http://cgi.ebay.com/ebaymotors/KSPORT-13-PROCOMP-BIG-BRAKE-KIT-89-99-BMW-850I-E31_W0QQcmdZViewItemQQ_trksidZp3286Q2em20Q2el1116Q QhashZitem562995f1aeQQitemZ370064880046QQptZMotors Q5fCarQ5fTruckQ5fPartsQ5fAccessories

Ksport makes some pretty good stuff, and would even make up a rear set for the E31, though they don't advertize it. I spoke with Ksport-USA directly nearly two years ago about this though.

I would need the piston sizes to determine how much of an upgrade (if any) in stopping power. I might talk to them about some help on the front. I don't think their 354mm kit would work well on our cars without thrust arm reenforcement. Also, IIRC such a kit would (might?) not fit under OEM 17s.

That said, I might work with them to develop a porcshe kit using OEM 345mm disks.

If you want to go big, what to think of Thomas Engl's 380 mm brake disks with 8-pot calipers? You'll probably be looking at a rim upgrade too. Talk about overkill :D

http://img212.imageshack.us/img212/7276/attachment39d972.jpg

Engl also offers 355 mm disks with 4-pot calipers.

(for those who don't know Thomas, he's a regular on the German E31 forums and manufactures many upgrades for the E31, like exhaust headers, complete exhaust lines, Alpina clone hoods,...)

Honestly for E31s, the best disk size for performance is 345-365 MAX. Still looks damn good though.

That is BADASS

not sure I remember who brought it up, but the issue of the brembos that came stock with the 840Cis thru whatever years are apparently not as "powerful" as the later year 850Ci brakes? I believe it had something to do with the brake assist (which does not seem to work well with 840s). The only real thing I could do to improve it was turn the sensitivity of the brakes as high as it will go, put better pads in and SS brake lines. I think a kit like this would be a great choice if the results would be substantial over the stock 4 pots.

ALL late E31s (save the CSi's) had Brembo lotus calipers specially made for BMW mounting points. (at least in America).

The piston sizes were 38 and 40, IIRC, which works out to LESS clamping force then the earlier single pot 60mm piston calipers.

Yet the later cars stop better. Why? The shift to more rear bias improves braking balance. Basically, the fronts don't overload as easily.

JFR, CSi Euro calipers match the pistons of the Brembo F50 caliper (44mm and 40mm).

thanks for clearing that up bro. it's just odd for the size of the brakes, despite the 8ers massive weight, how difficult it feels to stop sometimes.

Bump up the rears more with a set of E38 750iL (must be 750, not 740) rear brakes with the SS lines aforementioned.

is it that big of an improvement? What's the main difference, what do a set of rears go for? I can probably get them easily but if someone here has them available please let me know.

It is marginal, but, if your rear brakes needed to be changed, I would do it.

As used set varies widely. 200-350 for a rear pair with caliper carriers. Just get new rotors (also E38 750iL). It the same piston size as Euro CSi, and the same rear disk as Euro CSi. (Effectively a rear CSi match without the M logos...328x20 Vented rears with a 39mm piston vs the OE 322x10mm solid rear disks. Parking brakes will work just fine and it clears the OEM dust shield...barely!)

JFR, confirmation of filament was the result of collaboration between Ed (Mwrench), and I. I must give credit where it is due. I am currently running this setup on my dinky V8. ;)

oh, wow. that's awesome. Marginal is a lot to me, I'm pretty sensitive about my braking. I have a company 2001 750 that brakes just oh so sweet compared to my 8.

Edit: Added more info to earlier post

To add regarding braking....IIRC, our friend in the UK is working on adaptor brackets to allow the Brembo Lotus caliper to work with the Euro floating 345mm disk. This should also improve braking as well as handling in the front end.

man, that would be so awesome. I'll look into the e38 rears tho, it's pretty cheap for a brake upgrade :).

it's just odd for the size of the brakes, despite the 8ers massive weight, how difficult it feels to stop sometimes.If you wanna stop better, Upgrade your brake lines to Stainless steel and a better pad choice, I've had 8,6, and 4 pots up front and the biggest difference was the brake lines and pad choice, I hope people know that if they go the 8 pot route, They will be throwing away there money, The rotors and hats will set them back a Thousand alone, Another 30 to 40 pounds clamping force from the rear calipers is a diserable brake bias, Which is achieveable with Euro Csi rears, The car stops extreemly flat and stops right now with this set up.

Marv read ^^^^ I already did that lol. SS lines made a very nice noticeable difference, I'd still like it to be a bit smoother :).

The way you go from one subject to another, I could'nt tell if you did it or not? Anywoo! I was just 2 centing what worked for me.

:(...

Yea. I realized that, hence my pointed recommendation.

I am due for some pad replacement. Might want to get some SS line as well.

SS Brake lines give you a much better pedal "feel" due to their inherent inability to flex/swell when the brake pedal is depressed. The Phoenix product is also nylon coated to prevent dirt and grime penetrating the braided ss sheath causing chafing and grinding within the braids during hose movement. Also are available in a variety of colours. Have most colours available here in North America. Mine are Wuffer Red of course! 8-)

Here is a good read.

Braking Systems…in Plain English
http://www.teamscr.com/motorsports/tech-articles/34-braking-systemsin-plain-english.html

Quoted from article above:
"You can take this one to the bank. Regardless of your huge rotor diameter, brake pedal ratio, magic brake pad material, or number of pistons in your calipers, your maximum deceleration is limited every time by the tire to road interface. That is the point of this whole article. Your brakes do not stop your car. Your tires do stop the car. So while changes to different parts of the brake system may affect certain characteristics or traits of the system behavior, using stickier tires is ultimately the only sure-fire method of decreasing stopping distances."

Its funny I can still remember when my instructor explained that to the class. The tire traction rating is braking traction so if you tires don't have the traction to brake then skidding happens to where ABS and ESP systems try to cope with the loss of traction.

Here is a good read.

Braking Systems…in Plain English
http://www.teamscr.com/motorsports/tech-articles/34-braking-systemsin-plain-english.html

Quoted from article above:
"You can take this one to the bank. Regardless of your huge rotor diameter, brake pedal ratio, magic brake pad material, or number of pistons in your calipers, your maximum deceleration is limited every time by the tire to road interface. That is the point of this whole article. Your brakes do not stop your car. Your tires do stop the car. So while changes to different parts of the brake system may affect certain characteristics or traits of the system behavior, using stickier tires is ultimately the only sure-fire method of decreasing stopping distances."