Master Cylinder Sizes

[Mando]

I think understand your explanation but does it mean the proportioning valve would be in the rear brake line only?

Regards.

[jon@harrison.ne]

As a mechanical engineer I appreciate Mikes thorough explanation or brake line mechanics. I would only add that we should be more precise about terms like force and pressure especially regarding units. "Force" has the units of pounds , "pressure" has the units of pounds per square inch, and "torque" is in "inch pounds" or, dividing by 12, foot pounds. Braking is achieved by applying a force to the pedal which then produces a different force (probably larger due to the pedal leverage and balance bar) to the master cylinder piston. This creates a pressure in the brake fluid which in turn creates a force on the wheel cylinder piston. This force results in a torque on the wheel (torque=caliper force X pad coefficient of friction(dimensionless,i.e. no units) X rotor radius.
Also I would like to thank Merv for his kind comments about my slabside Cobra. In light of the recent discussion of JCF it is an example of what can be made from his hardware if you take the time and are concerned with authenticity.

[Aussie Mike]

Originally Posted by jon@harrison.ne

As a mechanical engineer I appreciate Mikes thorough explanation or brake line mechanics. I would only add that we should be more precise about terms like force and pressure especially regarding units. "Force" has the units of pounds , "pressure" has the units of pounds per square inch, and "torque" is in "inch pounds" or, dividing by 12, foot pounds. Braking is achieved by applying a force to the pedal which then produces a different force (probably larger due to the pedal leverage and balance bar) to the master cylinder piston. This creates a pressure in the brake fluid which in turn creates a force on the wheel cylinder piston. This force results in a torque on the wheel (torque=caliper force X pad coefficient of friction(dimensionless,i.e. no units) X rotor radius.

Thanks Jon,

I'm no mechanical engineer, just a layperson. I've no formal training in this stuff but an interest in all things mechnical I've always been fairly good at looking at a system and visuallising how it works. Probably because I pulled everything apart when I was a kid.

I've gone back through my post and fixed up some of my incorrect terms. Hope it makes more sense. most of the time I'm thinking faster than I can type.

Cheers

[stephen low]

Mike

Thanks for the explanation and you are hitting on what Bernie asked I try and have done but not yet tested.

The change of spring I sought for my proportioning valve is I am presuming softer (lower pressure actuated) to allow earlier change of bias to the rear brakes.

This is as Bernie suggested and gives me the ability to press harder on the brake pedal increasing braking force without locking front wheels for a higher retarding capacity.

I'll wait for the real road test to see how it pans out.

Cheers

[stephen low]

This may lead to some tweaking when I'm back on the road as I'm positive my brake master which had come with the kit, had come off a falcon wagon. This was the descriptor my brake man used when he had to replace the brittle fluid reservoir in my early build days.

Knowing now one should at least chase a ute brake master for the fairly neutral bias balance, I have some work in front of me I suspect. Time will tell.

Thanks again Prof Mike!

[Maurice Butler]

Try checking this article http://www.autospeed.co.nz/A_110601/cms/article.html for what effect the crack point has on brake bias

[NASSTY]

There is also another option that I have seen on only one cobra, use an ABS module from I think an EL Falcon. It's a stand alone system and all you need to do is sort out the sensors. The owner of this particular cobra said that the brake bias issues disappeared after he installed it.