I want to do a front brake conversion on my 95 240sx. This car was auto w/ABS, and I swapped it to manual, keeping the ABS, so I have the larger brake booster, and 15/16 (bm44) bmc. I was reading about brake bias, and I saw that the S15 came with the same front brakes as a z32 and had the same rears the s14 has. Since I was not looking to swap the rears anyway I was hoping I could use the bmc from an s15, and maintain the most even bias I could. I looked around and it appears the s15 bmc was a bm50 or the 1".

Now my question is do all (bm50) 1" bmc have the same internal bias for front and rear? or would I have to source one specifically for the S15 (which means I would have to find one that was for a LHD car too)? Is there a (bm50) 1"bmc that would have the same split point as the s15 did, that is used on another car? I know the 300zx had a 1" bmc, and so does the Nissan pathfinder (90-95). How does one go about finding the split point pressure for each considering the model is the same (bm50)?


EDIT: after looking around I saw that the S15 has a MC split point of 427psi and a MC reducing ratio of .2. Does anyone know if any other USDM bmc have the same specs?

ok, so I think I was able to partly answer my own question. It appears the Nissan Pathfinder or d21 pickup from 1994 came with a BMC that was 1" like the S15 that had a Split point of kPa (kg/cm2, psi) 2,942 (30, 427) and a reducing ratio ´ 0.2. Exactly the same as the S15 as well. There are 4 bmc options for this suv/pickup, the one you want is the bmc used with the rear abs drum brakes.

On the down side the ports on the bmc are on the wrong side for the brake lines to hook up, so I would have to come up with some custom piping. For those of you with no ABS it appears this system has three holes for brake lines instead of just two.

I am going to see if I can find look through some more fsm and find a bmc that has the same split point and reducing ratio, that will bold right on.

EDIT:
After Further research I found the 98 Frontier 4wd and the 2000 Xterra both have the same 1"bmc, split point and reducing ratio. Both options have 2 holes for brake lines (better for people with ABS) the holes are mounted on the wrong side, of the bmc, so redoing some of the brake lines would be necessary.

If anyone knows of a BMC that has the same specs as the one from the S15, and has all the holes for the brake lines to fit without modification, please let me know.

From experience, trying to run Z32 fronts with anything but Z32 rears creates WAY too much front bias. Even with the Z32 rear, I was never able to find a bolt-on MC that created enough rear bias. Most OEM brake systems are purposely designed for too much front brake bias. They want you to plow head-on into something as apposed to spin if you panic brake.

Before I was able to get the brakes sorted out so that I was happy with the bias I sold that car. I now have an S14 that I'm trying to sort the brake bias out on. Right now I have Q45's on the front and on the rear I'm running a stock S14 caliper, Z31 caliper bracket, and 02-11 Altima rear rotors. For the BMC I'm running a Wilwood compact MC, no booster, and modified pivot point on the stock pedal (I have a top mount T4 turbo and had clearance issues). I have a proportioning valve to adjust rear bias, but it's turned off because I STILL don't have enough rear braking, although it's the best it's ever been with any setup I've had to date on any S13/S14 I've owned. My next step is probably going to be a more aggressive pad in the rear so that I can actually control the rear bias with my adjuster.

I'm telling you this because I see A LOT of people upgrading the front brakes and ignoring the rear. If you just want street cred, then have at it. If you want to actually improve the braking, there is A LOT more to it than that.

Why don't you just get a manually adjustable proportioning valve, like the one wilwood sells?

I have that proportioning valve and I ended up turning it off because I still didn't have enough rear brake.

id never used one, just in theory if you had the right one I would think it would work. Which valve did you have? I will be doing this upgrade soon.

IIRC, it was this one;
http://www.jegs.com/i/Wilwood/950/260-1 ... tId=744516