Craig;

Here is some more "food for thought" stuff.

If I was going to do it, this is the bracket that I'd weld to the housing.



It would serve the function of having the bearing pads for the spreader and also the shoe stop.

It would be positioned where I'm holding the scale in the following photo;



If after fabricating and installing it looked too weak (at the top), it would be possible to add a stiffener on the car side that matched the radius.

Personally, I'd just go with the 924 spreader (straight pull), but if you used the BMW one, the opening for it could be smaller. (the opening wouldn't have to clear the "tangs" on the 924 spreader, just the arm it's self.

Wes (I've got to get a life) Vann

In the middle of the day today a stray thought about this subject crossed my mind, and in the process got stuck.


What does the stop block everyone adds to the trailing arm actually do?

When the brake is off, the shoes rest against it.

When the brake is on, the shoes are held outward by the spreaders, and they don't touch the stop block.


So why do we need it?????????

Not sure if that's accurate. I believe they pivot off it.

Make a circle in front of yourself with your thumbs and forefingers. The spreader would be between your forefingers. Open the circle pivoting off your thumbs. The pivot offers stability for the shoes and prevents them from simply being ripped off by the wheel if engaged while moving.

Much needed. I believe the stop block is in the wrong position above. It should be below and the spreaders should be above.

Wait... rethinking. You're right.

The spreader creates the pivot.

I don't think the shoes pivot off the stop block. They would have to pivot off the star wheel adjuster. The stop block is on the end with the spreaders....

Ok.. then what does the added stop block do??????

(I call it a stop block because I don't know what else to call it.)

I think another way to say what Eric is saying is...

While you have the pins that keep the shoes attached to the backing plate, pretty much the shoes, spreader and adjuster pretty much float. If you didn't have what we are calling the "stop block" or "spacer", if you engaged the e-brake and tried to move the car, it would either rip the pins from the backing plate or break the pins as the shoes, spreader and adjuster rotated with the disk/drum and the backing plate remained stationary. You also wouldn't rotate much before your cable broke or yanked the spreader out from between the two shoes.

So while the spreader moves them apart, most likely one or the other shoe (depending upon which way the car wants to move) is in contact with the stop block. This is why in my opinion you should not weld the stop block to the thin walled 911 backing plate. And as you mention Clay the 944 backing plate it a heavier cast part and not a thin stamped part because it includes the stop block and can take the load.

The load at rest on the level is probably pretty small/next to nothing. But I think that the load is much higher if you tried to engage the e-brake while moving or if you are parked on a hill.

I agree with what Richard is saying.

Think of the shoes, adjuster and spreader as an assembly that is free to float.

To play with numbers:

When you first pull on the parking brake, each shoe moves away from the block an equal 1/8". You then push the car forward, the assembly would rotate until one of the shoes came in contact with the block. Then you push the car rearward, the assembly would rotate in the other direction and the other shoe would come in contact with the block.

Using those numbers, if you rocked the car back and forth, the spreader would move 1/4".

If you yank on the parking brake while the car is in motion, one of the shoes is going to hammer into the block!!! All of the rotational force gets transfered through that small contact surface on ONE shoe!!!!!

Wes

Richard & Wes are right. You can see the rub marks on the block on a 911 where this happens. The block on the early steel trailing arms is ~1/4" thick. IIRC, The aluminum ones are even thicker. I have both at the house and can measure tonight. This is one place you want to use something beefy.

Guys, you have to have a firm stop and the shoes have to float. When you apply the parking brake when moving the entire shoe assembly rotates . Picture the rotating drum, the shoes go out and when contact is made the spinning drum tries to rotate the entire shoe assembly. That's why the bottom is not anchored. It's called self energizing and uses the rotation of the drum to help with the braking action. It's supposed to rotate against the stop and why the flimsy sheetmetal backing plate can not be used to stop the rotating force. That method is an accident waiting to happen. You ever wonder why car brake shoes have more material on one side than the other? It's the self energizing effect that shoves the shoe harder against the drum and the driven shoe gets more material to compensate.

If you anchored top and bottom it wouldn't work worth a crap.

I almost had it

The "stop" prevents the shoes from being ripped off the entire assembly.

That problem seems solved.

Lots of good information this is a fun thread and totally different what Wes has started
I hope you don't mine about your thread being hijacked.
I was going to use the one from the BMW and use a bell crank to operate it until
Richard Casto brought up about using the 924/944 spreader and hooking up direct.
So today I explored this a I think its going to work as there will be no bell crank to make.
Clay brought up an interesting point about the shoe stop. I checked to see if the shoes could be twisted back and forth and they could plus you can see a shiny area where the shoes would make contact with the stop.
Here is what I found out today as I tried the 924/944 spreader

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Checking cable line up. Going to cut and realign cable mount and make a rod extension to reach the spreader.

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In the relaxed position

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In the pulled position

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Mocking up a shoe stop I'll make them up this weekend. The stop will have to have support blocks welded on to reach the rear of the spreaders.

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This show why the spreaders need rear support as you see the shiny spots

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I have NO problem with how this string has morphed!! (I originally just wanted to brag about finding that VW bus cable)

There has been a lot of good information covered and ideas explored. I like the idea of it being in one area!

I like what Craig is doing, however I think using a hard connection between the spreader and 914 cable would be easier to do than a cable. Think high strength threaded rod (from McMaster Carr) and clevis's.

Am I correct that there is a "left" and a "right" version of the BMW spreader? It would seem that there would have to be in order to have the angle of pull match the side it's mounted on.

Wes

Craig;

Here is an idea for you to think about;

Make up a clevis with a female m6x1.0 thread (I think that's the thread size, I'll check), then use that longer VW bus cable. It screws into the clevis and has a jam nut. By doing that, you would have a continuous cable (with about 18" exposed between the 914 sheathing bracket and the clevis).

The bracket for the 914 cable sheathing would have to be re-located and pointed in the correct direction. Which you will have to do anyway.

You would still have to make a cable end at the firewall area, but that's been covered.

Wes Vann

This comment has me confused!!

As I read it, you are saying that there is a "stop" that limits how far to the side the spreader can move. (in addition to rubbing on the "backing plate")

I can't see the need due to the fact that the shoe will only move outward a certain amount and that would limit the side to side movement.

(as you pull on the cable, it would pull the spreader and shoe assembly off to that side and stop once that shoe is in contact with the drum. Then continuing to pull would spread the other shoe outward)

It may have somthing to do with the fact that there will always be a certain amount of tension on the cable??

Maybe I'm just reading your comment wrong!!!

If you could add an arrow to the photo showing the wear pattern on the spreader, it may make it clear.


That brings up another subject!

Are you planning on installing a "return" spring (as shown on that sub-cable)? I haven't seen anybody show consern about it, even in bell-crank versions.

In most versions, everybody is counting on the shoe return spring (the one near the spreader) on pulling the cable back!!!!!

In the original 911, there isn't an additional return spring, but that's a straight pull.

What was there in the original BMW installation?? (wish I had a black E30 to look under!)

Wes

"Are you planning on installing a "return" spring (as shown on that sub-cable)? I haven't seen anybody show consern about it, even in bell-crank versions.

In most versions, everybody is counting on the shoe return spring (the one near the spreader) on pulling the cable back!!!!! "

A spring like this? It pushes the spreader back when tension is released off the cable.

Click to view attachment

Paul

Wes, you are a good sport for allowing the thread hijack. And Craig stop me if I am way off base here.

So, I "think" that what Craig is saying when he says the "rear of the spreaders" is the part that would be next to the backing plate. And that in addition to pushing against the shoes, the spreaders also need to push against something along the other axis to prevent from putting an un-needed side load on the shoes.

The image below is without a plate for the spreader to push against. The green arrow is the force from the cable. The red arrows is the force from the spreader on the shoes. So you see in addition to the force that pushes the shoes against the drum, you also have an un-needed side force.

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In the image below, the blue is a plate for the spreader to push against. The green arrow is the force from the cable. The red arrows is the force from the spreader on the shoes. The purple arrows is the force from the spreader on the blue plate. So here the only force on the shoes is the ones pushing them against the drum.

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Also in the above photos you can see how the two pivot points on the spreader are offset away from what would be the backing plate. So if I understand Craig correctly, I think he is saying that in addition to just bending a flat section of metal 90 degree to create the “stopping block” that he may also need to weld in something extra (what I show in blue above) onto that to take into account that offset.

In the image below, you can see the bent "stopping block" but with two extra sections welded on to account for the offset and meet up with the spreader.

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Looking at this image again and since I don't have the parts in hand, only Craig can answer this, but he may be sneaking his 90 degree bend section under the shoe a bit so that the two extra bits I just mentioned above may not be needed. That means the spreader might be able to rest directly on the part he has roughed out above.

Continuing to think out loud here. I promise this is my last post for awhile.

Here is the backing plate for a 924 (image from PET)...

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The yellow is what we are calling the "stopping block". On the 911, this is not part of the backing plate, but rather part of the arm. You can see how thick this casting is on the 924 vs the thin 911 stamping. The blue section that rises up higher than the surrounding area, is what I think the spreader pushes against. I think it rises up to account for the offset seen in the photos above. This might be what Craig is calling "support blocks" in his post above.

Craig and others, what do you think??

Richard;

I think your "drawn" diagram is what Craig is talking about when he says he has to weld on something additional. (that's the only thing that makes sense)

As you said, if the L shaped bracket is within the shoes, then it can be positioned such that added blocks wouldn't be required.

Wes

Heres a pic of an early steel 911 arm. The late aluminum arm is slightly thicker (didn't get a good photo on that one.) FWIW, the bracket is 39-40mm wide on both of them. I got to thinking - the tab is probably thick to account for shoe & rotor wear. The worst case limits are a new shoe on a new rotor (smallest ID) and worn shoes on worn rotors (largest ID). You don't want the lip of the shoe to slip over the block. That would wedge it in and lock the wheel in a big way.

I think there needs to be some sort of return spring. The little lever has a very high ratio. Cable drag could easily cause it to not fully release.

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Richard figured it out what I was trying to explain about the rear supports. In his diagram the spreaders need back support where he has the blue lines.
As far as the spring goes I was planning on having a coil spring over the cable that goes from the cable housing to the top of the cable like the one I have pictured. All the cars I looked at they had a return spring around the cable.

I would love to do this to my car. Does anyone know of a shop or someone that can weld up the required brackets on my trailing arms in Southern Cal? I do not own a welder and haven't welded anything since high school 30 years ago.

Thanks!!

Steve,

You are still going to need a set of rear p-Brakes. I paid $150. With the cables from Easy. Someone had a set with cables on the Pelican board for $175. Past that you can clean them up and paint them and them figure how to put them on. That is where I am. There are a few different ways to do it as shown by our members.

Bob

It looks to me that the aluminum arm style straight pull 911 spreader arm could be modified to be like the 944 spreader arm in a pinch and also if the leverage ratio needed to be changed, it could be done along with a different pull rod fastener if needed. ie a different size hole or etc.

Thats a great find on the angle spreader.

Thanks Bob!! I pm'd the guy on Pelican but I haven't heard back from him. I will call some wrecking yards tomorrow and see what I can find.

I bought some 911 rear brakes and aluminum arms on samba and ebay. You probably need to know which years you want though. The two sets I have I think are 74 911 and 84+ maybe 944?, thats what I marked on them when they were sold to me. The 74 are straight pull and the 84 are angle pull. The straight pull come out the cavity for the stub axle and the angle pull comes out a angled port in the aluminum arm. The later arms are for a wider wheel. It seems from what everybody has contributed that the deal is to use the 911 backing plate with the notched brake shoes and the 944 spreader or the straight spreader and a neat two piece bellcrank like the one already designed. It won't be long and this could be a kit for the guys that don't fab.

On looking back at wes's thread on the cable/backing plate install, which is GREAT I wonder if you could just use the inner 1/2 of the original 911 rivet style spreader and make it pull only with a simple bellcrank and a rod to the bellcrank and a rod to the stock 914 cable? That way the replacement parts would mostly be early all 911. It sorta looks like the backing plate could be rotated 180 and put the cable and spreader on top maybe not.

I found this on the net. The spreader might be called a expanding lock, they also have a support and shoes but I will probably just have mine relined. http://www.bavauto.com/se1.asp?dept_id=168 The angled spreader is called a expanding lock, it's part # 34411163709 it's down the parts list aways.

I just called Larry at 20th st in AZ. and told him I wanted early 911 backing plates off of the steel arms and 84 944 expanding lock's and adjusters and even shoes if he has them and he said he didn't have any 924 rear brake parts at the moment but he will call me when he gets them. A guestimate was very reasonable. http://www.20thstreetauto.com/porsche/porscheparts.htm#924
He seemed to have a knowledge of the application we are working on. Seems like a good place to get the small stuff so I won't need to rob the complete arms I have.

Added 01/06/09
Ok the guys at 20th st called back. Larry and Mathew. I got early 911 (68?) backing plates off of steel arms, 84/944 shoes, and all attaching hardware with the angled expanders for 140.00 + shipping. That is a little expensive for some but porsches are a little hard to come by in Crawford. At least the part chasing is done for this deal. If you mention my name they know what you are doing. Charlie Wittmer

01/07/09 found another good place to get the parts, it's planetporsche the guys name is Bill Martin They have lots of porsche stuff I originally found them on ebay He had some new shoes and a good 944 cable that I may use with a 944 brake handle. I kinda want the emer.handle in the center.

It looks like with a little imagination a bolt on support could be fabbed up and the support could be a drill and tap the arm and mount the support deal for the ones that don't fab.

I bought these parts from Parts Heaven. They do not look right but there is no part number on the brake shoes. Are these the correct brake shoes? As you can see in the picture the holes do not line up and they are hitting the brake shield bolt hole.

Here's the one with the bolt holes.

You happen to get a later year e-bake assembly that had the trailing arms with a wider bolt spread. All you have to do is file or grind the bolt hole to match your trailing arms. I got the same one as you have and had to do this. As far as the brake shield tab goes you have to cut them off.

Hi guys , I too have been wanting a 911 ebrake setup similar to what is going on here .I have been studing all the threads on the forum and figured that there was a "different " way to do e-brakes , Craig is on the same path that I come up with including the little box that the spreader works in and rchard is right about the raised portion of the backing part of the box. This setup will work on the angled pull similar to tha 924 , taking the 90 bend out of the eqation and moving the cables closer to the arm for protection, I haven't posted any of my workings yet as they are in my parts colection , but have spent a few hours studing the parts and their operations , personnaly this IS the most effective setup I've seen yet and should prove to be an asset to guys wanting a reliable e-brake setup . I got most all of the parts mention here off of the e-place , was just patient and got most for very cheap , 928 rear hubs spindles e-brake,shoes spreaders , partial cables $50 something delivered!! Isee welding an shoe stop to the arm similar to the E-30 part with a tube perhaps that would give the angle of the 924 , either with cable if possible or a rod of sorts , but like Craig has mentioned it has to have the springs on it for return of the spreader . I like this thread !!!!!!!

Jaxdream

Actually, if you have good cables the two springs in the backing plate assembly and the one in the cab are plenty to easily retract the shoes and cables. However it would not be difficult to install a coil spring over the cable like most American cars
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I think I still have a complete 86 944 rear suspension if you guys want/need any pics of the original configuration. Not sure if at this point ti would help or not

The later angle pull spreaders are to me the best solution. You can grind the little notches in the early shoes if thats what you have. You might need to remove the center pull or push studs off of the early shoes though.

Thanks Craig for the reasurance. I just wanted to make sure before I start grinding away at the thing.

-Steve

Click to view attachmentI finally put mine together and tested it out at Willow Springs short track. I am running Boxster rear brakes and 944 turbo front brakes. I ended up copying pretty much everyone. Thanks again to Wes for welding up the stop plates on my trailing arm. For the least amount of hassle I ended up using 914 clutch cables, cut to length and stock 914 emergency brake outer sheathing.

Click to view attachmentHere's a picture of the fabbed up cable. You can see in the picture that i used the stock 914 outer sheathing and a piece of the 914 clutch cable outer sheathing. I used a 2" piece of 5/8th OD copper pipe to tie them together. I notched the copper pipe to support the stock C clip on the 914 E. brake cable. I pretty much copied Clay, but used a piece of the clutch cable sheath versus bending a piece of conduit. Pro's and con's on all the techniques, but mine was the least amount of hassle for me and my lack of welding and fabrication skills!!

Here's another picture of the copper pipe before I covered it with shrink wrap.
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