unsatisfied crank length rant

there is nothing available between 110mm and 125mm…POOPY!

I’d like to see more options between 125 and 150. I really like the black steel BE cranks and wish they at least made 140’s.

Theres always custom ones avialable :slight_smile:

i did a search a while ago and turned up some guy who made custom cranks for bmx riders, can’t remember the url though.

realy though jagur for someone as fussy as you, getting stuff custom made is prety much your only option sometimes

i’m sure i have seem 112mm cranks somewhere maybe rogers site?

fussy? just cause i put my thoughts and purshases out in a public forum doesnt mean im fussy.

don’t take it like that, i didn’t say fussy was a bad thing.
i’m fussy about cranks too, to the extent that i’m considering selling my profile hub and replacing it with a qu-ax hub.

fussy is good, it gets you what you want, not second best.
i was on the verge of getting custom cranks for my trials uni not long ago.

evilewan,what your e-mail address? do you use your unicyclist,com email?

I’ve ridden a 24 with 89, 102, 110, 125, 127, and 150mm cranks, a 26 with 170 and 150mm cranks, a 28 with 102, 110 and 125 mm cranks, a 20 on 102, 110 and 125mm cranks, and a Coker with 125 and 150mm cranks.

For a medium sized unicycle (say 24 - 28 inch wheel):

In the mid range (say about 110mm - 125mm) longer cranks equal less speed but more control.

In the long range (150mm or more), longer cranks give more ‘grunt’ up and down hills, but at a sacrifice of smoothness.

In the short range (102mm or less) very short cranks can allow very high speeds but with much reduced control.

So, Jagur is talking about the mid range - he asks, why is there nothing between 125mm and 110mm?

125 - 110 = 15
15/125 = 0.12, meaning that the 110s will be about 12% faster.

However, there are lots of other variables, so you can’t say that the difference will be exactly 12%.

A typical brisk pace on a unicycle? Somewhere either side of 10mph? So changing from 125s to 110s will make about 1mph difference. Choose a crank length in between, and you’d be splitting that difference. Maybe 117mm cranks would be 0.5mph faster than 125s.

I used to ride big distances on a bicycle, and set it up so that the gears were as near to 10% apart as I could achieve. Then I found I usually skipped a gear when changing. Racing bicyclists, of course, care a lot more about the exact gear ratio.

I guess you’d have to be unicycling at a very high level indeed for you to notice any clear advantage from a 5% change in crank length in the mid range.

thanx Mike,your rants are the best :slight_smile:

in this case im not going for speed,im going for torque. the 110’s on my 20" freestyle are good but when i hard idle,like when i go for a Koosh Koosh it feels like my knee cap is going to pop off under the pressure.by putting the my 125’s back on my knees are happy but durring a tight turn,my pedal scuff the ground.

i feel that 117’s would be just the hair i’d like to split.

A higher volume tyre might also provide some relief; what you got on there now?


i took the 1.95 hookwerm off and put on a 2.1 Primo just for that thought.So i cant go any bigger if i wanted to,plus theres only 3mm of clearance above the tyre now.(Sem Long Neck)

First, to illustrate a principle with easy maths:

If you double the length of your cranks, you double the available torque, but halve the theoretical speed.

(In real life, of course, doubling the length is unlikely.)

If you add 1/3 to the length of your cranks, you get 1/3 more torque, but you lose 1/4 of your speed.

(Add 1 to 3 to get 4, your adding a third; take 1 from 4 to get 3 and you’re subtracting a quarter.)

Now back to 125s and 110s. The difference is 15mm. If you change from 110s to 125s then:

15mm = 13.6% of 110 so you get 13.6% more torque.

Conversely, 15mm = 12% of 125, so you lose 12% of your speed.

So, I was thinking in terms of speed, and saying that 'splitting the difference’would make around 6% difference. Jagur was thinking of torque, so 'splitting the difference’would make a difference of half of 13.6, or 6.8%.

There are loads of other variables. Jagur mentioned ground clearance. Will 7.5mm make a real difference? I doubt it, except in very special circumstances. (I enjoy trying to ground my pedals on my 20 with 110s - I can do it sometimes and stay on.)

I bet you could save the 7.5mm with a different design of pedal.

Adj crank lengths

Adjustable cranks can be had for a price at:

Click on the Adj crank lengths at the left margin.

The guy will even take the spider off according to a friend of mine.