Genuine BMW 'Big' 25mm Master Cylinder, BMW E30 M3

Ideal forBBK
From Anonymous of Cincinnati, Ohio on 10/20/2013.

I recently switched from a Brembo BBK to the phenomenal VAC/AP Racing BBK for my 1991 E30 M3 and after replacing everything, and adding new VAC braided SS lines and a UUC clutch pedal bushing, I still felt that there was a small amount of room for improvement. The car is dressed with the full (OEM) EVO III body parts (carbon fiber), the S14 is being built to EVO III spec while a Euro S50B32 I6 and its 6-speed manual gearbox have taken up residence in the engine bay (and a custom carbon fiber driveshaft mates the UUC ultralight clutch + flywheel to the Quaife LSD), the interior remains just civilized enough that I am unafraid to carry a passenger on the street thanks in large part to the lovely and lightweight Recaro Sportster CS seats (carbon and Kevlar shells and Alcantara surface, and an assortment of wheels and tires keep the car pinned to the road (mostly 17", from Kinesis and custom J-Lines to D-Force and Apex Racing, Michelin Pilot Sport Cup and Supersport to Pirelli P-Zero Corsa;an entirely overhauled suspension keeping them attached to the rest of the vehicle)...
So, after the swap from the 190bhp S14 I4 to the 321bhp 3.2L I6, the Brembo kit that had served well enough suddenly made the car feel very under-braked. My first instinct was to go with a PF kit, as they have been the most impressive brakes I've ever used on a BMW (my 328Ci and E46 M3 both wear 4-wheel kits), I decided to see what the fellow track addicts here at VAC had to offer. I was impressed with the VAC/AP kit's spec's and especially it's price, and so off came the front Brembo kit and on went the AP/VAC one (the rear retains the Brembo 4-piston calipers and 320x28mm 2pc discs), and I would be lying if I didn't say I was immediately impressed, in fact even while bedding the pads I felt a significant amount more bite and pedal response. It didn't hurt that in a car built around the wise words of Colin Chapman ("add lightness "), that I saved exactly 8lb 3oz per corner with the new kit!
I installed all new braided lines, filled the system with all new Motul RBF660, and enjoyed the kit for some time like this. However, I still felt like there was a slight room for further improvement, and so back to VAC I came.
It turns out that this relatively simple upgrade was the final piece of the puzzle that revealed what I believe to be the ultimate in E30 M3 brake kits (the rear now houses Wilwood monoblock 4-piston custom anodized calipers and 322x28mm 2pc slotted rotors, shaving off 5lbs per side).
With a heavily modified motor that puts out 321bhp stock (another 65 on top of that, give or take, from the careful selection and installation of various parts), and a chassis lightened and stiffened compared to anything out of the factory, I put the suspension and especially the brake system at the very top of the priority list, with only tires coming close in terms of importance. I believe that engine power is only as useful as the ability to put it to the ground and more importantly to stop the car.
I can honestly say that I finally have enough braking power to continue to mess with the engine, with headroom to go F/I even!
This would not be possible without the incredible package provided by VAC/APR along with the improved master cylinder on this page.

I highly recommend it, and while you're in there, make sure to replace all hoses and the fluid, with Motul RBF660 having my endorsement above all else (I have boiled all ATE fluids, in fact I nearly lost a car because of the pedal going to the floor at 115mph, and the StopTech Trophy kit was bled before and after every race as is proper, and it even had fresh-ish pads and rotors).