Short Cranks

[Tom Roberts]

I noticed on the Cruzbike website that short cranks are now available. I purchased the Campy groupo with my Silvio which has 170mm cranks. These are all I've ever used. The short cranks come in lengths from 145mm to 160mm. I have an interest, but without having tried any of these how do you decide which one is best for you? Or is it impossible to know with trying them. I'm 5'-8" if that makes any difference. Any input would be appreciated.

Tom

 

[John Tolhurst]

I inadvertently published that page. Its a product I'm looking at - I don't know what the demand would be for them, but they won't be cheap, about $250 a set including triple rings. What they would be though is the world's only short crank built to today's high end component specification, commensurate with Shimano Ultegra or Sram Force.

 

[bentrider1a]

I think they would be a great add to your list of bike parts

Steve

 

[Mark B]

I did a short crank trial on my commuter bike. It was also a compact double, so I was trying two strange things at once. Anyway, I flip flopped from 155s on a compact double to 175s on a triple crank on my good bike. After riding the short cranks all week, it would take a minute to readjust to the long cranks and I thought I was getting some phenomenol speeds out of it. When I went back to the 155's after the weekend, it would take a few minutes to adapt to that and I also thought I was pretty speedy. I ran like this until my commuter was due for a rebuild and I went back to longer cranks and a triple on my commuter.

My conclusion was that short cranks didn't really make that much of a difference for me. I DO believe that swithching back and forth helped, oddly enough, by keeping my muscles confused. As weird as that may sound, I do believe it made some difference. That being said, I did not consider it worth the money to have a set of cranks cut down by Mark, though I did have a couple conversations with him about it and I gave it some thought.

Mark

 

[Peder Torgersen]

I have 155 mm cranks on my Sofrider V1.
That length feels good for me on the Sofrider.
I will probably upgrade the drive train. I thought about using one of these on my Sofrider; http://www.twbents.com.tw/HTM/crankset.htm

I have tested the 155mm on my Phantom I have only used it on a couple of rides the crank arms that were on it are 172.5mm. I also have a set with 165mm that I can test.
Climbing might be better with shorter cranks but the top speed seems to be better with the longer cranks. I have not tested them enough to find out what works best for me on the Phantom.

I have short cranks on my unicycle 135mm that is also my slowest bike.

Peder

 

[Doc Reyman]

Hello Tom and all others,
I have used short 155mm cranks on my Optima ORCA (SWB suspended High Racer) for a little over 2000 miles.
My best DF bike has 172.5 mm cranks, it is a 56cm frame and I am just over 6' tall.
My new SILVIO has 170mm cranks and I have 250 miles on it in about 8 rides.
So what can I say for sure? NOT MUCH!
IMHO short crank usage is some science and some more folklore and as usual, in the end analysis, a whole lot of personal preference!
Mark B. may have done the most "apple to apple" comparison and ultimately it came to just what felt good.

But one feature of short crank usage is a fact, you can get out of interference problems in the cockpit set-up at times by switching to the shorter crank.

The Optima SWB ORCA like the SILVIO has above seat steering with the handle bars behind the upper portion of the thigh, when the leg is pulled up in flexion. The shorter crank creates a smaller diameter circle the foot is traveling through. This allows the bottom bracket axis to be extended farther from the hip joint and the legs to come back towards the handlebars a lesser distance. This was needed when I set up the cockpit of my Optima, because with a 170mm crank I was getting interference as my thighs were striking the handlebars.

Setting up my SILVIO in February, I was able to use the 170mm cranks and avoid the thigh/handlebar interference by the adjustments of the TFT. SILVIO has a MBB which eliminates heel strike/interference with the front wheel when making turns, but that risk on the Optima was improved/lowered by using the short cranks.

The late Sheldon Brown discusses crank length on this page.
http://www.sheldonbrown.com/cranks.html

My observations did not produce an opinion since there were too many variables in the equation. Just consider 3 bikes DF/SWB/SWB-MBB; 20#/37#/ 27#bike; 16 speed/27speed/20speed; 32spoke 700c wheels/32spoke 26" wheels/20spoke 700c wheels. Believe me each of those bikes ride different and only one has short cranks, but what portion of the ride quality is due to the crank length, I can not begin to tell.

Best of luck and enjoy the learning process.
Larry

 

[John Tolhurst]

Those references from Sheldon Brown are pivotal (pardon the pun). It would be nice to actually read the study and see the graphs and data. On the other hand, p=<0.05 offers some certainty over the result. With n=16, the differences must have been quite large to generate p=<0.05.

Do flexible frames suggest better results with a slower cadence, where the frequency of loading and unloading the structure is lower, or would a flexy frame do better with short cranks where the peak loading is less each time.

In the study, how and where was power measured and was frame flex controlled?

 

[Doug Burton]

I have traditionally not been a short crank guy, after trying 155mm on my old Rotator Tiger. I found my cadence to be uncomfortably high ("movin' meat instead of pushin' feet").

My Silvio and Sofrider both use 170mm cranks, as did my red bike.

But the Quest 559 (155mm cranks) was a revelation, it was perfect on the charity ride last Saturday.

The red bike is getting 155mm cranks, a 54-39-26 TT/MTB ringset, and a 14-25 close ratio cassette to test close ratio, wide range gearing, plus a few Vendetta ideas, but Quest accessory and folding development is taking precedence right now.

We bought a Powertap to get some real data on what all this stuff really means.

It promises to be an interesting summer.

Best,

Doug

 

[Tom Roberts]

Thanks for all the input,

...so John,
Are you going to make the short cranks available or no. If so, when?

Thanks,

Tom

 

[Doc Reyman]

Tom,

Here is one more opinion about the "proper" crank length to fit a person's size, (ie, one size don't fit all!).
This particular writer is a proponent of longer cranks for taller people and offers "his formula" to determine proper length.
Just a little something extra to confuse, while you ponder shorter cranks.

http://www.nettally.com/palmk/crankset.html

The learning goes on every day.
Larry

 

[John Tolhurst]

We talking about recumbents here, so I have no interest really in various creeds or dogmas on the subject theorised by preachers to the upright rider congregation.

I am simply observing that many riders feel they like shorter cranks on their bents than they do on their uprights, for whatever reason. And then I am putting forward the observation that short cranks with quality similar to shimano ultegra or sram force are not available. Are those propositions true? I think so.

 

[Doc Reyman]

Hello John T.,

I agree with your propositions "quality short cranks" are usually only found when you sacrifice a "quality crankset" and send it off to be cut down, drilled and threaded. And short cranks and recumbents do seem to go together like the beach and sunshine!

My curious nature has me exploring these other ideas, especially with something like crank length which always seemed arbitrary. Maybe I'll figure out something whether it is from the bent world or the DF side. Doug's post, discussing the use of a power tap hub is a step in the right direction. It will be an interesting summer!

Curiosity must be good for you, that is how I found CruzBike and now I have a SILVIO and am trying to sell an ORCA!!

Depending upon the weather--it must be dry--I am intending to put the Silvio into this race

2010 Indy Fest HPRA Racing
http://www.recumbents.com/wisil/racing2010/indiana-brochure.htm

on Sunday the 25th.

After all, it is in my hometown and all of BROL says bring the Silvios out to play!!
Sadly 2 inches of rain is in the forecast.

Larry