Brake bias calculation

[stevieturbo]

Just fit a bias valve and stop fking about lol.

You'll never calculate to cover every scenario, so you're wasting your time trying.

Adjust the valve so it works as you want it, on your car, for your driving style and for the road conditions, tyres etc etc etc you use.

Anything else is just a waste of time.

[RX-709R]

If it was my car, I'd look at changing spring and/or damper rates to better manage weight transfer.

[Dave Brand]

Mignon said:

Yes strictly speaking pad area is not relevant to the calculation if you have the coefficient of friction for that particular pad area. I know the coefficient of friction is not "supposed" to change with contact area but then we'd never find any purpose to fitting wider tyres. Every vehicle on the road would manage quite happily on bicycle tyre thicknesses and clearly that doesn't quite work out.

Tyre grip & brake friction are two vastly different concepts. In braking you have a non-elastic friction material (well, non-elastic for all practical purposes) in rubbing contact with another, smooth-surfaced non-elastic material with the load applied undirectionally. With a tyre you have an elastic material in rolling contact with a rough, variable surface with the load applied in constantly-changing directions. Even the friction components of the two cases are different - for brakes it's the dynamic coefficient of friction that's relevant, for tyres it's (sort of) the static coefficient of friction that comes into play.

[The Wookie]

Personally I'd replace the standard bias valve if you haven't already, they can fail. That said TVRs in general do have the problem of large rear axle load variation due to their layout (varying amount of, luggage and passengers sat on the back axle) so it is hard to spec a one side fits all brake bias without a rear axle load operated valve or EBD

I don't think it's unacceptable to fit an adjustable prop valve if you know what you're doing.

[thebraketester]

renalpete said:

So for the standard front setup of a 291mm disc, AP CP5200 4pot caliper (see spec tab), I get

pi * (38.1+41.3+38.1+41.3) * ((291/2) - (55.8/2))= 58668

Adding all the diameters together gives you an incorrect figure for the area.

[PaulKemp]

stevieturbo said:

Just fit a bias valve and stop fking about lol.

You'll never calculate to cover every scenario, so you're wasting your time trying.

Adjust the valve so it works as you want it, on your car, for your driving style and for the road conditions, tyres etc etc etc you use.

Anything else is just a waste of time.

As above
It's about how it feels and how it works on the road in the real world.

You loose braking when wheels lock so biasing the rears away from locking is a wise move
If you ultimately find you need more braking a change of pad material, larger front discs etc will give you that then you can start to unbiased the rears.