Why doesn't my right ebrake work?, It's the asymmetric cables, dummy. |
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Why doesn't my right ebrake work?, It's the asymmetric cables, dummy. |
davesprinkle |
Dec 3 2009, 10:14 AM
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#1
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Senior Member Group: Members Posts: 720 Joined: 13-October 04 From: Berkeley, CA Member No.: 2,943 Region Association: None |
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 |
Dec 3 2009, 10:47 PM
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#2
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Excellence Magazine Project 914 3.6 Group: Retired Members Posts: 1,278 Joined: 20-May 06 From: Central California Member No.: 6,031 Region Association: None |
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)
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davesprinkle |
Dec 3 2009, 11:35 PM
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#3
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Senior Member Group: Members Posts: 720 Joined: 13-October 04 From: Berkeley, CA Member No.: 2,943 Region Association: None |
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. QUOTE 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. QUOTE 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 |
Dec 3 2009, 11:51 PM
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#4
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Excellence Magazine Project 914 3.6 Group: Retired Members Posts: 1,278 Joined: 20-May 06 From: Central California Member No.: 6,031 Region Association: None |
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. QUOTE 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. QUOTE 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.... |
914Mike |
Dec 4 2009, 12:11 AM
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#5
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Member Group: Members Posts: 330 Joined: 27-January 03 From: San Jose, CA Member No.: 198 |
My cars both grab the driver's side rotor first, and let the passenger side slip. I just figure it's designed in difference. That's how I rotate the engine while the car is in the air, just put it in fifth and rotate the passenger side rear wheel, there's even timing marks on the bottom of the flywheel for this.
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davesprinkle |
Dec 4 2009, 09:07 AM
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#6
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Senior Member Group: Members Posts: 720 Joined: 13-October 04 From: Berkeley, CA Member No.: 2,943 Region Association: None |
My cars both grab the driver's side rotor first, and let the passenger side slip. I just figure it's designed in difference. That's how I rotate the engine while the car is in the air, just put it in fifth and rotate the passenger side rear wheel, there's even timing marks on the bottom of the flywheel for this. Mike, this is exactly the problem that I fixed when I lubricated the cable. Both brakes should grab equally. |
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