Balancing caravan brakes - driving me slightly insane.

[FullEnglish]

Hi all,

Van is a Sprite Alpine 1964.

I took the brakes apart, derusted, checked the springs, shoes etc, and reassembled them as all the parts were good. Balancing them took ages, as they were fine until I activated the brakes a few times, whereupon they were out of balance again and I had to start over. I finally got them right, took the caravan for a test run of a few miles, and found out that one brake drum was really hot and was dragging. Balanced them *again* (last night), took the caravan to be inspected (like an MOT) only to have it fail on brakes - out of balance. One side now has twice the effect of the other side.

Does anyone have any idea how to go about adjusting the brakes so that they STAY correctly adjusted?

All ideas greatly appreciated!

Cheers.

[FullEnglish]

The rain stopped. Finally. Briefly.

Jacked the van up, and the brakes are indeed still balanced.

The inspection showed that one side has half of the braking effect of the other side. The brake shoes were whole, undamaged and had plenty of meat left when I inspected them, but I'm supposing one side must be glazed/contaminated.

Is it possible to get away with sanding down the pads and cleaning the inside of the drum? Although they are at least 20 years old, and possibly original to the van (1964) so could well be asbestos.

I'd change all four of them for the sake of it, but finding new ones can't be the easiest thing in the world.

As you might have guessed, I know naff all about drum brakes...

[outnumbered]

is this off any help.
http://uk-trailer-parts.co.uk/adjusting-knott-brakes
mike

[rogerthechorister]

Back when I was a Morris Minor man we regularly used to sandpaper off glazed shoes, and clean them off with petrol too if they had been contaminated with grease. We were bold in those days!

[FullEnglish]

Mike; my system is older than the ones described in your link, but thanks for posting, I appreciate it.

The rain stopped again (it's actually a beautiful summers evening now) so I took the "bad" side apart. As I suspected, it was beautifully glazed. I decided I was probably immune asbestos dust due to the protective properties of caffeine and nicotine and filed the surfaces until they were nicely, er, deglazed.

I then took the "good" side apart, to do the same thing so I had shoes that were in the same condition on both sides. The "good" side was also quite glazed. So I don't know if my braking imbalance will remain, albeit with more braking effect over all. Trouble is, I don't have a brake testing machine (although I do have a cunning idea to make one).

Of course, if I'd known anything about drum brakes I'd have spotted the glazing first time round. One learns. Sigh.

I've reassembled everything and now even with the adjuster slackened right off, the brakes are dragging a lot. I suspect I need to drive over some potholes to allow everything so settle into its proper place and then adjust again.

rogerthechorister, I actually used your petrol trick as I couldn't be bothered to drive into the village and buy brake cleaner.


Of course, if all else fails, I'll just add a smear of grease to the "good" side. What could possibly go wrong?

[BugEyed]

Originally Posted by FullEnglish

Of course, if all else fails, I'll just add a smear of grease to the "good" side. What could possibly go wrong?

Nothing!

Coming from the other era of technology (20's and 30's drum brakes) I'd also check whether the drums are dished. Most drums are pressed from flat sheet and when heated (dragging brake for example) they start reverting to flat. Then the inside of the brake shoe is all that is engaged and hence efficiency drops off dramatically. The only solution is to skim the drums or replace them.

Most van shoes are from car parts so can be replaced cheaply.

Good luck.

Duncan