Master cylinders for this pedal box. Help please

[DeanR32]

Hi chaps

I'm looking to buy this pedal box in the coming weeks

http://www.obpltd.com/Pedal-Boxes/Pro-R ... BP0162PRTC

The problem I'm having is how to spec brake and clutch cylinders to work with my standard brake set up on the 02. I'm more than likely going to run minus servos, so I'll of course need the box with two brake cylinders, but how big was the standard brake master, and what size pairing do I need with this box?

Same goes for the clutch cylinder, although this one must be more straight forward. What size is the standard one, so I can swap it for one to mount on this box. 

And the page I linked says something about pedal ratios. Would this play a part in what size the cylinders need to be? The car, if it matters, is a standard brake, U.K. (Twin servo) uk 02

Questions coming thick and fast at the moment. Sorry guys

Cheers

[gracer]

Your master cylinder size will be determined by the size and number of pistons in your calipers.  I am assuming that you are going to have calipers in the rear.

The clutch cylinder should be 19MM or .75"

I would suggest calling http://www.wilwood.com/

They have always been a great help to me.  G

 

[DeanR32]

Cheers for your reply 

 

At the moment, the car has its standard brake setup. I've had Gaz coilovers made up from the standard struts, so does that limit me in upgrade options?

 

 

[TobyB]

Realoem is your friend.

Stock is 20.6mm or 13/16.

stock pedal ratio is about 4:1

With rear drums, a residual pressure valve in back's a good idea.

 

But now, there are a lot more variables.

What are you using this car for?

What pad/shoe combo are you using?

What tire size?  How strong is your right (and left) leg?

What is the airspeed of an unladen swallow?

 

Street cars are usually biased 60 front/ 40 rear brake, with

some form of limiter on the back to keep the rears from locking in a panic stop.

ABS cars are even more messed up than that, and they then fix it with computers.

Tilton recommended 70 front, 30 rear for race pads, and they were within 4 turns of center

on my bias bar.

 

What you will find is that a relatively small master will work fine- 3/4", maybe, front and rear.

It will be even harder to get a good bleed, but once ALL the air is out, you'll have good feel and

pretty high effort.  If you want lower effort, you can go to an even smaller master, and that will work,

at the cost of some rock- hardness of the pedal.  Your rear shoe adjustment will become critical.

(I went to discs to get rid of this.  It was worth it.)

Most of us who have gone down this rabbit hole have an assortment of masters now-

your first guess is only a guess, and afterwards, you fine- tune the adjuster until you

run out of travel, then up or down- size one or the other or both until you are happy.

My version uses 528 front calipers and Nissan Sentra fronts as rears, so my numbers

won't work for you...

 

Hope this helps.

 

t

 

 

 

Edited January 7, 2017 by TobyB

[DeanR32]

Cheers for the explanation Toby and Gracer

 

I'll have to decide on a brake upgrade all round as a first port of call. I'll buy and mount the pedal box first, then pick up cylinders after. The clutch one seems pretty straight forward

 

 

 

 

Edited January 7, 2017 by DeanR32

[TobyB]

Yes, that's wise- with dual (front/rear) masters, your choice of rear components is much easier,

since you can size the master to match whatever caliper works best for you back there.

And since it all works together, it's easier to do it all at the same time. 

 

t