Why doesn't my right ebrake work?, It's the asymmetric cables, dummy. Options

[davesprinkle]

Here's why most modern cars have the ebrake handle in the middle of the car -- it's so the cables running to the wheels have identical length and path. How do I know? Here's the anecdote:
For the last year, I've been struggling with my ebrake system. The right caliper just wouldn't clamp as tightly as the left. I've got rebuilt calipers, new pads, new cables, proper clearance, but no worky.

Finally found out why. It's the internal drag of the actuation cables. The passenger-side cable is substantially longer than the driver side. Also, the right-side cable has 3 right-angle bends vs the left-side cable with none. This results in so much internal friction that the cable just binds solid when it's pulled.

I was able to improve the situation somewhat by lubricating the cable. Still not perfect, but much better.

[PRS914-6]

The length of the cable should not effect it. The cable has a T yoke that will equalize the pull. Of course if you have cables that need lubing they should probably be replaced after 30 years of grit and grime. I have stock cables and handle with 911 rears and they work perfectly (new cables and everything clean)

[davesprinkle]

The length of the cable should not effect it.

A longer cable will have more of the inner cable in contact with the outer cable, so the length WILL affect the friction.

The cable has a T yoke that will equalize the pull.

Yes, the mechanism has a force balance. But it cannot compensate for friction mismatch.

Of course if you have cables that need lubing they should probably be replaced after 30 years of grit and grime.

As I mentioned, my cables are new.

[PRS914-6]

The length of the cable should not effect it.

A longer cable will have more of the inner cable in contact with the outer cable, so the length WILL affect the friction.

The cable has a T yoke that will equalize the pull.

Yes, the mechanism has a force balance. But it cannot compensate for friction mismatch.

Of course if you have cables that need lubing they should probably be replaced after 30 years of grit and grime.

As I mentioned, my cables are new.

Sorry, the friction difference between two new cables, installed properly would be very minimal. The problem is elsewhere. While you might feel a slight difference by hand, the amount of leverage applied with the handle is a lot. Crawl underneath a pickup and you will see tons of vehicles with one side WAY longer than the other without issue. Most cables are teflon lined and have minimal friction if routed smoothly. Mine slide easlily with the bends. The problem lies somewhere else.....not cable length

Disconnect them at the caliper and have someone pull the handle. Do the cables come back easily?

Cheap aftermarket cables?
Cables not seated properly on the tube?
Calipers not working properly?
Cables kinked somewhere?
Clamps on the cables too tight?

Keep looking....

[davesprinkle]

Sorry, the friction difference between two new cables, installed properly would be very minimal. The problem is elsewhere.

Well, you're wrong about that. The problem was in the cable. Period. I didn't arrive at this conclusion lightly. I chased this problem for the better part of a year. I went through every piece of the brake system. New cables, new pads, rebuilt calipers, close attention to pad clearance, cable routing, and force balance position. The problem was only resolved after I lubricated the cable.

While you might feel a slight difference by hand, the amount of leverage applied with the handle is a lot.

At least here you're correct -- the handle has a large mechanical advantage and can generate large tension force in the cable. But that's exactly the problem -- tension force in a straight cable turns into a normal force when the cable is bent, loading the inner cable against the housing. Refer back to any high school physics text -- friction force is proportional to normal force.

Crawl underneath a pickup and you will see tons of vehicles with one side WAY longer than the other without issue. Most cables are teflon lined and have minimal friction if routed smoothly. Mine slide easlily with the bends.

The debate is not whether the asymmetric cables have dissimilar friction. They do. The debate here is really whether the force mismatch is large enough to cause actuation problems.

In my system, the friction force caused actuation problems. Lubricating the cable reduced the friction enough for acceptable actuation. It'll never be perfect as long as the cables differ, but it's a substantial improvement.

I'm glad you don't have any actuation problems, but I'll bet your system doesn't work as well as you think it does.

The problem lies somewhere else.....not cable length

Again, you're wrong. To the extent that cable length increases internal friction, then it DOES play a role.

Disconnect them at the caliper and have someone pull the handle. Do the cables come back easily?

Yeah, I've been through this. Disconnecting the cable removes the tension force, thus removing the normal force and reducing friction. Sorry, but this is not a valid test for a loaded system.

Cheap aftermarket cables?

Maybe? Purchased from Pelican. I don't recall if they're OE or not.

Cables not seated properly on the tube?

Cables are seated fine.

Calipers not working properly?

Rebuilt calipers. (Thanks, Eric.)

Cables kinked somewhere?

Factory routing.

Clamps on the cables too tight?

Clamps were removed.

Keep looking....

No need. I already found the problem.