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11-02-2008, 11:34 PM | #1 |
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135i Brake Pistons Revealed
After finding some serious cracking in the face of the pistons in the 135i race car, a lot of speculation has been floating around the Internet about the construction of the pistons, the performance of the pistons and the reasons as to why the face of the pistons were cracking.
Similar issues have occurred with other teams as well already. This thread is basically a continuation of... http://www.1addicts.com/forums/showthread.php?t=18453 On to the pics and findings... Attachment 13434 Attachment 13435 At first, we though the pistons were made of aluminum. We thought the race pads we were running (Hawk HT10 from Turner Motorsports) on the race car were getting so hot that the aluminum was melting. Turns out, we were wrong. They are made of stainless steel and a ceramic insert. We are not using any brake cooling at this point, yet we have added some weight (cage) and some power (Dinan Software) to the car - not fun for the brakes. Especially when you factor in racing tires (Nitto NT01) and racing at heaving braking tracks (Buttonwillow and Infineon). We took the car to the dealer and of course they didn't want to have anything to do with it. Spreading the news to BMW of North America or researching this problem was of no interest to them. We connected with a local North American Brembo distributor and shared some pics with them, but I don't think we got to the right Brembo people because I got the feeling that all they wanted to do was use this piston cracking issue to sell the 135i BBK kit they have for sale (which actually does look awesome - and Fred uses on the Evolution Racewerks 135i - but we can't use due to the Stock-Class we run in with BMW). It was mentioned that the pistons have a ceramic insert similar to a Porsche of some sort. I thought - Hmmm… lets take a closer look at this. I had some time today to remove the pistons from the 135i brake calipers. Here are my findings.... Attachment 13436 The 3 piston sizes are 28mm, 32mm and 36mm. They are a total of 30mm tall each with the cup taking up 22.5mm and the ceramic insert taking up 7.5mm. Attachment 13437 It seems the pistons are in fact made up of 2 parts, a main cup and a ceramic insert. The ceramic insert seems to be gently pressed into the cup and held in place with (what I think to be) green Loctite - which is sleeve retainer. Attachment 13438 ***Please note, I did crack the ceramic a bit on all 3 of the pistons as I removed them from the caliper. They were not this badly cracked prior to the removal. Attachment 13439 Attachment 13440 Attachment 13441 The piston backs are flat and made of stainless steel. Attachment 13442 The ceramic insert has a small hole in it to allow the internal air pocket to expand and contract. I used this hole to remove the pistons by making a small hook out of a thin screwdriver. Attachment 13443 Attachment 13444 The dust seal is then inserted in the gap between the piston body and the ceramic insert. Attachment 13445 We are really hoping for BMW to address this issue. Regardless of the fact that we race this car, BMW needs to realize that the 135i is going to be taken to driver schools and driven hard by both students and instructors. Yes, we know ceramic is a very fragile material. Yes, we have been changing pads a lot (street pad to to track pad and visa verse X10). Track rats are going to be swapping out pads just the same once track pads become more readily available. Another thought on ceramic being a bad choice here is due to the fact that over the years, people are going to be rebuilding these calipers with new seals and dust boots. Rebuilding more standard BMW calipers in the past (E30, E36 or E46 M3 for example) has never been a problem due to the 1-piece steel design of the brake pistons in those cars. This fragile ceramic material is going to easily break in the hands of your average shade-tree mechanic - leaving him stranded. Whatever discussion and additional speculation follows this post, one thing remains clear, this is a huge issue and needs to be addresses ASAP! This problem will show up for the life of the car unless something is done about it. Dear BMW & Brembo - Dibs on being first in line to have the recall performed. If you like more info or detail on this, you can reach me at ralphwarren@yahoo.com -Ralph Warren
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11-02-2008, 11:43 PM | #2 |
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911 GT3 Circonium Ceramic Inserts
I just found this in text written by Porsche regarding the 911 GT3.
"To reduce the transmission of temperatures from the brakes to the hydraulic fluid, brake caliper pistons are separated by heat-insulating zirconium ceramic inserts."
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11-03-2008, 12:18 AM | #4 |
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Well written Ralph, hats off for you . Now I won't hold my breath for BMW or Brembo to respond.
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11-03-2008, 01:42 AM | #5 |
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I have the official word from BMW Australia. You took the car to the track, you went over the accepted tolerance that was built for the car. What a joke. This was through the dealership, who contacted (with email photos) BMW Australia as they didn't know what to do. I am going to call BMW Australia on Weds (tomorrow is public holiday here due to a horse race) and tell them that I don't care if they don't want to replace my caliper (I'm going to go aftermarket anyway), but I will be the first to volunteer as an expert witness if brake fails on another customer's car who were not aware of this.
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11-03-2008, 01:46 AM | #6 | |
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11-03-2008, 02:05 AM | #7 | |
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btw Ralph, that was a fantastic and informative write up. Bravo! |
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11-03-2008, 06:24 AM | #9 |
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so wait, is there an expected recall on them for the 2008 models?
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11-03-2008, 07:08 AM | #11 |
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For racing, would stainless steel inserts be possible? You might overheat the brake fluid, though. Just so I understand - the piston itself and the hydraulics are fine - it is just the ceramic insert between the piston and the pad that is overheating and disintegrating?
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11-03-2008, 07:14 AM | #12 |
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No one knows that yet. It is all speculation on a recall. They are just trying to bring this to people's attention and to BMWNA and BMW of Australia...or anyone else who cares to listen....
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11-03-2008, 07:58 AM | #13 |
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Thank you for the information!
Life is full of irony... These calipers were part of the "feature list" the CA used to sell the car to me! I hope it stays that way. EspressoBoy |
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11-03-2008, 09:07 AM | #14 |
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Let's NOT start recall rumors here.
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11-03-2008, 09:35 AM | #15 |
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I think I read over in the other thread that some of these aftermarket guys are looking into making titanium inserts. How easy would it be to just swap the ceramic ones out? I think this one might chaulk up for a loss when it comes to getting BMW to do anything about it. It's just one of those parts that run out when the warranty does. I haven't done anything(aftermarket) to my car but I would be willing to go for insert upgrades, even if my ceramic ones are fine. It would just be nice to have piece of mind. I guess this is a call for the aftermarket guys to get their wheels turning, if they haven't already!
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11-03-2008, 09:55 AM | #16 | |
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11-03-2008, 10:48 AM | #17 |
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If 911 GT3 is using Circonium Ceramic Inserts then it is a good idea to follow; but it looks like BMW's used different kind of ceramic insert which would break apart easily. I think BMW needs to look into this seriously.
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11-03-2008, 10:57 AM | #18 |
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You guys need to note that these guys were using non-OEM brake pads. Who knows what could have happened here? Fitment could have been off, excessive sheer forces could have had an effect, abnormal heat exchange was most surely involved, etc. Unless people that are running a purely stock set-up are having this problem, I don't think its going to be something that will lead to a recall. I'm checking out my calipers this week. I had my car at the track last week and I'll see if anything looks astray. Everyone else that has put their car through the paces should too, and note whether they stuck with the stock pads or non-OEM pads.
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11-03-2008, 11:11 AM | #19 | |
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Thanks to all you guys how are putting in this work for the rest of us too!!! :respekt:
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11-03-2008, 03:21 PM | #21 |
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If I had a set of good inserts to measure, I could possibly machine some out of stainless steel. However, since we let Ralph/Scott borrow ours which got messed up as well, that's going to be difficult.
Titanium would be out of the question. They would cost so much, you might as well upgrade to Brembo BBK's. BMW will not do a recall. So far it's only been 2 people and that won't warrant a recall. That and these failures are seen by them as "racing". Brembo can't do anything either, even if they wanted to. OEM parts are licensed to the manufacturer. Brembo cannot sell due to contractual agreements. Since this is a special brake caliper developed for BMW, I don't think there's a Brembo aftermarket part you can use as substitute. Ralph, did you contact our Brembo rep I gave you? Any help? Are there any intact inserts or are all of them damaged? If I can get ahold of a good one, I can do the CAD and machine some new stainless steel ones. |
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11-03-2008, 04:29 PM | #22 | |
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