Spa Trackday: BIBLICAL FL brake failure (Glowing Disc!)

[Radiation Joe]

Originally Posted by Gearhead999s

A box of the bronze caliper bushings came with my 1st set of Hawk pads.I have little taper wear on my used pads since I put them in.I am pretty sure that my pad supplier had them made up for me.

They are not difficult to make. I'm just surprised they are not readily available for our cars. Can you teach me the secret handshake to get a set? Do I have to run Hawk pads to enter this secret society of the bronze bushings?

[lucid]

Originally Posted by Radiation Joe

Those rubber guides that the caliper slides on deform under pressure and cause the pads to contact the disk unevenly. This probably caused the piston failure.

Joe, can you clarify what you mean above? How does uneven pad/rotor contact result in piston failure? Are you saying that also results in uneven pad/piston contact and that somehow loads the piston in a manner that results in failure?

[Gearhead999s]

Originally Posted by Radiation Joe

They are not difficult to make. I'm just surprised they are not readily available for our cars. Can you teach me the secret handshake to get a set? Do I have to run Hawk pads to enter this secret society of the bronze bushings?

They came in a brown paper bag!My buddy that supplied them to be no longer works there as he is recovering from a road accident.I will follow up with him to see what I can dig up.

[Gearhead999s]

Originally Posted by lucid

Applying the braking torque more evenly does not mean you will have less heat to dissipate in the system (I can't tell if that is or isn't what you are saying above). The heat is being generated during the conversion of the kinetic energy of the car to, simply put, heat. That's what a brake system does. If you go faster, you have more energy to convert into heat. Ideally, the heat would be transferred into the rotor entirely, but obviously that is not the case.

As to how the heat generated at the pad/rotor interface is trasferred to the rest of the system other than the rotor. The pad makes direct contact with the caliper at various places, so there is conductive heat transfer there. The pad also makes contact with the pistons, so there is conduction there as well. And there is conduction between the caliper and the pistons. (Never mind the convective and radiant heat transfer between the rotor and everything else). Would having more pistons decrease piston temperatures? I don't know as that depends on the specifics of the contact areas in all of the interfaces and many other variables such as the masses and materials of the individual components, but I don't think we can simply assume that it will. If you have more total pad/piston contact area, you might even increase piston temperatures (more energy might flow into the pistons as opposed to the rotors). You'd need to analyze the entire system as a thermal curcuit.

In general, the bottom line is when there is excess heat in the rotor that you can't transfer into the environment via rotor cooling, everything will eventually heat up, and parts of the system will begin to fail.

Check out what they do on a Nascar Cup car.They weigh 3400 lbs with 850 bhp!

http://www.prosystembrakes.com/catalogpg016.htm

They usually run 3 ducts per wheel with inline blowers to ensure plenty of air flow to cool the brakes.All this in a 15" wheel!

[lucid]

Originally Posted by Gearhead999s

They usually run 3 ducts per wheel with inline blowers to ensure plenty of air flow to cool the brakes.All this in a 15" wheel!

Sound heavy duty indeed. Do you have pics of the cooling setup?

[Gearhead999s]

Originally Posted by lucid

Sound heavy duty indeed. Do you have pics of the cooling setup?

Good article here.

http://www.stockcarracing.com/techar...rol/index.html

Interesting stuff here.

http://www.renagadecomposites.com/NASCAR.html

[lucid]

Originally Posted by Gearhead999s

Good article here.

http://www.stockcarracing.com/techar...rol/index.html

Interesting stuff here.

http://www.renagadecomposites.com/NASCAR.html

Thanks. Quote from that article:

"Your brake temperatures really need to stay below 400 degrees Fahrenheit," says Derek Spencer of Performance Friction, who works with race teams on their brake packages. "And 400 is kind of pushing it. If you get above that, the seals in the calipers start to crack and deteriorate. If you can keep your maximum temps below 350, you are doing good. Anytime you find you have exceeded 410 degrees, it's a good idea to go ahead and rebuild your calipers."

Not sure what part of the brake system he is referring to, but I don't see how one can keep rotor temperatures that low on the E92 M3.

[Gearhead999s]

Originally Posted by lucid

Thanks. Quote from that article:

"Your brake temperatures really need to stay below 400 degrees Fahrenheit," says Derek Spencer of Performance Friction, who works with race teams on their brake packages. "And 400 is kind of pushing it. If you get above that, the seals in the calipers start to crack and deteriorate. If you can keep your maximum temps below 350, you are doing good. Anytime you find you have exceeded 410 degrees, it's a good idea to go ahead and rebuild your calipers."

Not sure what part of the brake system he is referring to, but I don't see how one can keep rotor temperatures that low on the E92 M3.

I think that is refering to caliper & fluid temps.

[Radiation Joe]

Originally Posted by lucid

Joe, can you clarify what you mean above? How does uneven pad/rotor contact result in piston failure? Are you saying that also results in uneven pad/piston contact and that somehow loads the piston in a manner that results in failure?

There are myriad problems caused by the flexing of the caliper in it's mount. Here are the first three that come to mind.

1. uneven pad contact results in reduced friction and braking power.
2. pads actually bend (as shown in one of Junior's photos).
3. When pads unevenly contact the rotor, the piston is loaded unevenly. This can cause the piston to cock in it's bore, potentially sticking.

[lucid]

Originally Posted by Radiation Joe

There are myriad problems caused by the flexing of the caliper in it's mount. Here are the first three that come to mind.

1. uneven pad contact results in reduced friction and braking power.
2. pads actually bend (as shown in one of Juniors photos).
3. When pads unevenly contact the rotor, the piston is loaded unevenly. This can cause the piston to cock in it's bore, potentially sticking.

I see what you are saying with 1 and 2, but not really related to piston failure. 3 might be an issue, but hard to tell to what extent. I still think this particular case is mainly related to the overheating of the entire system and the seals failing in the process.

[lucid]

Originally Posted by Gearhead999s

I think that is refering to caliper & fluid temps.

Most likely. I've never measured caliper temperature on this car. I will next time I drive it on the track. My only basis from personal experience is that the caliper paint has cracked and fallen off--very much like the cracking of paint in the pics the OP posted--but I don't know at what temperature that is likely to happen.

[JCtx]

I'd rename the thread as 'Biblical brake abuse' .

But yes, even though our 1-piston calipers are not the same as on Hondas and such, there's no excuse to at least have 4-piston calipers in the front and 2-piston on the rear on a high-performance V8 car IMO (like all the M3's competitors). At least as an option. Take care.

[Radiation Joe]

Originally Posted by lucid

I see what you are saying with 1 and 2, but not really related to piston failure. 3 might be an issue, but hard to tell to what extent. I still think this particular case is mainly related to the overheating of the entire system and the seals failing in the process.

I'm postulating that the piston failure caused the excessive heat. Note in one of the earlier posts, the OP noted that the other side didn't wear as much.

[Gearhead999s]

Originally Posted by lucid

Most likely. I've never measured caliper temperature on this car. I will next time I drive it on the track. My only basis from personal experience is that the caliper paint has cracked and fallen off--very much like the cracking of paint in the pics the OP posted--but I don't know at what temperature that is likely to happen.

Here is what you need to use.Temp strips

http://www.performancefriction.com/pages/access.htm

[lucid]

Originally Posted by Radiation Joe

I'm postulating that the piston failure caused the excessive heat. Note in one of the earlier posts, the OP noted that the other side didn't wear as much.

I see. I missed that. Please articulate how piston failure would result in such excessive heat generation--to the extent that the brake line failed and fell off. If you have a stuck piston, sure there is more heat generated at the piston/caliper interface when you apply the brakes, but how much heat can that generate relative to the heat transfer into the caliper from the normal operation of the system due to friction at the pad/rotor interface?

[Gearhead999s]

Originally Posted by MERCSUk153

As much as I love the M3 I would have to say the GTR is definitely not ugly. While many say the S4 looks plain the M3 beside a GTR looks plain IMO. The M3 is a beautiful car but the GTR looks exotic.
They raised the price of the GTR like $20,000 crazy, when it initialy came out I could have gotten one for $80k-85k cdn. M3 loaded is like $75k so initially not that far apart but I guess it is now.

Well everybody has different tastesHave you driven a GTR?I have and i was not impressed.Fast yes,but not something that I could live with as a everyday car.As yes it is ugly

[Radiation Joe]

Originally Posted by lucid

I see. I missed that. Please articulate how piston failure would result in such excessive heat generation--to the extent that the brake line failed and fell off. If you have a stuck piston, sure there is more heat generated at the piston/caliper interface when you apply the brakes, but how much heat can that generate relative to the heat transfer into the caliper from the normal operation of the system due to friction at the pad/rotor interface?

My guess is that the piston was not fully releasing. So that brake just sits there generating heat while the other three corners get a rest between applications. It won't take long for a major failure in this scenario.

[lucid]

Originally Posted by Radiation Joe

My guess is that the piston was not fully releasing. So that brake just sits there generating heat while the other three corners get a rest between applications. It won't take long for a major failure in this scenario.

Well, that would result in strange/uneven handling if it is to generate significant heat. Hard to believe that a pro driver would not notice one of the brakes dragging like that...Anyway, the good thing he didn't end up in a wall or something.

[TOOMANYCARS]

I think the stock brakes are perfectly fine handling street duties, but if you plan to track it on weekends, it's "Logic 101" that you HAVE to do the BBK upgrade.

[swamp2]

Wow very warm rotors. This image looks to be around 700°C or 1300°F. Warm to say the least.

[Trier Germany]

Originally Posted by Lemans_Blue_M

Dude,

You abused the stock braking system past the point of no return.

Oh, and by the way...'cool air into the wheel arches' wouldn't have helped you in this situation...

Unless you direct that cool air into the center of the brake rotor disc (via backing plates), it won't cool the rotor down to prevent overheating.

BTW: You actually spent time making improvements...and you didn't upgrade the softer OE rubber brake lines with Sainless Steel units?

The 'problem' as I see it...is the person sitting in the drivers seat.

You didn't upgrade your brakelines! Fowl on you! Definately brake abuse!!!

[swamp2]

I also firmly agree that piston count is no where close to equivalent to lower operating temps. Heat generation is based on primarily how much speed is scrubbed off, how often that happens and how much your car weighs. The problems with the M3 system are:

1. Car weighs too much compared to rotor mass.
2. Not enough cooling flow to rotors (of course this was probably mitigated in this case).
3. Insufficient rotor vane cooling of the rotor.

Last but not least I firmly agree with those who have pointed out that in this case the car was firmly out drivered. I'd bet the OP could easily toast most Audi and Merc brake systems as well.