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what is the basic split for front rear brake bias?
will121 - 23/12/10 at 12:37 PM

i am going to fit a larger servo/master cylinder to my track car and a rear brake bias valve, going to take it to a MOT tester to make sure brakes works ok before next trackday, but what is the basic front to rear bias split should i be looking for? wondering if there was any guidance in expected IVA pass criteria i could use as a starting point?

thanks

nick205 - 23/12/10 at 12:50 PM

For SVA the basic criteria was for the fronts to lock before the rears - which the examiner tested physically by driving the car and performing an emergency stop. I can't recall if the efficiency or balance was tested on the rollers though - could well have been. Also not sure if this has changed for IVA.

If you can adjust it then the basic front locing first check should get you in the right area, then you can fine tune to preference on the track.

britishtrident - 23/12/10 at 01:01 PM

MOT rollers are useless for setting brake bias.

You need to road test at slow speed on smooth clean dry tarmac as already said fronts must lock first under all conditions.


Don't fit a servo just a smaller bore master cylinder.

jossey - 23/12/10 at 01:42 PM

99% rear
1% front.

oh it would be fun :O)

dave

will121 - 23/12/10 at 02:41 PM

quote:
Originally posted by britishtrident

Don't fit a servo just a smaller bore master cylinder.


need bigger servo/master cylinder as have upgraded calipers and currently have too much pedel travel and limited feel

bitsilly - 23/12/10 at 04:41 PM

quote:
Originally posted by jossey
99% rear
1% front.

oh it would be fun :O)

dave



Thats what handbrakes are for!

britishtrident - 23/12/10 at 04:59 PM

If you have too much travel and no feel the calipers aren't set true to the disk --- the caliper has to present the pad absolutely square to the disc 1mm delflection at the pad equates to 50mm + at the pedal. It pays massive dividends if you to take time doing some traditional hand fitting to get the caliper brackets just right.

Fitting a bigger master cylinder & servo will rob the brakes of feel and the servo will increase travel

Peteff - 23/12/10 at 06:00 PM

Most standard set up is around 70% front 30% rear. Servos don't make brakes work better they just make the pedal easier to press for girly ankled drivers

interestedparty - 23/12/10 at 07:48 PM

If you need to pass an IVA, then the ONLY place you will get an accurate result is the IVA rollers. This is because the tester will test at at least 5 different pedal pressures. I watched a friend's car pass on the full pressure (we had already tried it at an MOT place, but fail at the lower pressures.

Testing on a road won't work. Possibly a skid pan with different levels of grip (thus giving different pedal pressures in order to lock the wheels).