I've come across a problem (so has Pete). We are looking at running a bias brake pedal on a Coupe.

I'm not 100% sure which brakes Pete is running on the front, but he is putting X1/9 rear brakes on the rear. I am running MGF rear brakes and standard mini brakes on the front.

The big question is how do you calculate the size of the master cylinders?

Does anyone know the size of the slave cylinders? What ratio should be applied as a standard, with front to back balance? Should 50/50 be a good starting point, or should it be 60/40?

Any help gratefully recieved.

Give me a couple of days and ill dig out my spreadsheet

but as a guide

i have my own design of bias pedal, 5.25 ratio and 0.625 m/cyl front and rear, standard 8.4 discs front and my rear disc conversion which uses a bigger disc 9 inch and cosworth calipers, with this setup i have to run alot of front bias but once i have done the big fronts the balance should be a bit better. the MGF and X19 calipers have smaller pistons than the cosworth so should be in a better position than myself on a balance point of view than my current set up.

If i was to keep my current set up i would fit a larger cylinder for the rears but as im planning to go big front hoping this will balance things out well.

My current brakes are quite awesome just could do with being a little larger for more initial bite from high speed i feel, the front big disc project is one of the next projects on the list, its an never ending list at the mo

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I don't suppose that you have still got the designs for your pedal box?

think i have some of the cardboard templates, if i get time over the next few days ill have a look a bit busy amoungst another project for the car at the min

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What set up are you using on your pedal box, Neil?

Are the cylinders vertical, or horizontal? I am trying to mount everything under the bulkhead, so I can maximise the amount of room under the bonnet.

I've designed and made a bias pedal box with approx 6.5:1 pedal ratio and also used .625 cylinders. I run Metro 4 pot AP calipers on the front and standard drums on the rear. My version has pendulum pedals and the m/cyls are horizontal. The whole assembly is adjustable for legroom in increments of 2cm. I'm 1.88m and my wife is 1.60, so this was essential! The bias can be adjusted with a screwdriver from under the bonnet.
The whole lot has been fabricated from scratch, using 4mm steel plate for the pedals and 2mm for the pedal box. It is very compact, but does require you to cut a hole in the top of your footwell and weld on some angle iron. By adjusting the bias, I can get it to lock up either end no problem: far better than before.
EBC greenstuff pads on the front also help reduce pedal pressure.
i have comprehensive working drawings if they're wanted.

Ian

Yes please. Sounds spot on. My front bulkhead has been cut out at the moment, so I've got plenty of room to work with. What format are the drawings? Can you send them to my email?

Cheers

tim my pedal box is out of formula ford. the brake master cylinders are 5/8 .........0.625, my clutch master cly is same size,, front discs are vauxnall viva, calipers at the moment my choice are ford capri whitch i have still to find,,,, back brakes are 7.5 coper s, calipers are fiat x 19 as tim is suplying, ,,,,with a rear encine car can your run more back brake bias than as front engine car, having spoke to tim on the phone we are looking for a safe setting for bias, before we start to experement with ajusting brake bias

pete can i suggest 8.4 rear discs minimum otherwise you will struggle mot time with the handbrake, as mine only just about passed and thats with 9 inch discs on the rear. my thoughts for getting around this is to have a hydraulic handbrake as well as the cables thereby keeping the mechanical link required for mot, or to increase leverage onthe handbrake lever,

if you want me to give you some suggestions based on my experiance ill need to know the size of the discs you want to use, the size of the pistons in the calipers also, front and rear. That way ill be able to give you some guidance which hopefully will get you to a good starting point

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west. i am going with 7.5 as all are new, fiat calipers as it got hand brake mecanisam, olso going hydraulic hand brake to, front dont no what sise viva discs are find out later this week, belive front calipers are ford p16,

Tim: I can send you photocopies of my drawings, but scanning and emailing doesn't come out very well.

If you give me your email address, we can discuss how to get them to you..

Ian

Ian,

My email link at the bottom of any of my posts will work.

Cheers

Hi Ian, I've been musing over a pedal box for a while now, if you wouldn't mind I'd love to see your drawings too.

Hi, I new to the site but I too have been playing around with rear disc brake ideas. I have come up with using a Std front mini drum hub, changing to cooper S/1275 bearings (larger CV joints) Std 8.4 discs and 1998-2001 Golf Gti or similar VW calipers on fabricated mounts. This has a good mechanical handbrake as well as the Golf uses 215mm/10mm discs with a perfect offset to the 1275GT setup. This has great benifits as parts as easy to get and reletively cheap.
I have also redesigned the brake pedal box to allow for a tandem master cylinder setup. This runs 2 Cooper S master cylinders with the second cylinder running off a fake second brake pedal attached off the first. Took a bit of designing but works perfectly and is a lot safer. Bias is taken care of by a remote bias valve located by the handbrake.

Got a picture of your VW setup?

As i looked into the VW calipers when i did mine but ended up going cosworth due to part/information availability i do not remember any VWs coming up when i researched with a 215mm disc.

reminds me ill have to dig out my Rear disc conversion stuff again and post it up here seeing its gone with the old forum

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