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General Category >> Marketplace >> WTB 155 OR 160 MM 130 BCD CRANKS
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Message started by Phantom Rider on Sep 23^rd, 2016, 5:26pm

Title: WTB 155 OR 160 MM 130 BCD CRANKS
Post by Phantom Rider on Sep 23^rd, 2016, 5:26pm

I'd like to try shorter cranks on my CA2 to see if my knee pain will be relieved. currently running the stock FSA Mega GPX BB with SLK light carbon 170mm cranks. I do plan to upgrade the BB in the next week or so to the Enduro XD-15 with ceramic bearings...jayg and cruzbikechris made me jealous...

Alternative solution would be a 39/53 crankset with either 155 or 160mm cranks.

Title: Re: WTB 155 OR 160 MM 130 BCD CRANKS
Post by Rat Rider on Sep 25^th, 2016, 5:36pm

This might be helpful.

http://www.bikesmithdesign.com/Short_Cranks/

Title: Re: WTB 155 OR 160 MM 130 BCD CRANKS
Post by Phantom Rider on Sep 25^th, 2016, 6:07pm

Thanks, been thinking about calling him.

Title: Re: WTB 155 OR 160 MM 130 BCD CRANKS
Post by jayg on Sep 26^th, 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.

Title: Re: WTB 155 OR 160 MM 130 BCD CRANKS
Post by Phantom Rider on Sep 26^th, 2016, 4:11pm

jayg wrote:

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

Title: Re: WTB 155 OR 160 MM 130 BCD CRANKS
Post by jayg on Sep 27^th, 2016, 7:17pm

Joe, the Bikesmith website has some crank length selection guidelines for riders with and without knee range-of-motion problems. Using the no range-of-motion problem guideline, I should be using 160 mm cranks. Probably wouldn't work for me, as 165 mm cranks hurt my knees. I plugged my numbers into the "Crank Length Calculator" on the Recumbents.com site, resulting in a 135 mm crank length recommendation for a 90 degree knee angle. Big difference. I just guessed when I selected a 150 mm length. Luckily, it worked for me. 155 mm might have worked, and would have provided a little more leverage.

I ride the 46T ring most of the time, including when I climb short hills. About the only time I ride the 34T ring is when I encounter a steep, long hill. Don't have any problem transitioning from the big ring to the small ring. When I do, I don't spin crazily, I just slowly turn the crank and rapidly upshift the chain on the cassette. I'm not strong enough to spin out the 46T ring on the flats in the smallest cassette cog (363 watt max short term output). When I spin out on long downhills, I just coast the rest of the way to the bottom.

Regarding your "high BB" vs. "medium BB" question - I would think your CA 2.0 would have a high BB and a Cruzbike Silvio a medium BB.

Reference your ceramic BB comment - Several years ago, I read a test report for wattage loss of a number of ceramic and steel bottom brackets. Seems the bearing type was not significant, as far as wattage loss was concerned. It was the seals and lubricant that had the most effect on wattage loss, with the tightest seals and most dense lubricants causing the most loss. I installed Omni Racer ceramic bearings on three of my recumbents. On two of them, the ceramic bearing BB-equipped cranks spun more freely than when they were equipped with steel bearing BBs. A MegaExo, steel bearing BB-equipped crank on my Metaphysic bike spun more freely than when the crank was equipped with a ceramic bearing BB.

Title: Re: WTB 155 OR 160 MM 130 BCD CRANKS
Post by Phantom Rider on Sep 29^th, 2016, 12:46pm

Today I took the plunge and Mark has my money so there is no turning back. After much research and advice from other riders and a long discussion with Mark the decision was made. I have ordered a set of 150mm sram APex cranks with compact double Rotor Q rings 36/52 and the Enduro XD-15 ceramic BB(different source).

Many thanks to you guys for suggesting I talk with Mark, there were others who suggested him as well. The knowledge this guy has is phenomenal and his willingness to break it down for my simple mind was truly appreciated. I'm expecting arrival in about a week and the real fun begins because my knees won't hurt anymore and I can ride like the crazy old white haired pony tailed nut I am. More to come after installation and some miles.