Fitting 4W disc brakes? Other wheels?

ubercrap · Post by **ubercrap** » Tue Nov 29, 2005 1:58 pm

raygreenwood wrote:I just held in my hands this weekend...a very nice rear caliper bracket that is made for type 1 and 3. It is cast steel...and very nice machine work. It will bolt right up under the rear bearing cover on the type 4. Hands down nicer than the type 1 and 3 aluminum unit CB makes. It fits front caliper bolt spacing from a super beetle. The guys said they can order brackets only. It looks like it can easily be made to fit...if it does not already...either 914 rear calipers or type 4 front calipers. I have a scheme for the e-brake that should be easy.

I know where to get them...but the guy said that he is notsure of the manufacturer. It was marked AC industries. It should use either a 914 rear disc....or a Saab 900 rear disc with few mods to the center hole.
The disc unit that came with it was very nice but heavy. It was a single complete casting that incorporated the disc, the "hat" and the outer flange to bolt thewheel to. It had bolt hole spacing for all cars...and had holes in it complete for 4 or 5 lug. It has a splined center for types 1 and 2...but also there is a version for type 3 available. Ray

That's sweet! I know Mid America Motorworks sells some similar brackets from what it sounds like, but it is hard to tell from a tiny picture exactly what is what.

raygreenwood · Post by **raygreenwood** » Tue Nov 29, 2005 4:40 pm

Yes...you are correct. I saw some of these brackets in the backs of mags...and was happy to read that they were either "sintered iron" or steel...instead of aluminum. But....I could not tell anything useful from the pictures. I was happy to actually see one...and see that the quality was right on.

I commented that it would be nice if they just sold the brackets. The guy said "we do!". I will call tommorrow and get a price on them for type 3.

I am figuring this: Since the type 3 and 4 use the same drum...and basically the same backing plate...and use the same bearing cover, but a different stub axle.....that the type 3 caliper bracket should use the same offset. If that is correct.....then the simple part of using either 914 or saab 900 rear discs...is that you can simply open the hole in the center and bolt it all up. Then cross drill that bad boy and you will have a nice rear brake.

Now....the 914 rear caliper would probably be adequate and all...but are getting hard to find.

Picture this: Put front calipers from the 411/412 on the rear. you may need a spacer...and a slight bolt hole adjustment somewhere ...I will have to measure it.

For a parking brake....I have been thinking about installing the equivalent of a line-lock ...made from a single circuit master cylinder with a resoivoir accessible through a cover plate under the back seat....on a bracket under the car...about where the original brake balance unit was (and then installing a new brake balance unit right next to it). This will be activated by the parking brake cables. It will plumb into the calipers via "Y"' unions....or even "T" unions.

Yes...it will not have "safety" margin while driving....in case of hydraulic lien failure....as teh cable ones will....but its a thought. Ray

Wally · Post by **Wally** » Tue Nov 29, 2005 10:38 pm

raygreenwood wrote: Parking break: It will plumb into the calipers via "Y"' unions....or even "T" unions.

Yes...it will not have "safety" margin while driving....in case of hydraulic lien failure....as teh cable ones will....but its a thought. Ray

That won't be an option for most european countrys as we would fail yearly inspection. The parking break needs to be a seperate break system...

raygreenwood · Post by **raygreenwood** » Wed Nov 30, 2005 5:18 am

Yeah...I hear ya! I also do not like that option. One thing I did see is that the flanges on the bracket may be large enough to drill for spacing for a girling type caliper that goes on the rear of an audi 4000 or 5000. That is a single piston sliding type caliper that has an emergency brake lever built in, similar to the 914 rear calipers. The stock cable would need minor mods to the ends.
I have also heard...that Wilwood may make a friction type emergency brake that is basically a cable pulled caliper. I do not know if it would be TUV certified.

Picture this as well. I was "sketching" (mentally) in the shower this morning.

Most Teves type twin piston calipers (like those on the front end of the 411/412) require anti-rotation plates for the piston. i also use on mine....some Raybestos steel anti-rattle shims made for the 914. They are like $18 at Pep-boys. they have high temp adhesive and are very nice. They stick to the back of the pads...and are about .030" thick. They are very high quality and keep the pads from squeeling when hard pads are used.

Picture....that shim......but longer. Where it is not actually under the pad...it is tapered. Like a ramp. It would have to have a spring assembly. Still "designing" that part....but one edge attaches to the brake cable. You pull the brake and the wedge section pushes under the pad....wedging between the pad and piston....driving the piston against teh rotor. Not a lot of power for stoipping...but more than enough for a parking brake...and better for nothing in an emergency. Ray

func412 · Post by **func412** » Thu Dec 01, 2005 8:13 am

I was thinking, what should the brake balance be? I mean how big single cylinder caliper is good to rear when using 4x38 calipers at the front? ...if the discs are the same size.

I tried to find how big the porsche 911 brakes are but I didn´t find the answer...

Or is it just testing, testing... and finally the pedal box or pressure regulator.

raygreenwood · Post by **raygreenwood** » Thu Dec 01, 2005 8:46 am

Yes..balance is just testing. Ifind it best to install an after market brake balance unit right where the original was. Then cut a clean hole in teh sheet metal under the back seat...and install a black VW/audi gasketed cover plate ...similar to what covers teh heater glowplug. Then it looks factory.
In testing...remove the back seat and leave it home. Then you can get on a large parking lot and test..then reach back and adjust.

You want to warm the brakes up....then do a series of panic stops. The rear brakes will lock up. Adjust some pressure away...then repeat until that stops. Then cool teh brakes and test again. Ray

func412 · Post by **func412** » Mon Dec 26, 2005 11:52 pm

Heres two pictures of BMW 296 mm discs in the "412-audi-BMW-Volvo" setup. Maybe 302 mm BMW discs would fit better.

ubercrap · Post by **ubercrap** » Fri Dec 30, 2005 5:43 pm

Hey, I had a crazy idea. What if you bolted the caliper on the OTHER side of the mounting flange? I found a good deal on some rebuilt Volvo calipers, but I haven't received them yet, so I don't know if that is possible, but it looks like it from the pictures. It looks like it might allow you to use a Mercedes rotor from a 91-93 400/500 SE/SEL/SEC. It is part # 09.5716.10 on the Brembo site your referenced. 300mm Diameter, 5x112 bolt pattern. The rotor "hat" is not nearly as deep as the BMW rotor, but maybe the caliper would be moved toward the front side of the hub far enough by mounting on the other side. The advantage is that the bolt pattern would be the same as Audi (no drilling necessary) and the center bore would just have to be enlarged 1mm to fit the Audi hub (no adapter needed). The clamped part of the disc is the same thickness too, I believe. I'll have to do some measurements when I get my calipers.

Edit: Oh, I just considered the clearance of the caliper to the wheel spokes. The caliper looks almost flush with the wheel mounting surface of the hub when mounted normally. I wonder if there are wheels that could clear if the caliper was mounted on the other side? I would assume, though, that wheels for a car with a shallow rotor hat would have the clearance...

func412 · Post by **func412** » Sun Jan 01, 2006 3:12 am

ubercrap wrote: Hey, I had a crazy idea. What if you bolted the caliper on the OTHER side of the mounting flange? The rotor "hat" is not nearly as deep as the BMW rotor, but maybe the caliper would be moved toward the front side of the hub far enough by mounting on the other side.

Thats good idea. I must say I tried that too, but unfortunately the brake fluid lines are located between the caliper bolt section. If you move the calipers other side of the mounting flange, there is not enough space to attatch the brake lines.

ubercrap wrote:It looks like it might allow you to use a Mercedes rotor from a 91-93 400/500 SE/SEL/SEC. It is part # 09.5716.10 on the Brembo site your referenced. 300mm Diameter, 5x112 bolt pattern. The advantage is that the bolt pattern would be the same as Audi (no drilling necessary). The clamped part of the disc is the same thickness too, I believe.

Good thinking! You made me think again the system that is used in porcshe. The disc is bolted to the other side of the hub. Maybe I could use wheel bolts attatch disc in place. The MB disc measurements reguires spacer approx 6 mm spacer between hub and disc to bolt on. In that case the center hole of the disc should be machined bigger.
One example of porsche hub is here -> http://www.vdubcustoms.com/Tech/tech_944t2T.htm

ubercrap wrote:
Oh, I just considered the clearance of the caliper to the wheel spokes. The caliper looks almost flush with the wheel mounting surface of the hub when mounted normally. I wonder if there are wheels that could clear if the caliper was mounted on the other side? I would assume, though, that wheels for a car with a shallow rotor hat would have the clearance...

I think there is available wheels, which have the clearance. If you look audi or MB wheels, they have a place for calipers, which comes out from mounting surface. I´m not sure how much, so it would need some research... I just bought old 1992 Audi quattro with 5x112 bolt pattern so I can look how this thing goes.

And I´m very pleased that i got someone else thinking of this issue too! Thanks!

Edit: one good solution could be BMW 09.7116.10 300/20mm disc attached inside the hub. It weights 1,5 kg less than 302 mm disc!

func412 · Post by **func412** » Sun Jan 01, 2006 10:35 am

I just looked more carefully those discs and rear disc of 540 (e34) is used in this BMW model only... and second, it takes cooling air from wheel direction. The measurements would be just perfect to bolt it "behind" the hub, but the cooling would maybe not be the best for front brakes.

Here´s the measurements of 535 (e34) front disc to compare- >

raygreenwood · Post by **raygreenwood** » Mon Jan 02, 2006 11:59 am

You are going to find...,that 4x38mm front calipers...are slight overkill....but nice

. The real problem is that the stock master cylinder is nowhere near the volume needed to operate those.
That is also teh next issue when going to rear discs on anya car. The drum wheel cylinder requires very little colume compared to a twin piston disc. This reason...and economy of manufacture....is the reason why so many companies use single piston sliders on the rear.....that and ease of parking brake addition. I think twin pistons calipers are better.
Take alook at Volvo. Saab and BMW rear brakes that uses discs. You will note...that most use a much smaller caliper system...as that is all that is needed.

The rear brake bias...should stay close to what stock is. That would be about 65-35 front to rear. Ray

Wally · Post by **Wally** » Mon Jan 02, 2006 12:34 pm

raygreenwood wrote:You are going to find...,that 4x38mm front calipers...are slight overkill....but nice . The real problem is that the stock master cylinder is nowhere near the volume needed to operate those.

I don't agree there with you. In theory that sounds logical, but I have the utterly too large 928S4 Brembo 4-pot brakes front and rear (!) on my 1303. The disk at front is 32mm thick!!
Originally I used the original 19/19 mm M/C: Travel was not more than with the stock brakes (!), but bias was out (too much front action)
I now have the 23/19mm 944 early M/C and put the 23mm to the rear to help the brake bias. (other way around made it worse...)

That is also teh next issue when going to rear discs on anya car. The drum wheel cylinder requires very little colume compared to a twin piston disc.

No, sorry, but I disagree again: Its almost the other way around imo irl: the wheel cylinders in drum brakes usually need a much longer travel before they are contacting the complete circumference of the drum. That takes more volume than the tiny travel that disk pads have to make to contact the disk fully.

I have had the above experience with going to disks front and rear with both my 1303 and type 3 squareback (944 rear disks, stock M/C, much harder and higher brake pedal than ever before)

Besides: the 911 had the same (up to 1976?) 19/19mm M/C without power boost. Thats the same size like a stock bug and had also disks all around...Nice coincidence he

The 411/412 has an even bigger 20/20mm M/C, so I don't see any problem with the size of our stock type 4 M/C at all.

Ray, did you also personally outfit your aircooled VW with rear disks or are you speaking purely from theory here?

Best regards,
Walter

vwbill · Post by **vwbill** » Mon Jan 02, 2006 7:20 pm

Hey Guys, it's great that you are working this issue and the conversion issues!! Sounds like by the end of this post there will be some great brake setup options for us to use! Brakes were a big issue for me on my old 412 2d sedan and it needed alot of bleeding and maintance! My sister had a pedal fade in the car and had a accident but I thought it might have just been a traffic and heat issue! I always worked alot on the brakes after that to make sure they were top notch and I never had any issues but think a rear disc brake setup would maybe help with the bleeding issues maybe shorten brake distance? So is it true that the front brakes do 65 of the braking and the rear 35 percent? Does the engine being in the rear effect that or is it a total weight issue? Hey what did Tuna use for his racer setup? bill

raygreenwood · Post by **raygreenwood** » Tue Jan 03, 2006 5:53 am

Your large disc thickness is nice...especially since it is ventilated. The more vents the better...as long as its not overkill for the application. That is not what my point was in my post.
The fluid volume that is required to drive the actual stock wheel cylinders in the rear on the type 4...as compared to the front calipers...is lower that that required for the calipers. Its deceiving. I've done the calculations. The stroke on the wheel cylinders is long (but not that long)....yes...but the diameter is small...and there are two cylinders compared to four pistons up front at roughly 4 times the diameter. Also, the rear drums at several times the surface area are not designed to work at the same pressure as the front discs. The cut-out on the brake balancing unit is in the neighborhood of 518 pounds for the rear. Much over that and they lock up.
The reason why swapping the front line to rear on the master cylinder does not work as well...has little to do with the volume though....as swapping lines front to rear on the stock master cylinder has the same poor effect of making the rear brakes work worse...even though it has teh exact same volume on both circuits. It is because the rear circuit does not activate or move at teh same timing as the front. There is a delay to to spring compression difference between the two circuits. All dual circuit master cylinders...at least on VW are made this way. Front circuit is front circuit...rear is rear.... always. Swapping them around is not optional...unless....you change tehspring to make the rear start its pressure movement at teh same time as the front.

With the stock master....and then adding 4 piston calipers...you cannot hope to generate as much clamping pressure as stock. But...with the surface area of the pad increased...you may not need it.

Yes...I have run rear discs on my first 411. I used welded scratch built brackets and calipers from an Audi 5000. That caliper sucked...but had an e-brake that fabbed up nice. I would never do them that way again. I was in college...and was less exeperienced with fabbing anything. I used rear discs from a 914. Originally I used 914 calipers as well.....but there were pressure issues with the original master cylinder. Either way.....ever since then I have been looking for a good bracket system....instead of having to fab everything.

Rear discs that are like those also did not outperform the rear drums. They had slightly less dive and no fading but marginally same stoipping power.
I do believe that calipers of the same size as the front would do well.

Wether you need that much more rotor than what is availabel stock on the front...is debatable...depending on what you want to do with the car.

Power brakes....on the 411/412....have already shown (at least in stock trim)...to not shorten stopping distance at all ....only lessen effort. But that is in stock trim.

Just ventilating the front rotors, and going to a superior pad with teflon stainless lines already greatly shortens stopping distances on stock.

Be careful on overkill though. I say this...because a great many people have already proved the point. In order to use a much larger volume caliper system...you need the master cylinder volume to drive it. If you cannot get high enough clamping pressure...you cannot generate the heat needed to work with high performance pads. If your rotor is overly large for teh performance application in mind...and overly ventilated....and your heat generation is down.....your system will be less efficient.

The good example being...that most street 911's braking ( as shown in quite a few skid pad tests)....is actually slightly down compared to heavier cars with lesser brakes, until the brakes are beaten on or heated up . This probably more of a problem in this country than in Europe....as most 911's have huge brakes...and are rarely driven or used even close to their potential. Add to that ...its a light car. The 911 brakes are designed with the eventual top end use of the car in mind. Yes...pad composition is important.

Its sounds like you are doing a great job of designing your brake systems. I am not speaking negative of your work at all.
I am mainly speaking for the beneift of others who may not be so circumspect. The 411/412 is actually not that heavy of a car. Ray

Wally · Post by **Wally** » Tue Jan 03, 2006 7:23 am

raygreenwood wrote: . The stroke on the wheel cylinders is long (but not that long)..

Ah, yes, but theory or not, my experience as described above, strongly let me believe that the wheel cylinder stroke displaces more fluid than most well seated calipers/brake pads do on a disk.
This is especially true with the early 944 rear disk set-up, which is so awesome with just stock m/c, whether be it with type 1 (1303) or type 3 cars.
You did have a point with the benefit of the sliding nature of the 944 calipers tho: the one piston in those does only need half the brakefluid for the same action, so that helps as well. Never looked at it that way: thanks!

The reason why swapping the front line to rear on the master cylinder does not work as well...has little to do with the volume though....as swapping lines front to rear on the stock master cylinder has the same poor effect of making the rear brakes work worse...

That was just my example with my stepped 23/19 alu stock 944 m/c in my (streetracer) 1303, which (obviously) really has differently sized pistons. You must have missed that part Ray

Thanks for sharing your experience on the 914 disk rear set-up you once had. I actually was contemplating that route...

Finding a strong big-ish rear caliper with the handbrake lever embedded in it does not seem easy tho (I looked through 634 ebay listings of calipers yesterday...

)
Unless s/body shows me the 944 part that Bill pictured fitted to the rear of a 412

Greets,
Walter