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Bias Bar Limits?
RazMan - 17/5/07 at 12:03 PM

I've been fiddling around with my bias bar (it's legal ) and I wondered how much actual bias that it actually gives - i.e. if we assume that dead centre is 0% bias, if I screw the adjuster all the way to the rear m/c how much of the braking force is moved to the rear brakes?

I suppose the only true way to figure this out is to calibrate it on a brake tester like the MOT guys use.


britishtrident - 17/5/07 at 02:52 PM

Priciple of Moments (aka Varigon's Theorem)

Moment = force x lever length

Sum of moments in clockwise direction = sum of monents in anticlockwise direction.

To put it simply Force is distributed in inverse proportion to the distance from the central bearing.

Example master cylinder centre lines are 100mm apart.

Balance bar is set so the the centre of the centre bearing is 25mm from the centre line of th front circuit.

Then front circuit gets 75% of the force and rear circuit gets 25%.


RazMan - 17/5/07 at 04:52 PM

Ta muchly


John Bonnett - 18/5/07 at 12:29 PM

Just a thought Raz, are your master cylinders the same size?

John


RazMan - 18/5/07 at 02:29 PM

Good point John - front is 0.625" and rear is 0.7"


John Bonnett - 18/5/07 at 05:58 PM

Hi Raz
With SVA not too far away, brake balance has taken on a whole new importance to me. I had fitted a pair of 0.750 master cylinders but following a chat with a very helpful lad on the RAW Stand at Stoneleigh, I was advised to do what they do on the Striker and fit 0.625 on the front while keeping to 0.750 on the rear. The same as you have Raz. They set their cars up for SVA to full front bias and they pass. I've now changed the front master cylinder and I'm going down the same route as RAW although I shall only grubscrew rather than rollpin through the shaft. I appreciate that the setting( if not the grubscrew) will get the brakes through SVA but it may well not be the optimum setting for maximum braking.

Probably best to hire a circuit for an hour or two and experiment.

alb

John