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quick brake up/downgrade sierra based
baz-R - 18/4/14 at 08:24 AM

i have had to convert my rear to sierra disc after fitting an lsd

now i have 50/50 brake ballance and rears lock first, bias valve was fitted but it doesent appier to reduce it enough (max60%) think its duff to be honest

im competing next wekend and realy could do with a quick, easy to get hold of and reasonable price way of sorting it out

i have sierra std 240mm discs up front with oe pads and at the rear i have std sierra solid discs and calipers with oe pads

improve fronts or reduce rears

car is a 7 rep with sierra donor parts

help

ragindave - 18/4/14 at 08:31 AM

Try and get 260mm xr4i discs and calipers for the front but it depends on what size wheels you are running

mark chandler - 18/4/14 at 08:36 AM

I just try dropping in some softer pads in the front, Mintex 1144 or EBC green stuff

[Edited on 18/4/14 by mark chandler]

MikeR - 18/4/14 at 08:43 AM

Cut groves in rear pads to reduce pad area / friction?

mcerd1 - 18/4/14 at 08:56 AM

the quickest fix is probably to stick some better pads on the front like mintex 1144
(avoid EBC green stuff they are overpriced rubbish)

and you could maybe try a different / better bias valve

on the sierra / granada etc that had the 253mm solid rear discs they use 260mm vented fronts with slightly bigger calipers - but thats probably overkill for a lightweight car and will add a fair bit of weight too...

a pedal box with twin master cylinders and a balance bar is probably the best fix, but that will take too long to fit

Dick Axtell - 18/4/14 at 11:21 AM

quote:
Originally posted by baz-R
....bias valve was fitted but it doesent appier to reduce it enough (max60%) think its duff to be honest...(


Is your reducer (bias) valve from Sierra donor? If so, that's probably main reason. These valves were known as G-valves, because they were supposed to be decel-sensing. Girling developed these by making them flow-sensitive, to initiate valve operation prior to full decel, so you got some rear brake pressure reduction (relative to fronts).

BUT - they never worked fully satisfactorily. Very difficult to test, under working conditions, which is why they went out of favour with vehicle manufacturers.

Better to replace with e.g. in-line reducer valve, such as that which was fitted to older Ford Fiesta.

baz-R - 18/4/14 at 01:08 PM

quote:
Originally posted by Dick Axtell
quote:
Originally posted by baz-R
....bias valve was fitted but it doesent appier to reduce it enough (max60%) think its duff to be honest...(


Is your reducer (bias) valve from Sierra donor? If so, that's probably main reason. These valves were known as G-valves, because they were supposed to be decel-sensing. Girling developed these by making them flow-sensitive, to initiate valve operation prior to full decel, so you got some rear brake pressure reduction (relative to fronts).

BUT - they never worked fully satisfactorily. Very difficult to test, under working conditions, which is why they went out of favour with vehicle manufacturers.

Better to replace with e.g. in-line reducer valve, such as that which was fitted to older Ford Fiesta.


no its a after market "motorsport" one

britishtrident - 18/4/14 at 01:42 PM

quote:
Originally posted by baz-R
quote:
Originally posted by Dick Axtell
quote:
Originally posted by baz-R
....bias valve was fitted but it doesent appier to reduce it enough (max60%) think its duff to be honest...(


Is your reducer (bias) valve from Sierra donor? If so, that's probably main reason. These valves were known as G-valves, because they were supposed to be decel-sensing. Girling developed these by making them flow-sensitive, to initiate valve operation prior to full decel, so you got some rear brake pressure reduction (relative to fronts).

BUT - they never worked fully satisfactorily. Very difficult to test, under working conditions, which is why they went out of favour with vehicle manufacturers.

Better to replace with e.g. in-line reducer valve, such as that which was fitted to older Ford Fiesta.


no its a after market "motorsport" one


Ah it is designed to work at pressures way above the line pressures in your car. Seven style cars generally have brakes that work at quite low hydraulic pressures compared to saloon cars.

You could use the a reducer valve from a small to medium size FWD car this might be a good scrap yard source.
Because they use diagonal split hydraulic circuits not many modern cars have single circuit pressure regulator most have two valves fitted to one block so you need to use one of these and either only use one circuit or use both circuits and fit after the rear T.
The Vauxhall Corsa around year 2000 has a suitable valve as do Rover 25 and 45. These cars have that are located under the bonnet and are easy to remove.
You can make an adjustable single line valve from Fiat Strad/Ritmo or Uno valve also used on Lada 1500, Brakes International can supply these very cheaply. - check the pipe thread pitch of the fittings.


[Edited on 18/4/14 by britishtrident]

[Edited on 18/4/14 by britishtrident]

baz-R - 18/4/14 at 01:48 PM

quote:
Originally posted by britishtrident
quote:
Originally posted by baz-R
quote:
Originally posted by Dick Axtell
quote:
Originally posted by baz-R
....bias valve was fitted but it doesent appier to reduce it enough (max60%) think its duff to be honest...(


Is your reducer (bias) valve from Sierra donor? If so, that's probably main reason. These valves were known as G-valves, because they were supposed to be decel-sensing. Girling developed these by making them flow-sensitive, to initiate valve operation prior to full decel, so you got some rear brake pressure reduction (relative to fronts).

BUT - they never worked fully satisfactorily. Very difficult to test, under working conditions, which is why they went out of favour with vehicle manufacturers.

Better to replace with e.g. in-line reducer valve, such as that which was fitted to older Ford Fiesta.


no its a after market "motorsport" one


Ah it is designed to work at pressures way above the line pressures in your car. Seven style cars generally have brakes that work at quite low hydraulic pressures compared to saloon cars.

You could use the a reducer valve from a small to medium size FWD car this might be a good scrap yard source.
Because they use diagonal split hydraulic circuits not many modern cars have single circuit pressure regulator most have two valves fitted to one block so you need to use one of these and either only use one circuit or use both circuits and fit after the rear T.
The Vauxhall Corsa around year 2000 has a suitable valve as do Rover 25 and 45. These cars have that are located under the bonnet and are easy to remove.
You can make an adjustable single line valve from Fiat Strad/Ritmo or Uno valve also used on Lada 1500, Brakes International can supply these very cheaply. - check the pipe thread pitch of the fittings.


[Edited on 18/4/14 by britishtrident]

[Edited on 18/4/14 by britishtrident]


im on m10x1mm pipe fittings

baz-R - 18/4/14 at 08:36 PM

ok an online calculator tells me i have 54% front static bias if i uped the pads to m1144's i would get 63%f witch still is not great

i think what i realy need is either bigger front setup or possibly a smaller piston rear caliper (sierra is 42.8mm) i hear there are vw alloy units in 36 or 38mm but fitment is a bit unclear if it bolts directly up to ford lugs

i see there are more than one way to fit bigger fonts fom kits to a mix and match of ford parts usualy using cossy 283mm discs with mondeo v6 caliper or cosworth's and so on

im not finding much on flebay today not even complete 260mm abs sierra calipers

Kev99 - 18/4/14 at 09:08 PM

Have a look at this Thread its what ive got on mine been on track and road from 2006 no problems just not adjustable

Uno Brake Compensator

scott h - 18/4/14 at 09:14 PM

If the bias valve you are using is a knob type check that you are turning it the correct way. Clockwise will usually increase the pressure to the back brake which is the opposite of what you may think if you compare it to a tap on a kitchen sink.

britishtrident - 19/4/14 at 09:39 AM

quote:
Originally posted by baz-R
ok an online calculator tells me i have 54% front static bias if i uped the pads to m1144's i would get 63%f witch still is not great

i think what i realy need is either bigger front setup or possibly a smaller piston rear caliper (sierra is 42.8mm) i hear there are vw alloy units in 36 or 38mm but fitment is a bit unclear if it bolts directly up to ford lugs

i see there are more than one way to fit bigger fonts fom kits to a mix and match of ford parts usualy using cossy 283mm discs with mondeo v6 caliper or cosworth's and so on

im not finding much on flebay today not even complete 260mm abs sierra calipers


Don't put too much faith in online calculators there are too many variables that either they don't allow for or you can't measure.


You cannot perfectly balance the brakes for all conditions by sizing the the brakes sizes anyway.

Fitting a valve has advantages one of which is in low g braking (ie in the wet) the rear does a greater % of the stopping, this one of the reasons car manufacturers fit them.

The quick fix is a Corsa/Rover/Fiesta valve, the best longer term fix is an Fiat/Lada valve with a custom broker to make it adjustable. Fiat valves only cost £20 or less new.
Mintex pads are also a good move so called"standard" pads vary a great deal in friction and fade characteristics.

[Edited on 19/4/14 by britishtrident]