Girling brakes in the wet

[Peter Naulls]

Over the past couple of years I've noticed the brakes on our Ruby occasionally pulling to the right quite badly in wet weather. When it first happened I assumed it was water in the nearside drum but it has got progressively worse. This morning I drove to work in the dry and the brakes were balanced fine, On the way home it was very wet and it seemed quite clear that the nearside front brake was having little if any effect.

I've removed the drums and the linings look to be matched. The balance quadrant for the cable is free to move as it should and the levers are both roughly vertical when applied. The tyres are matched and both at the same pressure. What am I missing?

[bystander]

Have you tried swapping the drums over to see if the problem reverses? Or next, more drastic step, swap everything from one side to the other - drums, shoes, wheels and anything else that is reversible!

[Andy Bennett]

The nearside being closer to roadside puddles is perhaps getting soaked whilst the other isn't?
Worth a look after a wet run to see if differences can be immediately spotted.

Andy

[Bob Culver]

I have noticed on my old not Austin cars that if the car stands for weeks in humid conditions the brake characteristics are quite fierce for the first many applications. Is it possible the odd shoes have been fitted, different one side from other?

[Peter Naulls]

All good ideas thank you. I think I can rule out the kerbside puddles as part of the journey is on single track roads. I shall try swapping the drums first to see what happens.

[Bob Culver]

Swapping drums can be misleading as now often been resized different. Can gauge with a metal or plastic rod, length of heavy wire, sheet metal carefully fitted to length

[Denis Sweeney]

My front brakes are not girdling but the rear are, however my front brake drums are 20 thou’ difference in diameter and have to include Shims to balance the fronts.
That doesn’t answer your question but does confirm other comments here.
Denis S

[Chris KC]

If the brakes are balanced when dry and imbalanced when wet, you are looking for something which changes unilaterally when the brakes get wet.
This may be something which is not matched side to side (e.g. different linings) or a tendency for one side to get wet (or perhaps more wet) when the other doesn't.
I fear that swapping parts is more likely to confuse the issue and upset the good balance I understand you to have in the dry, especially if they are nicely bedded.
What led you to conclude that your initial assumption (water in nearside drum) was in error?

[John Cornforth]

Hi Peter

It occurs to me that the Semi-Girling arrangement uses cylindrical plungers between the cam and each shoe tip. These are steel running in an alloy casting with just enough clearance to give a sliding fit. The dissimilar metals are a recipe for corrosion, so I suggest you try removing the drums and actuate the levers by hand to make sure everything is running free.

The only other thing I can think of which is humidity related is that the brake drum swept surface can get a thin film of corrosion (rust) which will considerably increase the coefficient of friction. Other posters have mentioned this. However, the effect is normally noticed after the car has been unused for a period. A couple of brake applications usually kills off the "sharpness". Maybe your drums have a different surface condition, not necessarily visible to the naked eye ?

[Peter Naulls]

I appreciate all your thoughts, on and offline. The more I think about it the more it seems likely that the linings are the cause but it does seem odd to me that the drums get particularly wet - and I would expect any water to disperse very quickly. Just how absorbent are asbestos linings I wonder?

I shall get the drums off at the weekend and have a more thorough look. 

I intend to rebuild the whole braking system over the winter but want to make sure I solve this issue in the process. When I reline them am I better to use old stock asbestos linings (which I have) or go for the oft-mentioned green gripper bonded linings?