensive, the BBK front pads last easily 10 track days (and the rears last more than 20). So, if you track a lot, and you like to use nice pads, the cost of the consumable starts to drop significantly with the larger BBK pads that last a lot longer.

Good luck with your decision!

@ JEllis - fwiw, my bushings had 14k miles when I was getting the shaking initially. Now the same bushings have 40k along with the BBK and no shaking.

[mlhj83]

While BBKs are most definitely capable on track, the OEM discs are up to the job for a good number of hot laps when combined with the right pads and fluid. Many people, and indeed professionals, do run this set up on track and it works well. If you are managing to get vibration with the OEM discs with racing pads, then it is very much down to inappropriate technique and lack of bedding in. Again, I'm not saying that a good BBK isn't better than OEM, but it may be better to be proficient in the use of what the OEM discs can offer, before deciding whether you really need a BBK.

Vibration during braking, is caused by uneven pad deposition on the surface of the discs, due to the pads overheating. The right pads and correct bed-in procedure prevents this from happening, and allows an even layer of pad transfer onto the discs, resulting in a homogenous blue/grey colour on the friction surface of the discs. Vibration gets worse as heat builds up, due to the fact that the uneven pad deposits on the disc build up more and more as the spots of pad deposit generate more friction and heat, thus attracting more pad deposits.

As to other causes of vibration, you can have a look at my vibration sticky in the maintenance section.