OEM brakes toast after each track day

[roastbeef]

i don't know what role the guide pins play. i got rid of my oem brakes after one track day. hand drilling is never going to be as precise as machining. i think you found your problem though.

[jritt@essex]

A couple of issues that I see straight away:

1. Running DS1.11 on the front and DS2500 in the rear- The DS1.11 has a greater mu than the DS2500. By running a higher mu compound in the front, you're effectively shifting more work to the front brakes. I'd suggest running DS1.11 on both front and rear to balance things out.

2. Your ducts may be hurting you more than helping you. Do you have any pics of the back side of your discs, and how the air is feeding into the disc? From the pic below, it looks like the plate holding the duct to the disc is covering part of the disc face. That traps heat against the disc face, and you don't want to do that! The back plate on the inside of the disc should not cover any portion of the disc face, and it should seal as tightly as possible against the inner diameter of the disc. Also, no air should be blowing directly onto the inner disc face, only into the center of the disc.

Did you try running the car without ducts prior to installing them? In most cases we suggest no ducts, because they often create more problems than they solve on a street car. About 95% of the duct setups we see on street cars are poor implementations.





For any hope of the duct being effective and not causing problems, it should look something like one of the examples below:

[jritt@essex]

Some other points...

The long brake pedal is absolutely indicative of air in the system. You definitely need to bleed the brakes. Also, Castrol isn't the highest dry boiling point fluid, which is what you need. All the marketing jumbo about 'wet boiling point' is rubbish for a modern road car on the racetrack. The dry boiling point of SRF is 608F. For the top fluid like AP Racing R4, it's 644F.

The underlying issue however is that you're putting to much heat into your calipers. That problem begins further upstream in the discs. If your discs are running hot, it causes everything else in the brake system to run hot. Hot discs lead to hot pads, hot pistons, hot caliper bodies, and hot brake fluid. You need to address the issue at the root, which is the discs. If you don't fix that issue, there isn't a brake fluid in the world that will help you.

Step one is to verify if your ducts are helping or hurting you. If you haven't run the car without them, I'd remove them. You can keep the hose dumping fresh air into the wheel well, but don't pipe them down to the disc, and make sure you remove the plate behind the inner disc face, as it is likely trapping a lot of heat in that area. See if that solves your problems. Before you remove them however, see if you can take some disc temperatures at the track in the hot pits immediately after coming off track.

If we discover that your ducts are actually helping (I'm doubtful based on the pics), then you clearly need A) more thermal mass in your discs or B)more efficient discs that flow more air and can better leverage the ducts, or C) Both of the above...a larger disc with more thermal mass, that also flows more air.

If you want to skip all the pain and suffering, go with one of our front brake kits, remove the ducts, and never worry about your brakes again. That's the easy button, but it will cost more. Our options can be found here...again, you only really need a front kit if you go that route: https://www.essexparts.com/my-vehicl.../BMW/M3/%20E92

Seriously though, I'd love to see the plate implementation on the back of the discs. I think that could be the root of your problem. Melting pistons is extreme. The only times I've really seen that is when there is metal-to-metal contact between the disc and the caliper somewhere (the caliper was installed off-center), and an obscene amount of heat was generated because of that friction.

[strokemycocktus]

Originally Posted by jritt@essex

Some other points...

The long brake pedal is absolutely indicative of air in the system. You definitely need to bleed the brakes. Also, Castrol isn't the highest dry boiling point fluid, which is what you need. All the marketing jumbo about 'wet boiling point' is rubbish for a modern road car on the racetrack. The dry boiling point of SRF is 608F. For the top fluid like AP Racing R4, it's 644F.

The underlying issue however is that you're putting to much heat into your calipers. That problem begins further upstream in the discs. If your discs are running hot, it causes everything else in the brake system to run hot. Hot discs lead to hot pads, hot pistons, hot caliper bodies, and hot brake fluid. You need to address the issue at the root, which is the discs. If you don't fix that issue, there isn't a brake fluid in the world that will help you.

Step one is to verify if your ducts are helping or hurting you. If you haven't run the car without them, I'd remove them. You can keep the hose dumping fresh air into the wheel well, but don't pipe them down to the disc, and make sure you remove the plate behind the inner disc face, as it is likely trapping a lot of heat in that area. See if that solves your problems. Before you remove them however, see if you can take some disc temperatures at the track in the hot pits immediately after coming off track.

If we discover that your ducts are actually helping (I'm doubtful based on the pics), then you clearly need A) more thermal mass in your discs or B)more efficient discs that flow more air and can better leverage the ducts, or C) Both of the above...a larger disc with more thermal mass, that also flows more air.

If you want to skip all the pain and suffering, go with one of our front brake kits, remove the ducts, and never worry about your brakes again. That's the easy button, but it will cost more. Our options can be found here...again, you only really need a front kit if you go that route: https://www.essexparts.com/my-vehicl.../BMW/M3/%20E92

Seriously though, I'd love to see the plate implementation on the back of the discs. I think that could be the root of your problem. Melting pistons is extreme. The only times I've really seen that is when there is metal-to-metal contact between the disc and the caliper somewhere (the caliper was installed off-center), and an obscene amount of heat was generated because of that friction.

Thank you so much for all the info and sorry for a late reply, I was away for last 2 weeks.

I understand and agree about running different mu pads on both axles. I cheaped out on the rears, but I'll get a proper set for next year for sure.

The brake shields are from Mumbray Motorsport, which I believe is a trusted company. I contacted them and they confirmed that the duct is designed to guide air directly to the hub. Photos attached.

I have run the car with no ducting and it was worse, I burnt the DS 1.11 completely in one track day. Also the stock disc shields are 2x larger than what I have now. I believe that's enough to say that the ducts are rather helping here.

Paul from Mumbray Motorsport said that Ferodos are not enough for such heavy car and recommended pagid rsl19.

As I mentioned this season I am running Motul rbf 700. Seems to work ok, but it looks like I still have some air in the system. I tried the bleeding procedure from INPA, but ultimately did only 2 wheels before I ran out of spare brake fluid.

Sure, I know a proper bbk would solve all the issues. I usually run 2-3 track days a year, but I would still maybe consider it if I was living in the USA. Being located in Europe makes all parts super expensive (add 23% of tax, a few % of duty fees and about $400 shipping for a bbk). And believe it or not, we don't have any local manufacturers.

I plan to check the whole caliper assembly, bleed the ABS again, check the cooling ducts. For the next season I'll probably get the PFC DD V3 rotors which should help a lot. I'll use them with PFC 11 pads on all corners.

For now I am still worried about my rotors. Both of the front ones have 0.8mm deep grooves on each side, in exactly the same place. I'll have them checked by a mechanic and maybe have them skimmed to even the surface. They have only 5k km on them (including 4 track days and 5 sets of pads lol). I have no idea how did it occur, but I noticed it after the track day I ran the street Textar and Ferodo pads (2 sets gone in 1 day).

[MVEED3]

Don't take offense to the following suggestions as they are intended to help narrow down the issue...

1. Braking technique
You may be riding your brakes more than you need to. There are many options in isolating this behavior. Best is to invest in a data logger and compare your brake application to what the average is for your local track. Another option is to enroll in an M-school day and see if you melt the brakes on those cars

2. Improper wrenching
There seems to be a mix of work done by you and your mechanic so this won't be straight forward unless you have everything overhauled by a trusted race shop. The pad swap is a good 1st step. It's worth the safety of others, yourself, and your car to have a known pro do the work while you are tracing down the cause.

[Z K]

One thing that I'll offer that no one else in this thread offered is that maybe you need to replace the brake master cylinder.

I had the brake master cylinder go bad on me during a track day. It caused the brake pad to drag on the rotor all the time and I burned through a new set of track pads in 20 minutes. It not only destroyed the front pad, it also melted the brake caliper boots and the heat even started melting the brake line. This is not normal. After replacing it with another set of pads, the next session, I noticed the same behavior and pulled out early.

We took apart the caliper which looked fine. After that, I decided to replace the master cylinder and that solved the issue. I've not had any problems in the years since.

I'd say if you have pedal softness after multiple bleeds and unusual brake pad wear, look into the master cylinder.

[ppatel14]

Originally Posted by strokemycocktus

That got me thinking and I remembered that when I was installing the brass bushings I had to make the bores wider since the pins didn't fit and move freely. I used a 12mm drill and smoothed it out with fine sandpaper. They fit and move freely, but what maybe the tolerance is just a bit too tight and when it all gets very hot the pins and bushings sell and the sliders stick.
I could buy a 12.1mm or even 12.2mm drill and make the bores just so little bigger to make the fit by 0.1 mm looser. This shouldn't introduce any play and should allow free movement in all extreme conditions.
What do you think?

I'm thinking it could be the brass guide pins that might be sticking. Did you do all 4 corners? What brand? Also have you been cleaning and greasing the pins regularly?

Can someone chime in on the frequency of cleaning and greasing the brass guide pins? I recently installed the BW kit for the rear before my last track day and now this thread has me wondering how often is enough.

[strokemycocktus]

Originally Posted by Z K

One thing that I'll offer that no one else in this thread offered is that maybe you need to replace the brake master cylinder.

I had the brake master cylinder go bad on me during a track day. It caused the brake pad to drag on the rotor all the time and I burned through a new set of track pads in 20 minutes. It not only destroyed the front pad, it also melted the brake caliper boots and the heat even started melting the brake line. This is not normal. After replacing it with another set of pads, the next session, I noticed the same behavior and pulled out early.

We took apart the caliper which looked fine. After that, I decided to replace the master cylinder and that solved the issue. I've not had any problems in the years since.

I'd say if you have pedal softness after multiple bleeds and unusual brake pad wear, look into the master cylinder.

After properly bleeding the ABS pump once again and doing the DSC unit adjustment the pedal feels much firmer.
The mechanic told me that the rotors are trash, I probably damaged them by running OEM pads on track to bare metal once. They also told me that these deep grooves may contribute to worse pedal feel since the contact surface is uneven.
The damaged and grooved rotors may have been the reason for overheating.
I have ordered new OE rotors just to move around, I also have a set of new PFC 11 pads. I'll try out this setup for one track day on a cooler day and see how it goes. But overall I am rather leaning towards a ST40, I plan to hunt for some deals (Black Friday probably).

Originally Posted by ppatel14

I'm thinking it could be the brass guide pins that might be sticking. Did you do all 4 corners? What brand? Also have you been cleaning and greasing the pins regularly?

Can someone chime in on the frequency of cleaning and greasing the brass guide pins? I recently installed the BW kit for the rear before my last track day and now this thread has me wondering how often is enough.

The kit was made by a Canadian company called SRS Customs, I went with their kit because they supply dust caps and they don't require such cumbersome install as the ECS ones that are the only alternative. I grease them every pad swap during track season and before l/after I install my spacers for winter wheels.
I checked the bores with a 12.1mm drill and they all were the same, so I am guessing the sizing is correct.