Brake Master Cylinder Help

[Dave Westy]

I'm struggling to understand how to solve my brake problem

I have a Westfield with a bias pedal box. I have Willwood calipers all round and Willwood master cylinders

The brakes work well but I only have about 1" of travel at the pedal and so not much feel. I would idealy like 3-4" of travel

The bias is set towards the front and when I press the pedal the front master cylinder actuator rod moves about 1" whilst the rear moves about 1/8" - so does that mean I need more travel in the rear master cylinder
The Front master cylinder is .625" and the rear is .750"

The obvious answer is to alter the ratio of the pedal - That's not that easy.

It looks like I need more travel on the rear master actuator rod, but as I understand it if I reduce the bore of the rear master cylinder that will increase the pressure to the rears and make the problem worse. I am already using the largest rear cylinder bore and the smallest fron cylinder bore available from willwood.

Hopefully there's someone clever out there who can explain what I should do to give me a longer pedal and more feel.

Thanks in advance

Dave

[Mr2Mike]

For a fixed caliper piston area and pedal ratio, the only way to increase stroke is to reduce the bore of the master cylinders. Since the volume displaced by a master cylinder is proportional to the square of it's diameter, a small change can make quite a big difference.

Unfortunately 0.625 is the smallest commonly available Girling-type master cylinder, so unless you can source a smaller one then your options appear rather limited. Reducing the bore of the rear master cylinder isn't going to improve things very much since you would have have to wind the bias bar even further toward the front to maintain the same bias.

Changing the pedal ratio looks like the only sensible option.

[Dave Westy]

Thanks for the response

I'm thinking of fitting a smaller rear master cylinder and a pressure reducing device in the rear line - is this a sensible option?

Dave