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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Brakes
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<blockquote data-quote="Black Flash" data-source="post: 83434" data-attributes="member: 433"><p>David Dumfey sent me the article of the Bert W. Modification quite a while ago.</p><p>I was first tempted to do it but finally didn't for some reason.</p><p>The design actually turns your sls brake into a servo brake. While I am not against trying that due to the small size of brake lining and drum diameter I think I have to tell you that there is a common belief that this kind of brake is unusable and highly dangerous on a motorcycle.</p><p>With a good 2ls front brake or even more with a 4ls as my Grimeca you can feel the self servo effect while breaking hard. Usually the brake linings need a certain temperature to work best. With the Grimeca on a cold brake you need to squeeze the lever hard for breaking hard. Once the brake is up to temperature and having to break hard you feel that the self servo effect starts as without changing the pressure the braking is getting harder still. You actually have to ease the grip on the lever to counteract the increasing bite of the brake.</p><p>Now imagine this self servo effect actually presses the second brake shoe even harder into the drum than you will ever be able by squeezing the lever and it all happens really fast... This sounds like big trouble.</p><p>Secondly from an engineering point of view what you want is the brake shoes to return to a specific resting point when not using the brakes. With this mod the shoes are only centralized by the spring near the brake cam and two little rubber O-rings at the bottom which I am sure will loose their shape very soon. </p><p>Every servo brake I had seen while working in the trade had a positive stop for the leading edge of the second shoe who was moved against this stop by a substantial spring. </p><p></p><p>Please don't get me wrong. I am the last person that does not like modifications and as I mentioned at the beginning the mod may and probably will work well due to the small breaking area and drum diameter. But a servo brake always has something vicious in its behavior and I would rather bite the bullet and pay for a readily available known to work 2ls conversion. </p><p>Saying this I will probably build my own 2ls conversion just because I like doing things, but I will stay away from a servo brake for sure </p><p></p><p>Bernd</p></blockquote><p></p>
[QUOTE="Black Flash, post: 83434, member: 433"] David Dumfey sent me the article of the Bert W. Modification quite a while ago. I was first tempted to do it but finally didn't for some reason. The design actually turns your sls brake into a servo brake. While I am not against trying that due to the small size of brake lining and drum diameter I think I have to tell you that there is a common belief that this kind of brake is unusable and highly dangerous on a motorcycle. With a good 2ls front brake or even more with a 4ls as my Grimeca you can feel the self servo effect while breaking hard. Usually the brake linings need a certain temperature to work best. With the Grimeca on a cold brake you need to squeeze the lever hard for breaking hard. Once the brake is up to temperature and having to break hard you feel that the self servo effect starts as without changing the pressure the braking is getting harder still. You actually have to ease the grip on the lever to counteract the increasing bite of the brake. Now imagine this self servo effect actually presses the second brake shoe even harder into the drum than you will ever be able by squeezing the lever and it all happens really fast... This sounds like big trouble. Secondly from an engineering point of view what you want is the brake shoes to return to a specific resting point when not using the brakes. With this mod the shoes are only centralized by the spring near the brake cam and two little rubber O-rings at the bottom which I am sure will loose their shape very soon. Every servo brake I had seen while working in the trade had a positive stop for the leading edge of the second shoe who was moved against this stop by a substantial spring. Please don't get me wrong. I am the last person that does not like modifications and as I mentioned at the beginning the mod may and probably will work well due to the small breaking area and drum diameter. But a servo brake always has something vicious in its behavior and I would rather bite the bullet and pay for a readily available known to work 2ls conversion. Saying this I will probably build my own 2ls conversion just because I like doing things, but I will stay away from a servo brake for sure Bernd [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Brakes
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