Hi,

Has anybody gotten around to measuring the piston diameter and length on the JCW front calipers?

If anybody has this information, please share it. If not, I'll find out as soon as I get mine and share it with all. I might be able to get a nice rebuild kit DIY.

Thanks for looking

Manny

 

The callipers are the exact same as the original model 135, so you will probably have more luck looking for that, as there are lots more around.

I have converted mine to metallic pistons, using a 135 kit.

 

I was referring to the JCW 4-piston calipers, not the GP2 6-piston calipers.

I converted my R53 using the 135i Brembo calipers and also did the stop-tech aluminum piston upgrade based on the BMW forums.

There's a thread on the first gen forum I started about it.

I want to do the same for some JCW 4-piston calipers I got for my other cooper.

 

Sorry had a brain fade and thought I was in the GP thread

There is a conversion kit available for the JCW 4 pot. These guys do it. I can't find it on the website, but I know they do, so drop them an email. This is where I got the GP steel pistons from http://www.racingbrake.com/

 

Sneed has the SS kit for regular JCW brakes. RB does not.

 

The precise diameter of every stock piston of 4-pot R56 JCW Brembo is 37,96 mm.
The precise length is just 26,17 mm.
Such a short length is the first reason why JCW Brembo are so tolerant of X-factor of the discs. The second reason is relatively small thickness of pads.
Here is a SS vented piston which I gonna use in my JCW 4-pot.

 

YOU are the man! Thanks! That is the info I needed.

 

Thanks a lot for the info man!!! I was looking for it too!



This is the piston from the Sneed? Or it's a regular brembo piston? Would you mind to share the part # if it's a brembo?

Thanks!

 

It doesn't have any part number. I made the draft by myself and the turner made the pistons according to it.

 

Yeah, I've still to find anybody making replacement pistons other than Sneed. I'm guessing I got lucky finding replacements using stop-tech for the 6-piston jcws.

Are the oem 4-piston jcw pistons really that bad?

 

I've got brand new calipers and I have desided to put SS pistons prior to the installation on the car. I use my car on the track and need reliability - that is the reason for me for using SS pistons. SS pistons will never be oxidized. Stock pistons isolate heat affectively because of something like plastic insets, but as you know they can be cracked in extreme heat conditions. For DD car and light track stock pistons are fine.

 

One more question @cooper_a, the length (26,17) is without the "ceramic" top? I'm asking because I could find only brembo pistons with 30mm length x 38mm diameter. Would it fit?

What about the seals? Would the regular 38mm brembo seal fit?

Thanks again!

 

26,17 mm is the overall length of the piston including the "ceramic" top. I don't know another Brembo caliper with such short length of the pistons. Probably JCW 4-pot calipers are unique in this way.

I did not try to find the alternative seals. It would be interesting to compare the original seals and dust boots with the parts of other different Brembo calipers with 38 mm pistons.

 

The pistons which are longer than stock will not fit.

 

Once again, thanks a lot!

In regards to the dust boots I bought a kit from ecs (https://www.ecstuning.com/b-genuine-...r/34106784593/) and received the brembo kit with part number 98.5032.40, I haven't installed yet but I hope they sent the right one

For the seals, for now I could only find these:
https://www.zeckhausen.com/catalog/p...oducts_id=6565
http://www.sneed4speed.com/high-temp...brake-caliper/

 

Yea, those are the Gen 2 Four Pot JCW boots. One Kit per caliper. 34106784593

Thanks for the order.

https://www.ecstuning.com/Search/SiteSearch/34106784593/

 

Maybe?

http://www.ebay.ca/itm/Brembo-205461...-/361341074441

Brembo 20546162 26mm Long - 38mm Diameter Flat Base Piston

 

.

 

This probably is not going to help anyone directly, but ..

Brembo do make a metal piston that fits directly into the 4 pot brembos. Around 7 years ago when I was first racing my JCW I had problems with the pistons. My mechanic sent my calipers away to the local "go to" motorsport brake worshop that did most of the professional race teams in my area. They were also a brembo dealer. They measured my calipers and replaced the pistons with an off the shelf brembo parts. I was told at the time they were from a racing specific caliper.

Unfortunately I don't have the part number, and those calipers were sold 5 years ago. The brake shop also went out of business unfortunately.