Shorter Cranks on Giro 20

[Loomis]

I have just had a reasonable run on my Giro 20 after fitting shorter cranks and the difference is marked. The standard 170's always felt too long on a recumbent, though I never had a problem on my upright bikes in the past. I noticed that things were not well with unusual knee pains, despite heeding advice to spin more up the hills, rather than use a high gear and brute power. I went for 160mm. By far the cheapest triple was from Spa Cycles, and the only people that I could find that keep them in that size. I chose 28,38,48 and combined with XT 11,32 cassette gives (for me) perfect gearing and saving a bit of weight into the bargain. It was fun to dig Richards' book out again and work out all the possible gear combinations; something I had not done for years. Despite smaller crank circles with potentially less torque, I actually found that I could apply more efficient power to the cranks with my legs less bent. The whole experience felt much more relaxed and 'RIGHT'. Maybe taller people might not find such a problem with larger crank lengths, but at 5 foot 8 I have found this an excellent conversion.

[[XAP]Bob]

Do you find yourself spinning faster as a result of the shorter cranks? (i.e. are you using the same force, but over a greater angular speed)

Bob

[Loomis]

Can't say I noticed much difference in the one ride so far, although I do spin the cranks quite fast as normal. That is possibly one of the reasons I found the 170's such hard work.

[UpWrong]

My small frame Giro 20 came with 165mm cranks which I've found OK, though the same length gave me knee problems on a trike. On my trike I am using 150mm cranks from SJS. I've thought about shorter cranks on the Giro since they also reduce the height of the pedal under power, so a bit like having a lower bottom bracket which suits me better. My concern is whether starting become more difficult with the shorter push off you get because of the smaller diameter of the crank circle.

[Loomis]

Can't say I notice a problem with dropping down from 170-160, though the 150's might be a different story.

[Si]

there was a debate about this on CC not long ago with very divided opinion, can't remember what the outcome was.

Also, Mike Burrows wrote a bit about it in one of the mags. He tried using very short cranks (poss down to 140?) and found them to be extremely good on a 'bent IIRC.

Something I'm tempted to try once I get properly used to the 'bent...at least it would reduce heel overlap.

[zoxed]

...Also, Mike Burrows wrote a bit about it in one of the mags...

FYI there is a PDF of the artcile somewhere on the CTC site.

[zoxed]

...My concern is whether starting become more difficult with the shorter push off you get because of the smaller diameter of the crank circle.

When I first tried 140mm cranks on my Flux V220 I felt that problem: but when I later fitted them to my Kett, PDQ and Zox I did *not* have that problem.
Either a) it was because I was often towing a child trailer with the Flux (hence needed a bigger push), or b) I have got used to it !

[squeaker]

My concern is whether starting become more difficult with the shorter push off you get because of the smaller diameter of the crank circle.

Can't say I've noticed a problem (with 150 / 152s): in some ways they're easier 'cos your 'pedal on' foot is closer to the ground in the 'ready' position, but nothing I'd shout about....

[Rob Archer]

I've just switched to 160 cranks (Spa Cycles - excellent value!)on my Street Machine Gt. It took a few miles to get used to them but I don't notice now - even when I ride my upright bikes - all of which have 170s - then switch back. I definitely spin faster with them, and actually find hill climbing easier. On a longer hill (we have got a few in Norfolk!) I find I get into a 'rhythm' sooner. I'll be trying them out in Scotland later this year!

Rob