E36 Brake Woes

RodneyWright · **Posted:** Tue Nov 21, 2006 9:12 pm

Good idea to split the thread, sorry I hijacked it for a brake bitch....

Update: Talked to Dave Davis today and here's the theory that Dave laid out. First, he doesn't believe it's the MC since it's braking but with a soft pedal. Since I was into the ABS most of the time coming into turn 3 at the Rockingham HPDE, I was really pounding the brakes. Since there is inherent flex for the single piston caliper on front, there is some "rotation" of the piston as the agressive brakes grab the rotor. If you look at the pads from a sideways view, you can see the pad material is actually shaped like a wedge, hence the problem.

There is initial contact from the tall side of the pad, then it stays spongy until the piston is rotated and pad is forced flat to the rotor. Plan on putting the hawk HPS pads back on tomorrow and remove the hawk HP+. These pads were working very well when they came off, we'll see how the brakes respond with the swap.

I guess a sideways question from this is, is it possible to take the wedge out of the pads? Is there anyway to true up the pads? I hate to toss a set of $100 pads with only 150 miles. Is it possible to put them on a belt sander? Just asking...

thanks

steve remchak · **Posted:** Tue Nov 21, 2006 9:38 pm

hmmnn, can't answer that one Rodney. but welcome to the club. seems to me a multiple piston upgrade would be cheaper in the long run.

i got 5 events out of my Hawk Blues. i really only pushed them for maybe 2.5 of those events. and when they went (similar to your experience) they were a challenge to maintain. basically pumping prior to the braking zone as much for pedal as for reassurance.

sounds to me like you are in need of more pad. cheaper than the big brake kits. again, welcome to the addiction Rodney. you will need to refer to pads as "consumables" henceforth.

oh yeah, i found out today that some time during all that brake pumping i tore a rear sway bar mount loose from the sub-frame. broke the weld loose apparently. i must say, i do love VIR-South. a workout worthy of any Euro engineering.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Well if this is what is affectionately known as "pad taper" then welcome to the effects of tracking your car :wink:

While I'm not a Bimmer guy. The C5 suffers from leading edge pad taper in the front caliper. On my car this is caused by the fact that the caliper is aluminum and flexes under high heat and load. After a couple of years they get annealed (sp?) and it is best to throw them away. The pad taper just gets even worse. The only cure for pad taper for me is to use a 4 or 6 piston front caliper.

In order to stretch the amount of events/miles I get out of a set of pads. I swap the pads outside/inside on the same side of the car after every event when I go to bleed off some fluid.

Also if you are having problems bleeding the system and it is due to air in the ABS module. Not sure about BMW but on the GM cars you have to have the system bled using a Tech II system. It cycles the ABS while bleeding and does a complete flush.

steve remchak · **Posted:** Wed Nov 22, 2006 12:07 am

Graham Jagger wrote:

Well if this is what is affectionately known as "pad taper" then welcome to the effects of tracking your car :wink:

While I'm not a Bimmer guy. The C5 suffers from leading edge pad taper in the front caliper. On my car this is caused by the fact that the caliper is aluminum and flexes under high heat and load. After a couple of years they get annealed (sp?) and it is best to throw them away. The pad taper just gets even worse. The only cure for pad taper for me is to use a 4 or 6 piston front caliper.

In order to stretch the amount of events/miles I get out of a set of pads. I swap the pads outside/inside on the same side of the car after every event when I go to bleed off some fluid.

Also if you are having problems bleeding the system and it is due to air in the ABS module. Not sure about BMW but on the GM cars you have to have the system bled using a Tech II system. It cycles the ABS while bleeding and does a complete flush.

hey, i thought the C5 Z06 had a 4 piston front caliper?

RodneyWright · **Posted:** Wed Nov 22, 2006 5:15 pm

Graham Jagger wrote:

Well if this is what is affectionately known as "pad taper" then welcome to the effects of tracking your car :wink:

Call this what you will, but I think "pad taper" sucks. Pulled the HP+ pads and checked them with a caliper, definately a high side and low side. Worst case was almost .01" difference with an average of .007" out of tolerence. You can see on the rotor where only half of the pad was engaging under normal driving. Right now I have to say that 328 single piston brakes perform less than adequate in performance braking.

Not sure if there is any salvaging of the HP+ pads. I'm going to try to bring them back down to even with a belt sander. Just need to rig up some kind of pad holder so I can control the pad take off. I figure, what do I have to loose, can't use the pads as they are now.

Anyway, installed the HPS pads and the brakes are back and feel great again. MC was not the issue, just bad pad taper.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

RodneyWright wrote:

Call this what you will, but I think "pad taper" sucks.

So don't we all, unless you go to 4-6 piston front calipers.

Does the inside or outside pad taper the same way? Same amount?

If so then you're stuck. If not then swap pads inside/outside at the end of each day at the track. You'll get more use out of the pad and it'll force you to check the caliper/rotor/pad each day.

Along with pad taper comes rotor cracking. The more aggresive the pad and the harder the particular track is on brakes. Rotors start showing small heat checks. One of them will expand during cool down and crack end to end on the outside face. If you're standing near a car that is doing it you'll hear a nice "tingggg" sound. Rotor gone. Next...

Rotors and pads are disposables.

Good luck grinding your pads. Let us know how that works out.

DanDurusky · **Joined:** Sun Apr 10, 2005 7:31 pm **Posts:** 686

Any of you E36 guys use brass caliper bushings? i'm still a noob, but i run them daily/autox and on track and both my daily/autox and track pads look and feel decent. It'll be interesting to see how they wear w/ more track days on the pads, but so far so good

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

RodneyWright wrote:

Well, I think I've come to conclusion as to what's wrong. Been reading bimmerforums (and sifting thru the junk posts) and looked over the bentley manual and have it narrowed down to a bad master cylinder. Fails the bentley test for pumping the brakes up 10 times with the engine off and then turning on the engine with your foot still on the brakes. According to the manual, the brake pedal should fall "just a bit" after you turn on the engine. Mine falls completely to the floor.

rats....

The bentley manual, which is usually quite good, totally misses the mark with this test. "Just a little bit" can feel like a LOT. It's way too subjective. As I mentioned before, test for a leaky MC with the car running.

markodell · **Joined:** Wed Jul 27, 2005 6:19 pm **Posts:** 65

I have stock BMW brakes on both my BMW track cars (E30 M3 and E46 328i), and have seen pretty significant pad taper on both of them. My E46 328i actually has the larger E46 330i brakes, which are roughly the same size as an E36 M3 brake rotor.

Despite this, while I've noticed the brakes do get a bit spongier as the pads wear, its not anything I can't live with. I don't have to pump up the brakes, it just seems to increase the initial travel of the pedal a bit before I get activation. If you are finding the braking to be unacceptable, then I can think of a couple of alternatives.

According to some of the folks on other forums, the stock E46 330i brake calipers and rotors will work on an E36 32x. If you could find some used calipers on Ebay, that would be an extremely cost effective upgrade. Here is a link which talks about this.

http://www.mail-archive.com/bmwuucdiges ... 06421.html

Another alternative is to upgrade to E36 M3 brakes, however it does require the hub be replaced. Turner sells a kit, but of course Ebay would be cheaper.

http://www.turnermotorsport.com/html/de ... toM3brakes

Good Luck!

steve remchak · **Posted:** Thu Nov 23, 2006 10:11 am

DanDurusky wrote:

Any of you E36 guys use brass caliper bushings? i'm still a noob, but i run them daily/autox and on track and both my daily/autox and track pads look and feel decent. It'll be interesting to see how they wear w/ more track days on the pads, but so far so good

yes, but the issue still exists. Rodney, i have some old HP+'s you can have if you want to look at them. probably still have 1/2 or more left.

i pitched them because i was overdriving them. Blues were the ticket for that.

RodneyWright · **Posted:** Thu Nov 23, 2006 9:41 pm

Graham Jagger wrote:

Does the inside or outside pad taper the same way? Same amount?

I found this to be an interesting question, so I placed the right side and left side pads together. Wasn't what I expected. The face of the pads fit together perfectly. Also using the digital caliper again, I found that there was on the average about .0015 difference from end to end by measuring from the outside of the backing plates. I would have expected them to be tapered more on one end than the other.

The way they look now, it's like the rotor was twisting and caused the tapering. I've checked the front rotors and had Dave check the front end and there's no problem with the front bearings that I'm aware of, but it sure looks like a twist of the bearings/rotor. I guess what was happening was the entire brake assembly was twisting. Damn, talk about some brake forces being applied!!!!

Steve Remchak wrote:

Rodney, I have some old HP+'s you can have if you want to look at them. probably still have 1/2 or more left.

Steve, I'd be happy to take these off your hands. Maybe I can salvage something out of 8 pads.

Mark Odell wrote:

According to some of the folks on other forums, the stock E46 330i brake calipers and rotors will work on an E36 32x. If you could find some used calipers on Ebay, that would be an extremely cost effective upgrade. Here is a link which talks about this.

http://www.mail-archive.com/bmwuucdiges ... 06421.html .

Mark, great information!! The only problem is if I do this, knocks me out of STS. Someone in the club long ago stated, build the car the way you want it, and class it accordingly. May have to take that advice.

markodell · **Joined:** Wed Jul 27, 2005 6:19 pm **Posts:** 65

RodneyWright wrote:

Graham Jagger wrote:

Does the inside or outside pad taper the same way? Same amount?

I found this to be an interesting question, so I placed the right side and left side pads together. Wasn't what I expected. The face of the pads fit together perfectly. Also using the digital caliper again, I found that there was on the average about .0015 difference from end to end by measuring from the outside of the backing plates. I would have expected them to be tapered more on one end than the other.

Yep, that's exactly what they do on mine as well. Believe it or not, that is normally how they wear.

Bernie Baake · **Posted:** Fri Nov 24, 2006 9:18 am

RodneyWright wrote:

Well, I think I've come to conclusion as to what's wrong. Been reading bimmerforums (and sifting thru the junk posts) and looked over the bentley manual and have it narrowed down to a bad master cylinder. Fails the bentley test for pumping the brakes up 10 times with the engine off and then turning on the engine with your foot still on the brakes. According to the manual, the brake pedal should fall "just a bit" after you turn on the engine. Mine falls completely to the floor.

rats....

Sounds like there's more to it than a .0015 variation in the pads. Rotor twist also seems unlikely and it should be measurable. Whats causing the brake pedal to fall to the floor during the bently test??? Rotor twist that causes the pedal to fall to the floor, I would believe to be visually detectable. Just an opinion I don't have a lot of experience with brakes.

markodell · **Joined:** Wed Jul 27, 2005 6:19 pm **Posts:** 65

Although I know you weren't planning to go this route, I should also mention if you decide to do one of the brake upgrades I mentioned, it will require 17" wheels....

RodneyWright · **Posted:** Fri Nov 24, 2006 3:26 pm

Bernie Baake wrote:

Sounds like there's more to it than a .0015 variation in the pads. Rotor twist also seems unlikely and it should be measurable. Whats causing the brake pedal to fall to the floor during the bently test??? Rotor twist that causes the pedal to fall to the floor, I would believe to be visually detectable. Just an opinion I don't have a lot of experience with brakes.

I guess I should have posted this, but after I put the HPS pads back on, I ran the same brake test. It passed with non-tapered pads installed. Pumped up the brakes and then turned on the engine. The pedal fell, but not to the floor. I guess having the bad tapered pads produced a positive bad test for the MC. I also agree that it's not rotor twist based on Mark's statement that he see's the same thing on his bimmers.

Mark Odell wrote:

Although I know you weren't planning to go this route, I should also mention if you decide to do one of the brake upgrades I mentioned, it will require 17" wheels.....

Thanks for the heads up Mark. Already running 17" wheels, so no problem there. I read the post and it looks like I can replace both the front and rear brakes with the rotors, calipers and calipers mounts from the 330. I didn't see anything else mentioned. Is that all I need to purchase?

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