H: Hubs, Wheels and Tyres Modern brake linings

[john998]

My outfit front brake with modern linings, after a steap hairpin descent lost all clearance. Luckily I felt something wrong and stopped.
The brake was over heated and needed both adjusters on the balance beam screwed several turns to free the brake. If this was not corrected it being a sort of positive feedback it would have been dangerous on a solo. When they cooled it needed resetting to the original adjustment.
Previous experience with over heated brakes has had the opposite effect, the lever coming back to the bars.
Could this be something to do with the linings? John.

 

[davidd]

John,

It is very hard to tell because there are too many variables. One of the things I wondered was what was the original clearance, meaning the difference between the arced shoes and the drum I.D. If it were very close I might suspect that the initial braking may have heated the shoes quickly causing them to self apply the hotter they got. With more initial clearance this might not happen.

In general, I think the modern linings are good at resisting heat, but of course they are quite good at making heat. In older linings the resins that bonded the material into a solid form, assuming it is not woven, would break down very quickly if they were over-heated. This could mean that once they faded they just did not recover as well as they could have ever again. In modern linings the resins are much more resistant to heat and the linings tend to recover to a higher level of performance.

David

 

[passenger0_0]

I want to start this story with 'A friend once........" tightened up the clearance of the front brake cables for our 6 monthly mechanical inspection (warrant of fitness). Forgetting to back off the adjusters, he (read me) then rode at motorway speeds for 50 miles before noticing the exhaust note had got progressively louder and that it required more throttle than usual. Opps!
Rolling off the throttle the bike soon pulled up - smoke bellowing off the burnt paint from the drums and small grease fire. Linings had turned to cardboard which you scrape off with a fingernail.
The cable definitely got tighter as it got hotter so a different phenomena to brake fade and pulling the lever into the bars.
Maybe 'Beyond brake fade' and closer to 'grease inferno'?