Rear Disc Conversion

[steveg]

If anyone's interested, my rear disc installation is almost ready for the first drive.
Photo essay:
https://www.pbase.com/stevegerow/healeyreardiscs

 

[Lin]

Hi Steve,
I must confess I used the Cape International kit for my rear disc brakes, but you did a great job with your conversion at probably considerably less cost. Where did you source your rotors?
Lin

 

[steveg]

Richard Mayor (Boyracer) made several sets of brackets and modified BMW rotors.

 

[HealeyRick]

Nice work, Steve. Looking forward to hearing the results of the test drive.

 

[RAC68]

Hi Steve,

I agree with the others, your implementation really looks great and I look forward to hearing your drive experiences. I hadn’t considered rear disks as I was unsure of how to proportion fluid pressure. Also, as I understand, the rears should grab inversely of the front brakes in that they are initially applied with greater force and then the more pressure applied the weaker the pads grab, what pads have you chosen for the conversion?

Last, although I know this may be obvious to some, what are the benefits of having rear disks as apposed to the original drums other than reduced unsprung weight and rotational balance?

Again, a really nice job but I would have expected no less from you.

Ray (64BJ8P1)

 

[jcsb]

Hi Steve,

Last, although I know this may be obvious to some, what are the benefits of having rear disks as apposed to the original drums other than reduced unsprung weight and rotational balance?

Again, a really nice job but I would have expected no less from you.

Ray (64BJ8P1)

Disc brakes dissipate heat better and perform better in wet weather. Repeated high speed use with drum brakes lead to fade quicker than disc brakes.

John

 

[dougie]

Disc brakes dissipate heat better and perform better in wet weather. Repeated high speed use with drum brakes lead to fade quicker than disc brakes.

John

Much easier to inspect and change pads between races:welcoming:

 

[steveg]

Hi Steve,

I agree with the others, your implementation really looks great and I look forward to hearing your drive experiences. I hadn’t considered rear disks as I was unsure of how to proportion fluid pressure. Also, as I understand, the rears should grab inversely of the front brakes in that they are initially applied with greater force and then the more pressure applied the weaker the pads grab, what pads have you chosen for the conversion?

Last, although I know this may be obvious to some, what are the benefits of having rear disks as apposed to the original drums other than reduced unsprung weight and rotational balance?

Again, a really nice job but I would have expected no less from you.

Ray (64BJ8P1)

I have a proportioning valve and a Fiat 124 dual remote master cylinder and installing them will be the next phase. Want to do one thing at a time in order to avoid confusion in troubleshooting.

I'm not a racer, but enjoy building projects like this. I regard the car as "performance art." The disc-drum setup was an interim, inexpensive, solution and I wanted to take the Healey to the next level.

 

[stretchit2]

Steve,

Job well done. Terrific photos.

It is great to have a mad scientist as a friend.

Bravo,

Jeff

 

[John Turney]

Looks great, Steve. Special thanks for the photos and dimensions for the parking brake lever. It will help me fix mine.

 

[John Turney]

Hi Steve,

.... I hadn’t considered rear disks as I was unsure of how to proportion fluid pressure. Also, as I understand, the rears should grab inversely of the front brakes in that they are initially applied with greater force and then the more pressure applied the weaker the pads grab, what pads have you chosen for the conversion?
...

Ray,

I'm using a Nissan 1200 master cylinder for mine. It proportions the front/rear by applying pressure to the front first, then the rear. The front pressure is higher through the whole range.

 

[steveg]

First test drive a success. Took an easy drive up and down the street. Can report pedal pressure from all-ceramic pad setup not noticibly different from drums, but with greater stopping power - booster stays in box.

 

[andrea]

Compliments - now we expected, the wet road tests

 

[RAC68]

Steve,

No Booster on a full disk setup? I appreciate that you are doing slow speed testing and will be adding to the installation before going faster but I was under the impression that disks with ceramic pads would require additional force for cold low speed stopping. Could it be that the master cylinder you have chosen produces the additional force needed? I am really impressed with the look and initial results of your preliminary test .... good job.

John, am I correct in understanding that your Nissan MC eliminates the need for a proportioning valve? Also, have you eliminated the need for a booster as Steve's implementation may have? I really like what you guys have accomplished.

How does the emergency brake function on/with the disks?

All the best,
Ray (64BJ8P1)

 

[steveg]

Steve,

No Booster on a full disk setup? I appreciate that you are doing slow speed testing and will be adding to the installation before going faster but I was under the impression that disks with ceramic pads would require additional force for cold low speed stopping. Could it be that the master cylinder you have chosen produces the additional force needed? I am really impressed with the look and initial results of your preliminary test .... good job.

John, am I correct in understanding that your Nissan MC eliminates the need for a proportioning valve? Also, have you eliminated the need for a booster as Steve's implementation may have? I really like what you guys have accomplished.

How does the emergency brake function on/with the disks?

All the best,
Ray (64BJ8P1)

At present, I'm using the stock BN6 .75" master cylinder. Since I haven't tried the other pad materials available, have nothing to compare to - all I can say is, starting with new discs and ceramic pads, the booster is not necessary.

I'm going with the Fiat .75" dual remote becuase the Nissan has an integral reservoir, which won't work with my manifold/air cleaner setup. I'll be installing a second stock reservoir next to the original for a mostly stock look.

Haven't tried the disc e-brake yet as other than a parking brake, but they're not known for doing much besides holding the car on a gentle grade. The stock disc-drum setup is in effect a dual system because the drum e-brake is capable of stopping the car.

Function: this type of e-brake pinches the disc like a pair of pliers, with the lever simultaneously pulling the outer "plier" via the adjuster screw and pushing the inner plier via a cam action. The lever internally contains a ratcheting self-adjusting nut.

The winter's pretty dry here, so may be a while before I drive the car in the wet. Will have the proportioning valve installed in the next week or so.

 

[John Turney]

John, am I correct in understanding that your Nissan MC eliminates the need for a proportioning valve? Also, have you eliminated the need for a booster as Steve's implementation may have? I really like what you guys have accomplished.

How does the emergency brake function on/with the disks?

All the best,
Ray (64BJ8P1)

Thanks, Ray.

My set up is Denis Welch, so I can't take the credit that Steve can.

The Nissan MC seems to be doing just fine. One of the things that also helps is the choice of pads front and rear, based on advice from Denis. I would have to go back through old files to find the type of pads, since they were installed ~10 years ago.

Without doing what Steve has done with the bracket, or some other change, the p or e-brake doesn't work.

 

[steveg]

Thanks, Ray.

My set up is Denis Welch, so I can't take the credit that Steve can.

The Nissan MC seems to be doing just fine. One of the things that also helps is the choice of pads front and rear, based on advice from Denis. I would have to go back through old files to find the type of pads, since they were installed ~10 years ago.

Without doing what Steve has done with the bracket, or some other change, the p or e-brake doesn't work.

The difference in pads is interesting. Harder rear pads requiring more pressure would be a form of proportioning.

 

[healeyblue]

As a comparison, My Porsche 914 has a 19mm (about .75") master cylinder and discs at all 4 corners and has no booster and the braking is superb, as are most Porsches until around 1980 when the finally added a booster system.

 

[AJAX50]

I considered rear discs for my BJ8, but decided to go fo a rebuild of the standard setup with competition linings. The rear drums at enormous and with improved ventilation don't fade. The whole setup word amazingly well, really good feel, great power and no fade, John Chatham did the work. As an additional comment the car has 200 flexible bhp so it needs good brakes.

 

[steveg]

Today, after breaking in the rear pads, I did my panic stop - the car fishtailed fairly dramatically, thus demonstrating the need for the proportioning valve.
The hard braking from 50 - 15 required by the break-in process didn't reveal this.

Will have post-proportioning valve results soon.