# Scirocco MK2 rear brake bias



## 20v_boost (Jan 29, 2002)

I'm feeling the need to increase rear brake pressure on my 16v Scirocco. It just locks up the front wheels too easily. The car has an essentially stock brake system and has been lowered with coilovers. What's the best way to adjust the brake bias? I'm trying to stay away from changing it with brake pad swaps.

-Alex


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## greyhare (Dec 24, 2003)

20v_boost said:


> I'm feeling the need to increase rear brake pressure on my 16v Scirocco. It just locks up the front wheels too easily. The car has an *essentially stock* brake system and has been lowered with coilovers. What's the best way to adjust the brake bias? I'm trying to stay away from changing it with brake pad swaps.
> 
> -Alex



Is it stock or not?


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## 20v_boost (Jan 29, 2002)

I have a 22mm Corrado master cylinder (same bore as stock 16v) MK3 brake booster, MK4 rear calipers, stainless braided lines all around, ATE type 200 brake fluid, HAWK HPS pads all around, stock size brembo rotors all around, original front calipers and proportioning valves.

The rear calipers are from a New Beetle and are 38mm bore which is slightly larger than stock. The parking brake works fantastic now.

Also, I'm running 195/50/15 Yokohama S drive tires.

-Alex


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## OddJobb (Nov 6, 2004)

Does the car have a proportioning valve on the rear beam? If so, you may be able to adjust it like you can on non-ABS MKIIIs.


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## 20v_boost (Jan 29, 2002)

No, just the pair of in-line valves.


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## OddJobb (Nov 6, 2004)

Where are the 'in-line' valves located? At the master cylinder? Are they adjustable for the fronts or rears only? Installing a rear proportioning valve found on non-ABS VWs would be a cheaper option. New they can be had for around $100 (for the ones found on MKIIIs). From a junk yard, much less. You would have to re-do the rear brake lines but you would have some ability to adjust after that.


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## 20v_boost (Jan 29, 2002)

On the 16v, there are a pair of proportioning valves in-line with the rear brake lines right near the master cylinder. In fact, one is screwed into the master cylinder. The rear left and front right wheel are on one brake circuit and the rear right and front left are on another. I'd kinda like to keep it that way. With the MK3 valve (which I assume goes on the rear beam) I'd have to run both rear brakes on one circuit right? I also looked at generic adjustable proportioning valves like from summit racing and others but didn't want to loose the diagonal circuits. Is this what most people do? Am I being a wuss?

Oh and yes I could make up brake lines no problem.

-Alex


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## OddJobb (Nov 6, 2004)

20v_boost said:


> On the 16v, there are a pair of proportioning valves in-line with the rear brake lines right near the master cylinder.


So why can't you adjust the rear bias with these then? Are you saying that if you try to adjust one of the rears, the front on that same cicuit will also be adjusted?

I'd have to go look at my MKIII, but I belive the master cylinder has 4 lines coming off it. The two lines to the rears run under the car to the proportioining valve on the rear beam.

Honestly, most people don't even bother with attempting to adjust the bias on their cars (in the MKIII forums anyway) even after lowering them.


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## 20v_boost (Jan 29, 2002)

As far as I can tell, my proportioning valves are not adjustable. I wish I was wrong.

Maybe there's something else wrong with my system, but it just feels like the front brakes are doing all the work.

-Alex


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## OddJobb (Nov 6, 2004)

Did this car have drums as original equipment? And you converted to discs? If so, this could be the problem. On MKIIIs there are two different versions of the proportioning valves: one for drums and one for discs. When converting to discs the proportioning valve requires adjustment because the specifications for pressure to the rear lines are different.

Reading around the Scirocco forum I find that there are different versions of the proportioning valves for these cars also. Apparently they are also non-adjustable. If you haven't already, see this thread:

http://forums.vwvortex.com/showthread.php?5287208-Proportioning-valve&highlight=proportioning


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## 20v_boost (Jan 29, 2002)

Thanks for the thread. There's some good info there.

No, the car wasn't converted. 16v Sciroccos came stock with discs in the rear. I think I'm going to go with a pair of adjustable proportioning valves from wilwood, one on each circuit.

-Alex


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## 20v_boost (Jan 29, 2002)

Just a quick update for anyone who reads this in the future. I took the car on the track (Homestead, FL) this weekend with the original proportioning valves and the brakes worked great. Once the tires got hot, everything changed. There was tons of braking power before the tires would lock up (in fact they never did). So I attribute my original problem to street tires that don't grip much on the street.

-Alex


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