Quote from jayg on Sep 26th, 2016, 2:48pm:Joe, I bought my first 150 mm crankset from Bikesmith Design (Machine my own in my home shop, now). Mark Stonich does really nice work.
If you want to use a double-ring, GPX crankset, Bikesmith shortens SRAM Apex 10-speed cranksets. I have one of those installed on my 11-speed ICE VTX. Nice crankset that works with 11-speed chains, should you want to convert your 10-speed bike to 11-speed in the future. I ordered a cyclocross crankset (46T/36T chainrings), machined the arms to 150 mm, and replaced the 36T ring with a 34T. In a 46T/11T gear combination, theoretical speed at a 100 rpm cadence is 32 mph. The VTX weighs 33 lbs 8 oz, ready-to-ride. I can climb my steep test hill OK in the trike's 34T/32T gear combination. I also have a 150 mm cyclocross crankset installed on my 27 lb 2 oz, 11-speed Metaphysic high racer, and can climb that same hill OK in the bike's 34T/28T gear combination. You might want to consider using a 50T/34T crankset, instead of a 53T/39T, to make it easier on your knees, because you will be applying greater forces to the pedals with shorter crank arms. Lower gearing will lessen these forces.
Hope short cranks work for you. I suffered with knee problems for years, until I installed 150 mm cranksets on my recumbents and set the booms so the angles of my knees were not less than 90 degrees at the beginning of the power strokes.
Jay
Appreciate your insight very much, but have a couple questions for you. First and foremost how did you arrive at the 150 length? I have visited the recumbents.com site, did the math and plugged in the numbers to see a wide range without any real definition of what a high versus middle BB really is. Secondly, today I ride. 30/39/52 with 170mm cranks, I have yet to encounter any hill that I cannot ride on the 39 and the 30 has never been used on the CA2. Previously I rode a 50/34 on my rifle and was quite often frustrated when shifting down to the 34 when climbing as the gap was so large that I would spin out of control until I could get the cassette shifted up to find a comfort zone. This and this alone is part of my logic in going to a 53/39 and I do occasionally spin out on the 52 when I push on a downhill at 40+ mph. I also want to change the BB and go to ceramic bearings as I believe I've that will also aid in leveraging the energy output by being more efficient, although I have nothing to prove that with.
Your insight is truly appreciated