some of you might have read my other post. but here is my story.

I have Stoptech BBK 355mm 1 piece rotors with PFC 97s. I've done 5 individual track days so far. and my rotors have sever cracks. not small cracks that you find on regular tracked rotors. and I do know this is because of heat. I emailed this matter to Stoptech and the cracks seem to be ok for now, but they are recommending to use extra caution for a next track day. Fine for daily driving, but eventually the cracks will get to the edge of rotors. if that happenes, i have to replace to the new rotors immediatly.

I am usually in advanced group for DEs, I brake hard. at the same time, I take a cooling lap seriously and never use brakes during cooling lap where some people use brakes. also i do drive around a pit for a while to keep it cool down.

So, right now, my only option is to get braking ducts AND get new rotors. Since i have 1 piece rotors, I can either get a pair of 1 piece rotors again, or upgrade to 2 piece rotors. According to Stoptech, 2 piece rotors are lighter, and has better cooling function. At the same time, costs double. For 1 piece, $240 a piece, and $500 a piece for 2 piece. so if i were to upgrade to 2 piece, i am gonna have to invest another $1000.

I just spent $2000 for BBK back in May. I am not sure if I can justify this cost since the cost is becoming my issue.

So here is my options.

1. get 2 piece rotors so that i can be in debt.

2. get 1 piece rotors again.

3. sell stopteck BBK and go back to stock brakes. buy PFC 97 again for stock calipers, use OEM rotors untill they wear out and buy floating rotors.

The reason I am considering stock brakes are that I've seen two E43 M3 drivres who can drive better than I do (and assuming braking as hard as I am or even harder) are using stock system with good pads, rotors, fluid, and lines. They told me it works fine. and in long run, even when stock rotors wear out, the replacement cost would be much cheaper. Pads are slightly cheaper for stock calipers too.


So my question to track junkees...sorry advanced drivers, what should I do? do you guys think stock brakes are fine for heavy use? or BBK is still a lot better than stock system?


also, if you have ducts, where do you get them? I think i've seen it on bimmerworld but it was 400 bux or something....is it really that expensive?

This sound dumb but you've done 5 track days and are in the advanced group :)

In addition you are in the advanced group and you are seriously asking this question?

By reading your question I assumed you've never done a track day on the stock brakes so why did you get BBK's in the first place?

Sorry just busting chops...

How about do 2 less track days and get the two piece rotors. Seriously you bought BBK's for a couple grand and are going to sell them because you can't afford rotors? But you drive an M3 and just spend over a thousand bucks on brakes and over a grand in track time and are using PFC 97's for BBK's which are over 200 bucks a pair.

This sound dumb but you've done 5 track days and are in the advanced group :)




I did it in 4, really doesn't mean squat tho.


Anyways, I've always thought that cracks on rotors develop not from purely overheating them, but from 'extreme' heat cycles. Meaning that they are cooling down too much and too quickly. But I'm not a materials engineer.

Hmm, the big advantage of a BBK is greater thermal mass and greater surface area for cooling. If you are having thermal cracks in BBK rotors it would seem to me that you'd have worse problems with OE brakes. Providing more cooling to the brakes would seem to me to be the best solution.

The reason I am considering stock brakes are that I've seen two E43 M3 drivres who can drive better than I do (and assuming braking as hard as I am or even harder) are using stock system with good pads, rotors, fluid, and lines.
More than likely they are driving smarter, rather than harder. Their lines and judgement is better and they carry more speed through corners, which means that they don't use the brakes as hard. I know that when I first started doing DE's I asked a lot more from the brakes than I do know. And at the same time I'm a lot faster around a track than I was initially. Granted, the cars are different and your M3 is going to be able to reach speeds that I can't touch, so you will need more from the brakes than my car does. But you have the evidence that shows that there is a smarter way around the course.

Anyways, I've always thought that cracks on rotors develop not from purely overheating them, but from 'extreme' heat cycles. Meaning that they are cooling down too much and too quickly. But I'm not a materials engineer.
I think that's mostly correct. Thermal stress cracks result from repeated cycles of rapid heating and cooling. That induces stresses in the surface of the rotor when its temperature is markedly different from the bulk of the rotor. That suggests that better cooling for the rotors can help, as that will limit how hot the rotors get. And the pads used are another way to limit the problem. A pad with a high MOT that is also relatively soft will help limit temperatures by shedding heat via ablation of pad material.

PFC97 is a low wear pad and it may be a factor in the rotor cracking.

This sound dumb but you've done 5 track days and are in the advanced group :).


sorry for the confusion. what i meant was that I've done 5 track days with stoptechs. I've done a lot more with my previous cars. so its not like 5 track days..boom i am in advanced.


In addition you are in the advanced group and you are seriously asking this question?

By reading your question I assumed you've never done a track day on the stock brakes so why did you get BBK's in the first place?



ok, so you read my thread and you thought my question was too noob for you? i am sorry maybe i do not have that much of knowledge as an advanced class driver. but the fact that i am in advanced class is based on my instructor's judgement. not because of my arrogance. also, you always learn when you get into troubles. which mean i never had this problem before hence i am asking question. You sound like peolple should be ashamed of asking questions.

and i have done 1 track day with stock brakes. the reason that i bought BBK was that my stock brakes were fading really bad. also i had some brake problem (mechanical failure prior to track day), so i wanted to make sure i have a good brake system. Safety is #1 and if i dont trust brakes, i dont go to a track. also i've read numorous threads that people are saying stock E46 M3 brakes aren't good enough. and that's what I thought too.

But like i mentioned, there were few people with stock brakes with upgraded sutff and they were doing fine. thats something i didnt find out while i was surfing on the web. i went to a race track, talked to people, and found that out. one of a those guys actually had the best lap time of the day.


How about do 2 less track days and get the two piece rotors. Seriously you bought BBK's for a couple grand and are going to sell them because you can't afford rotors? But you drive an M3 and just spend over a thousand bucks on brakes and over a grand in track time and are using PFC 97's for BBK's which are over 200 bucks a pair.

Ok, let's do math. i bought BBK for $2000 in May which is 4 months ago. and now, I have to spend $1000 more to replace them. "IF" i keep driving the way i am driving, i am gonna have to spend another $500 in 4 months. and don't forget, there is also brake pads wear, tire wear, gas, track day fee, hotel...etc. there is tons of hidden cost for track day. have you been to one? I was asking this question based on my experience and my situation.

and what is wrong with my financial situation? I do want to spend all of my money into cars. I have another things to spend money on. and i am just asking what is the most cost effective way.

if you can afford M3 and BBK, it doesnt mean you can afford to expense almost $5000 just for brakes in an year. hope you understand what i mean.

I did it in 4, really doesn't mean squat tho.


Anyways, I've always thought that cracks on rotors develop not from purely overheating them, but from 'extreme' heat cycles. Meaning that they are cooling down too much and too quickly. But I'm not a materials engineer.


thats what i heard too but then how can I not to cool down quickly if i am doing that right now?

some people say brake duct will help preventing...it sounds contradicting to me...

More than likely they are driving smarter, rather than harder. Their lines and judgement is better and they carry more speed through corners, which means that they don't use the brakes as hard. I know that when I first started doing DE's I asked a lot more from the brakes than I do know. And at the same time I'm a lot faster around a track than I was initially. Granted, the cars are different and your M3 is going to be able to reach speeds that I can't touch, so you will need more from the brakes than my car does. But you have the evidence that shows that there is a smarter way around the course.


yea i guess i should have put it that way. they brake more effectively. i guess i am at a stage where i accomplished to manage brake late and late, try to brake as hard as i can. and also laptime showed a lot of improvement. the next step will be to use it more effectively.

anyway, I've got ride in this fast M3 with stock brake caliper. his driving was very smooth. but at the same time he did brake hard. probably the only difference is that he didnt brake hard as long as I did. i was probably stepped on brake pedal so hard for too long. that's probably the problem.

see? this is why i cant stop going to track! never stop learning new things!!! :redspot

anyway, I've got ride in this fast M3 with stock brake caliper. his driving was very smooth. but at the same time he did brake hard. probably the only difference is that he didnt brake hard as long as I did. i was probably stepped on brake pedal so hard for too long. that's probably the problem.
That driver is probably hard braking for a shorter period because he/she can carry more speed through a corner. The next time you ride with an instructor, take note of how fast they are going at various points around the track. Best to pick points where you could afford a glance at your speedometer. Even when you aren't riding in an E46 M3 you'll probably find that the fast drivers are carrying more speed.

Smoothness and consistancy is the name of the game. And it is easier to learn how to do that by not trying to drive as hard as you can. The speed will come when the other elements are mastered.

That driver is probably hard braking for a shorter period because he/she can carry more speed through a corner. The next time you ride with an instructor, take note of how fast they are going at various points around the track. Best to pick points where you could afford a glance at your speedometer. Even when you aren't riding in an E46 M3 you'll probably find that the fast drivers are carrying more speed.

Smoothness and consistancy is the name of the game. And it is easier to learn how to do that by not trying to drive as hard as you can. The speed will come when the other elements are mastered.

Yup, spot-on. You only want to brake just enough to scrub off the speed you need to make the corner, and no more. You don't want to brake for comfort, else you will significantly over-brake & also heat up your OEM brakes.

thats what i heard too but then how can I not to cool down quickly if i am doing that right now?

some people say brake duct will help preventing...it sounds contradicting to me...

It will keep them from reaching such extreme temperatures. That way, cool down won't be an ordeal that cracks rotors.

Ok, let's do math. i bought BBK for $2000 in May which is 4 months ago. and now, I have to spend $1000 more to replace them. "IF" i keep driving the way i am driving, i am gonna have to spend another $500 in 4 months. and don't forget, there is also brake pads wear, tire wear, gas, track day fee, hotel...etc. there is tons of hidden cost for track day. have you been to one? I was asking this question based on my experience and my situation.

This is a question you can only ask yourself. You have to do what you can afford. I can't tell you what that is. Either you tone down your driving 5% (which will do wonders for longevity of brakes), or you get less expensive equipment. I would just tone it down slightly. As others said, get seat time with the best drivers you can find and see how they use their brakes. Get the ducting kit, modify your braking and you should be just fine.

I'll chime in as a driver that recently joined the ranks of the Advanced group. I'm guessing that the advice about carrying more speed and breaking less is spot on. I until my last few sessions of my last DE, I was over braking before every turn. I was also overheating my brakes. Now that I've backed off, I'm carrying a lot more speed through the turn and my brakes are much happier. My over heating problem has completely gone away.

-bj

Definately focus on braking technique. I drove a e30 318is on track for 3 seasons at Watkins Glen with nothing other than fresh fluids, rotors and track pads. Since driving a 318 is pure momentum driving, I didint use the brakes much, but when I did I did it, late, hard and short to loose the least amount of momentum as possible.

That experience has carried over to my current car, a '98 M3 with just Slotted OEM rotors, PF97s, Stoptech SS lines and ATE Super Blue fluid. Repeated braking from 130+ mph on the backstraight to slow down for the bus stop was a non event.

Never experienced any fading at all with that set up.

Sounds to me like there's a problem here.

My guess would be braking technique. But it could be pad choice or the rotors them selves. Most likely the former.

When we learn to drive on the street, we're taught to be smooth and not make abrupt stops. Start braking gradually, increase the pressure to slow the car enough and finally slowly reduce the pressure when coming to a stop. Brake sooner rather than harder to be smooth.

On the track, that will overheat the brakes. On the track, you want to brake as hard as possible for as short a distance as possible. You still want to be smooth on and off the brakes but right on the edge of ABS while braking.

I and many others use factory calipers and rotors on our race cars. I have been using track pads for several years and have never had to replace rotors due to cracking or wear. I'm currently using euro floaters which have been on the car for at least 25K street miles and 15-20 track days.

I recently added ducting because of 100+ degree track days in the summer. But I have to tape them off most of the time because my pads (HT-10s) will cool too much.

IMO, you absolutely do not need a BBK. And, if you have one, I don't think you should be having these kinds of problems. I suggest you work on your technique and also talk to Stoptech to see if they might have a different pad recommendation. Not sure, but I think some with a BBK use a less aggressive pad compound than those of us using OEM brakes.

Another thought is that since you have the larger 355mm rotors, you may not be getting enough heat in the pads. You could try using some heat range paint to find out how hot your rotors are getting.

Good luck - Jay

FWIW... I use stock rotors and calipers and just throw on a set of Cobalt Spec VR pads and things have been great for me. And relatively economical too! :alright

Anyways, I've always thought that cracks on rotors develop not from purely overheating them, but from 'extreme' heat cycles. Meaning that they are cooling down too much and too quickly. But I'm not a materials engineer.

You're more likely to see thermal induced stress cracks when you have a large temperature swing. You can cool a piece of steel from 500 to 200 deg F fairly rapidly all day long and it'll be fine, but you go from 1300 to 500 deg F too many times and you're probably going to get some cracking.

FWIW... I use stock rotors and calipers and just throw on a set of Cobalt Spec VR pads and things have been great for me. And relatively economical too! :alright

Spec VR's rock! I will be going straight to those over the winter. GT Sports stink for road course's (what I initially had on the car so I used them this past year).

Stock brakes let you show things like this to all your friends!

http://www.nrubenstein.com/albums/album10/bent_dtc70.jpg

i saw that picture on m3forum. thats crazy!

I've got no problem with pad taper like that. Might be because I run the brass bushings but I didn't have taper that bad before I upgraded to them either. Maybe I just don't use my brakes enough ;)

Jay

Stock brakes let you show things like this to all your friends!

http://www.nrubenstein.com/albums/album10/bent_dtc70.jpg

the stock brakes are adequate for use in even a 3100 #, (w/driver) GrpN Car at the 24 hours of Nurburgring.

I've got no problem with pad taper like that. Might be because I run the brass bushings but I didn't have taper that bad before I upgraded to them either. Maybe I just don't use my brakes enough ;)

Jay
That's WITH brass bushings. :eek:

That's WITH brass bushings. :eek:

That's some weird schict! Looks like the backing plate is severely bent too.

Jay

That pad is tapered....for her pleasure.


;)

You're more likely to see thermal induced stress cracks when you have a large temperature swing. You can cool a piece of steel from 500 to 200 deg F fairly rapidly all day long and it'll be fine, but you go from 1300 to 500 deg F too many times and you're probably going to get some cracking.

Bingo...we had cracking problems as a result of cooling our brakes too much. I think we've managed to get temps right where we want them, without over-cooling, by eliminating the cooling ducts and going to a rotor with slightly more mass (1.5 times more vanes than our old rotors).

Last year there was an e46 competition m3 at one of our events that was toasting its brakes for about half a day until they unplugged the factory brake cooling ducts. Severe brake fade until then though...

Gary

Last year there was an e46 competition m3 at one of our events that was toasting its brakes for about half a day until they unplugged the factory brake cooling ducts. Severe brake fade until then though...

Interesting data point, but it leaves me wondering if the cooling ducts didn't just happen to coincide with the driver improving his braking technique or backing off just the slightest bit on his braking aggressiveness...you'd be surprised how small the line can be between burning up the brakes and having them run perfectly. I only say that because I can't imagine how the stock brake ducts feed any useful air to the rotor whatsoever.

Interesting data point, but it leaves me wondering if the cooling ducts didn't just happen to coincide with the driver improving his braking technique or backing off just the slightest bit on his braking aggressiveness...you'd be surprised how small the line can be between burning up the brakes and having them run perfectly. I only say that because I can't imagine how the stock brake ducts feed any useful air to the rotor whatsoever.

I wouldn't doubt that was a factor, I believe it was his first track day out in the comp m3 after switching from a 528 or therabouts. It might take a morning to get used to gobs of speeds generated by the new ride, hence the overbraking. Tough to tell for sure, but I know I had a much harder time getting around him in the afternoon.

Gary

Please read our postings on RacingBrake two-piece stock replacement rotors for E36/E46 M3 here:
http://forums.bimmerforums.com/forum/showthread.php?t=675285