bias pedal box - anyone fitted one ?
bias pedal box - anyone fitted one ?
Author
Discussion

magpies

Original Poster:

5,203 posts

211 months

Sunday 14th August 2011
quotequote all
I'm building my S to use in motorsport and wondered if anyone else has gone down the route of fitting a bias pedalbox?

Alan Whitaker

2,054 posts

211 months

Sunday 14th August 2011
quotequote all
Hi Mick
Just a thought but don't they have 2 master cylinders for the brakes ?, I was looking at that but I don't think there was enough room to put 3 cylinders side by side, I could be wrong on this.

Alan

magpies

Original Poster:

5,203 posts

211 months

Sunday 14th August 2011
quotequote all
if it stops raining I'll check out how much room there is - would mean doing away with the servo though

Alan Whitaker

2,054 posts

211 months

Sunday 14th August 2011
quotequote all
Hi Mick you can get a bias bos which uses a remote servo or will fit to your existing one.

link http://www.compbrake.co.uk/Bias-Pedal-Boxes/Univer...

May just fit?

Alan

Edited by Alan Whitaker on Sunday 14th August 15:15

GreenV8S

31,017 posts

313 months

Sunday 14th August 2011
quotequote all
I've used one, but not on the S.

It's just a way to set the static brake balance if your calliper and rotor sizes don't give you the right balance. It's not a substitute for a bias valve.

You can set the static balance just by sizing the callipers and rotors correctly. This will establish the line pressure, and you can use that to calculate the bias curve you need to account for weight transfer. Then you can either fit a bias valve with the right characteristics or, more usually, just fit an adjustable one and use your calculated pressure curve to set it to roughly the right setting. It would need fine tuning to get it spot on in any case.

If you decide to use a balance bar, the main reason for doing that is that the front/rear circuits don't run at the same pressure (because the calliper/rotor sizes don't match the weight distribution) which implies that the front/rear master cylinders will have different travel. In that case you need to be especially careful that your balance bar doesn't run out of travel since the brake balance will change suddenly and perhaps catastrophically if that happens. It also introduces some nasty failure modes if you misadjust the master cylinder (or you get wear and gunge build up) preventing it from coming back fully against the stop since that can lock one of the circuits on.

If I were you I'd stick with an ordinary tandem master cylinder, keep the brake servo and just size the front / rear callipers and rotors to get the static balance right. Remember to fit an adjustable bias valve and set that up properly too.