Disk ebrake

[H20rider]

All the commonly found rear disk brake conversions seem to rely on the GM style of cable actuated parking brake. That is, the hand brake cables connect to the rear calipers, and through levers and springs, when the parking/ebrake is employed, the caliper piston extends and grips the rotor.
I have this on my ‘68, but it does not function well. By that, I mean that even when fully applied, they will not hold the vehicle from some rolling. So, on even mild hills, I must rely on using the ebrake AND leaving the truck in gear. This is unsatisfactory.

Apparently, this style of ebrake is finicky and, although supposedly self adjusting, can be weak. There are videos online demonstrating various ways to calibrate these calipers, but even carefully applying the recommended techniques does not improve the ebrake performance. Note that the rotors, pads, and hydraulic system is all solid, bled, proportioned, etc. also, the ebrake cables are properly adjusted and unimpeded.

There may be some other trick that I have not found, but at this point I want to replace the calipers in hopes that a better /different set will function properly. I do not just want to swap to osome ther questionable kit-quality rear caliper and likely encounter the same issues.

So…. Are the suggestions for high quality rear gm style calipers?
Or a different, but effective ebrake set-up?

 

[ntsqd]

Although there is one kit out there with hydro-mechanical calipers (like the GM calipers) that apparently does work well as a parking brake, historically it has proven difficult to create enough clamping force on the brake pads without resulting a long p-brake pedal or lever travel distance. More leverage requires a longer push or pull.

The other problem with the GM calipers is that they use too large of a caliper piston. You can get away with this if all you do is low speed stuff, but highway speeds require a p-valve that dials them way, way down. Why put it there if you're not going to be able to use it?

Research the Explorer RDB conversion here and otherwise. The caliper piston size is a much better match to an EB driven on the highways. The p-brake is a drum, which are far better suited to that type of braking function than a disc. I have a couple years on the next bigger version of the Explorer RDB's, the Expedition RDB's on my FSB (Explorer kit couldn't be made to fit the D60). Even marginally adjusted they work well enough in most cases.

 

[SteveL]

For the gm calipers you can try redrilling the hole in the pivot bar out wider for more range. Check out a few of the u-tube videos on getting the calipers adjusted correctly. There is also an electric kit with a hydraulic piston to activate the e-brake instead of the pedal..

 

[Shimmy]

@H20rider have you looked thru this thread yet? ... starts to show pics at page 6. Maybe this is an option for you.

https://classicbroncos.com/forums/t...ney-using-the-bb-76-77-9-inch-rearend.328758/

 

[Johnnyb]

I second this. My WH (GM style) e brake sucks. I have it hooked up to the stock pedal, was wondering if a lever would allow better application (more cable travel)?

-JB

 

[ntsqd]

For the gm calipers you can try redrilling the hole in the pivot bar out wider for more range. Check out a few of the u-tube videos on getting the calipers adjusted correctly. There is also an electric kit with a hydraulic piston to activate the e-brake instead of the pedal..

There is also a write-up here on setting up the GM calipers to work their best.

The author now has Explorer RDB's on his Bronco.

 

[H20rider]

I second this. My WH (GM style) e brake sucks. I have it hooked up to the stock pedal, was wondering if a lever would allow better application (more cable travel)?

-JB

I have a floor lever that I installed. Improved the situation marginally. The problem is that the pistons just don’t behave the same way with cable initiation as with the hydraulics. BTW, I used a floor ebrake from a Viper.

 

[ksagis]

There was a thread a while back where somebody modified the mechanical advantage at the undercab pivot that seemed to produce an improvement

I have it saved someplace, let mw know if you can’t find it

 

[ntsqd]

Changing the leverage ratio means that you're going to need a pedal or lever with more travel. Even if/when you get the leverage worked out you're still at the mercy of corrosion screwing up the internal adjuster mechanism. There will always be at least a hint of moisture in the brake fluid. At last known to me there are no replacement parts for those adjuster mechanisms. The high volume rebuilders don't have any parts to fix these either, so sending in your calipers just means that you're getting someone else's problem parts.
Factor in that the brake bias is all wrong and the only reasons that I can see to keep these calipers is economics and/or stubborness.

 

[H20rider]

Wilwood makes a separate ebrake caliper but they do not have a bracket on which to mount it. My rear discs do not have a backing plate…..and I suspect that is the case for most of the GM RDB conversions. Nor is there an apparent way to adequately mount the ebrake claipers without a strong backing plate. Dorm am makes “universal” backing plates, but they are flimsy sheet metal that do not seem strong enough to properly support the ebrake caliper when in use.
Ideas?

 

[H20rider]

Okay, I think I figured out an appropriate bracket.

Question: On GM rear conversion calipers with the integrated parking brake, if tha parking brake is not used, will the hydraulic piston self adjust?
There are comments suggesting that if the parking brake on the caliper is not routinely engaged, that “it” will not self adjust. Is the “it” the hydraulic stopping brake or just the parking brake?
Given that I am employing a separate parking brake, I do not want my rear brakes to slowly become weaker and weaker. If necessary, I will use regular (non GM) disk calipers.

 

[fordguy]

What size tires and wheels?

 

[ntsqd]

Okay, I think I figured out an appropriate bracket.

Question: On GM rear conversion calipers with the integrated parking brake, if tha parking brake is not used, will the hydraulic piston self adjust?
There are comments suggesting that if the parking brake on the caliper is not routinely engaged, that “it” will not self adjust. Is the “it” the hydraulic stopping brake or just the parking brake?
Given that I am employing a separate parking brake, I do not want my rear brakes to slowly become weaker and weaker. If necessary, I will use regular (non GM) disk calipers.

I do not know for sure, but I am under the impression that they won't adjust without 'exercising' the p-brake function. Fortunately either std. D52 (2-15/16" piston) or D154 (2.5" piston) calipers made for the same rotor width should be a simple bolt-on.

 

[lars]

Assuming you are willing to spend the money, why would you not use the Explorer rear disc setup? It's been proven for decades, it works, it separates the hydraulic caliper from the mechanical e-brake (caliper handles dynamic braking, drum e-brake inside the rotor hat etc) and is widely accepted as a decent, if not perfect solution. The Explorer caliper pistons tend to be a good match for an EB. There are countless threads on this forum about it. I abandoned the GM/Cadillac setup 20 years ago after fighting to make it work. The Explorer setup just works. It does demand that you relocate the rear shock mounts. The backing plate to axle housing retaining bolts are a PITA to install. But that's not something you need to do annually, let alone daily.

 

[ntsqd]

Categorically a disc brake is far less than ideal when used as a parking brake, no servo-action like a drum brake has. The OEM's have known this for a couple of decades at the least. That is why the vast majority of rear disc brakes employ a drum type of parking brake. Volvo knew it way back into the 70's. The wilwood mechanical calipers, at least those that they made when I worked in their Engineering Dept. 20-odd years ago, weren't built to be parking brakes, they were built for use on small vehicles as their service brake. Think SAE Mini-Baja, JD Gators, golf carts, stuff like that.

ETA: The OP's first sentence is erroneous. It may have been correct 20 years ago, but it is not now. Now the two most common rear disc conversions with a parking brake are the Explorer kits and wilwood's similar kit (uses a Corvette drum p-brake design IIRC). With the exception of the calipers used in our friend from the North's RDB conversion and the "Caddy" calipers it is rare to see a hydro-mechanical caliper used for a parking brake.
If you really want/need more parking brake than the Explorer kits provide then look at the early 2000's Expedition RDB's. The p-brake drum is a larger OD, BUT the rotor is also a large OD (meaning likely doesn't fit inside a 15" wheel) and the caliper piston is slightly larger too. Those aren't necessarily a good thing.

 

[H20rider]

I do not know for sure, but I am under the impression that they won't adjust without 'exercising' the p-brake function. Fortunately either std. D52 (2-15/16" piston) or D154 (2.5" piston) calipers made for the same rotor width should be a simple bolt-on.

Thanks!