Question about brake setups for those of you with 24v motors...

[2002maniac]

I would stay away from Racing Brake, too many instances of cracking most likely due to poor metallurgy, plus poor design.

Good to know, I had not heard this.

[dude8383]

Nice. I'm jelly!!!

[Grinch337]

Yeah, I got one or two more sessions in. I had a great time overall. I didnt think the bench bleed would help you, but figured I would throw it out there so that you're sure youve covered all bases. Good luck with figuring it out.

Thanks again for letting me borrow your camera. Im looking forward to the video. No rush though.

[dude8383]

Wow those are getting seriously hot! At this level of track performance I'd say good ducting is mandatory. I have tried most of them and I think that Meyle does make the best blank Corrado rotor. You might want to try the Racing Brake rotors (have not tried them, too pricey for me). I think ducting alone will probably solve your problem, but you might end up needing the greater thermal mass and pad area of a larger rotor/superlite setup. Good luck!

Thanks for chiming in man.

I just ordered a set of hats from Lee and I'll be picking up rings from Emory motorsports. Hoping that the design will improve cool and I will DEFINITELY be purchasing ducting. I want to cover all fronts here! Wish I could go with a bigger caliper but then I'd have to address the rear. I'm also going to get a bias valve so that I can really dial things in.

I would stay away from Racing Brake, too many instances of cracking most likely due to poor metallurgy, plus poor design.

Yeh, so I've heard... but then again I'm going with a slightly different setup now anyway.

The way I figured it out is pretty easy. Get it on a lift(if you have one), start it up then put it in gear, and brake while running. Mine would lock the fronts, but the rears were barely rubbing, not enough to stop the wheels. Usually the pedal would feel like it goes further than usual.
Best of luck for a solution.

Interesting. I'll give this a shot the next time I have the car up on the lift! Thanks.

Hey Denis did your master cylinder ever go dry? I thought I may have once puked out all my brake fluid and I was concerned about whether putting the pedal to the floor blew out the master cylinder. I was given advice that I may need to bench bleed the master cylinder. It turned out I didnt need to do it, but its something you may want to do. It could also help you determine whether there is air trapped in the abs unit.

Here is the thread where I was given the advice:

http://grassrootsmotorsports.com/forum/grm/did-i-blow-my-master-cylinder/50898/page1/

Really want you to get this figured out. It wasnt as much fun out there knowing that you were in the garage struggling with this all day.

Sean

Hey dude. How was the rest of the day? Manage to get a few more runs in?

Good thread but I'm positive that I've never let the master cylinder run dry. I remember when I swapped over to the 7 series master from my buddies car I had made sure that there was fluid in there prior to fully removing it. He had it in the car for a very short period of time and had zero track days on it so I wasn't worried about the condition of it. To note, I've had over 15 track days on my current master cylinder.

I feel like the pedal feel is related to the extreme temps that my calipers are seeing. I'm going to get that paint as well for next season so that I can get a better idea of what the temps are... granted I'll have the bias valve, better rotors and ducting. Figure it will make sense to know these things anyway.

Btw, I'll try and get your video up on the tube sometime today or tomorrow :)



Slight aside, I also started a thread over on bfc:

http://forums.bimmerforums.com/forum/showthread.php?t=1917929

Lee provided some useful info too.

[Grinch337]

Hey Denis did your master cylinder ever go dry? I thought I may have once puked out all my brake fluid and I was concerned about whether putting the pedal to the floor blew out the master cylinder. I was given advice that I may need to bench bleed the master cylinder. It turned out I didnt need to do it, but its something you may want to do. It could also help you determine whether there is air trapped in the abs unit.

Here is the thread where I was given the advice:

http://grassrootsmotorsports.com/forum/grm/did-i-blow-my-master-cylinder/50898/page1/

Really want you to get this figured out. It wasnt as much fun out there knowing that you were in the garage struggling with this all day.

Sean

[Frankensteined]

How does one really know if the m/c is just working the fronts? Is there anyway for me to visually inspect it cause I'll remove the damn thing and make sure its operational! I really really want to get to the bottom of this over the winter :D

The way I figured it out is pretty easy. Get it on a lift(if you have one), start it up then put it in gear, and brake while running. Mine would lock the fronts, but the rears were barely rubbing, not enough to stop the wheels. Usually the pedal would feel like it goes further than usual.
Best of luck for a solution.

[seatown88]

I would stay away from Racing Brake, too many instances of cracking most likely due to poor metallurgy, plus poor design.

[2002maniac]

Wow those are getting seriously hot! At this level of track performance I'd say good ducting is mandatory. I have tried most of them and I think that Meyle does make the best blank Corrado rotor. You might want to try the Racing Brake rotors (have not tried them, too pricey for me). I think ducting alone will probably solve your problem, but you might end up needing the greater thermal mass and pad area of a larger rotor/superlite setup. Good luck!

[dude8383]

D

You know I wish u the best of luck in sorting this...as Ill b following your lead. I do not want to go 5 lug.....and bigger brakes really limit the use of 15 inch wheels...

and oh...w/ pad knock back, :you often see well versed drivers tapping the brake pedal on long straights just to reseat/reposition the pads for the next corner...

Heh, thanks buddy. I'm looking forward to some worry free track time. The only proper option is e30 m3 5 lug which would allow you to keep the 15" wheels but the "cost of entry" if you will is super high.

Ahhhh so that is the official term for it then. I've seen this multiple times (on youtube of course) and understood that they were reseating the pads.

I would judge from all the things said, and the picture in your sig, is that your fronts are doing all the job, and rears are not doing much.
I had an e30 that the cylinder went bad and would only brake with fronts, so check that.
Also bleed your system.
And as stated above. Build some cooling ducts. use something like the accordion style duct for dryers.

just my 2c

The temps from lightning (where that pic was taken) were 600+ for the fronts and 200-300 in the rear. So yeh, the rears were barely working. Having said that, the rear were definitely working at Thunderbolt yesterday because the temps were around 400 or so.

How does one really know if the m/c is just working the fronts? Is there anyway for me to visually inspect it cause I'll remove the damn thing and make sure its operational! I really really want to get to the bottom of this over the winter :D

Going to do the 2 man method this time around when bleeding. I got lazy at the track because I had the motive speed bleeder. I am ALSO going to rebuild my rear calipers.

Thanks guys.

[Frankensteined]

I would judge from all the things said, and the picture in your sig, is that your fronts are doing all the job, and rears are not doing much.
I had an e30 that the cylinder went bad and would only brake with fronts, so check that.
Also bleed your system.
And as stated above. Build some cooling ducts. use something like the accordion style duct for dryers.

just my 2c

[JRKOUPE]

D

You know I wish u the best of luck in sorting this...as Ill b following your lead. I do not want to go 5 lug.....and bigger brakes really limit the use of 15 inch wheels...

and oh...w/ pad knock back, :you often see well versed drivers tapping the brake pedal on long straights just to reseat/reposition the pads for the next corner...

[dude8383]

Edge of the rotor and edge/back of the brake pad backing plate.


Yeah, we ran without ducting first couple of races. Never had pad or fluid fade (Cobalt friction pads / ATE or the new Prospeed RS683 fluid), but we were also driving the car keeping in mind we needed to run a whole 7 hours, so not as hard on the brakes. Just more wear/heat than I like to see - you know shit is getting hot when wheel weights fall off when the car is sitting in the pits! (forgot to add tape to a wheel...)


Yeah, knock-back can/will happen first corner, not time dependent.


It sounds like you've narrowed it down correctly that there is too much heat in the system for how you are using the car. Small/thin pads, no cooling, higher speeds than stock and greater braking needs = too much heat. Add some cooling, maybe step up to a higher heat-tolerant pad. If still having issues, up-size the pad.

Awesome. Thank you man, really appreciate the help here.

As for up-sizing the pad... well I'd have to actually up-size the whole caliper and then I'd probably have to address the smaller rear. Hope that maybe just these few tweaks can make for a more solid system. I'm not really looking to race the car because I'd be way out of my league with whichever class my car falls into. This is more of a DE/track day car (at least I keep telling myself that).

Apply the temperature paint on the rotor in 1 inch+ segments. Surface prep is critical to the application of the paint, you want to make sure that the rotor is clean before applying the paint.


After they see a specific heat, they will change color. This picture shows my rear rotors reaching a temperature over 1100F.

Thank you sir. Appreciate your feedback in here as well.

Hopefully next season will be time less spent on bleeding brakes and more time spent lapping/learning!!!

[seatown88]

Apply the temperature paint on the rotor in 1 inch+ segments. Surface prep is critical to the application of the paint, you want to make sure that the rotor is clean before applying the paint.


After they see a specific heat, they will change color. This picture shows my rear rotors reaching a temperature over 1100F.

[NigelStu]

Edge of the rotor and edge/back of the brake pad backing plate.


Yeah, we ran without ducting first couple of races. Never had pad or fluid fade (Cobalt friction pads / ATE or the new Prospeed RS683 fluid), but we were also driving the car keeping in mind we needed to run a whole 7 hours, so not as hard on the brakes. Just more wear/heat than I like to see - you know shit is getting hot when wheel weights fall off when the car is sitting in the pits! (forgot to add tape to a wheel...)


Yeah, knock-back can/will happen first corner, not time dependent.


It sounds like you've narrowed it down correctly that there is too much heat in the system for how you are using the car. Small/thin pads, no cooling, higher speeds than stock and greater braking needs = too much heat. Add some cooling, maybe step up to a higher heat-tolerant pad. If still having issues, up-size the pad.

[dude8383]

Best part about the link seatown posted is the list of pads for temp ranges! nice to see that all in 1 spot.

I've used this stuff in the past. I like that it can show a range, instead of just chaning color once a temp is reached.

https://www.pegasusautoracing.com/productdetails.asp?RecID=4974

I'm running ChumpCar, so no fancy bimmerworld backing plates. just ducting. I'll have to build up a set of my own. Will need it for next year since the car will likely go from M20 to M50 power :)


You wont feel knock-back happening, but you will notice it when you apply the brakes - it feels a lot like a bit of air at the caliper, press the pedal and it goes almost to the floor, next application and brakes are there. Hitting rumble strips / curbing can move/shake enough stuff around to push the pad/piston back into the caliper a bit. First press on the brake pedal simply pushes the pad out until it contacts the rotor, next press solid brake. The difference compared to boiled fluid is the air is between the pad and rotor instead of inside a caliper or brake line. Had this happen on a 350Z with Brembos and all the time on my Spec Miata. Caliper flex, vibration and loose/worn hubs can cause knock-back.

O_O $74 for an ounce! Where do you apply this stuff? Directly on the caliper or the backing plate of the pad?

LOL, gotcha. Did you at any point run the car without ducting?

Thanks for breaking down the knock back deal. So as I was reading your description I thought that might have been what I was experiencing BUT... this would only happen after about 15-20min of lapping. Wouldn't something like this become more apparent in a shorter period of time?

I honestly think that the bloody pump has air caught in it because the pedal feel would diminish after engaging it.

*edit*

http://www.e36m3blog.com/brakes/

Reading here he talks about the pedal dropping to the floor after 20 laps... I'm beginning to believe that my brakes are just cooking EVERYTHING and in turn diminishing pad life and boiling the fluid.