TheSamba.com :: View topic - Rear disc brakes .... build your own kit! Thats what I did.

Wed Sep 05, 2007 6:38 pm

So I said eff drums, and decided to go to rear discs on my Vanagon (2wd)

After doing some research on what other people had done, I decided to go my own route.

Albeit I'm not done yet, but this is where I'm at so far.

Parts:

Mercedes Rotors
Audi/VW calipers/pads
porsche wheelstuds
custom brackets.

As I did not want a welded bracket I made my design with that in mind, I made the brackets thick enough to carry the calipers and be strong enough, and then proceded to make spacers to get the rotor out to where I wanted it. Since I was planning on running rear wheel spacers anyway, this killed two birds with one stone.

The starting point for all this fun:

this is what you're left with after you pull off all the drum brake goodies and the hubs. these two ears are what you mount the bracket to.

the difference in length of the porsche wheel studs, seeing as my old studs were way to short for the audi wheels i'm running, and the fact that all said and done with the rear discs i'll be another 18-20mm further out, these are perfect

the brackets! My waterjet guy cut these out for me, along with the spacers you see in the picture. as you can see, i did NOT have him make the holes for the caliper carriers as I wanted to do that myself as I had not decided if I was going to run the caliper on the front or the back.

this gives you an idea as to the difference in thicknesses between the spacer and the bracket, so everything fits without having to deal with funky offsets...

I just got home from picking the brackets up, and am going to head back out in a little bit for initial mock-up. I may not be done till next week as I'm failry busy, but I'll keep everyone updated, and I'll definately be able to answer any questions thus far.

Oh, and BTW, is anybody interested in buying brackets? I was talking with the waterjet guy and hashing up the idea to build these in bulk and perhaps sell them on here for anyone interested in making their own kit. I could sell just the brackets, OR the brackets and spacers (albeit it will only work with the combonation of stuff i'm using.

That is all for now.... let the questions roll in.

Wed Sep 05, 2007 6:50 pm

Which MB rotors?
Which Audi calipers?
Nice parts from 'water jet guy'.
Thanks for sharing.

Wed Sep 05, 2007 6:56 pm

Heh, sorry, I completely forgot the specifics.

Rotors: MB 190e rears. I went with these because there is SIGNIFICANTLY less machining to be done to the rear hub to fit them. Also, the bolt pattern and bolt hole thickness (14mmx1.5 studs) is a perfect match to the vanagon hub. MB ML320 rotors WILL slide right over the hub without machining, HOWEVER the rotor are QUITE a bit thicker and more costly. The thickness alone makes them impossible to use with the calipers I'm using. The cost on these 190e units were a steal at 20/each.

Calipers: I currently am going to run audi 5kqt rear calipers, which are the SAME as VW's MK2/3 calipers, same carries, the ebrake arm is in a different location, but other than that, same thing. I'm going to be puchasing VW MK4 rear calipers due to the fact that they are lighter, and have a larger piston. But for now, the audi calipers will be fine.

Wed Sep 05, 2007 6:57 pm

looks like a nice setup.

my only issue is that not alot of people have a waterjet guy

Wed Sep 05, 2007 7:03 pm

for those that don't, and want to do this, I am contemplating having these made in bulk. From my initial convo with the my waterjet guy today, the cost for making a set of the brackets AND the spacers, INCLUDING material would be around the 180-200 mark. This could change depending on how many are requested. Its not terribly expensive, although not terribly cheap, but it might give people the opportunity to do this that may not be comfortable welding/making their own brake brackets.

Don't get me wrong, the guy I used is not a close friend of mine, I got reffered to him from another buddy and he helped me out on pricing and whatnot. I also can get the program he used for my setup and email it to people that have their own source for waterjetting.

Wed Sep 05, 2007 7:26 pm

Bern wrote: for those that don't, and want to do this, I am contemplating having these made in bulk. From my initial convo with the my waterjet guy today, the cost for making a set of the brackets AND the spacers, INCLUDING material would be around the 180-200 mark. This could change depending on how many are requested. Its not terribly expensive, although not terribly cheap, but it might give people the opportunity to do this that may not be comfortable welding/making their own brake brackets.

i would, at least, be interested in finding out what the final cost would be - including shipping to tennessee. once you finish your install and i can find out what the total cost would be and how much work it would be i'll know if i'll be able to commit.

r

Ron Tipton
[email protected]

Thu Sep 06, 2007 4:58 am

What is the minimum rim size required. 14"??

Thu Sep 06, 2007 10:42 am

to be honest, i had planned on running 15" rims, however i will test fit with 14" rims, because they SHOULD work with that size.

Thu Sep 06, 2007 11:36 am

Do you have a file so we can find out how much it will cost to cut here, please?

What is the thickness of materials involved????

Those brackets are easy enough that they coud be flame cut too. Flame cutting is CHEAP. Then you clean up the cut by grinding. Drill some holes and you are happy.

Also, we have a water jetter we use here too.

We have the loose parts waiting to mock up here right now. I have some calipers, rear arms and used rear MB rotors.

TIA,
Walt...

Thu Sep 06, 2007 1:16 pm

I would be very interested in the electronic files for cutting the parts. Looks like a very tidy job. How much did you have to remove from the hub?

Erik D.

'82 diesel Westy, 1.9t 5 sdp

Thu Sep 06, 2007 2:52 pm

the thickness of the two plates are 7/16" and 5/8"...

I will get the files for the cutting and send them to whoevers interested. I need to get it emailed to me, then it'll be ready to go.

I was thinking about cutting the pieces with flame, but I wanted to have a nice tight fit around the hub, so I went with waterjetting.

As for the hub, I believe it was 2mm of milling, the paper I wrote that info on has magically disappeared, but 2mm is close if not exactly what it is. It was VERY close to fitting the rotors without cutting, just a little bit needs to go.

Thu Sep 06, 2007 9:01 pm

What about using the Benz 190E calipers along with the rotors? I will be parting out a 190E so I have the calipers to match

Thu Sep 06, 2007 9:21 pm

Quote: What about using the Benz 190E calipers along with the rotors? I will be parting out a 190E so I have the calipers to match

The rear calipers on the 190e has no mechanical emergency brake actuation like the VW units. Mercedes uses small brake shoes inside the rotor hub for an emergency brake (just like Volvo 240-740s-940s).

Mon Sep 17, 2007 8:18 pm

ok.... update, got them finished a few days ago, but had to go out of town before i had time to post the new info and pics up...

There were some changes since last time i posted...

The plate steel for the brackets was changed from 7/16" to 3/8" to cure some clearance issues.

The brackets were modified to work with the caliper carriers, which i had not really taken into account before, it was basically a mock up setup before.

I changed from Audi 5kqt rear calipers to vw mk4 rear calipers for a larger piston, better e-brake design, easier to work with e-brake location...not to mention a MUCH lighter caliper. These require use of the mk4 pads. The audi pads look close, but won't work. Also, the mk4 rears were nice because they came with a short flex hose (not all do, so if you're going to do this, make sure you get the hoses) which makes hooking up the calipers to the existing brake lines a SNAP!

now for pics:

With the rotor on the hub with the spacer in between the hub and the rotor hat. Note the porsche wheel studs...nice and long.

the new mk4 calipers.

you can see that black tab on the left side of the caliper, that is for the e-brake, should be a nice straight shot for the cable to go through, they're plenty long enough.

the new bracket design, with the old design on the far right.

bracket bolted on...

and the completed assembly (minus e-brake)

The e-brake isn't done yet, I ran out of time, but I'll be taking the van out camping this weekend to bed the pads in and see how things work out.

the camera ran out of batteries, so this is most of the pictures. if anyone needs some specific pics, or info, let me know...

Mon Sep 17, 2007 9:23 pm

Really nice work and thanks for documenting it so well.

Questions:

---where did you get your calipers? new? rebuilt? genuine vw?

---I don't need spacers on my wheels. How will that change the dimensions of the caliper carrier?

---How thick is the 190e rotor (at the studs)?

---do you have an electronic file of the carrier?

Thanks,
Jeff

Mon Sep 17, 2007 9:44 pm

izzydog wrote:

Questions:

---where did you get your calipers? new? rebuilt? genuine vw?

---I don't need spacers on my wheels. How will that change the dimensions of the caliper carrier?

---How thick is the 190e rotor (at the studs)?

---do you have an electronic file of the carrier?

Also, what is the piston size in those calipers?

Tue Sep 18, 2007 10:12 am

izzydog wrote: Really nice work and thanks for documenting it so well.

Questions:

---where did you get your calipers? new? rebuilt? genuine vw?

---I don't need spacers on my wheels. How will that change the dimensions of the caliper carrier?

---How thick is the 190e rotor (at the studs)?

---do you have an electronic file of the carrier?

Thanks,
Jeff

got my calipers from a local shop a friend of mine runs. they're new VW units.

without the spacer there is no way to run this setup, without pushing the rotor out away from the hub, there is no room to put the caliper on without building an offset or recessed bracket. to be honest, there wasn't a HUGE difference after this was all said and done.

the thickness of the rotor i'll have to get back to you on, I had a big paper with all the specs and whatnot, and it has since gone missing..

I can get an electronic file of the carrier as well as the spacers, and again, i may also opt to sell this setup for those that want to do this on there own...

Loogy, the info on the pistons is also on the piece of paper i lost, i'll have to find it and post back up...

Tue Sep 18, 2007 5:57 pm

Nice, Suuuweeet.
Be careful getting larger piston caliipers, that will change the brake bias, and it works backwards from what seems logical. Bigger pistons equals less pressure (really!)

Maybe good, maybe bad.

Nice setup, nice price off the shlf parts too.

Tue Sep 18, 2007 8:09 pm

Bern wrote: the thickness of the rotor i'll have to get back to you on, I had a big paper with all the specs and whatnot, and it has since gone missing
For whatever it's worth, the 190E rotors out in my garage measure ~5mm at the studs. They're OE Benz units (with part number and everything), aftermarket replacement rotors might be thicker in that area. This is almost the same combination of parts I settled on using last winter, but the calipers I've got are Mk2 Golf/Jetta rears I "inherited" from the guy down the road .. rear discs don't help much when a tree limb falls on the roof. :oops:

The project's been on the back burner for months, I got sidetracked by camping season.

Wed Sep 19, 2007 9:18 pm

camo westy wrote:
Be careful getting larger piston caliipers, that will change the brake bias, and it works backwards from what seems logical. Bigger pistons equals less pressure (really!)

A larger pistoned caliper DOES NOT equal less pressure. Just the opposite is true.

Hydraulic pressure = Force divided by the piston area. In this case, force equals the pressure being exerted onto the piston of the master cylinder and the piston area equals the square area of the piston(s) in the caliper(s).

For example, lets say we have a master cylinder piston with an area of 2 sq inches. When we place 400lbs of force onto that piston, the piston in turn places 200psi onto the brake fluid. Since the brake fluid is not compressible, the fluid itself exerts 200psi onto every surface that it is touching including the backside of the caliper piston(s). If the piston in the caliper is 2sq inches (just like the example master cylinder), the force that gets exerted onto the brake pad, via the caliper piston, is 400lbs (force on the piston = hydraulic pressure, 200psi, multiplied by the area of the piston, 2sq inches).

So now, if we increase the caliper piston to 4sq inches and keep the 2sq inch master cylinder, we will see how increasing the caliper piston size increases the amount of force exerted onto the brake pad.

400lbs of force into the 2sq inch master cylinder piston = 200psi exerted onto the brake fluid. The brake fluid transfers this 200psi onto all surfaces including the backside of the 4sq inch caliper piston. 200psi multiplied by 4sq inches = 800lbs of force onto the brake pad via the caliper piston.

A change in caliper piston size WILL affect the braking bias though. However, most street cars are set up with way too much front brake bias from the factory so as to error on the extreme cautionary side when it comes to braking stability (liability and all). Almost all cars can stand to have slightly more rear brake bias dialed in. Dialing in the correct amount of rear brake bias can dramatically reduce the stopping distance in some vehicles but can also make a vehicle very unstable during braking if taken too far.

Another thing that inreasing the caliper piston size will do is increase the pedal travel due to the increased volume of fliud that it takes to move the larger piston.