Perhaps a better answer is to do away with the ESA altogether and design a Cush drive similar to those on a bevel drive Ducati, which actually operate within a drum (with vanes in it) that bolts to the rear wheel in a similar way to the vincent brake drum bolts to the rear wheel. Someone who is more talented than me could probably come up with a design that looks a lot like the standard rear brake so it wouldn’t look out of place. The downside of course is that you lose one of the rear brakes. This system woks well on Ducati’s, mk111 commandos and many others and is easy to maintain, pretty much limited to replacing the rubber “spider” every few years. Not running in hot oil really helps the rubber to last! No doubt, cost and lack of demand would be issues but it’s something to consider. I’m sure I’m not the first to suggest this but since I have a shadow With the usual ESA and several bikes with rear wheel Cush drive , I know which I prefer.
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