135 6-piston OEM Brembo Retrofit... The DIY.

[cakM3]

looking good so far Chad! Subscribed

[Chad44]

It's snowing and my night class was cancelled so I broke out one of the calipers and started working on it!

First things first, there has been a snag in the process... Stop Tech put the incorrect sized pistons in both of my 32mm rebuild kits... both kits have 34mm pistons in them!!! I could have had both calipers rebuilt by now if this had not happened!

I called stop tech to discuss the piston thing, and they were helpful but the guy told me that the bmw 135 calipers use different parts than the ones I ordered. I took a ton of measurements(plus the 28mm and 36mm are already installed) and there are only minor differences. The kit they have for rebuilding the 135 brakes is only available in house, and is not sold to the public "only the manufacturing department has them".

The critical mechanical dimensions are exactly the same, the length of the piston and the diameter of the piston... I am assuming that the reason they say they will not work on the 135 calipers is a political reason.

The head of the stop tech piston is a different size than the original, but more critically; the groove that holds the dust boot is a different size. This means that if these were on a 135m and the owner had upgraded the pistons to stop tech but tried to use oem replacement dust boots, they would not fit... Which is a non issue for me, since I assume the stop tech dust boots are meant to take a bit more heat and wear than the oem ones were.

The head size of the piston may bother some, but it doesn't bother me, and it's up to you to make that decision... The surface area of the piston that touches the brake pad is smaller than that of the original pistons, and while there could be some draw backs to that design, I see it as a potential help in eliminating one of the reasons these fail in the first place... the smaller head will allow for a smaller amount of heat build up in the pad backing... potentially saving the brakes, allowing them to last longer, etc... I don't know, this is all theoretical but it's what I'm going with since it makes sense to me.

Here are some photos of the differences between pistons:







Stock pistons in the caliper:




Stop Tech pistons in the caliper:

[Chad44]

I just updated the beginning of the thread with the caliper rebuild info...

[UdubBadger]

damn puttin in werk bro

[cakM3]

Chad does not mess around when it comes to BMWs Great work Chad!!!

[Chad44]

Thanks, I got excited and wanted to play with my new toys... Now I have to do a return RMA with the incorrect pistons, then wait for them to confirm them and send me some new pistons. Hopefully I'll find the time and cutting bit to get these brackets shaved down this weekend.


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[derbo]

Interesting find! So is stop tech going to give you 32mm pistons or are they going to send you prototype pistons


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[Chad44]

Interesting find! So is stop tech going to give you 32mm pistons or are they going to send you prototype pistons


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Oops, I thought I responded to this days ago... No prototype pistons, just going to send me the right pistons... I'm still waiting for thmotorsports to give me an RMA # so I can send them back.... Hoping to hear from them Monday.


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[bullfrogs_M3]

Subscribed. Great work Chad. Looking forward to the caliper bracket modification. Curious to know how and where to modify the bracket.

[UdubBadger]

I have stock 135i brembo pads if anyone wants um.


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