Still another 911 e-brake thread, there are many like it but this one is mine.... Options

[John]

The SC rear calipers (having the same bolt spacing as the rear of a 914) will bolt up.

They do need small spacers to center them on the rotor. The required thickness is:

(2) 1/2" SAE FLAT WASHERS

I like the SAE flats as they are flat on both sides and are smaller in OD than standard washers.

The spacers can be between the caliper and the mount (together with longer mount bolts) or under the rotor hat. I prefer between the caliper and the mount.

The only other modification I made to the calipers was to open up the mounting holes to 9/16". This allowed me to move the caliper radially away from the center of the rotor just a little. I did not turn the rotors down at all. The rotors are stock.

While the calipers cleared the rotors, I felt that I wanted just a little more room in there for thermal expansion (in case the rotors grow radially when hot). I now have almost the same clearance as a 911 has between the rear rotors and calipers.

[Gary]

I would so be interested in a kit. My 911 ebrake cables are at best a kludge.

[John]

Keep me in mind in a couple of months if anyone may be interested in the belcrank kit.

Say late August to mid September.......


If there is interest then, I will make some up, but I have my plate full until then.

[andys]

Through trial and error, I decided not to utilize the small helper spring for the bow-ties.

I am also only using single bow-ties to expand the shoes. I read somewhere that some later 911's were done that way (but I didn't verify that)

I opted not to do the conversion because of my fear of using just the single bow-tie. Not sure if it is strong enough by itself.

Also, that helper spring aids in pulling the cable back, otherwise the shoes could drag. As on my Wilwood spot caliper setup, I found I needed a helper spring for this purpose to ensure the cable pulled back to it's at rest position.

Andys

[John]

andys,

Since the return springs are what retract the brake shoes (as is the case in all drum brakes), I made the decision to eliminate the "helper spring" between the two "bow ties".

Considering the amount of tension that the "helper spring" provides (very little) the decision to eliminate it seems legitimate. As long as the stock cables are in good shape, the tension provided by the return springs (which are quite strong) should be sufficient to retract the shoes and prevent them from dragging.

I made the decision to eliminate one of the bow ties because the design does not require two. Since my cable has a fixed end (unlike the 911 design which uses the second bow tie to anchor the cable end via the spacer tube) only one bow tie is required to spread the shoes. After reviewing the design of the bow ties, I determined that the strength of one bow tie is more than sufficient to spread the shoes and keep them spread as the angle of the opposing arms approach 180 degrees, the forces on the pivot points of the bow tie becomes less.

Only time will tell, but my decisions to modify the 911 design were carefully reviewed. It is not my intention to use the e brake as an e brake as much as I am a parking brake. "Helper springs" can always be added if necessary without much change, but if the cables are kept in good condition, this should not be an issue.

As a parking brake, the modifications that I made are more than sufficient as all the items will only see static forces. In the case where the car is attempted to be moved while the brake is set, the anchor block provides the resistance, as does the bow tie.

I will not go into some of the critical design issues that I see with the addition of the willwood spot calipers.

[jim912928]

I'd be interested in a kit...have carrera brakes to put on, all the hardware for the rear ebrake stuff off an 84 carrera...and the backing plate from a 71...I just need your setup!

[PRS914-6]

John, I am in the process of doing a similar installation except I have 69 911 parts and they go on without any slotting. On the 69, the shoe's are held from rotating by a welded block on the arm that goes up between the shoes. This prevents the shoes from rotating force when they are energized when moving. I did not see a a retainer on your set up and your pictures look identical to mine except the wider bolt circle. I ended up welding a similar piece of metal on the 914 rear arm that will prevent the rotation. How are your shoes restrained?, your pictures do not show a block. The hole on the welded piece on my arm is where the cable goes through

Where the block goes:
(IMG:http://www.sayegh.org/Paul/914/914pics/ebrake1.jpg)
The block off the 911:
(IMG:http://www.sayegh.org/Paul/914/914pics/ebrake2.jpg)
What I welded on my arm:
(IMG:http://www.sayegh.org/Paul/914/914pics/ebrake3.jpg)

[John]

Yes you need the anchor as I call it to be welded to the trailing arm. This is what resists the twisting forces caused by trying to roll the car with the e-brakes applied.

You have an excellent pic there. I didn't snap a pic of mine when I did it.

[PRS914-6]

I finished one side of this conversion. John really had a good idea on this system. The tough part is the goofy angles and the difference in height between the cable and the pull rod. The pull rod coming out of the shoe is difficult to keep straight as there is just not enough room. Because of this, I did not use a clevis, I instead used a 6mm stainless bolt and a piece of angle iron for the bellcrank to drop down in the low spot. It's very close to being straight. In addition, instead of welding a nut on the arm, I welded a 10mm bolt, using it as a stud but it amounts to the same. There was just the right amount of room to get the spring installed between the anchor block and the actuater arm to assist in retraction. Here is a picture, I hope it makes sense. John, good idea on this! I had been scratching my head trying to decide a method without making custom cables which I think would be nearly impossible to keep straight considering the angles.

(IMG:http://www.sayegh.org/Paul/914/914pics/IMG_0232.JPG)

[John]

One thing that may need to be addressed before you get too far down the path, is cable length. The passenger side is less of a concern as the cable is longer and it's unsupported distance is greater (allows more flexability).

The issue may come up where when you lower the car, the drivers side cable becomes tight and will actuate that side e-brake.

When I was determining exactly what the location of the cable anchor was on the drivers side, I discovered this potential issue. As the control arm is raised up into the vehicle (as it does when you sit the car down on the suspension), the distance between the cable tube on the body and the cable anchor on the trailing arm increases.

My solution was to leave enough slack in the cable that this would not be an issue under full compression of the control arm. When in the raised position, the e brake cable can touch the header on the drivers side, but when down on the ground, there is not enough slack for that to happen.

[PRS914-6]

John, couldn't you screw the outside cable adjuster out which will make the outer cable longer or install a short spacer between the outer cable retention blocks and the cable? Then fabricate a little extension piece for the inner cable if needed? Sounds like you only need a little bit, maybe 3/4"??

[John]

My setup is fine.

I was just warning others of a potential pitfall if not thinking out the whole problem from the beginning.

After I figured out that the effective cable length changed during suspension travel, I redesigned my belcranks to locate the cable anchors closer to the pivot of the trailing arm by approximately 1"

Yes, if you ran into a difficulty, a "cable extender" could be made, but I wanted to keep mine very simple and straight forward using stock 914 cables and as few parts as possible.

[Gary]

Hey John,

Still officially interested in a kit (IMG:style_emoticons/default/biggrin.gif) .

[John]

I'm still in a busy time of my life right now and will be for the next 3 weeks or so:

Closing on a house
Picking up a 914 Tub
Rearranging the garage for the other tub
getting these blank tripple gauge kits finished once and for all. (I shipped out the first two kits so far)

The list goes on.

The e-brakes are working flawlessly and I will be looking into a few "kits" of my belcranks and associated hardware in the weeks to come.

[dion9146]

Count me in too John. Not in a big hurry, but I wanted to indicate my interest as well. Having parked my 914 on a slopped driveway last night, it made me nervous leaving it in gear (and of course not a brick or block of wood in sight). Thankfully, my nice new 'really good compression' engine held its ground for a couple of hours. (IMG:style_emoticons/default/smile.gif)

Thanks,

Dion

[Jeroen]

keep us posted please!

[Aaron Cox]

looks like a killer setup.... (IMG:style_emoticons/default/smile.gif)

free interest bump (IMG:style_emoticons/default/tongue.gif)

[jim912928]

I'm still in for a pair when you have them!

[bd1308]

Let me ask a stupid Q

Are these able to be put onto standard /4 hubs?

[John]

Let me ask a stupid Q

Are these able to be put onto standard /4 hubs?

Britt, these are for use with vented 911 rear rotors with integral drum e-brakes.

4-lug rear discs do not have the drum inside.

You could potentially use redrilled 914/4 hubs with the 911 rear discs if that is what you are asking....

The whole reason for something like this is when you switch away from the stock 914 rear calipers that have e-brakes built-in.

I went with stock 911SC rear brake calipers/rotors/e-brakes.