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. |
Chicken |
Dec 4 2009, 11:16 AM
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#2
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Newbie Group: Members Posts: 8 Joined: 24-July 08 From: Houston Texas Member No.: 9,350 Region Association: None |
This is not a design flaw/issue it is an expectation of design- flaw.
And is a quite common one … only because I can’t get over this one.... The "E-brake" as you call it is not an "E" brake, it is a PARKING Brake, designed to HOLD the car in a standing position. The design intent with the Equalizer is to distribute equal force to both sides of the car. Left wheel Right wheel ONCE engaged. It is not designed to work the same a your speed reducing brakes with equal engagement at the same time, as this is not a concern of a Parking brake. Once the first set of pads make contact with the rotor.. if all is adjusted properly force will then begin to be distributed to the other set that has not made contact yet by using the equalizer bar. Once equalization of force is established additional travel by the hand lever will apply approximately the same value of force to both sides. Were this gets tricky is if the (equalizer) = cable lengths are too far out of adjustment and an equilibrium between cannot be reached before tension from the main cable is all applied to one side, on our 914s this is usually the Right side wheel that receives little force. Expecting “first contact” of both sides is not the intent of this design. If you have improved the timing of contact with lubrication /adjustment, ….fantastic! No harm… |
davesprinkle |
Dec 4 2009, 11:40 AM
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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 |
This is not a design flaw/issue it is an expectation of design- flaw. And is a quite common one … only because I can’t get over this one.... The "E-brake" as you call it is not an "E" brake, it is a PARKING Brake, designed to HOLD the car in a standing position. The design intent with the Equalizer is to distribute equal force to both sides of the car. Left wheel Right wheel ONCE engaged. Yeah, I'm aware how the force balance works. But it can only equalize forces at the firewall. Forces at the caliper will be reduced by the cable friction. That's the whole problem. And in fact, the mechanical brake IS intended as an emergency brake. It's a backup for hydraulic system failure. |
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