Bias valve
Turbo Mini Forums

So i have a bias valve on my car, and the chap who makes them said the less you wind in the less rear braking you get. So wind it in fully and it will have loads of rear braking?

now the bit i don't understand is......

surely no adjusment i.e. straightthrough would mean ormal brake operation? with adjustment made would be less braking effort?

I know it sounds odd, but has anyone got a diagram?

"Cars are a lifetime of pain"

He is correct in his description. If an adjustment bolt is added without modification or change to the internal spring then they can only be used to increase rear braking - 'standard' rear brake effort is their minimum.

Obviously if the rear cylinders are changed then the operating envelope changes.

They work by the internal spring holding a valve open so the brake pressure on the back of the valve will force it shut.
Wind the adjuster in you increase the spring pressure and hence more brake pressure is needed to close the circuit off.

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Edited by graemec on 20th Mar, 2009.

yep,

funny one this,


the valve shuts off pressure to the rear brakes above a certain pressure/ effort, the weaker the spring, the sooner is shuts off to the rears.

ok let me explain the setup a little better?

I have a remote brake master cylinder (non-mini) that does my front and rear braking. All through the samelines, no standard pressure regulator on the bulk head or on the rear subframe.

Then i have a bias valve in line with the rear brakes......so why when its no wound in should it make any difference? when i blow through it its just straight through?

"Cars are a lifetime of pain"

If it is not wound in it will reduce the pressure available to the rear brakes by the amount it would if it was none adjustable.
If it is wound in then the pressure at which it closes will increase - thereby giving more braking on the rear.

You will be able to blow through it unless you can blow harder than the hydraulic pressure the brake lines make.

you will be able to? or you won't be able to?

either way i now have two because i was getting 0-60% leaving a 60/40 split front to rear, which was to much rear braking, so i now have one on the rear subframe thats split from the 40 left over to 60% of that which is .....24% rear braking effort.....does that sound about right?

next year deffinately a bias pedel box

"Cars are a lifetime of pain"

yes,

unles you can blow the say 50 psi to make it shut it will pass through.

the valve will give a lot of rear braking compared to the front (light braking)until the point it shuts off... then it wont.

Hmm, i think i need to go back to my crayola drawing and work this out? consussing the hell out of me.....if it makes a difference its this type of valve...


http://cgi.ebay.co.uk/Brake-Bias-Propotion...bayphotohosting

"Cars are a lifetime of pain"

pmsl,

i just bought one of those as mine has started pissing fluid.

this is worth a read

http://www.stoptech.com/tech_info/wp_propo...ng_valves.shtml

right i think i understand, so the same pressure will be applied at first but will then slope of?

Hmm might have to get the bias rig sooner than expected? Anyone know of any good ones apart from KAD.

"Cars are a lifetime of pain"

why not just replace the rear cylinders? or are you using rear discs?

So it is not a modified Mini valve? My apologies, that is how I read your original post.

So, reading the desciption and what you have said (although you probably have more info than us) - screwed all the way in will give no restriction to rear braking, screwed all the ay out will give a reduction of 60% effort to the rear.

If you need more reduction than that then I would look at the rest of your brakins system as something sounds wrong or mis-matched.
What front brakes and what size rear brake cylinders do you have?

yep now your getting it,

just thought, you do have it plumbed in the right way? the inlet looks to be the one furthest from the knob.

turn the limmeter all the way out and see if the rear wheels will turn with somone pressing the pedal.

he has KAD 6 pots and rear discs.

mentioning the original mk1 bias valve makes me think, could i not just use one of these instead, my belief is that you can turn the rear brakes off (not that you would want to) with this modified of course?

"Cars are a lifetime of pain"

mine is simliar, wound in is maximum breaking power

this caused me a fright when i first fitted it

top tread mini 13

now can anyone tell me if its worth putting the split brake system on with the 4 pot's as era turbo ,i have the metro still at hand for the unions and alike , i would like to use the type 4 master with servo but as the metro has three outs one for rear with the comp valve i was not sure were to add it ?

have drawn a layout but no printer, could use adjuster valve in place of the compensation valve ?

Edited by minivan rick on 25th Mar, 2009.

Don't go slow !!! Go Turbo :))))))

yes you can use the adjuster in place of the compensation valve.

the metro has 2 sets of lines to the front calipers, you can just link these, minispares does a kit to do this.

stef, after last weekend i would advise that you remove that ebay adjustable valve and bin it!!

i had mine (been on the car 2 weeks) randomly pop a seal off thus turning it into a 1 way valve.... meaning the rear brakes locked on!! luckily this didnt happen while i was in motion!

According to Rob Hall, he has tried most valves and found the modded mini one to be best.

if you choped a bit off the spring, would that not reduce braking effort at the rear?

yes.

That's what I was driving at in the second post on the thread! Either shorten the spring or replace it with a weaker one.
Shortening it is the easy way, as long as it doesn't end up too short.