Brake Bias Tap

[aidy 0]

I have searched the threads and it has brought up lots of different pages mentioning Bias tap but im after more of a definitive answer.

 

 

Wanting to fit a bias tap to my 1.9 sprint car i am assuming the way to do that is as follows;

2 lines come out the master cylinder 1 for each front wheel,

2 lines come out the m/c to go to the rear wheels,

block 1 of the rear lines of with a bolt in the m/c, the other line runs to the bulkhead use a bulkhead connector then from bulkhead into the bias tap, out the bias tap to a T piece then from the T piece 1 line to each rear wheel.

was going to use a copper line out the m/c through the tap to the T piece and then braided hose from the T piece to the calipers

 

Have i got it right??

 

Thanx

[cybernck 400 1 Cars]

that's correct apart from the initial assumption about 1.9 m/c arrangement .

 

it has a cross-diagonal arrangement, meaning front left and rear right calipers

are connected to one pair of outlets (near or far from the servo) while front

right and rear left calipers are connected to the other pair of outets.

 

so it's obligatory to first rearrange it to seperate pairs of front and rear and

then either T the rear ones together or block one outlet, as suggested.

 

hope this helps .

[aidy 0]

Hi Yes it helps

 

just what i wanted to hear, thanx

[Henry 1.9GTi 36]

so it's obligatory to first rearrange it to seperate pairs of front and rear

 

is it possible just to block one of the rear lines with a bolt in the MC and then T the other line as suggested. I'm a bit unsure what is meant by the rearranging into seperate pairs.

 

Also, any recomendations on bias valves? Iv'e had a quick look and a search usually brings up tilton and willwood of the knob/lever type.

 

Cheers.

Henry.

[Rob Thomson 6]

Nah, it's dodgy to just block one port without replumbing the others. You'd have three brakes running off one chamber of the MC which can't be a good idea in terms of 1) running out of cylinder capacity, and 2) dying horribly if one of those three brakes failed (cos the other two wouldn't work either).

 

Oh yeah... bias valves. I had a Tilton lever valve in my trusty old 309 and it was s*it. Only 7 positions (5 of which were useless) and the lever rattled horribly when it was in anything other than it's most rear-biased position. On the other hand, my 106 had a much nicer AP knob valve which was much more nicely made and worked far more nicely. And it was probably double the price, but you get what you pay for.

Edited February 5, 2008 by Rob Thomson

[Henry 1.9GTi 36]

haha cheers rob

so when standing over the engine looking at a standard 1.9GTi MC which lines do i need to re-do to the front (left rear, left front etc.....) and which should be blocked? And then the last one I'll take to the rears

 

Thanks.

Henry.

[welshpug 1,626]

not quite correct rob, its exactly how the 1.6 is plumbed in, fronts from one half of the MC and rears from the other.

[Rob Thomson 6]

not quite correct rob, its exactly how the 1.6 is plumbed in, fronts from one half of the MC and rears from the other.

No, the question was whether he needed to replump the MC to be like the 1.6 set-up or just leave it with the diagonal split.

 

Henry, the MC's split into two cylinders, one near the servo and one far from the servo. Each cylinder has two ports which are in pairs the same distance from the servo. It doesn't matter which half of the MC you connect to, but the fronts must both work off the same pair of ports. The rears are then connected to one port of the other pair and the other port is blocked.

Edited February 5, 2008 by Rob Thomson

[Miles 331 1 Cars]

As Rob has said you pay for what you get, I;ve got a AP one and compared to the Willwood, Tilton ones, well need I say anymore

[Henry 1.9GTi 36]

ok thanks, so for a lamen like myself i use either the 2 rear or 2 front ports for the front brakes, then use 1 port from either front or rear for the rear brakes, and block off the remaining port.

 

sorry to drag this out, just don't want to get it wrong.

 

Henry.

[Rob Thomson 6]

ok thanks, so for a lamen like myself i use either the 2 rear or 2 front ports for the front brakes, then use 1 port from either front or rear for the rear brakes, and block off the remaining port.

Correct.

[engine killer 5]

Will this latest proportioning valve (CP4550-1) from AP works much easier and without re-routing the brake lines?

 

http://www.apracing.com/car/cylinder/pvalves.htm

[davev 1]

would the screw type work in the engine bay? i want to ditch the rear compensators but dont really want brake pipes running through the car as is just a road car. id put a sheld over it to reduce road grime

[bren_1.3 1]

would the screw type work in the engine bay? i want to ditch the rear compensators but dont really want brake pipes running through the car as is just a road car. id put a sheld over it to reduce road grime

 

the lines would only have to enter the inside of the car very briefly....

 

you would have to make new brake lines to remove the compensators, so an extra half a flour routing it inside the cabin would make sense IMO?

[jim205GTI 3]

They do??? Why do the lines need to come inside? surely if its in the engine bay thats where the adjustment would be? And so could keep the lines going underneath the car?

 

If the lines went inside the car with carpet over them would that be an mot failure? Could save a lot of faffing about with getting them over the petrol tank haha

[Miles 331 1 Cars]

I;ve got mine under the bonnet in the CTi as I rarely adjust the bias on that

[DirtyFlare 0]

Looking at Edp's project you dont have to run the brake line through the car. The post in question that shows this is HERE He is running a wilwood bias valve and is about the 3rd pic down.

Edited February 7, 2008 by DirtyFlare

[VisaGTi16v 1]

useful inside the car so you can adjust on the fly which would be handy for me when my rear drum self adjusters stop working, ie the whole time and I end up with a long pedal by the end of a track day. Going to put rear discs on but will still fit an adjuster.

 

For anyone that competes though, check the various regs and the msa blue book as I recall something about, you can have it inside but it must be far enough away that you cannot reach it when strapped in your seat so that you cant use it mid race/sprint/etc

[davev 1]

cheers for the answers. looks like a bias valve is next on the list. glad im not the first to ditch the compensators.

 

quick question miles, have you found the valve become hard to adjust from all the road grime or have you covered it?

[bren_1.3 1]

They do??? Why do the lines need to come inside? surely if its in the engine bay thats where the adjustment would be? And so could keep the lines going underneath the car?

 

If the lines went inside the car with carpet over them would that be an mot failure? Could save a lot of faffing about with getting them over the petrol tank haha

 

mis-understanding? in order to ditch the rear brake compensators you will need to make new lines that run underneath the car.

 

im just suggesting that while thats happening you can run the lines down under the car and then up through the floorpan (circa the side of the exhaust tunnel) around the handbrake region and into the bias valve, and then back out the floorpan. you wouldn't necessarily need to run lines through the entire length of the inside of the car...

[jim205GTI 3]

Ah i see what you mean now.......