I've been thinking about removing the rear brake bias valve on the GT and converting it to the standard brake set up. The valve is sticky and I will also be lowering the suspension so I feel this is the best option.

I also have some VW11 calipers to fit and I'm replacing all the brake lines so I'm best to do this now if I choose to do it. Has anyone removed this and found it to be detrimental to the braking? I cant see any problem as long as I replace the rear wheel cylinders to the non-bias type but some personal experience in the matter would put my mind at ease.

Also, is it advisable to fit a 22mm master cylinder whilst I'm doing all this work? I've always been in two minds about this modification because surely you loose some pedal feel doing this.

Thanks,

Scott.

I started off with a 1.0L, with no bias valve and VW1's.

Upgraded to VW11's and replaced all the lines just as they were.

There's no locking up of the rear wheels and there's still plenty braking ability up front.

Not sure about the rear wheel cylinders, I got a GT rear axle with the drum brakes included, the cylinders were needing replaced so just went for whatever came from ECP.

I think all the 22mm master cylindar does is reduce brake pedal travel.

Edited 14 April, 201511 yr by citrus

I think thats what I'll do. Ditch the valve and fit the basic cylinders. It would save a lot of hassle and be similar to what I had on my old car.

Thanks for the reply Citrus. I hope to catch up with you at a scottish meet soon. I like what you've done with your car.

Ross, your axle came off a G40 if I remember rightly, even though it is the same as a GT one...

Scott, with the VW11's up front with the bias valve or not there shouldn't be any issues with braking.

Been years since I've driven a Polo with a 22mm master cylinder so can't remember what it feels like.

However I do remember the LHD G40 I broke had a 20mm 4-port master cylinder fitted and the lines were setup so all 4 ports were used. So there was no T-piece splitting a line between the N/S front wheel and O/S rear wheel. The pedal feel on that was amazing, best I've ever felt in a mk3. So I'm using that master cylinder and line setup on the GT when I rebuild it.

Very interesting Steven. The question is: Why don't they use it on the RHD cars? Is there a clearence issue?

Wouldn't have thought so, from the port that is usually blanked off there is plenty of room to route the line down. On the steering rack there is a plastic clip with three 'holders?' for brake lines but only 2 are used. Then after that it is just a case of following the N/S rear brake line.

What are non-bias rear cylinders?

You can't have no piston in the rear drums.

In each of the drums you have a wheel cylinder (sometimes called a slave cylinder but this can often be confused with clutch hydraulics) and due to the polos having two different hydraulic systems (one with a bias valve that adjusts rear brake effort according to how much weight is in the rear and one that doesn't) there are slight differences in the cylinder designs.

Ok thanks - so after some searching on ECP I found the static bias is by the size of the piston in the rear wheel cylinder

17.5mm bore with a proportioning valve/brake power regulator/bias valve adjusted by weight in rear how much lowered.

and

14.29mm or 15.87mm bore for systems without.

That's some good info there! Are the two standard cylinder sizes to do with age or spec?

regarding the master clyinder ..i messed around with em on golfs and it just ruined the pedal feel

if yours locks the brakes and doesnt go too low when doing so id leave the standard size , i come to the conclusion vw engineers probably put some thought and research into whats right and know a bit more than me

I've decided to ditch the bias valve, fit non bias valve wheel cylinders and keep the master cylinder as standard. I'm also fitting braided flexibility pipes to help take away some of the soft pedal feel.

In my opinion though the brakes were never that bad if the rear shoes were adjusted correctly. That's the main issue that affects poor brakes on the mk2/mk2f.

I have a really good condition bias valve off a 6n and a few 22mm (I think) master cylinders from the same car if you do want to try it?

Also have some new vw rear shoes if wanted?

Can't comment on much to do with these, but for the week or so I had my mk2/f I did really have terrible brakes which would only really stop properly if the handbrake was up by 2 clicks - can only imagine it's this valve.

Thanks for the offer but I've decided to not have the bias valve on the car and keep the stock master cylinder on.

When you had the handbrake on 2 clicks, that was compensating for the ill adjusted shoes. If the gap between the shoes and drum isn't as tight as it should be then you will have lots of initial travel before the brakes start to bite.

I've also purchased some braided flexi hoses to help eliminate any feeling of a soft pedal.

^ yeah that 2 click thing is badly ajusted shoes , with the brake up thats what it would have felt like with properly set up shoes

In my opinion though the brakes were never that bad if the rear shoes were adjusted correctly. That's the main issue that affects poor brakes on the mk2/mk2f.

I genuinely think that this is the biggest problem with brakes on the mk2 / mk2f. People are doing all these modifications to their brakes but without removing the lip on the drum and getting a nice tight fit at the rear, all of these modifications are in vain.

That was most probably it then. My friend who used it for the other two weeks (it was stolen on week 4) complained about them and I think he took the drums off and ground the lip and adjusted them but said they weren't too bad, but they could have been way out for all I know :)

I was planning on over hauling the brakes but obviously never could.

I really miss that car, was the best polo I ever had and SOO much fun to drive, plus every time I parked up people asked if I wanted to sell it. don't get that' with most cars.

Funny you should say that. Even in the state that mine is currently in I've had a couple of students want to buy it!

Great wee cars.

The addition of a 256 MC means more force is required by you to emit the same braking force on the cylinders. Why do you think a bigger MC will improve your breaks? A bigger cylinder is designed to displace more fluid but it is only really needed if you have bigger slave cylinders. However, using standard brakes all you will achieve a harder pedal with reduced travel. I have a 256 MC on my Polo but then I have upgraded to MK2 golf 16v brakes all round. Pedal is firm but it stops well.

Edited 21 April, 201511 yr by prankstar2003

A bigger cylinder is designed to displace more fluid but it is only really needed if you have bigger slave cylinders.

Thats exactly why I asked the question. It didnt make much sense to me.

Its like using a smaller lever to move an object. You will have less movement but you need more effort.

if the pedal feels normal then leave it ...changing the size would either make the pedal go nearer the floor or like pressing a stone depending on what you fit

Sound advice. The pedal feel of a polo is ok I find (mk2 at least) even if you need thick legs. I think people assume bigger is better regarding braking components when really, all parts are designed to work together right down to the length of the pedal (lever) servo, distance of the calliper from the hub (again, a lever) etc. Although I have MK2 golf brakes, I'm still using the polo pedal and no servo, so it's even harder although this is partially balanced by the reduced weight of the car (hence force required) and larger braking area and moment at the discs when compared to the originals. Anything beats the postage stamps it came with mind!