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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Tuning Front Brakes?
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<blockquote data-quote="Tom Gaynor" data-source="post: 1000" data-attributes="member: 4034"><p><strong>Spongy brakes</strong></p><p></p><p>Flex (call it lost motion) in the hub can be multiplied eight times, because the radius of action of the cam (say 1/2") is 1/8 the radius of action of the lever (say 4"). Or whatever. This already multiplied lost motion is then multiplied again by the handlebar lever, by about five times. So 1/40" of an inch of lost motion at the cam will amount to 1" lost motion at the hand lever. The greater the mechanical advantage, the greater the potential for sponginess. (True also of hydraulic brakes...) My guess is that you are losing motion in the drum, thus gaining the full 40-fold magnification.</p><p>I haven't ever suffered from cable stretch, which isn't to say that others haven't, but compression of the outer is common. Just watch the cable trying to straighten itself out when you pull the lever hard on. Then multiply the change in length by five.</p></blockquote><p></p>
[QUOTE="Tom Gaynor, post: 1000, member: 4034"] [b]Spongy brakes[/b] Flex (call it lost motion) in the hub can be multiplied eight times, because the radius of action of the cam (say 1/2") is 1/8 the radius of action of the lever (say 4"). Or whatever. This already multiplied lost motion is then multiplied again by the handlebar lever, by about five times. So 1/40" of an inch of lost motion at the cam will amount to 1" lost motion at the hand lever. The greater the mechanical advantage, the greater the potential for sponginess. (True also of hydraulic brakes...) My guess is that you are losing motion in the drum, thus gaining the full 40-fold magnification. I haven't ever suffered from cable stretch, which isn't to say that others haven't, but compression of the outer is common. Just watch the cable trying to straighten itself out when you pull the lever hard on. Then multiply the change in length by five. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Tuning Front Brakes?
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