R32 Master Cylinder Upgrade

[Footnah]

Hey guys

I'm currently upgrading my front brakes to 4 pot wilwoods with 1.75" piston diametre and I don't think the standard master will cut it so I need an upgrade.

What do people normally upgrade to and what are the pro's and cons of the master?

Car is a 1989 GTS-4 Skyline with an RB20DET

[Roy]

What rotor size?My opinion is 1.75" pistons are waaay too big unless you want to be locking up all the time

[sweefu]

I'm not sure what bmc your r32 has now, but bm44 is a common upgrade. Bm50 is also available but massive.

[Footnah]

325mm rotors.

What's the bore size of BM44 and BM50?

[sweefu]

A quick Google search reveals:

BM44 = 15/16" and BM50 = 1"

[Footnah]

Has anyone found/ used a 1 1/16" bolt on BMC?

[sweefu]

A quick Google search reveals:

BM57 = 1 1/16"

Found on R33 GTR I think.

Really, though, you probably should do some Google searching, all of the answers you need can be found in about 30 seconds.

[Footnah]

I tried to google what master cylinder I had, but there's not a great deal of info on GTS-4s anywhere.

Will BMxx be stamped on the BMC somewhere I can check?

Although I could google the bore sizes of the master, it still leaves my initial question un-answered. Just because it's an available option, doesn't mean it's better than something else out there. I was more so after opinions, advice and feedback on what masters people have used and how they rate them.

[sweefu]

I understand about the opinions etc, but bore sizes are easily found.
Yep, the BMC will have 'BM44' or similar on the side of it, easy to check

[Footnah]

Yeah, I understand.

Cheers.
Will check it out tomorrow.

[KiwiRS4T]

Have D2 brakes so upgraded to BM57 m/c (R34 GTR or twin turbo Z).

[Roy]

Have you bought the calipers yet? If not buy the right caliper and you wont need to upgrade the BMC. BMC size isnt a performance thing...its a sizing thing. If you want better performing brakes for your Skyline you really only need to increase the heat dissipation....not the braking force. They have plenty std and are well balanced std. On an R32 perhaps they can do with a bit more bias. But you are getting that increasing the rotor size.

So what model caliper are you using . They can often be purchased with different sized pistons, get the right caliper and you are set

[Footnah]

I have a BM50 Master.

I decided on the 1.75" (44.4mm) piston diametre, because my calipers standard are 40.4mm and I personally find them rubbish for track use. And using these calipers because they, being radial mount, allow me to run any size disc.

[GTSBoy]

That's 20% more piston area. Even the step up to a BM57 is only going to bring another 13% MC piston area. You're still going to suffer a longer pedal.

[Roy]

For the sake of the discussion what is rubbish about the std setup? Assuming you were running std caliper with 280mm rotors? What pad were you running? Did you find the stopping distance rubbish, feel rubbish, fade rubbish? All of the above?

Do you have ABS?

Sure. go to a bigger rotor, best value brake upgrade you can do. But increasing rotor size increase brake torque. If you massively increase piston diameter as well then you will be increasing the fron brakign torque by a boat load...only to have no real rear brakign torque....onlyu to have to put in a massive master cylinder or change the leverage ration of the pedal...either way you are going to need to put in adjustable brake bias to tone down the amount of braking force you have at the front which brings us back to the original point.....why increase the front brakign torque by sooo omuch?

[Footnah]

I haven't bought any calipers or master yet, as the main reason for this post was to find out what options I have for a master if I went with my initial choice of caliper.

The brakes aren't "shit", but there is no way I'll get the times I want around the track on standard brakes. + If I'm going to use a bigger rotor, My caliper will need to be re-fit and it's easier to get a better radial mount that will withstand more punishment whilst doing so.
I currently have ABS, but pull the fuse for track use and I'm now at the stage of removal of the unit itself.

I'm currently up to about 3 pages of calculations in working out and I'm ready to pull my hair out haha. But so far, I think I'm heading in the right direction.
Will post up my findings once completed to hopefully give a better insight of the method behind my madness.

[KiwiRS4T]

I found GTT brakes with a M/C stopper, braided brake lines, Motul RBF600 brake fluid and quality pads perfectly adequate on the track for my 18ookg Stagea so I am sure they would do for your lighter GTS-4. I only got the D2s when I got the heavier RB30 in the front together with much greater kw and speeds!

[Roy]

Well if you think your sizinf is correct it will be interesting to see how it all goes then. I think no matter what caliper you do if you are looking at crunching out good times and your 4dr is AWD I think 325mm rotors wont last much longrer than std, irrespective of the caliper and ducting/pads etc you use

[r32-25t]

The 17/16 (1 and 1/16th) is actually a z32 master cylinder

[Footnah]

So do GTRs (32 V spec, 33 and 34) use a BM50 or BM57 BMC? Or something different again?