Rear disc brakes

Michael--so a search on here about the CB rear disc brakes.  As you will read, mine as well as other SOC members' came apart because the rotor is made with two parts , a larger aluminum part ---the outer part-- fused to a smaller steel part that fits onto the axle . I was warned about this and was told that if they are are torqued right when installing, this wouldn't happen.  They were and it did. So I had the inner steel part firmly onto the axle while the outer aluminum part could spin around the steel part.  It was a pretty good jolt when the slack was taken up! This happened in Richmond VA and it was an unpleasant long drive back home to Arkansas.  I was worried that the slack wouldn't take up and the outer part would freely spin around the inner part.

For me the cure was to get two new rotors to replace the faulty ones and I found solid steel rotors from SoCal Imports, p/n 113615601DNS at $ 84.95 each.

This was three years and the replacements have worked perfectly---and why not, they are solid steel!   The new steel rotors were plug and play and fit good onto the rear of the CB Performance disc brake kit.   You might look into the whole kit that So Cal Imports offers because the whole affair is designed to work together.  Call 'em and see what measurements you should provide to swap with the drums on your CMC. The number is 562/633-4979.

I read here that we don't "need" rear discs but a panic stop once out on I-40 with rear drums told me the truth---and we need all the safety we can get with these cars.

Good luck with it!  You are damned sure doing the right thing.

ps--My C.B. Ones were called "race strength" too. Disclamer--this was my experience and maybe CB Perf. has changed the way the two part rotors are made.  Call and find out.

Well, there's racing......   

And then, there's "Jack Crosby Racing"!    

The current "race strength" rear disc brakes use 914 rotors. They use studs pressed into a steel (I think) hub under the big nut and the studs pass through the rotors. The brackets for the calipers are aluminum. 

I would like to be sure they will fit before ordering them.

Thanks for your replies.

I was speaking with one of my customers who owns a high tech machine shop. He and his adult son race formula bee at Watkins Glenand he has quite a collection of VW performance goodies around his shop. I mentioned that I was considering a rear brake upgrade to discs

 He showed me his rear drum pads. They are made for the form v cars and have carbon steel as part of the pad material. He is not cheap but he loves these as they are tested and proven to stop better than the disc conversions! I trust him. He is an aerospace engineer.  Just one of my odd experiences.

Formula Vee!

Michael McKelvey posted:

The current "race strength" rear disc brakes use 914 rotors. They use studs pressed into a steel (I think) hub under the big nut and the studs pass through the rotors. The brackets for the calipers are aluminum. 

I would like to be sure they will fit before ordering them.

Thanks for your replies.

Yes, "pressed".  That's the problem.  Pressed doesn't hold together.

"He is an aerospace engineer.  Just one of my odd experiences."

Yes.....    In my experience, Aerospace guys are always kinda weird......  

Jack Crosby posted:

Michael McKelvey posted:

The current "race strength" rear disc brakes use 914 rotors. They use studs pressed into a steel (I think) hub under the big nut and the studs pass through the rotors. The brackets for the calipers are aluminum. 

I would like to be sure they will fit before ordering them.

Thanks for your replies.

Yes, "pressed".  That's the problem.  Pressed doesn't hold together.

 

Jack,

You had a problem with the CB wide 5 kit, Michael is talking about the 4-lug kit. Totally different animal. The "pressed" part he was talking about is the lugs, which are a world better than the screwed in studs. Regardless, I believe the steel hub centers on the wide-5 kit are friction welded, not pressed into the AL hub body. The hub separation you got with your wide-5 kit can't happen on the 4-lug kit because the entire hub on those is steel.

Michael,

I'm pretty sure they aren't truly "zero-offset", although I could be wrong. I just checked-- there are no competition 4-lug kits with E-brakes, only the heavier iron rot-hub kits are available that way.

Michael McKelvey posted:

The current "race strength" rear disc brakes use 914 rotors. They use studs pressed into a steel (I think) hub under the big nut and the studs pass through the rotors. The brackets for the calipers are aluminum. 

I would like to be sure they will fit before ordering them.

Thanks for your replies.

The most common way of adding 914 rear rotors is with type 3 hubs which add about 5/8" track per side, so I would double check with CB (or whoever you end up buying from) to see how they do it. I forget, Michael- is your car swingaxle (long or short axles and tubes) or irs?

Michael McKelvey posted:

I am considering installing CB's Race Strength Rear Disc Brake Kit, 4 Lug, IRS, With Emergency Brake.

 

@ALB, IRS

@ALB  are there any pictures of this type of install on an IRS rear end with the parking brake cables?

Terry Nuckels posted:

Michael McKelvey posted:

I am considering installing CB's Race Strength Rear Disc Brake Kit, 4 Lug, IRS, With Emergency Brake.

 

@ALB, IRS

Of course! Thanks Terry.

IaM-Ray posted:

@ALB  are there any pictures of this type of install on an IRS rear end with the parking brake cables?

I'm sure if you checked the Samba, Ray, you could find pics (I'm going to bed). Hot VW's magazine (Dec. '94) did an article titled "Adapting 914 Rear Disc Brakes To An IRS VW" and give plans for home fabricated caliper and emergency brake cable brackets. I could scan and send it to you if you like (it'll give me a reason to learn how to use the scanner function on the printer).

Sure that would be nice..

Here is something I just found ... 914 rear brakes and Mk IV VW and brackets & have emerg brake too ... Carrier brackets are billet alloy available from Sharpbuilt

sharpbuilt.com

Here is a good look at the kit and its installation:

http://www.huelsmann.us/bugman/Rear_Disc_Tech.html 

Thanks for posting

Yep, I see now that the kit you're talking about does have an ebrake.

That's a nicely detailed writeup you linked, Michael. I have the Airkewld rear kit for short axle swing, and it doesn't add any width at all. Not that that matters to you. But it does use the same caliper as the CB kit. Pretty much every single rear VW kit uses the Varga caliper.

The install went exactly as your link, the only exception in the Airkewld case is aluminum hub and powdercoat steel caliper bracket. It's not that big a deal to do the install.

Loosening and tightening axle nuts are always best done on the ground. If you don't have anyone to help, make a wheel chock with a 45 degree cut on a 2x4. 

I don't understand the whole Varga VW thing. There's got to be better, more common, lighter rear calipers available.

The jetta type IV caliper works well as does the e brake

Stan Galat posted:

Jack Crosby posted:

Michael McKelvey posted:

The current "race strength" rear disc brakes use 914 rotors. They use studs pressed into a steel (I think) hub under the big nut and the studs pass through the rotors. The brackets for the calipers are aluminum. 

I would like to be sure they will fit before ordering them.

Thanks for your replies.

Yes, "pressed".  That's the problem.  Pressed doesn't hold together.

 

Jack,

You had a problem with the CB wide 5 kit, Michael is talking about the 4-lug kit. Totally different animal. The "pressed" part he was talking about is the lugs, which are a world better than the screwed in studs. Regardless, I believe the steel hub centers on the wide-5 kit are friction welded, not pressed into the AL hub body. The hub separation you got with your wide-5 kit can't happen on the 4-lug kit because the entire hub on those is steel.

Michael,

I'm pretty sure they aren't truly "zero-offset", although I could be wrong. I just checked-- there are no competition 4-lug kits with E-brakes, only the heavier iron rot-hub kits are available that way.

My mistake-I was unaware he was talking about a 4 lug wheel.  

Jack, I still appreciate your response.

You know you are always welcome.  See you in Carlisle and it can't get here too soon!

DannyP posted:

 

Loosening and tightening axle nuts are always best done on the ground. If you don't have anyone to help, make a wheel chock with a 45 degree cut on a 2x4. 

If you go this route be very careful. I've had one of those 45 degree cut 4x4's pop loose under pressure. It flew up crack me in the shin.  I had to carefully take the pry bar/socket off the wheel nut before I could hop around on one foot and let loose with a string of profanities.

Torque Meister makes loosening and tightening the big nut very easy.

Michael McKelvey posted:

Torque Meister makes loosening and tightening the big nut very easy.

That is a very nice tool and I wish I had one / might still get one.

I learned a lesson a few years back while on a trip to Fla and found a nice garage near Bunnell where an older,  former racing guy had  shop that would work on anything foreign. He liked the speedster and I ordered a set of tires from him. Next day while supervising the workers do the install he gave the car a bit of an inspection at no charge. I was impressed and he found one front wheel bearing needed tightening and also the big axle nut right rear needed tightening. 

He went at it with the air gun to the point I got concerned but he just grinned at me and said in a heavy German accent..." dey gotta be tight". 

A year or two later I needed to get that nut off and it took about 800 ft.lbs of me on the far end of a long bar to get it off. The axle threads and the nut were toast. I think the recommended torque spec is either 212 or 216 ft.lbs. Lesson learned. 

Several years ago I suggested we might want to create a tool registry where we could list tools we are willing to lend others.  Then David would be able to find and borrow a torque meister.

I bought a huge torque wrench and a 36mm socket for the rear axle nuts from Railroad Salvage.  Cheap and well made.  Don't use it often but when I do it is an excellent tool.

IaM-Ray posted:

Here is something I just found ... 914 rear brakes and Mk IV VW and brackets & have emerg brake too ... Carrier brackets are billet alloy available from Sharpbuilt

sharpbuilt.com

I just got an email from Sharpbuilt and they still sell those brackets, I wonder if billet aluminum is stronger than the forged or the steel brackets that are available?

Billet will be stronger than some castings but not quite as strong as a real forged aluminum bracket. The disadvantage of billet- you start with a honkin' big block of material and carve it down to shape. If you're paying someone to make the part (from billet or forging) it can be expensive. An aluminum casting, if done properly, should be strong enough, although a billet or forging will have the advantage of slightly less material (and weight) for the same strength. Steel will, of course, be stronger, probably cheaper, and for most people easier to work with, but at 2 1/2 times the weight of aluminum, there is a penalty.

The torque spec on the axle nut is 270 ft-lbs plus the next available slot on the castle nut for the cotter pin.

edsnova posted:

The torque spec on the axle nut is 270 ft-lbs plus the next available slot on the castle nut for the cotter pin.

Because Murphy's Law says 270 ft-lbs will never be where the slot and the hole line up. 

Robert M posted:

edsnova posted:

The torque spec on the axle nut is 270 ft-lbs plus the next available slot on the castle nut for the cotter pin.

Because Murphy's Law says 270 ft-lbs will never be where the slot and the hole line up. 

I said 212 or 216 ft.lbs above and that was wrong. My apologies. My Muir book on page 342 says 220 ft.lbs. on type 1 and  3 and 253 ft.lbs. on type 2. Anyone know for sure ? 

My orange (late model Beetle and K.G 1970 and newer) Bentley manual says 217 ft. lbs (important- and then tighten 'till you can get the cotter pin in; never leave it out, and never back it off just a wee bit to fit the cotter pin!). Always used that figure for whatever year Beetle I had (and I had a few in the first 15 or so years of my driving career) and stock or hotrodded, street or offroad, never lost a rear wheel.

I'm sure the blue Bentley manual (earlier beetle and k.g.) has the same spec.

It's a "spot-torque" part. Tighten it until you see spots.

220 ft/lbs is a minimum value. I use a 450 lb air hammer on mine.

To get back to my original question, I called CB and was told this kit is 1/4" offset, although I am not 100% confident the women actually knew with certainty.

That would use up all the space I have on the driver's side between the tire and fender.

I'm in same boat as you - IRS CMC currently with 914 2L Fuchs and 185/65x15 tires.  Pinky finger clearance on drivers side. Might go with the CIP2 5 bolt Fuchs polished replicas with reported 5" back spacing.  It's that or a set of DrClock's skinny wheels!

Now I am thinking about AC Industries zero offset kit. Some sellers have it with a bent steel caliper bracket but Socal sells it with a cast nodular iron bracket. This will be heavier than the Race Strength but the bracket and disc may not be much heavier than the old drum.

Greg;

Isn't that 5" back spacing worse  than our Fuchs 2L  wheels.

I think I have missed something.  in any event, I also have a pinky finger clearance at the rear drivers side .