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Wed Feb 21, 2007 11:09 am

Finished the first side of my rear disc project. I'm not a huge drum fan, plus, I'm a big proponent of adding stopping power when adding engine power.

I'm using rear discs off a C5 Audi A6 (255mm x10mm), calipers/carriers off an A3 platform golf/jetta, machined hubs, and fabricated brackets.

Upsides to this conversion are
-Fits under 14" wheels
-Uses very available rotors
-Uses very available calipers
-Uses calipers that have a wide range of pad options
-About 85-90% of the stopping power of the smallcar/gowesty kit for much much cheaper.

In fact regarding the calipers, with carriers from an A2 (85-92 golf/jetta) or a 4-cyl A3 (93-99 golf/jetta) you can use the calipers from an A2, an A3, or an A4 (99.5-05 golf/jetta/new beetle). Obviously these were the most common cars VW produced, so they are very available in lcoal junkyards (people often throw then out). The calipers are essentially all the same with some external differences (same piston etc). The A3 calipers have an e-brake mechanism that pulls from the bottom instead of front to back and are a little more reliable (e brake) in cold weather compared to the a2 calipers. The a4 calipers are a little more reliable still in terms of cold weather e-brake operation and are aluminum, so they are a great deal lighter, they also use a banjo bolt instead of a standard brake line end. Obviously, the calipers increase in price with the newer generation cars, but this lets you pick the price point that works for you. Also, as I mentioned, because you use these calipers, you get a huge pad option. I'm using mintex redbox, as I have them on two of my other cars, and I'm very happy with them.

In terms of comparison to the 10.6" kits by companies, this is 95% of the diameter. The only difference with the 10.6 calipers is that they have a wider throat for the 20mm rotors. They have the same pad area, and same piston diameter. Therefore only the additional leverage supplied by the additional diameter contributes to the increased initial stopping power. Considering my setup is 95% of that diameter, I'm confident in my statement about comparison in stopping power. Now obviously the 10.6 kits use 20mm vented rotors, but thicker rotors don't increase intial stopping power, they only decrease fade. Because the rear brakes are limited by the stock proportioning valve and are restriced in the actual amount of braking they do, I don't ever plan to get the point where the rear brakes will fade anyway (it's a syncro, I'm not taking it to the track, the fronts will fade anyway first).

Downsides include the machined hubs (i'm comfortable with the amount of material left, but you do have to admit they were designed that way for a reason) and the fact that because of the offset of the rotor, it makes the brackets much more complicated to make then the 10.6 kits. While the 10.6 kits use essentially straight brackets, my brackets need to have offset mounting points for the caliper carrier in relation to where the bracket mounts to the swing arm tab. This means that I couldn't make the bracket out of one piece of metal with my capabilities (you could machine one, but it would be expensive), so my brackets are welded. I'm very comfortable with their strength (they are actually thicker then the 10.6 brackets at the stress points), but it makes them really difficult to mass produce (which I had initally thought I may do).

In the end, these were my costs
-Hub Machining, 30/hub
-Rotors, 28/rotor
-Calipers/carriers, 42/side at junkyard
-Metal for brackets, 5
-Pads, 39

For a total of right around 250$. I'm pretty pleased with that. Obviously, depending on your caliper choice, it could be higher (or lower).

(not final assembly, so don't get upset about dirty rotors and the backing sheets on the pads)

looks like the rim is sitting on the caliper here, but it's hard to get a shot of, the caliper drops in, so there is a probably a half inch clearance between the caliper and the stepped section of the wheel.

Wed Feb 21, 2007 1:33 pm

That's awesome! Way to go!

Make sure you update us on the final installation and performance.

Just curious, what is the piston diameter of those calipers?

Wed Feb 21, 2007 6:23 pm

i have a 1990 audi 100 parts car its an auto and the brakes wont fit my 91 quattro will any of the disc brakes fit up to my 87 2wd

Wed Feb 21, 2007 6:39 pm

devesvws wrote: i have a 1990 audi 100 parts car its an auto and the brakes wont fit my 91 quattro will any of the disc brakes fit up to my 87 2wd

It won't be bolt up, but with the right brackets (custom) you could make it work. I beleive those cars are 4 lug though, which makes using the rotors not really worth it. You could certainly use the calipers and carriers though (they are for all purposes the exact same as an A2 golf/jetta setup)

Thu Feb 22, 2007 2:59 pm

finished the other bracket today, it's much quicker the second time around.

a little a-platform rear caliper primer.

A2 caliper
http://www.germanautoparts.com/displayimage.php?file=372944511869543655

A3 caliper
http://www.germanautoparts.com/displayimage.php?file=38224757186708H718

A4 caliper
http://www.germanautoparts.com/displayimage.php?file=35264853146000J116

you can see how the a3 and a4 caliper e-brakes pull from the top down, and the a2 pulls from the back to the front. Other than that, and the a4 being aluminum and using a banjo bolt for the fluid line, they are interchangeable.

Fri Feb 23, 2007 3:00 pm

Got everything bled today and the van back out of the barn for the first time in a few weeks. Haven't really hammered on the brakes yet because the interior is still a mess with all the tools and equipment I've been using for various interior projects and I don't want it all flying around, but I'm pleased the bleeding was straight forward. You never know how long of a day it will be when you start trying to crack 20 year old bleeders. But everything works well and no surprises to report.

Also forgot to mention that the discs are thicker then the drums, so the rear track is pushed out 4-5mm, which never hurts.

Mon Feb 26, 2007 2:40 pm

Took it out to bed in the pads today. The brakes work GREAT. It makes it stop like (and in some cases better then) any other "normal" car out there. Stops are without drama, and you never have that feeling where as you are approaching the back of a car at a stop sign you keep pushing harder on the pedal and even though it moves further down it doesn't feel like you are stopping any quicker.

Very pleased.

Wed Feb 28, 2007 10:07 pm

Looking good. I was thinking about using those rotors but decided to go with Benz 190E units .. didn't like the idea of machining that much material off the hubs.

If you haven't already, pop over to the "Disc Brake Conversion...Audi Parts?" thread, specifically the last 2-3 pages where rear disc stuff has come up a lot. Fun stuff...

Thu Mar 01, 2007 5:05 pm

tristessa wrote: Looking good. I was thinking about using those rotors but decided to go with Benz 190E units .. didn't like the idea of machining that much material off the hubs.

You've got me interested in their "stats" now. Basically, I chose to stick with what I know :wink:

Finally got the ebrakes hooked up, and they work great. Used the stock cables, but cut the hook section of the caliper end off (leaving just the stop) and all but about 2" of the springs. I used 1/2" pvc tubing (great fit btw) to space the other ends of the cables out from the sockets where they pass through the frame.

As usual, my adjusted nut was seized solid, and it snapped the end of the main cable when I tried to loosen it, so I just clamped a 4" inch section of threaded rod to it using wire cable clamps which gave me the length and adjustment I needed (actually this is a good tip for anyone who doesn't want to shell out for a new main cable if/when they brake the threaded section off).

I'll try to get pictures tommorow.

Thu Mar 01, 2007 5:34 pm

rs4-380 wrote: Used the stock cables, but cut the hook section of the caliper end off (leaving just the stop) and all but about 2" of the springs.

It's good to hear that it's all coming together for you. Cutting the springs off the cable is fun, huh?

Thu Mar 01, 2007 6:05 pm

[quote="loogy"] rs4-380 wrote: Cutting the springs off the cable is fun, huh?

HUGE PITA. I ended up using a grinding wheel then pulling them off ring by ring.

Fri Mar 02, 2007 12:02 am

rs4-380 wrote: You've got me interested in their "stats" now. Basically, I chose to stick with what I know
Here's the Benz rotor I'm working with:

In another thread, Loogy posted hub diameters for Baywindow (134mm) and Vanagon (168.5mm), but the number for Bay doesn't jive with either what I remember from when I had the drums off last spring (when I discovered just *how* FUBAR my brakes are) or a picture from ratwell's site:

Plus I could see the complex bracket needed to use the Audi/VW rotor like you built .. I've got a MIG in the garage but I'm not confident enough in my welding skillz to try it, a welder I ain't.

I am *so* not looking forward to cutting those damn springs, but if I gotta I gotta. Still dicking with the brackets though, so it'll be a while.

Fri Mar 02, 2007 8:02 am

Keep up the good work Guy's
I will be looking at my brakes soon and all this info is great. 8)

Fri Mar 02, 2007 8:49 am

tristessa wrote:
In another thread, Loogy posted hub diameters for Baywindow (134mm) and Vanagon (168.5mm), but the number for Bay doesn't jive with either what I remember from when I had the drums off last spring (when I discovered just *how* FUBAR my brakes are) or a picture from ratwell's site:

tristessa, do you happen to remember the page of that HUGE thread where I said that? The only Bay hub diameters that I am familiar with are the fronts. I'd like to go back and read that part of the thread to make sure that there isn't any misunderstanding or maybe I need to re-word something. Sorry if I led you astray or was not cear in my description of the hubs.

Fri Mar 02, 2007 9:32 am

Ah, I found it! Yes that was a very misleading, unclear statement.

What I was refering to was the Bay front hub comparing it to the Vanagon rear hub simply from a materials standpoint. Both being cast steel, I was simply saying that turning a Vanagon rear hub down to 135mm isn't that much different than the Bay front hub being designed at 134mm. Jeez, does that make sense?

Here's how I changed the thread in an effort to clear that up:

loogy wrote: I don't see any problems turning it down to 135mm. A stock Bay front hub is 134mm in diameter. The Bay front hub is cast steel like the Vanagon rear hub (I'm simply using the Bay front hub as a materials vs diameter comparison). It is a bit thicker (13mm compared to 9mm) in the area where the studs press through, but the Vanagon hub has substantial strengthening ribs that protrude from the backside of the hub.

Sorry for the confusion.

Fri Mar 02, 2007 12:11 pm

loogy wrote: Ah, I found it! Yes that was a very misleading, unclear statement.

What I was refering to was the Bay front hub comparing it to the Vanagon rear hub simply from a materials standpoint. Both being cast steel, I was simply saying that turning a Vanagon rear hub down to 135mm isn't that much different than the Bay front hub being designed at 134mm. Jeez, does that make sense?
Yeah, the original post (outside the huge thread) wasn't exactly clear, I don't remember you making mention of front vs. rear hubs before the edit. When I read the original I assumed you were talking about the rear, as that's what r39o had asked about. Silly me. :lol:

S'okay. The post makes sense now, and I made an educated guess that I had the larger diameter to deal with anyway. :D

Mon Apr 09, 2007 5:36 pm

do you have any pics of the brackets? if its not too much trouble i wouldn't mind taking a look at them..

Mon Apr 09, 2007 6:26 pm

A vector file would be even better.

I regularly have stuff laser/water cut for my work and I could very easily get a quote on having them produced if we want to do a group purchase. It would be as easy as emailing him the file and specifying the material and quantity. You could even draw it up on a napkin and I could have one of the CAD designers at my work draw it up.

Food for thought.

We also regularly have stuff powder coated and it would be probably about $5 on top to have each bracket powder coated. To get that price they would end up being either metallic silver or 20% black, as those are the only colors we really ever use.

Mon Apr 09, 2007 7:29 pm

Bern wrote: do you have any pics of the brackets? if its not too much trouble i wouldn't mind taking a look at them..

I don't think I have any of them off the car... I'll try and get some good ones on the car, but as you can see, it's somewhat tight in there.

As for perfect measurements/vector files, no. These were total one offs, designed/built on the car. I'm sorry I can't provide more detail (as that was part of my original intent) other then to let you know that if you want to undertake it, it CAN be done and it DOES work.

Mon Apr 09, 2007 7:37 pm

Are the brackets made flat????? Thickness?