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Adjustable geometry bent

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    Posted: 18 January 2019 at 3:19pm

 
Basically, I have a problem with high BBs - I get rather large power drop and numb feet when BB gets higher than about 4 inches above seat (I've experimented with varying rear wheel size on my FWD). Once it gets high enough, I lose about 50 watts at same perceived exertion - my legs feel 'leaden' and start hurting as I try to push for power, and thing likely get worse from there.
 
Low BB, however, results in too much of an aero penalty, even when combined with a reclined seat.
 
Rising BB 'up to my maximum' might work, BUT will only work on flats. Climbing changes your orientation against gravity just like more recline/higher BB does, robbing you of power exactly when you need it most.
 
Only system that solves this conundrum and seems remotely viable (as in - not too heavy and complex/expensive mechanically) is manipulation of sag of rear wheel - say, install a shock with 2x travel you want, run 50+ percent of sag and have a system to quickly inflate/deflate your shock 'on the fly', hence giving you a rather decent amount of seat/bb height adjustement. I am planning using a part of the frame as air reservoir and use pneumatics to play with rear shock sag.
I am also planning a 'pivot brake' to lock front shock in collapsed position, that results in extra geometry change AND more trail due to rearward axle path (that becomes nearly zero otherwise).
 
 
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