Cause of grabbing brakes

[Dave Wortley]

Dave,
Has the fact that the king pin and the radarm bolt were broken also loosened the rivets attaching the front crossmember to chassis rails and the centre longitudinal member?
Dave.

[Andy Bennett]

I had a similar problem earlier in the summer and it turned out with that I had tried to be too clever with tightening up the adjustment. I slackened everything off just a little to give more slack in the cables and it seemed to allow the left to right adjustment and front to rear to just work together rather than grab at first application of the brakes.
Andy

[Ian Williams]

With that amount of force it is likely that the end of the radius arm which houses the brass cups has been spread allowing the cup to move within the arm. No matter how tight the centre bolt is done up movement will still be present under braking, get your friend to remove the arm's and check the fit of the brass cups, if this is the problem I would expect it to cause worse grabbing in reverse though. It seems obvious that something related to the accident has caused the problem, what else has been changed to repair the damage, to break a king pin and radius arm ball other components must have been damaged, axle, stub axle crossmember, steering and track rod arms? Is the new king pin a good fit in the axle, with that amount of force I would expect the eye would be spread and axle possibly bent.

[Charles Levien]

I agree with almost all of the above and like Ruairidh have found this issue linked to the radius arm ball, in my case the brass cups, through wear, were a poor fit in the radius arms allowing movement, rectifying this cured the problem.

I have the same problem on my RN, it's not going forward, its going in reverse I get the juddering. The problem I get going forward is the N/s locks up on full lock. It's in the garage now on stands so I can investigate the problem.

It's been said before but check your cotter pin nuts are to the front. I ran my special for years with the front cotters wrong way round and put up with locking up in reverse thinking it was just an Austin Seven foible.

Charles

[Dave Mann]

Had an update today, the owner has had all 4 brakes drums off and checked they are all round. He also cleaned the drums and shoes with emery cloth after which the brakes were initially almost non existent. then it was soon back to th grabbing problem.

[Reckless Rat]

Dave, whilst the drums may well be round, has the relationship between the drums, the brake shoes and the cams been verified? If you cover the lining material with chalk you can very quickly determine which parts of the brake shoe are actually contacting the inner surface of the drum as where it touches will be cleaned off. I suspect that the contact area isn't as great as it should be. The leading shoes may be the culprit as they have a self-servo action.

Just my two-penn'orth
Bruce

[Nigel was in Brittany]

I have the same problem on my RN, it's not going forward, its going in reverse I get the juddering. The problem I get going forward is the N/s locks up on full lock. It's in the garage now on stands so I can investigate the problem.

It's been said before but check your cotter pin nuts are to the front. I ran my special for years with the front cotters wrong way round and put up with locking up in reverse thinking it was just an Austin Seven foible.

Charles

I have looked today and the nuts are to the rear , are you saying the levers are on the wrong side of the car and I need to change the lever fitted to the left to the right of the car and visa versa  so the cotter goes through and the nuts face forward?

[Alastair Gill]

I had a problem with rear off side brake grabbing on when moving at slow speed either forwards or backwards. In addition there was a “metallic clunk” noise as if a brake shoe was hitting the back plate.

When travelling at speed, providing I had “test” applied the brakes in a safe place when setting out, I found there seemed to be no problem of grabbing.

I did the usual things of filing the leading and trailing edges of the brake lining - a gentle slope for the first half inch either end of the brake lining. Also gently filed off the sharp edge of the brake lining.

Checked various dimensions to see what might be causing the shoe to rock over and hit the back plate

Ultimately after extensive detective work, I noticed that there was a bright metal rub line running around inside the brake drum at the edge of the rubbing face furthest from the back plate. I noticed that the brake lining hung over the edge of the shoe a tad on the side furthest away from the back plate. Filed it back the brake lining to be flush with the brake shoe. Cured !  No more grabbing of brakes and no “metallic clunk” of the shoe hitting the back plate.

[Tony Press]

I have looked today and the nuts are to the rear , are you saying the levers are on the wrong side of the car and I need to change the lever fitted to the left to the right of the car and visa versa  so the cotter goes through and the nuts face forward?

Placing of the cotters from the front or rear has nothing to do with changing the levers in early brakes. they are the same left and right..