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Handbrake binding...again


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Hi all, working on the handbrake at the weekend. This is a thing I've been adjusting for years it seems! I can either have:

1. Binding brakes and a handbrake that functions

2. No binding brakes, but no handbrake! 

I've taken up the cable slack as per the manual, and now it seems it half works. However, after every hand brake application, the drums seems to bind for half a rev. Only adjusting the back plate screws help, but then the problem repeats itself after every subsequent application. Can anyone shed any light on this issue? 

 

Cheers 

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Grooves worn in the backplates by the handbrake levers where they swivel. Common fault and been discussed on here many times.

Stuart.

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Thanks again guys. I've had the drums off today, and the cylinder was sticking in the slot.

Free'd it up and lubed ut now but realistically how easily should they slide? I can now jimmy it back and forth with a screwdriver but i wouldn't exactly call it a free lubricated passage!  

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Hi, the grooves we are on about can only be seen when you remove the cylinder from the back plate, they are where the hand brake levers pivot against the back plate and end up fixing the cylinder in one position, it's a very crude design, and another example of how Triumph never intended these cars to be in use 50 or 60 years later!!

cheers Rob

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I should note it wasn't just the handbrake binding. It was after one application of foot brake too. So the cylinder was not free sliding. As these cylinders are not dual piston, it's my understanding that the piston side and the cylinder side both move fore/aft respectively WRT to the slot. Hence the need for free movement in the slot to achieve equal pressure on the front and rear shoe. 

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As has been stated - over time the pivot on the handbrake lever wears a groove in the back plate. Eventually this gets derp enough to prevent the cylinder sliding freely - paricularly when the handbrake is applied but to an extent when the footbrake is applied too. This results in the braking effort being applied to only one shoe with consequential reduced performance.

Strip down the brakes, remove rust/paint and put a dab of mig weld in the groove andgring flat and your back plate is as good as new.  When you reassemble I would suggest a tiny smear of moly grease on the sliding interface of the wheel cylinder and back plate. Before you reconnect the piles and cables grasp the wheel cylinder and check it slides freely.

Re assemble making sure that the cylinder operates normally with the hydraulic piston going in and out freely and that the handbrake mechanism is free.

Check there is not any blockage in the flexy pipes. (if showing any signs of age just replace them)

Old handbrake cables loose elasticity so when you pull them on by the time you have settled the handbrake onto the click the tension in the cable has reduced. A new cable is relatively elastic so maintains the tension as it drops onto the tooth of the handbrake mechanism.

When you adjust the brake shoes make sure the cable is slack first. Only then adjust the handbrake cable.

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1 hour ago, tjs said:

Thanks again guys. I've had the drums off today, and the cylinder was sticking in the slot.

Free'd it up and lubed ut now but realistically how easily should they slide? I can now jimmy it back and forth with a screwdriver but i wouldn't exactly call it a free lubricated passage!  

20220811_152602.JPG

By the looks of those shoes they havent actually been doing anything.

Stuart.

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Well i could fry sausage on the drum after 20 miles so they were!

Going to strip down as above. Just noticed the forked retaining plate has been installed with the two hooks facing in toward the back plate, probably grabbing it and causing more friction.

 

Cheers 

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TJS,  Just an observation,       I think you ought to put the bump rubbers back in place, if the shock takes the full bump it can break the rear part off the trailing arm, and usually does.

The trailing arm should hit the bump stop before the the full closure of the shock absorber.

John

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25 minutes ago, John L said:

TJS,  Just an observation,       I think you ought to put the bump rubbers back in place, if the shock takes the full bump it can break the rear part off the trailing arm, and usually does.

The trailing arm should hit the bump stop before the the full closure of the shock absorber.

John

Good spot. Yep I've got those ready to go on. 

 

Cheers Waldi. Yep covers were missing. Make fork plate installed backwards causing the hooks to grab and dig into the backing plate. All sorted now, minus the covers.

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15 hours ago, tjs said:

Good spot. Yep I've got those ready to go on. 

 

Cheers Waldi. Yep covers were missing. Make fork plate installed backwards causing the hooks to grab and dig into the backing plate. All sorted now, minus the covers.

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Did you check the backplates for grooves as well?

Stuart.

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14 hours ago, stuart said:

Did you check the backplates for grooves as well?

Stuart.

Back plates were measured against a refreshed one on a friend's car - surprisingly only about 1mm longer. The problems were;

1. No weather boot..

2. Male locking plate installed with hooks facing inwards, gripping the back plate.

3. Wheel cylinder was not sliding, and jamming up after every brake application. 

All sorted and greased now, just waiting for the boots to come.

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8 hours ago, tjs said:

Back plates were measured against a refreshed one on a friend's car - surprisingly only about 1mm longer. The problems were;

1. No weather boot..

2. Male locking plate installed with hooks facing inwards, gripping the back plate.

3. Wheel cylinder was not sliding, and jamming up after every brake application. 

All sorted and greased now, just waiting for the boots to come.

Yes but did you check for the wear grooves?

Stuart.

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Hi TJS (have you got a name?),

I think you may misunderstand the above post from Stuart. The groves develop over time where the pivot pushes “in” the back-plate, each time you pull the hand brake. See picture Harry posted above.

The pivot-pin will “fall” in this groove and then the cylinder can no longer slide freely. If there is a groove, sand it, carefully weld it up, grind it flat and that’s it.

Cheers,

Waldi

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9 hours ago, Waldi said:

Hi TJS (have you got a name?),

I think you may misunderstand the above post from Stuart. The groves develop over time where the pivot pushes “in” the back-plate, each time you pull the hand brake. See picture Harry posted above.

The pivot-pin will “fall” in this groove and then the cylinder can no longer slide freely. If there is a groove, sand it, carefully weld it up, grind it flat and that’s it.

Cheers,

Waldi

Cheers Waldi, all understood, nearside was fine no groove, offside checked today has a slight worn groove as just visible in the picture with cylinder slid back. Will get the back plate off and drop a bit of mig in there! Offside was also missing the third (smallest) retaining plate! Crikey.  Alex

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Edited by tjs
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Very good Alex.
On your picture you can see the pin is in/at the groove, and the cylinder had not been moving. You should have a noticeable improvement in hand brake efficiency in particular.

Also check the plunjer is moving freely in the cylinder. Not by means of the foot-brake without shoes/drum installed, as this will push it out (how do I know?).

Waldi

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You could have one more item to check, the pin in the brake lever, where its been running on the back plate will now have a flat on it for sure,  I knocked the pin out of mine and turned it 180 degrees and re fitted, so now its running on a rounded pin, and will slide better of the back plate hopefully!

John

Edited by John L
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Hi Alex, 

sorry me to read this post just now.

About the handbrake mechanism I posted enough.

Interessant to see is the missing bump stop on the trailing arm, as John stated.

And the fixing of the shock absorber on the thin metal sheet of the car body!

I know, lots of users out there don’t worry about.

Better and more solid is to use a bracket fixed on the car frame where the lever arm shock absorbers are fixed.

I swaped back to lever arm shock absorbers, they are more comfortable.

Ciao, Marco 

Edited by Z320
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Thanks all for the help and diligent QC. Love this forum. Rears are now working a treat. Fitted 2 recon Girling 16pb calipers today, so good brakes all round. Bleeding was a fiddle but got there in the end. 

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Edited by tjs
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