One of the more difficult things to put together on a kit is the parking brake requirement. First, what is needed? A general overview of requirements is that the parking brake has to be a separate system, usually mechanical, and it has to hold the car on a grade without slipping. Line locks don't qualify as they are hydraulic based - not a separate system.
Their use in an emergency, not so much - with dual hydraulic systems, you always have 50% available. It's why dual hydraulic is mandatory, and why the parking brake doesn't have to do that job. If you have used a parking brake to stop a car, you already know they are a joke in an emergency.
And, it's not about the lever and linkage - plenty of new cars use a push button to activate an electrically powered mechanism. Some are interactive with the transmission control.
If you are using dual piston calipers in the rear, then a separate parking brake is an issue, especially if the donor parts selected don't incorporate shoes that press inside a drum on the rotor.
What other brake options are there?
An additional mechanically activated caliper can be mounted on the rotors - and that's not limited to the rear. Some factory installations are front mounted.
A pinion or transmission mounted assembly can be used. Some don't work as well, but those are common on intermediate vehicles use commercially, and off roaders who have swapped to dual piston calipers in the rear. Kits are available.
In the realm of DIY, a parking pawl setup similar to an automatic could be done, too. It's basically a disc with gear teeth and an in-out tooth to block rotation. Another would be using a rear caliper with mechanical operation, and having the hydraulic side activated by a clutch master cylinder. The hydraulic side assists the mechanical and gets the caliper loaded for the racheting mechanism to hold.
With the large u-joint flange on the 8.8 IRS as an advantage, plus the proximity of large bolts to hold a bracket, I'm leaning toward a econocar rear caliper, pinion mounted, with hydraulic assist. It's mostly donor based, which makes it less expensive.
We all know what is out there - and the options aren't extensive. Looking forward to your thoughts on what we could do outside the box.
Sure wouldn't want to use anything that involves a parking pawl into a gear at any speed and expect it to slow or stop the vehicle . . . picture slammin' your car into Park at anything over a few inches per hour and the tranny is toast. And it's usless as a hill-holder in traffic . . .
Best option for our cars is the mechanical application of the rear pistons (or shoes if drum equipped), with a lever that provides a reasonable amount of mechanical advantage to the user, placed in an appropriate location so you don't have to un-harness yourself to make it work.
I, personally, am relocating my E-Brake to the left of the drivers seat with the "Fiero Brake Mod" this winter.
Just my 2¢
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We decided that the best option for cost and ease of implementation was the Wilwood spot caliper.
Good luck with that spot caliper. I tried to use it for 2 years and never could get it set where it wold not either drag or be so loose that it would rattle. I finally ended up chucking the idea and now I have the internal drum parking brake, which are working well.
Best place for a wilwood spot caliper is in the nearest lake.
Let's not forget the basics of the discussion - the parking brake does NOT have to stop the car. It only has to HOLD it on a grade.
Again, dual circuit hydraulic brakes are mandatory - and have been since 1968. You are required by law to have them. Our normal brakes already have emergency capability designed into them. The law recognizes that it's highly unlikely both circuits would fail simultaneously.
Since very few of us actually use the emergency brake as a hill holder in traffic, it really makes little difference if it's a disc brake or a parking pawl. And for those of use who drive automatics, it's usually the parking pawl doing all the work when parked - not the e-brake. That's because so many of us have driven off and cooked the e-brakes. They ARE useless as emergency brakes.
Millions of us use parking pawls dozens of times a day, no problemo. If anything, I haven't used, or even adjusted, the e-brake on an automatic car in years. By the way, most of us don't jam it in park while we're moving. We understand why not to do that.
Consider the trade offs - not having to buy two calipers, two cables, and use two discs, a pinion mount just uses one. It can cost half as much. And for all that, eliminating a caliper completely by using a pawl to grab a slot works even better. No lining to wear out, and it will hold on a grade beyond the tires capability to hang on. Ask a tow truck operator how often they have to disconnect the linkage on an automatic when no keys are available.
Frankly, I'm getting convinced a parking pawl set up would be superior to all the monkey motion of add on spot calipers. If you need a hill holder, there's something else for that, a line lock. In traffic, use the normal brakes. This is a discussion on the parking brake, and once we get over the mistaken notion that it's meant for emergency use, then we will be thinking out of the box.
Interestingly since I've moved to the US it looks to me as though you aren't really taught to use it at all whereas in the UK, you use it even when you are stopped at traffic lights, manual or automatic.
Additionally it's never really been described to me in the past as an emergency/e brake but simply as a hand/parking brake.
I like the idea of a pinion brake since it reduces unsprung weight on the rear and in theory reduces complexity however, I'm not really sure what the draw backs are yet.
Personally in my if-I-build-it plan, I wanted to use the pinion brake (although now I learn it won't fit ) with an electric motor attached to the hand brake cable and the motor is connected to an ISIS inMotion controller along with a momentary two way switch such as the one I had in my Jaguar XJR:
In America, we went with bench seats and the underdash parking brake, so it became more complicated in use. Ratcheting a hand brake up and down wasn't accepted until the '60s, when ironically, the British sports car introduced us to it. A few sport and economy cars followed with it, but it's not had a big impact. Most of us just sit at the light with our foot on the brake waiting - further effort is considered more than it's worth.
The p-brake you describe seems to be within the allowed methods. We have DOT, plus state regulations, which can affect the kit car but generally must conform to Federal guidelines. Basically, it cannot depend on the hydraulics of the main system - so, line locks aren't legal parking brakes. It has to operated my the drivers muscular effort, and the system hold on whatever normal grade my exist for typical traffic without rain and snow.
Worst case scenario, some of the hills in San Francisco, or small town in the Ozarks.
The disc on the pinion brakes isn't all that large, 7 or 8", of which only 4" would stick above the u-joint flange. The caliper itself could be mounted in any part of the rotation, likely from 90 degrees one one side up and over to 90 on the other. Remains to be seen how close that would be to the cross tubes at the rear of the chassis.
It is very much not an e-brake. With the required dual hydraulic setup, whether front/back, or the cross connected Euro style, there's always one functioning system with about 50% capacity. Far more than the puny cable brakes attached to rear shoes we usually assume to do that job.
Having had far too many customers drive around all day and burning them up, not so much.
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