Opinions on line-lock as a park brake/308?

It would be a possibility, as David Clarke, previous owner of 365 P2/3 S/N: 0826, needed to fit a parking brake system in order to pass UK's MOT test. He used a brake lever from an English sedan and looped the cable around back to the brake pedal (making sure it would not hang-up, or interfere with brake pedal action while driving). It worked for him and I suppose, this system would be semi-legit, as it was mechanical/cable operated. Reference article: Cavallino #52, Aug./Sept. 1989.

As you suspect, not too sure if constant pressure from a line-lock would affect the brake seals. Maybe not, as I'm sure the parking brake levers on the old 308 calipers acted directly on the pistons anyways. How would you make sure the line-lock isn't accidentally released (a parking brake has a ratchet-locking mechanism)?

 

One of the things i worry about with a line lock is very slight leakage/seepage over time, that is how well does the seal in the valve hold the pressure for say a day or week or month. Can the master cylinder leak just a tiny bit over time, or anything else. Having the brake come off enough to allow the car to roll......not good.

I don't know about long term pressure causing deformation in master cylinder seals or caliper seals.

Given the relatively light amount of pressure used to "set the brake" and the lack of temperature at the caliper end would probably not cause any undue stress on these parts, but i just have no clue as to the long term use of the lock.

We need long term users to testify.

chris

 

I've seen line-locks used on many (drag race) cars as a parking / on-the-trailer brake and it seems to work fine. One friend of mine used it and passed the Connecticut DMV inspection on a street car.

I think there may be some confusion on what the line lock does, as it does NOT keep the master cylinder activated. You step on the brake pedal, then activate the line-lock and then release the brake pedal. The line-lock solenoid valve keeps pressure on the line downstream (to the caliper) only. So you can use it on one wheel or one axle, depending on your preference. And you could certainly use the existing parking brake handle to activate the electric switch for the line-lock, which would preserve the stock appearance from the interior of the car.

As to Chris's concern about long term leakage... my thought is that if any leakage is occuring while the line-lock is being used, then you have a brake system problem anyway - brake lines and components should NOT leak. I suppose you could worry about the line-lock solenoid valve leaking (or loosing its seal), but I would consider this unlikely for such a device, as it uses the "trapped pressure" in the brake line to hold itself closed - like a door on a Amphicar (wow - what a tangential example !).

I do agree with Chris's opinion that no damage will occur to any brake component - you will not try to push the brake pedal thru the floor, just press it enough to prevent any motion of the car while parked.

And FWIW - I'd rather use a block of wood than risk a rube-goldberg "cable to my brake pedal" solution. Too much chance of interfering with real braking function for me !

 

Greg,

Are you going to be driving the car on the street, or is the upgrade primarily for track use? If you are only driving the car on the track/off road, and you only want the line-lock for parking the car, it sounds okay. But if you are driving the car on the street, especially if you're using it regularly, IMHO you really need the separate parking brake. After all, it's not really a parking brake. It is really called an "emergency brake." The idea is, if your hydraulic system fails, you can still stop the car by means other than running it into something. Maybe it's just me, but I'd never drive a car on the street without a functioning emergency brake, even in a car with split dual system.

Steve

 

IMHO your line-lock solution is a feasible answer to a difficult issue. I understand the concerns regarding the lack of an actual mechanically actuated emergency brake system but ask yourself this: Do you know of anyone 1st hand who has had a total brake failure where the emergency brake saved their butt? A possible scenario but, IMHO, statistically remote.
Of course my opinion could be completely wrong!

 

Lincoln LS' use a hydraulic park brake as well, not sure yet if it locks all 4 wheels but with traction control and abs it wouldnt be any harder to control all 4 rather than the rears only. I would do the line lock thing but doesnt it require power to keep the valve activated?

 

My stock 308 parking brake won't hold anything!
If I had a hydraulic brake failure, wind resistance from opening the door would be better than my parking brake for slowing down.
Maybe mine is worse than normal?
A place I worked for had line-locks on the fork lifts, and the way this manufacturing company used these fork lifts, the line-lock were set & released hundreds of times a day, never had a problem.

 

The seals in hydraulic brake systems, caliper seals, even master cylinder seals were never realy designed to keep constant pressure on them over time, and depending on the stiffness (spring rate) of the enclosing material (calipers) will loose pressure over time, thus lessening the clamping force of the brake. Cable operated system have a relatively low spring rate and so a little relaxation in the "stretch" of the cable over time, will not markedly reduce the clamping force. Race cars do not have parking brakes and are held stationary in reverse gear.
Martin Jansen

 

The line lock brake makes sense in almost all applications. It will work as an emergency brake for those times when one should be used, ie, stopped on a hill and then moving forward without rolling backwards, or to hold the car once stopped while the engine is running. I never leave a emergency brake on while the car is in storage nor while sitting over night in the garage. And how many of us ever use the brake while parking? Normally, we just leave it in gear. As to stopping using a mechanical brake in an emergency, go out and try it. Chances are something else will stop you first.
And to the question that using the line lock may cause leaks, well, I'd rather find that out while parked, rather then when I apply the brakes going down a hill...

 

OK Greg why the big concern over the hand brake. I don't think I have used one on any of my cars since my 66 e-type. I guess if you have machining capability you could adapt any large brake calipers from any new car or if you look at the xke rears they had a seperate pad set for the handbrake. Enjoy the ride

 

Greg -

Maybe too simple of a solution, but if there is a dashboard indicator light for having the handbrake on, then this electical circuit can be used to control the line-lock's electric solenoid. Light on = line-lock on :>)

 

Another way to do this is in the style of rally racing cars.

They use a conventional handbrake lever attached to a master cylinder plumbed in line with the rear brake calipers. when the lever is pulled, only the rear calipers recieve pressure. Your lever has ratcheting stops, rally levers do not, they are spring loaded to return as the driver lets go. So your secondary MC would have pressure until you release the lever as normal.

This can be done and avoid the wiring and battery drain of a line lock. These complete units are available at rally racing supply houses such as demon tweeks out of the UK.
Have a look.

By the way, the Brembo rear e brake caliper as used on the F360, Lamborghini, and Jag models will run you about $1000 each. Race technologies has them. The jaguar uses a simple stepper motor to pull the cable instead of a lever.
Take a close look at the Stop Tech parking caliper, it is very good, and they can help you.
Also, Wilwood is now selling a drum-in-hat bolt on assemby that you might be able to adapt to the hub. You may need a new rear rotor bell to have drum contact, but its a possibility also.

Have a think on that.

-E

 

Can I just say "I disagree" or do I need to clarify that I disagree with you on EVERY point offered here? I note the irony of saying it works great as an EMERGENCY brake for all of your non emergency applications. I use my parking brake every time I park the car. Much better than putting it in gear and then being sloppy when I get in and lurching my car forwards or backwards into the next car when I hit the starter.
If the world belonged to me I'd say "YOU ARE WRONG!" but it doesn't, so all I can say is I disagree!

 

Rally cars need to lock the rear end alone to slide around corners and rotate the car. They use a vertical handle without any ratchet mech that is spring loaded to return. They just yank it to lock the rear up and let it go as they get back into the throttle.

Your e brake lever will remain as stock in the cockpit. You can modify the crank mech underneath, or use the cable, to push or pull a small MC mounted in a fabricated bracket. Brake lines need to be fabbed up, and the rear lines need to be modified. You run lines from the pbrake MC into the rear lines with a one way check valve. As you actuate the MC via the lever, pressure is applied to the rear calipers. Lever off and pressure is off. Sounds easy but like everything else suggested here, there is alot of R&D time and effort to get it right. A hint is that motorcycle some MCs have sealed reservoirs and can fit in small places.

Keep in mind that if there is a hydraulic failure in a rear caliper or line, the ebrake is also out. DOT specifies a mechanical Ebrake and not line locks or hydraulic systems for that reason.

I have done a similar system for another car, but I havent looked at the specifics of the 308 e brake handle and so on.

Thats about as much as I can tell you without charging you for engineering time. Just kidding.

-Eric

 

fwiw, if your calipers can't hold normal braking pressure (as maintained per the line-lock) while you go in and have dinner, run into a store, eat lunch, etc. then you have a much bigger problem...

I just don't see how the line-lock is a bad idea. Personally, I'd do a mechanical one instead of electric, but that's just my preference.

I use my parking brake everytime I park the car, plain and simple, a good habit to get into. I don't see the problem with the linelock here though, we're not talking about standing with both feet on the pedal and quickly flipping the lock on. Barely touching the brakes is enough to keep the car from rolling on all but the steepest hills.

fwiw#2, I think the old man's 04 Silverado has a hydraulic parking brake as well, it sure as hell feels like it. Keep in mind, 6000lb truck, etc. vs 3000lb car. Just my $.02.

 

I'm curious what makes the parking brake feel like it's hydraulic?

 

It's like mush almost, with no ratcheting noise and pushes right to the floor (with normal parking brake pressure). It might be cable actuated, I haven't read up on it or gotten underneath to check, but it's unlike any I've felt. It's silent all around, don't hear a cable tension, etc. And when you pull the release, the pedal comes up slowly. I can't picture it relying on the ratchet itself to apply pressure, ie hold a cable, based on how softly it releases. Apparently it's strong enough to hold the truck no problem, so kudos to GM however they did it.

 

I'm sure it would be a cable system, as earlier stated, it's a requirement and I suspect the slow action of this one of yours is due to drag of the cable in it's housing, or along it's routing to the rear brakes. Cable may need lubing.

It should get progressively harder as you press further, with a ratcheting noise/feel and should snap quickly back when released.

For my cars, I do both, apply parking brake and put it into 1st gear when parked.