Front Brake Conversion - Sanity Check - Page 2

Addicted · 08-09-14, 12:31 PM

Do you know what caliper was originally fitted? i.e the one paired with the 239mm solid disc?

Emjay · 08-09-14, 01:25 PM

Not without checking up and that will take a few days. IRC they came of a Golf but that's about as far as I know for know

What are you thinking?

Addicted · 08-09-14, 03:09 PM

Just doing the maths as to whether you really do need a 22mm master cylinder (rather than taking it as fact from forums

)

If we take the mk1 golf, that had the VWII caliper with a 20mm master cylinder. The VWII has IIRC a piston diamter of 37mm. That gives a ratio of 11:1

The mk2 golf 16v, with the Girling 54 caliper had a 22mm master cylinder. That gives an improved ratio of 12:1

So if you upgrade to Girling 54's but keep the 20mm master cylinder you end up with 14.5:1

Thats quite a bit. With servo assistance that will give quite a lot of pedal travel.

Now the 256mm Girling 54 setup I have came off a B2 Audi, therefore there must be a B2 Audi with a 22mm cylinder, would that not be suitable for you?

Emjay · 09-09-14, 07:58 PM

re edited my original post as follows for accuracy

Blimey this brake upgrade thing is a bit of effort. Having sourced and confirmed the front caliper set-up I've started the search for a 22mm bore tandem brake cylinder. So far I've identified two potentials. One is from a Scirroco 16 valve and the other is from a Coupe.

The only down side to both is the fact there is no way to fit the brake light switch. If anyone knows of a unit that can also take the brake light switch I'd be interested to hear from you.

Thanks

Martyn

Addicted · 09-09-14, 08:48 PM

Right, you're not going to like this.. But..

You have the mk1 golf type master cylinder and servo, depending on year it may even have a 171 part number (mk1 golf number). Its made by ATE and is 20.64mm diameter.

With that servo you cannot upgrade to a 22.2mm master cylinder, you have to swap the servo also as the interface is different. This where it gets tricky as the servo for the 22mm master cylinder is of a bigger diameter (9" diameter) and may not fit your bay due to fouling brackets etc.. As you probably have a 7" servo (you need to check)

Also, the 22mm master cylinders only have 4 m10x1.0 outlets. Which means you need to insert T pieces in your front and rear lines for the brake light switches. Or fit the brake light switch from an auto which is on the pedal.

If you have a 9" servo you're laughing as you can just swap in the new servo and master cylinder assembly

One of the old school conversions was to use a merc SL master cylinder, fits existing servo, uses existing fluid reservoir, one port for rear brakes, one port for fronts and one for switch...

Emjay · 10-09-14, 11:19 AM

tbh that's very helpful as it gives a clearer indication of what I'm dealing with.

On the positive side, tee-ing in the brake light switch is easier than wiring in a new light switch under the brake pedal so if that's feasible then that's a big plus.

Going to see if I can hunt out a Merc master cylinder and measure up the servo situation

Addicted · 10-09-14, 12:19 PM

I just googled the merc master cylinder.. looks like it has a 19mm piston for rear brakes and a 23.8mm piston for the front... strikes me that would take careful setting up, unless my memory is fuddled and it was a different merc master cylinder people used.
I had one on a GTI 20 years ago and I'm sure it had 23 cast into the side (used it with some AP calipers)

EDIT:

This looks perfect! from a typ 44! Audi part number 443611021. 23mm, same servo, same reservoir, 4 M10 x 1.0 ports... and its genuine ATE

http://www.ebay.co.uk/itm/BRAKE-MAST...item2ecac802f7

Emjay · 10-09-14, 01:21 PM

funnily enough the Porsche 924/944 had a similar split MC. 19mmm for the rear and 23 for the front brakes for Bias set up

ChrisG · 10-09-14, 06:06 PM

I've run 256 front on my 80 Sport for many years.
I didn't change the master cylinder ( at the time didn't want the extra hassle as the car was a daily driver then.)
The pedal travel is a bit longer but the brakes still work well !
I keep thinking I should complete the job....and it wouldn't matter if it was off the road for a month!

Addicted · 10-09-14, 06:43 PM

Quote:

Originally Posted by ChrisG

I've run 256 front on my 80 Sport for many years.
I didn't change the master cylinder ( at the time didn't want the extra hassle as the car was a daily driver then.)
The pedal travel is a bit longer but the brakes still work well !
I keep thinking I should complete the job....and it wouldn't matter if it was off the road for a month!

Does it only have a 19mm master cylinder? I thought the 256's were standard on the 80 sport..

08-09-14, 12:31 PM	#11
Addicted Grown up member Classic Audi Club Member Join Date: Oct 2008 Posts: 591	Do you know what caliper was originally fitted? i.e the one paired with the 239mm solid disc? __________________ 1985 Type 81 2 door 2.8 V6 1983 Golf GTI track weapon 1977 Scirocco G60 1968 Sand Rail 2006 A4 2.0 TDI Avant = DEAD due to oil pump failure.. then alive.. then DEAD due to cam belt tensioner failure! and ALIVE again!!!

08-09-14, 03:09 PM	#13
Addicted Grown up member Classic Audi Club Member Join Date: Oct 2008 Posts: 591	Just doing the maths as to whether you really do need a 22mm master cylinder (rather than taking it as fact from forums ) If we take the mk1 golf, that had the VWII caliper with a 20mm master cylinder. The VWII has IIRC a piston diamter of 37mm. That gives a ratio of 11:1 The mk2 golf 16v, with the Girling 54 caliper had a 22mm master cylinder. That gives an improved ratio of 12:1 So if you upgrade to Girling 54's but keep the 20mm master cylinder you end up with 14.5:1 Thats quite a bit. With servo assistance that will give quite a lot of pedal travel. Now the 256mm Girling 54 setup I have came off a B2 Audi, therefore there must be a B2 Audi with a 22mm cylinder, would that not be suitable for you? __________________ 1985 Type 81 2 door 2.8 V6 1983 Golf GTI track weapon 1977 Scirocco G60 1968 Sand Rail 2006 A4 2.0 TDI Avant = DEAD due to oil pump failure.. then alive.. then DEAD due to cam belt tensioner failure! and ALIVE again!!!

09-09-14, 08:48 PM	#15
Addicted Grown up member Classic Audi Club Member Join Date: Oct 2008 Posts: 591	Right, you're not going to like this.. But.. You have the mk1 golf type master cylinder and servo, depending on year it may even have a 171 part number (mk1 golf number). Its made by ATE and is 20.64mm diameter. With that servo you cannot upgrade to a 22.2mm master cylinder, you have to swap the servo also as the interface is different. This where it gets tricky as the servo for the 22mm master cylinder is of a bigger diameter (9" diameter) and may not fit your bay due to fouling brackets etc.. As you probably have a 7" servo (you need to check) Also, the 22mm master cylinders only have 4 m10x1.0 outlets. Which means you need to insert T pieces in your front and rear lines for the brake light switches. Or fit the brake light switch from an auto which is on the pedal. If you have a 9" servo you're laughing as you can just swap in the new servo and master cylinder assembly One of the old school conversions was to use a merc SL master cylinder, fits existing servo, uses existing fluid reservoir, one port for rear brakes, one port for fronts and one for switch... __________________ 1985 Type 81 2 door 2.8 V6 1983 Golf GTI track weapon 1977 Scirocco G60 1968 Sand Rail 2006 A4 2.0 TDI Avant = DEAD due to oil pump failure.. then alive.. then DEAD due to cam belt tensioner failure! and ALIVE again!!! Last edited by Addicted; 09-09-14 at 09:10 PM.

10-09-14, 12:19 PM	#17
Addicted Grown up member Classic Audi Club Member Join Date: Oct 2008 Posts: 591	I just googled the merc master cylinder.. looks like it has a 19mm piston for rear brakes and a 23.8mm piston for the front... strikes me that would take careful setting up, unless my memory is fuddled and it was a different merc master cylinder people used. I had one on a GTI 20 years ago and I'm sure it had 23 cast into the side (used it with some AP calipers) EDIT: This looks perfect! from a typ 44! Audi part number 443611021. 23mm, same servo, same reservoir, 4 M10 x 1.0 ports... and its genuine ATE http://www.ebay.co.uk/itm/BRAKE-MAST...item2ecac802f7 __________________ 1985 Type 81 2 door 2.8 V6 1983 Golf GTI track weapon 1977 Scirocco G60 1968 Sand Rail 2006 A4 2.0 TDI Avant = DEAD due to oil pump failure.. then alive.. then DEAD due to cam belt tensioner failure! and ALIVE again!!! Last edited by Addicted; 10-09-14 at 12:26 PM.

08-09-14, 01:25 PM	#12
Emjay Man Fettler Extraodinaire Classic Audi Club Member Join Date: Jul 2008 Location: Up my own arse blowing smoke Posts: 7,417	Not without checking up and that will take a few days. IRC they came of a Golf but that's about as far as I know for know What are you thinking?

09-09-14, 07:58 PM	#14
Emjay Man Fettler Extraodinaire Classic Audi Club Member Join Date: Jul 2008 Location: Up my own arse blowing smoke Posts: 7,417	re edited my original post as follows for accuracy Blimey this brake upgrade thing is a bit of effort. Having sourced and confirmed the front caliper set-up I've started the search for a 22mm bore tandem brake cylinder. So far I've identified two potentials. One is from a Scirroco 16 valve and the other is from a Coupe. The only down side to both is the fact there is no way to fit the brake light switch. If anyone knows of a unit that can also take the brake light switch I'd be interested to hear from you. Thanks Martyn

10-09-14, 11:19 AM	#16
Emjay Man Fettler Extraodinaire Classic Audi Club Member Join Date: Jul 2008 Location: Up my own arse blowing smoke Posts: 7,417	tbh that's very helpful as it gives a clearer indication of what I'm dealing with. On the positive side, tee-ing in the brake light switch is easier than wiring in a new light switch under the brake pedal so if that's feasible then that's a big plus. Going to see if I can hunt out a Merc master cylinder and measure up the servo situation

10-09-14, 01:21 PM	#18
Emjay Man Fettler Extraodinaire Classic Audi Club Member Join Date: Jul 2008 Location: Up my own arse blowing smoke Posts: 7,417	funnily enough the Porsche 924/944 had a similar split MC. 19mmm for the rear and 23 for the front brakes for Bias set up

10-09-14, 06:06 PM	#19
ChrisG Senior Member Classic Audi Club Member Join Date: Dec 2007 Location: Bracknell, Berks. Posts: 1,465	I've run 256 front on my 80 Sport for many years. I didn't change the master cylinder ( at the time didn't want the extra hassle as the car was a daily driver then.) The pedal travel is a bit longer but the brakes still work well ! I keep thinking I should complete the job....and it wouldn't matter if it was off the road for a month!