Front brake conumdrum

petert120r · Post by **petert120r** » Mon Jul 12, 2010 6:12 pm

Road testing latest project - 1961 Model 31. All fine expect for front brake, which is anaemic to say the least - about as much retardation as a pushbike! New exchange JSL shoes were fitted and on inspection a shiny black deposit over the linings, which I cleaned off with meths. Old grease on the drum, I thought, so thoroughly sponged it with hot water and Fairy liquid, then meths and kitchen role to get rid of any vestigal traces, roughened up the drum surface with a Dremel sander as I did with the shoe linings. Centralised the drum, actuator at correct angle to the cable, back on the bike, no improvement.

Repeated the process, this time having heated the drum brake surface with a gas torch to burn off any possible oil traces, rode it down the lane for a mile or so with the front brake tight on, which only succeeded in causing fade. Stripped it down again, same black deposit.

In desperation stuck on a spare lever with wider radius centres to give more pull, still no better!

I know these brakes are pretty crap anyway, but I've never had one as bad as this. Is there some problem with the new linings? I've got some old shoes which I'm going to try but I wondered if anyone else has experienced anything similar.

It's got me tearing my hair out, or would do if I had any.

Flash · Post by **Flash** » Mon Jul 12, 2010 6:40 pm

Yes I believe that the modern linings are pretty useless, the old ones I have in mine I believe, if I remember correctly are red & work better than a tls on a Truimph hub that I have on a Gold Flash, I think the modern type are asbestose free & definitly are crap.

Regards John

ianselva · Post by **ianselva** » Mon Jul 12, 2010 6:54 pm

I don't think you're helping by roughening the surfaces of the drum and lining, as you're are reducing the surface area in contact with each other. What you need is maximum contact area but spotlessly clean of grease etc.

Ian

atreyu · Post by **atreyu** » Tue Jul 13, 2010 1:00 am

Get decent linings put on and have the drum machined to suit

wilko · Post by **wilko** » Tue Jul 13, 2010 2:02 am

That's strange my old linings covered in filth & grease are a one finger over the bars effect. Must be that old fashioned grease from fifty years ago that does the trick!

1608 · Post by **1608** » Tue Jul 13, 2010 10:18 am

Oil or grease on the linings can cause the brakes to grab or snatch, I,ve learn't this from experience from some of the older cars I've owned. As previously stated the drum should be perfectly smooth ( not sanded or 'roughed-up' ) in order to maximise the friction area btn shoe and drum. Roughing -up the drum will lessen the disired effect and cause premature wear of the shoes. Theres no point in keeping on blaming modern materials.

mike.dowling · Post by **mike.dowling** » Tue Jul 13, 2010 12:50 pm

Why not look at this topic which seems to work. you have nothing to loose so give it a go.http://www.ajs-matchless.com/topic.asp? ... ral+Topics
I know it improves the braking.
Regards
Mike d.

Stan Palmer · Post by **Stan Palmer** » Tue Jul 13, 2010 2:31 pm

It would be useful to have some kind of gude to effectiveness of these brakes. Perhaps some numbers for distance of stopping from 30 MPH, front brake only. Probably difficult to find a bit of road quiet enough to conduct the test these days. If half a dozen did it that would give a decent curve to check if a particular bike was well out of sorts and to put a value on improvements

Don't blame me if anybody ends up sprawled in the dirt trying this, it's all in the cause of science !

Stan

hawkes · Post by **hawkes** » Tue Jul 13, 2010 4:13 pm

The red brake linings are i believe amosite which is a type of asbestos from africa ! Rich

petert120r · Post by **petert120r** » Tue Jul 13, 2010 6:35 pm

Gentlemen, thanks for your suggestions. Now, hopefully, for the "denoument".

Tried the old shoes but still the same. In the circumstances I did what any sensible person would do, walked away and went down the pub. Halfway through the second pint, the eureka moment! One more pint, just to check the logic, then back to prove the theory.

If I used plenty of blackboard chalk on the drum and JSL shoes, spun the wheel with the axle held in the vice then applied the brake. I reasoned this should highlight where the grease deposits were. In the event. slightest pressure on the actuater and it locked solid.

Wheel back on the bike, down the drive, dramatic improvement. In view of aformentioned pints, didn't take it down the lane, but I'm pretty confident about tomorrow. Chalk, of course, would absorb the grease.

Stan, I like your idea of a test to set a norm, but one person's idea of a handful of brake will differ from another's. However, assuming I've cracked the problem, I'll try it and report back.

Thanks again, everyone.