Brake bias valve question

[Fungus]

So,

I'm converting my polo to rear discs, which will require a bias valve to set up the brake balance.

The master cylinder has four outlets, so each brake has its own line.

What would be the best way of installing a bias valve, bearing in mind that there are two lines running to the rear? I was thinking I could T them I to one line in the engine bay, add the valve there, and then T the output of the valve back into two lines.

Apparently, another way to do it would be to blank off one of the master cylinder outputs and have one rear brake line, and T it into two after the valve. I can't figure out whether that would give me far less pressure at the back due to using only using one M/C output for the two brakes.

Any suggestions?

Thanks in advance.

[welshpug]

what did disc brake models use?

also what does it have from the factory?

if you want to use an adjustable valve you need a blanking plug and a pair of tee pieces, unless you buy a particularly expensive dual line valve.

[Fungus]

There wasn't a a disc model, I'm using Mk2 Golf rear discs and Mk4 Golf calipers on a Mk2 Polo.

Where would the two T pieces go?

Thanks

[welshpug]

duuh, sorry only one tee piece !

did the polo have pressure limiters in the wheel cylinders?

[steveo3002]

some of the vw's used a small cylinder looking limiter inline , could fit those anywhere along the run where it looks neat

gti with the rear disc had a big ol lump bolted to the rear beam which had a lever that moved depending on the load of the car

[swampy76]

Fairly sure the mk2 and 4 golf use a valve thing that attaches to the master cylinder

[Fungus]

I liked the idea of an aftermarket one as it would allow me to adjust the balance, I don't really see how a standard golf one would work on the polo with its different weight distribution.

Would blanking off one M/C output and feeding the other into a valve and then teeing it off work properly? My idea was to tee both rear MC outputs into the valve, and then Tee it back into two lines after the valve. I'm not sure if there would be any different with these two options

[swampy76]

The prolem you have with joining the rear lines is that there is an inbuilt safety system in that you have what is called a split diagonal system, so if a hose bursts you still have some braking on two opposite corners

But you can do it as you say

[welshpug]

worked fine on a 1.6 205 gti

[vtecpowergt]

I have in the past on a volvo 340 that we fitted a line lock on for burnouts works the same as a bias valve that had 2 lines independent to the rear what we did was to blank one of the outputs from the mater cylinder using a bleed nipple that we had from an old renault wheel cylinder luckily the same size then from the single line into the bias valve and then to a t piece before going to both rear brakes it worked fine just need to remember you lose the safety aspect if you have a line burst or a leak as the fail safe is normally opposite corners on one circuit but we didnt mind as most classic cars only ever had single line systems as standard hope this helps.