What's Your Crank Length?

[thebean]

I am really curious if anyone is experimenting with different crank lengths on the Silvio. For six years I have been running 150s on my Ti Aero, and 155s on my other recumbents. Then enters the Silvio with the 170 cranks and they have bee working really well! Maria apparently runs 172.2s, which I find fascinating. My physical therapist have even seen benefit with shorter cranks on his DF bike.

 

[Andrew 1973]

172.5

I am fairly certain mine are that long. I appreciate the extra leverage which allows me to climb quickly at a lower cadence.

 

[Eric Winn]

The Quest has 155mm cranks.

The Quest has 155mm cranks. Vendetta 170mm. I'm finding the 170 crank a little more comfortable.

-Eric

 

[super slim]

I had 175 mm cranks in my Silvio, and when I bought the Quest V1 with its 155 mm crank, I noticed a lot less knee problems at the end of a 100 km ride. I then moved the BB and cranks from the Quest to the Silvio, and bought 153 mm cranks with MTB sprockets from bikesmithdesigns for the Quest. The shorter cranks reduce the amount of knee rotation, and allows the handlebars to move 20mm further away from me.

SS

 

[thebean]

I am wondering if Maria and

I am wondering if Maria and Jim have done any experimenting and if they can add any comments as far as efficiency gain.

 

[John Tolhurst]

We don't see difference in

We don't see difference in efficiency on our bikes from different cranks. But if you had a long unsupported boom, then yes, a shorter crank will reduce the flex and power loss.

 

[Alan Dolbeer]

Crank Length

http://www.powercranks.com/cld.html

As in the link above, there seems to be some support lately for cyclists using shorter crank arm lengths (than the standard of approx 170mm to 175mm) When buying the Silvio, I had some reservations about the 155mm crank length that the bike came with, having never used a crank shorter than 170mm. But after nearly two years on the Silvio, I am happy to be using the shorter crank length. As SS mentioned above, it can allow better handlebar adjustment vs leg interference, not mention better aero dynamics with the legs presenting a smaller profile to the passing air. I recently bought a mountain bike and am considering shorter cranks for it as well (mtb came with 175mm cranks).
I am surprised to read in this thread that Maria's RAAM bike is equipped with 172mm cranks. If this is a fact, I would be interested to hear the reasoning for using the longer crank arms.

 

[John Tolhurst]

yes , it is a fact that Maria

yes , it is a fact that Maria uses 172.5 or 175. She has always used this and has a relatively slow cadence. We have looked at it over and over and tried to encourage a higher cadence. But what are you going to do, she's got records in 12, 24 hour, 100, 200 mile events. You want to twist her arm to use shorter cranks? You'd be a braver man than me.

 

[thebean]

Thanks everyone for you

Thanks everyone for you input! John, that is hilarious that Maria is so stubborn! But who can argue with her records!

I will plan on experimenting when I get the new Silvio. Knee clearance has been tight for me, so the 155s I have might work nicely.

 

[Alan Dolbeer]

Crank length

John,

Far be it from me to tell any rider what crank arm length they should use..., much less Maria. Thank you for confirming Maria's crank length and history of always using a more traditional longer armed crank. Will Cruzbike continue to spec the shorter 155mm cranks for full build bikes like the Quest and Silvio? I personally am satisfied with the shorter 155mm length, though I am curious about E-rings. The Ultegra triple on my Silvio has rings which seem to integrate with the spider in such a way that I figured a switch to E-rings might require a new crank.

 

[John Tolhurst]

There is sense in keeping

There is sense in keeping crank length proportional to leg lengths. Mine are similar to Maria in length, (but less generally appealing otherwise). So I can usually ride her race bikes without much messing around. But I am happier on 170 or 165. I guess there is not much in it really.

I'm happy with the spec of 155 on Quest and Sofrider. I like to encourage a higher cadence, it makes handling a little bit easier. (Over time we have pretty much killed off the riding handling question by making many many slight adjustments.)

 

[Alan Dolbeer]

Thanks John.
I am bicycle

Thanks John.

I am bicycle poor at the moment (just bought a really nice mountain bike) but intend to buy a Quest at some point in the future. Then will figure out a way to add fenders as it would be my all weather/touring bike.

 

[mickjordan]

Varying crank length

The received wisdom seems to be that you should run shorter cranks on a 'bent compared to a DF bike, because it helps you spin at a higher cadence, which is supposed to be a good thing. However, as we know, some people are spinners and some are mashers and it's not at all easy to switch. I think that if you have a knee problem it is probably important to fine tune your setup to minimize discomfort but otherwise I think you can ride varying crank lengths without issue.

For example, I ran 175 on my Trek 5200, then 172.5 on my Waterford, on the advice of my bike fitter, then 175 on the Silvio, 160 on my Bacchetta Aero and 165 on my Lightning P38. I can ride all of these bikes long distances without (knee) problems and I'm don't think I am even aware of the difference when on the bike.

Alan is correct about not being able to use (E) Rotor rings with the Ultegra 6700 on a 'bent owing to the shape of the spider. A 6600 works but they are not easily found now. Otherwise you need to go to a custom crank. And if you have the Ultegra you will also need a new bottom bracket. I use da Vinci cranks and Rotor rings on my Aero and a 6600 (that I originally bought for my Silvio) on the P38.

 

[Jake]

Experiment

I'm still experimenting with different crank lengths - I've ridden 155s on both my cruzbike conversion and Bacchetta Giro for the past 6 months. Noticably less knee strain and easier to maintain a higher cadence. I've just switched back to 172.5 on the Giro just because it's a much better crankset - I'll see how I get on.

Things to note:

Shorter cranks require the seat to be moved back or the bottom bracket to be moved forward. Thus for a 20mm change in crank length the bottom bracket can be moved forward 20 millimeters. Thus at the opposite end of the peddle cycle (it's most bent position), the knee will be 40mm further forward (relative to the hip) - this is what causes the reduction in knee pain.

Shorter cranks require a corresponding lower gear to be selected, ie if moving from 170mm to 155mm you'll need to change your gearing by approx 10%. Generally this just means you'll be peddling in 1 gear lower than normal most of the time, but you may wish to switch your granny ring to something 10% smaller, or you'll find that you won't be able to get up the steepest hill that you could with long cranks.

Take time to evaluate it. It's sure to feel wierd at first, but give it a good tryout ( but hold on to your old cranks for a while!).



130 BCD cranks are hard to come by, Origin 8 cheapies are available here ( I can't source them in black though) : http://www.amazon.com/gp/product/B002I7ICC6/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1

Jake