ZPOST
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   ZPOST > BMW Z4 Technical Talk > Track / Autocross / Dragstrip / Driving Techniques
  TireRack

SUPPORT ZPOST BY DOING YOUR TIRERACK SHOPPING FROM THIS BANNER, THANKS!
Post Reply
 
Thread Tools Search this Thread
      01-22-2014, 12:25 AM   #1
dschultz
Private First Class
dschultz's Avatar
26
Rep
195
Posts

Drives: 07 Z4MC
Join Date: Sep 2012
Location: Bay Area

iTrader: (2)

Why are my brakes cooked?

Help!

My front brakes seemed to be chattering a bit so before I take them to Laguna Seca this weekend I decided to have my mechanic check them. They said they had been badly overheated and that the calipers needed to be rebuilt. I trust these guys and no reason not to believe them. I have all of 4 track days in this car. My last track event was at Thunderhill in November. I never felt any brake fade, I don't think I was particularly hard on the brakes, I am certainly not the fastest or more aggressive driver out there. I am very careful on the cooldown lap and do a couple of laps around the paddock after every session before parking. So... what gives? Is it my driving style? Braking style? Z4MC, ATE Blue brake fluid, fresh before the last event. ... the only mods are a cup holder and stubby antenna!
Appreciate 0
      01-22-2014, 12:42 AM   #2
i2ichal2dZ4M
Lieutenant
61
Rep
516
Posts

Drives: 2007 BSM Z4MC
Join Date: Mar 2011
Location: Los Angeles, California

iTrader: (1)

explain chattering, definition/symptom may be differnt between others. did you try to rebead the pads?
__________________
2007 BSM Z4M Coupe - 18" VOLK TE37 - 18" Apex ARC-8 - GC Track/Street
Appreciate 0
      01-22-2014, 12:52 AM   #3
Finnegan
Dog Listener
Finnegan's Avatar
United_States
701
Rep
7,850
Posts

Drives: Z4M/. Z3M, E36/46 M3
Join Date: Oct 2008
Location: Teaching the dog to slalom

iTrader: (22)

Quote:
Originally Posted by dschultz View Post
Help!

My front brakes seemed to be chattering a bit so before I take them to Laguna Seca this weekend I decided to have my mechanic check them. They said they had been badly overheated and that the calipers needed to be rebuilt. I trust these guys and no reason not to believe them. I have all of 4 track days in this car. My last track event was at Thunderhill in November. I never felt any brake fade, I don't think I was particularly hard on the brakes, I am certainly not the fastest or more aggressive driver out there. I am very careful on the cooldown lap and do a couple of laps around the paddock after every session before parking. So... what gives? Is it my driving style? Braking style? Z4MC, ATE Blue brake fluid, fresh before the last event. ... the only mods are a cup holder and stubby antenna!
Lots of folks here with lots of track days, not many with cooked brakes. So, .

The most common cause of chatter, vibration, or "warped rotor" feel is uneven pad deposits. Floating rotors don't warp (very hard to do). Uneven pad deposits, however, are easy to acquire. There are numerous causes. The most common would be using the wrong pad for the application (e.g. stock pads or low MOT pads, etc.).

Not that I'm saying your mechanics are wrong, but the last person I know with a Z4M who "cooked" their brakes and had to rebuild really cooked them--as in they were smoking and pretty much on fire. And a rebuild in that case was really replacing the seals, not new pistons. While it's possible a caliper rebuild is needed, it doesn't sound like you've gotten the brakes hot enough to do that. Perhaps the prior owner did?

Even if you need a rebuild, that may be an independent issue from the chatter, which I'd again attribute more to deposits. Deposit issues are easily fixed with a re-bedding of pads in most cases, or, swapping out for an aggressive "cleaner" pads like hawk blues for a short period. Rebuild is more about safety IMO, and, that's if really needed.

If you're using stock pads, you might want to move up to a higher MOT pad, re-bed, or scrub the rotors as noted in the link, or some combo. No one right answer here, it depends on the cause.
Appreciate 0
      01-22-2014, 07:37 AM   #4
z3papa
Captain
United_States
190
Rep
969
Posts

Drives: 11 E92 M3 ZCP, 07 335i
Join Date: Oct 2009
Location: Bloomington IL

iTrader: (2)

I'd agree that most likely it is warped rotors or pad deposits. Braking technique has a big impact on rotor wear/heat. I don't know your style but I tend to be on and off brakes very fast since I try to minimize the time from brake to accelerator while getting to the threshold of optimal braking as quickly as possible. While not for the feint of heart, this minimizes transitional lift issues, and puts far less stress on the rotor than a slower progression of braking some implement much as if they were driving on the street.
__________________
Sold 2011.5 E92 M3 ZCP.
Appreciate 0
      01-22-2014, 10:48 AM   #5
mfanatic325
///M-fanatic
mfanatic325's Avatar
Taiwan
192
Rep
3,885
Posts

Drives: '01 911 Turbo
Join Date: Oct 2007
Location: Cupertino, CA.

iTrader: (23)

I'm willing to bet that it's just your brake pads *bleeping* on your rotors, causing the terrible brake feel.
I'm also willing to bet that the shop you're going to just wants to make a quick buck...stock calipers can't possibly need rebuilding so soon

For the record, OEM rotors are damned good. It's the OE fluid and pads that can't stand up to even medium track use. But you knew that already

BBKs might be on your shopping list down the road if you seriously want to get into tracking and know that you'll be going several times a year. They're quite expensive, but well worth it. The peace of mind you get from not having to worry about any of your braking while on track is beyond anything words can describe; simply blissful
Appreciate 0
      01-22-2014, 11:21 AM   #6
The HACK
Midlife Crises Racing Silent but Deadly Class
The HACK's Avatar
1817
Rep
5,337
Posts

Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day

iTrader: (1)

It's either the cup holder or the stubby antenna.

You didn't say what sort of brake pad compound and tires. Those could go a long way to figuring out what exactly is wrong with the brake system.

As for the rebuild recommendation by the mechanic, it's entirely possible that the dust boot on the caliper has melted under the extreme heat introduced by tracking, especially if you go to very brake intensive tracks like Laguna Seca. I've noticed on the OE calipers, when the pistons are fully retracted (i.e. when new pads were installed) sometimes the boot does not retract or "tuck" the right way, causing it to come in contact with the pad backing plate. Imagine the heat from the brake system that is capable of making solid iron glow red...It'll make minced meat out of some rubber boots.

Ever since "new" I've had to double check my dust boots when I put new pads on, and make sure that the boots are tucked right so as to not come in contact with the pad backing plate. That problem has mostly been alleviated now.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
Appreciate 0
      01-22-2014, 07:26 PM   #7
dschultz
Private First Class
dschultz's Avatar
26
Rep
195
Posts

Drives: 07 Z4MC
Join Date: Sep 2012
Location: Bay Area

iTrader: (2)

Thanks all. To answer some of the questions:

Pads are Axxis/PBR MetalMasters. I installed new rotors and pads before tracking the car. They have 4 track days on them (and are barely worn).

I haven't confirmed exactly what the shop did, but I believe they just replaced the caliper seals and boots. Will know more tomorrow.

Full disclosure... when I replaced the original rotors I noticed some minor damage to the caliper boot. It looked like a small nick, no outright melting. But I've never seen badly overheated brakes before so I may not recognize it if it's not really obvious. That's one of the reasons I wanted them to do a thorough inspection in the first place. (The recent chatter was the other.) So it's possible that the damage was from PO. Dunno.

I trust these guys, they've always done right by me. They also race bmws (nasa I think) and have done my track inspections for free (even when I *didn't* need additional work done!)

The chattering is recent, started happening long after my last trip to the track. It's a mild high frequency chatter, not what I would typically associate with warped rotors. Kind of "gravelly". Almost like ABS pulsing, but I'm pretty sure it's not ABS. The deposit/glazing theory sounds likely. I haven't tried to rebed the pads since it started happening. I'll give that a shot if it's still happening.

I guess I'll see what happens at Laguna Seca on Saturday. I'll pay extra attention to how I'm transitioning on/off the brakes. I've never had an instructor point out poor braking technique to me, but perhaps that's just because there are so many bigger issues.

Thanks for all your help.

@mfanatic325 -- "brake pads *bleeping* on your rotors"? Huh? Haven't heard that one before!
Appreciate 0
      01-22-2014, 07:29 PM   #8
dschultz
Private First Class
dschultz's Avatar
26
Rep
195
Posts

Drives: 07 Z4MC
Join Date: Sep 2012
Location: Bay Area

iTrader: (2)

Oh... tires... Michelin Pilot Sport PS2s. No R-compounds yet.
Appreciate 0
      01-22-2014, 10:25 PM   #9
mfanatic325
///M-fanatic
mfanatic325's Avatar
Taiwan
192
Rep
3,885
Posts

Drives: '01 911 Turbo
Join Date: Oct 2007
Location: Cupertino, CA.

iTrader: (23)

Quote:
Originally Posted by dschultz View Post
@mfanatic325 -- "brake pads *bleeping* on your rotors"? Huh? Haven't heard that one before!
I've had many sets of OEM pads *bleep* on my rotors after Laguna track days. This was all while I was still under warranty of course, and could get free brake pad replacements. The local stealershits got to know my car REALLY well; as they'd see my car in for another set of pads every month or so two years ago
Appreciate 0
      01-23-2014, 02:20 AM   #10
Finnegan
Dog Listener
Finnegan's Avatar
United_States
701
Rep
7,850
Posts

Drives: Z4M/. Z3M, E36/46 M3
Join Date: Oct 2008
Location: Teaching the dog to slalom

iTrader: (22)

Rubber boots--totally possible. Sounds like the mechanics know their stuff, so, I think it's all good. The chatter is an independent issue and it's a good bet it's pad deposits.

There's this guy on the forum here who has a great piece on braking techniques. Have a look. I found applying what I learned very helpful in both being consistent and getting the most out of managing my brakes. (Btw, that guy is "The Hack" .)
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 07:06 AM.




zpost
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST