[ToddPhilly]

I did a 3-day track weekend out at Thunderbolt at NJMP this past weekend. Apparently I got the brakes pretty hot. When I came in there was some plastic smelling smoke coming out of the right front brake area. I swaped out my Hawk HP+ pads with OEM yesterday and I noticed that the black rubber surround of the brake piston is toast. Can I leave it that way? Brakes seem to feel fine this morning. Is it just to keep dirt and whatnot out of the piston? Any long term impact?

[leftcoastman]

It is just a dust boot. It keeps grit from getting inside and destroying the actual piston seal. Brakes need rebuilding. You can just do it once a year.

Put it this way. I put on brand new boots. Fried them in ONE session, even with titanium shims. If you're running track oriented pads, r-comps and especially upgraded power, you will fry your boots.

Feel proud. You are heating up the brakes nicely.

[ToddPhilly]

Originally Posted by leftcoastman

It is just a dust boot. It keeps grit from getting inside and destroying the actual piston seal. Brakes need rebuilding. You can just do it once a year.

Put it this way. I put on brand new boots. Fried them in ONE session, even with titanium shims. If you're running track oriented pads, r-comps and especially upgraded power, you will fry your boots.

Feel proud. You are heating up the brakes nicely.

So I should NOT drive over the winter with this boot destroyed...

How hard is it to replace the boot. Can you do it yourself?

[leftcoastman]

Originally Posted by ToddPhilly

So I should NOT drive over the winter with this boot destroyed...

How hard is it to replace the boot. Can you do it yourself?

Well, being that you're in the NE and subjected to road salt, I wouldn't. You don't want your pistons to be scored by the grime.

Google "rebuilding calipers". That's what you'd be doing. Not technically difficult, but can be messy and frustrating the first time. All BMW floating calipers are essentially the same, so rebuilding instructions for an E36 would be similar to the E9x.

Another thing to consider: Seals are $30 for each caliper. Factor in time to install it. New calipers can be had for about $300 each.

[ToddPhilly]

Originally Posted by leftcoastman

Well, being that you're in the NE and subjected to road salt, I wouldn't. You don't want your pistons to be scored by the grime.

Google "rebuilding calipers". That's what you'd be doing. Not technically difficult, but can be messy and frustrating the first time. All BMW floating calipers are essentially the same, so rebuilding instructions for an E36 would be similar to the E9x.

Another thing to consider: Seals are $30 for each caliper. Factor in time to install it. New calipers can be had for about $300 each.

I assume no chance of being covered under warranty. This kind of bugs me. Basically BMW brakes are garbage. I have friends who track their porsche 40 days a year without having to 'rebuild' their calipers routinely.

[satakal]

does the free 50k maintenence apply here?

[S4to335]

Originally Posted by leftcoastman

It is just a dust boot. It keeps grit from getting inside and destroying the actual piston seal. Brakes need rebuilding. You can just do it once a year.

Put it this way. I put on brand new boots. Fried them in ONE session, even with titanium shims. If you're running track oriented pads, r-comps and especially upgraded power, you will fry your boots.

Feel proud. You are heating up the brakes nicely.

Alcons are my friend.

[ZBMW]

"I assume no chance of being covered under warranty. This kind of bugs me. Basically BMW brakes are garbage. I have friends who track their porsche 40 days a year without having to 'rebuild' their calipers routinely."

I rebuilt calipers regularly on my E28 after HPDE's. There's nothing wrong with the brake setup. It has everything to do with the pads you use. Back in the 80's metalmasters were the hot pad but on a fast track they would emit sparks braking for a slow corner. That would toast the dust boot. Later I went to carbon fibre based pad which lasted years and I never had to replace boots even though my speeds were much faster.
I'm not looking for an argument but I was under the impression that Porsche brakes, while very good, were a high maintenance item. In any event, you've got the right car.

[ToddPhilly]

Originally Posted by ZBMW

"I assume no chance of being covered under warranty. This kind of bugs me. Basically BMW brakes are garbage. I have friends who track their porsche 40 days a year without having to 'rebuild' their calipers routinely."

I rebuilt calipers regularly on my E28 after HPDE's. There's nothing wrong with the brake setup. It has everything to do with the pads you use. Back in the 80's metalmasters were the hot pad but on a fast track they would emit sparks braking for a slow corner. That would toast the dust boot. Later I went to carbon fibre based pad which lasted years and I never had to replace boots even though my speeds were much faster.
I'm not looking for an argument but I was under the impression that Porsche brakes, while very good, were a high maintenance item. In any event, you've got the right car.

I may need to look at the "cool carbon" pads. The Hawk HP+ pads are metallic based, and clearly get VERY hot.

I really can't speak from personal ownership of dealing with Porsche brakes, but I go to the track with PCA. The "Big Red" brakes on 996 & 997 911's seem to be fantastic. Having driven a few 996's on track, they perform great. My brakes are not even in close to the same league.

[ToddPhilly]

Originally Posted by satakal

does the free 50k maintenence apply here?

This brake boot isn't really a maintenance/wear item. It would be more of a warranty item. Regardless, I'm sure they'll reject due to being on track.

[leftcoastman]

It's not a BMW brake problem. I vaporized the boots on my aftermarket calipers. I just helped a friend rebuild his $7500 Brembo GT brakes. If you get the brakes hot enough, rubber will vaporize. They don't make magic rubber. Many race calipers do not come with dust boots for this very reason.

I could run stock pads, stock power and stock tires and do track days till the cows came home and the rubber boots would be fine. Increase power, increase grip and increase braking "friction" and you will fry boots.

In some sense, brake pad material - if it isn't as "hot", it will also not be as grippy. You have X amount of speed to bleed off. You can do it over a long period of time (think stock pads) and hope the brake cools some as heat is being added through braking...or you can get race pads and brake harder and generate more heat in a short period of time. Or since kinetic energy increases as a square of speed, you could pull your turbos off and you'll be fine on the stock brakes for all eternity.

Try titanium shims as a heat shield. They may help as they reduce piston temps by ~70deg.

Steve - with your Dinan St2 and wider Rcomps and if you do race pads, I assure you that you'll fry your dust boots. Alcon does not make voodoo rubber.

[Mr. 5]

I've seen the titanium shims, but what's the difference in getting a titanium sheet and cutting them yourself?
I was thinking of doing this but I don't know the thickness of normal shims.

Also, when putting the shims in place, do you use any brake quiet or anything in between the shim and pad or shim and piston?

[leftcoastman]

There is no difference. You can do it yourself.

I used 6AL-4V titanium with a 1mm thickness. But since your rotora fronts are the same shape as the Stoptech 6piston, you can just buy em from Zeckhausen...precut.

I only use shims on track, so obviously didn't put any disc brake quiet on em. I highly doubt you could ever get the brakes hot enough on the street to necessitate Ti shims. Even if you're doing a canyon run, I presume you won't be running full race pads. Even if you were, you wouldn't be doing the same level of braking as you would on track.

[Mr. 5]

Originally Posted by leftcoastman

There is no difference. You can do it yourself.

I used 6AL-4V titanium with a 1mm thickness. But since your rotora fronts are the same shape as the Stoptech 6piston, you can just buy em from Zeckhausen...precut.

I only use shims on track, so obviously didn't put any disc brake quiet on em. I highly doubt you could ever get the brakes hot enough on the street to necessitate Ti shims. Even if you're doing a canyon run, I presume you won't be running full race pads. Even if you were, you wouldn't be doing the same level of braking as you would on track.

Well, I'm using the yellowstuff pads and they worked pretty damn good with both street and track so if I put the tatinum shims on, they're staying there.

[leftcoastman]

Give it a shot...should be fine without any antisqueal.

If you really need it, you can put it on. I bet that stuff melts though. that could be a nasty surprise if it melts and gets on your rotors.

[ToddPhilly]

Originally Posted by leftcoastman

It's not a BMW brake problem. I vaporized the boots on my aftermarket calipers. I just helped a friend rebuild his $7500 Brembo GT brakes. If you get the brakes hot enough, rubber will vaporize. They don't make magic rubber. Many race calipers do not come with dust boots for this very reason.

I could run stock pads, stock power and stock tires and do track days till the cows came home and the rubber boots would be fine. Increase power, increase grip and increase braking "friction" and you will fry boots.

In some sense, brake pad material - if it isn't as "hot", it will also not be as grippy. You have X amount of speed to bleed off. You can do it over a long period of time (think stock pads) and hope the brake cools some as heat is being added through braking...or you can get race pads and brake harder and generate more heat in a short period of time. Or since kinetic energy increases as a square of speed, you could pull your turbos off and you'll be fine on the stock brakes for all eternity.

Try titanium shims as a heat shield. They may help as they reduce piston temps by ~70deg.

Steve - with your Dinan St2 and wider Rcomps and if you do race pads, I assure you that you'll fry your dust boots. Alcon does not make voodoo rubber.

I'm more concerned it's a cooling problem. I'm sure BBKs and the Big Red's on porsche cool much more efficiently than my stock BMW brakes. I'm sure the Porsche also does a better job at getting cool air to the brakes. The tiny air duct on my car couldn't cool a hot slice of pizza.

[leftcoastman]

It's always a balancing act. If you overcool the brakes on the street, that could also cause problems. Excessive heating and cooling cycles will result in cracked rotors. Been there, done that.

Keep in mind that Porsches don't weigh what our cars weigh and in the case of the Cayman, Cayman S and 911 (non-S, non turbo), don't generate the same speed on the straights.

I've been around racing long enough that just about everyone accepts that you have to rebuild calipers if you're tracking the car. Do a google search on "brake dust boot track use".

I may develop direct cooling ducts for track use. I'll block em off for street use. Next time you're around an e9x M3, take a look inside the front wheel well. You'll notice something is missing: any brake ducts at all.

[nicknaz]

Originally Posted by ToddPhilly

Apparently I got the brakes pretty hot. Hawk HP+ pads

I was under the impression from speaking with Hawk sales people that the HP+ pad and the HPS pad have the same (low) maximum operating temperature

I'm sure I'm missing something here, but how are you able to heat up the brakes enough to melt the dust boot rubber and not overheat the HP+ pad in a huge way? (perhaps the overheat/melting of the HP+ contributed to this melting of boot?)

Apples and oranges to compare a WRX to a E9X but I've melted Hawk HPS/Brembo 'performance' (misnomer) pads and other street pads before without harming the rubber seal so something seems fishy here

I buy the argument that r comps, race pads and big power with generate big heat, but with HP+ (essentially a grabby street pad) in the picture are we sure there is really THAT much heat in the system?

[leftcoastman]

The pad can overheat, reduce it's coefficient of friction and still generate more heat.

Secondly, pad thickness is related to heat transfer. Thin pads will transfer more heat to the piston.

Thirdly, even if you don't fry the boots the first time out, the multiple heat cycles will weaken the material until it goes kaput.

The final problem, which is really really bad is if the caliper is sticking. It will overheat the crap outta the pads and cause the boot to fry as a result. Beentheredonethat, too.

[ToddPhilly]

Originally Posted by leftcoastman

The pad can overheat, reduce it's coefficient of friction and still generate more heat.

Secondly, pad thickness is related to heat transfer. Thin pads will transfer more heat to the piston.

Thirdly, even if you don't fry the boots the first time out, the multiple heat cycles will weaken the material until it goes kaput.

The final problem, which is really really bad is if the caliper is sticking. It will overheat the crap outta the pads and cause the boot to fry as a result. Beentheredonethat, too.

I think leftcoastman hit the nail on the head...pad thickness. It wasn't until my last run session of the last day that I cooked the boots. By my last run session, the pad thickness was pretty thin...moreso on the right side than the left for some reason. However, both boots are toast. I'm curious now to check the rear boots. I'm running stock pads on the rear. I'll be really surprised if I cooked the rear boots as well.

[leftcoastman]

Originally Posted by ToddPhilly

I think leftcoastman hit the nail on the head...pad thickness. It wasn't until my last run session of the last day that I cooked the boots. By my last run session, the pad thickness was pretty thin...moreso on the right side than the left for some reason. However, both boots are toast. I'm curious now to check the rear boots. I'm running stock pads on the rear. I'll be really surprised if I cooked the rear boots as well.

My passenger pads always wear faster than my driver's. That has been true for the all 6 sets of pads I've gone through.

My reasoning is that the passenger pads get extra heat from the oil cooler exhaust. And pad wear is a function of pad temperature.

[ToddPhilly]

Originally Posted by leftcoastman

My passenger pads always wear faster than my driver's. That has been true for the all 6 sets of pads I've gone through.

My reasoning is that the passenger pads get extra heat from the oil cooler exhaust. And pad wear is a function of pad temperature.

Was the same for me. Passenger side wore faster...which makes you wonder why BMW put the brake pad sensor on the driver side!