Crank length thoughts.

[mark aldridge]

It all comes down to price.
To get a crank re-drilled by a reputable company like Highpath is not cheap.
If you can do it yourself or cheap and take the risk of messing up the cranks it might be worth doing.
Alternatively source cheap short cranks or kiddy cranks on ebay and sell them on if you don't get on with them.
Short cranks are well worth having but as with everything cycling you either get on with them or you don't.
155mm is a good starting point and not too big a jump from a standard 175/170mm crank but lots of recumbent/velomobile riders use 140mm with no problems
Good luck

[Marc]

Is it feasible to just re-drill cranks and cut threads to suit on old or cheap cranksets, before making a buying decision ,and replacing longer cranks.
I am happy ,at the moment with standard set up, but I may find an advantage to go shorter.

It depends on the dimensions of the cranks in question. If there is enough material around the new pedal thread, yes.

I had shortened a bunch of crank sets to 155mm, 145mm and 143mm. Since a member of the German forum does a very good job drilling new threads in cranks and does it for €35 + shipping, I just send them to him.

One of the more affordable 155mm crank sets with triple chain rings (€79 + shipping) for square taper bottom brackets is sold by Icletta (German ICE Trikes Importer): https://icletta.com/en/products/crankse ... 9266504992

[UpWrong]

Spa sell the XD-2 with 160mm cranks for £30. As a triple it's for 7/8/9 speed, but not higher. As a double or as converted super-compact double you can use spacers to make it 10 speed.

[Jdsk]

Many people who ride bikes will be happy about adjusting seats and bars but baulk at changing cranks.

Crank shorteners could be used to test whether shorter cranks are better. I fit them for children on the back of the tandems: one current pair give a 35 mm reduction and the other a choice of 40 or 80 mm. Continuously variable designs are available but I've never played with them.

Of course they do place the pedals slightly further outboard.

Jonathan

[freeflow]

I recently switched from 175mm cranks to 160 mm cranks and I'm very happy with the new setup.

[rjb]

Lots of good advice here if gong down the DIY route using children pedals. 1/2" thread.
"Extra short cranks - bodger's delight - Cycling UK Forum" viewtopic.php?t=130539

[mark aldridge]

Further thought.

Unicycle cranks come in a variety of lengths and I have seen them used on lash ups. The quality is not of the best but they are super strong.

I got my new Milan yesterday (thanks Nick) and in a box of spares were these cranks with 120/140/160mm holes. they are a meaty pair of cranks but give you the opportunity to experiment. i think he said he got them from Velomobiel.nl.

A question what effect would it have if you had different crank lengths on each side. It would look weird a bit like out of sync tandem cranks.

[Marc]

A question what effect would it have if you had different crank lengths on each side. It would look weird a bit like out of sync tandem cranks.

If you have more than the "usual" leg length difference (since birth, or due to an accident, etc), having slightly different cranks length that fit exactly your legs will reduce rocking of your hips with every pedal revolution. My guess, it would be significant if your legs length is more than 1cm (10mm) different.

[Marc]

There are some good articles available that focus on crank length, like this one:
https://www.applemanbicycles.com/resour ... ank-length

Crank length is super weird.
For some riders, crank length is the key to a good fit—while others seem unfazed by it.
Shorter cranks may enable pain free riding for one rider—while it causes pain for another.
Crank length is confusing.
It’s an emotional and triggering subject for many, so this article will try to be gentle for those with tightly held beliefs while also enlightening those whom are interested in a fresh take.
Let’s take a look at the mystical and magical creature of crank length.

Here an online 'Recumbent Crank Length Calculator':
http://www.recumbents.com/wisil/misc/crank_angle.asp

These scientific papers delve into crank length vs performance:

Determinants of maximal cycling power: Crank length, pedaling rate and pedal speed:
https://www.researchgate.net/publicatio ... edal_speed

The effect of bicycle crank-length variation upon power performance:
https://www.researchgate.net/publicatio ... erformance

And Saukki already made a video:

[hercule]

How would you fit chainrings to unicycle cranks? The ISIS standard ones on my uni just look like two left hand cranks (though they do have mirrored pedal threading). If you do have an answer I can recommend unicycle.com for variety and service.

[[XAP]Bob]

Use a schlumpf mountain drive - both cranks are just square taper

It's a fairly expensive option though.

[admin]

My 2p-worth:

On an upright bike you can happily almost straighten your legs at the bottom of the pedal stroke, so you can get a big range of foot movement. Saddle height is usually set so you can just pedal with your heels, maximising leg extension and pedal stroke.

However you don't want to straighten your knee so much when your leg is mostly horizontal, as you need to support the leg against gravity. Worst-case your knees might go "over center" at full leg extension and lock. This means that you need to have your hips closer to the crank axle, rather like having your saddle too low on an upright.

So if you rode an upright bike with the saddle too low, would it be easier with shorter cranks? I think so, but it might be just down to what your muscles are used to. My Windcheetah still has 170mm cranks, like my upright bikes, but this does feel a bit long.