Handbrake/emergency brake cable problem.

Hi all,

Working on my GT4 to get it ready for the annual MOT inspection over here. The e/handbrake goes up quite far when I pull it on and our testers seem to like only a few clicks on the lever to pull the brakes on.

So I checked the rear brake adjustment, including the cable between the callipers (big red circle). All looks ok, with just a little play to ensure the brakes are free when the handbrake lever is off.

Trouble seems to be that the cable from the lever to the pivot (small red circled) doesn't readily return down the tube it comes from. I can adjust the cable at the pivot end (small red circle) to give me fewer clicks on the hand lever, but then this puts just a little too much pull on the callipers and they drag - but I can get underneath and pull the main cable back out of the tube a little to slack off the brakes - hence the main cable seems reluctant to return all the way out when the hand lever is off.

Am I right in thinking that the only things that return the cables to off are the two wound springs on top of the callipers ? Should there be any other springs in the system ? I guess it there's more return spring at the point when the brakes are fully locked, but as you return the handbrake to off, the last pit of movement isn't pulled with too much force from the calliper springs (also reduced at the near off position by minimal deflection of the two pulleys).

How easy is it to get the main cable out or look at the point where it's attached to the lever - I figure maybe the tube is full of gunk, or the cable it really dry or something ?

Also how many clicks of the lever do other folk get ?

thanks

Lee
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2-3 clicks.

First order of the day is to look at the actuating lever at both brake cylinders, making certain it actually is able to move. Best to remove the cable and use a wrench as it requires some force.

Quite often, the eBrake piston actuator gets stuck. When that happens, adjusting the cable does nothing as the brake never moves. Even when one side gets stuck, the other side doesn't actuate either.

If you find the caliper isn't moving, there is a good writeup on Birdman's web site with instructions on curing the problem.

 

Lee, kind of an oldish post here but nevertheless...

Yes, there's one more spring in the picture here - it's in the hbrake mechanism intermal to the caliper. It's not as heavy a spring as the external spring however. The hbrake mechanism on your calipers may be gunked up and binding. They aren't that tough to clean and rebuild - there's a repair kit available from superformance in the UK that has all the correct seals and such.

Personally, I'd start with taking the caliper off and doing a clean and re-seal on the bench just to make sure that's not binding and complicating matters.... Incidentally, the rear 308 caliper is the same caliper that's on a porsche 914/6.

 

Not quite true on the 914/6 rears.
Check out this excellent post by PMB Performance-page 2

Even if you found 914/6 GT rears, the bleed would be on the wrong side.

But the big main springs on the cable lever are responsible for most of the cable's return.

 

Thanks Clyde. I have a set of calipers from a 914/6 with the 10mm spacers and they are identical in all respects to my 308 calipers (including positioning of the bleeder). No doubt PMB knows what they're talking about however.

Yes, the main spring on the lever is responsible for the majority of the return on the handbrake, with the smaller internal spring doing a lesser job of it.