Brakes: Brake/handbrake question

[leftfootleashed]

Hi all,

I'm a bit confused with the situation after replacing all four sets of discs and pads. I've had a look at some old threads on here but can't seem to get my head round the problem.

After replacing all the discs and pads, I bled from the rears. I was hoping this would be sufficient since I hadn't opened the front bleed nipples and the rears are first in the sequence anyway. After a test drive, this clearly isn't the case so I need to either a) bleed from the back more thoroughly, or b) carry on and bleed from the fronts.

Anyway, before I do that, my handbrake doesn't work. The lever was very loose, but even on tightening the adjuster bolt, I can't get it to hold at all. It appeared that it was quite unbalanced, but after working one cable a bit, it seems to have evened out. So now the lever will only travel maybe 7 or 8 clicks (certainly not all its travel) if you pull really hard, but no braking force.

I've not worked on a car with a handbrake that operates the same pads as the footbrake before. Does the air in the system affect it? i.e. when I pull the handbrake lever am I just compressing the air in the system?

I'm wondering whether I've wound the pistons in too far, or unequally. Is that possible?

[ww1dm1]

You mean you are only able to pull the lever 7-8 clicks before you no longer have the force to pull it and it still doesn't hold, or does it simply hit the edge of it's travel?

The handbrake mechanism is unaffected by the brake fluid and air in it. It's a simple screw mechanism where pulling the lever pulls an ear on the caliper via cable and "screws" the piston into the pads and into the disc. If it's tight - it should hold. If it's tight and doesn't hold - the handbrake screw mechanism is stuck and is unable to screw in when force is applied. Refurbishing might help (magnificent guide here).

If the lever is "floppy" - the cable is loose and needs tightening. One side might be loose without floppiness, but you should see that one side is tighter than the other at the metal clip where adjustment and tightening is done. The clip will be at an angle.

Are you sure you cleaned the discs off with brake cleaner before use?

[leftfootleashed]

Originally Posted by ww1dm1

You mean you are only able to pull the lever 7-8 clicks before you no longer have the force to pull it and it still doesn't hold, or does it simply hit the edge of it's travel?

I don't have the force to pull it - it's definitely not using all the travel.

Well it's good to rule out any influence from the hydraulics. I'm not sure why it would stick now and not before I changed the discs. Maybe because the pistons are in a different position (and now the mechanism is working on a previously exposed, corroded part of its travel)? Hard to know without knowing the internal workings of it. I'll take a look at the refurb article, that may help.

It may be that there's an imbalance and one side is holding - I need to get the back end up again to check further. I didn't have any more time tonight. I would expect it to hold it on one side though, and I couldn't even feel a difference between the lever pulled and released when I let it off on a slope.

If there is unbalance, is there any way of sorting it? I can't see any mechanism for it. Most cars I've worked with have an adjuster nut on each cable so you can set the tensons separately.

Originally Posted by ww1dm1

Are you sure you cleaned the discs off with brake cleaner before use?

Yup, cleaned thoroughly, both sides. I know they'll need bedding in, but they should have more bite than this from new.

[ww1dm1]

Originally Posted by leftfootleashed

If there is unbalance, is there any way of sorting it? I can't see any mechanism for it. Most cars I've worked with have an adjuster nut on each cable so you can set the tensons separately.

Well, if there is an imbalance then either one of the cables is stretched more than the other or one of the calipers is sticking, I don't think separate adjustments are necessary if the system is looking good. Just take off the rear wheels and have someone tug the handbrake a few times with you observing the handbrake ears. You'll figure out what's going on quick.

I attached a rough diagram of how such a handbrake mechanism works. The guide should complete the picture.

[leftfootleashed]

Originally Posted by ww1dm1

Well, if there is an imbalance then either one of the cables is stretched more than the other or one of the calipers is sticking, I don't think separate adjustments are necessary if the system is looking good. Just take off the rear wheels and have someone tug the handbrake a few times with you observing the handbrake ears. You'll figure out what's going on quick.

I attached a rough diagram of how such a handbrake mechanism works. The guide should complete the picture.

That's a really helpful diagram. I'll have a closer look tomorrow when I've got the back up and an assistant and see what's what.

Thanks!

[cheshired5]

Originally Posted by leftfootleashed

I've got the back up and an assistant

Get your assistant to raise and lower the handbrake lever whilst you look at the mechanism on both rear calipers.
You should see even movement on both sides so if you don't see even movement or you see little to no movement, that's why it isn't working.