140 vs 145mm cranks for trials

[TonyMelton]

Has anyone used both 140 and 145mm cranks on a 20" trials uni?

I briefly rode a pair of Dotek 140mm cranks on my tuni (trials uni). The Doteks bent pretty easily, but felt OK for trials. Now I'm considering going bigger - to 145's. I suppose the 145s would give more leverage and stability but would hit the ground more easily during sharp turns. Is this trade-off an acceptable one? Opinions, please...

Right now I'm trying to decide whether to upgrade up current tuni to Profile 145's or get an entire new tuni in the form of a KH20 with its wonderous 140mm crankset.
My other consideration is weight - my upgraded tuni would be 5.5kg vs the 6.4kg of a KH20. [Thats a 2 pound difference for you non-metric folks.] Obviously lighter is better when hopping up on to benches, picnic tables, etc. Is there any way to easily reduce the weight of the KH20? ie which are the heaviest parts to target for upgrading to lighter components?


Any comments welcomed.


Tony

[Rowan]

G'day Tony,
I have no experience in trials Unicycles so my input is not very useful as far as crank lengths go. I plan to get 145mm cranks for my 24x3" to see how it feels, hopefully with your next order when you get the KH Unicycles. I was thinking about getting a Suzue hub to put in a 20" and get a wheel built to resurrect it, but after hearing your plans to upgrade from the Suzue I am not so sure. I read a comment earlier by Dan Heaton which may interest you. He said

I was able to ride on the shorter profile cranks for the first time and they are perfect. I always thought the 145mm length would be too long, but I think they are the best length for 20" trials.

To reduce weight... carbon fibre spokes? Polystyrene seat? Helium or Hydrogen in the tire? Go on a diet! Just kidding, I don't know how to reduce the weight without going to a planet with less gravity. My guess is that all the parts contribute to the weight and if you have strong material for everything it is bound to weigh more than a whimpy setup.

[evilewan]

5mm, diference is pretty small, id make a choice based on price and availability
which right now would be kh hub and 140mm
but qu-ax is showing some lovely preproduction splined hubs that come with 127mm cranks
right now i have a profile hub but the prospect of trading in for the qu-ax is very tempting if it ends up in production anytime soon.

[Mikefule]

145mm cranks are 3.5% longer than 140mm cranks, so they give 3.5% more leverage.

Of course, it's not quite that simple, because there are other variables like the rider's weight, leg length and so on.

I don't do trials, but I do MUni and some speed & distance work on a variety of wheel sizes, and I've tried cranks from 170mm down to 89mm. I cannot imagine 3.5% increase in leverage (and theoretically, about 3.5% reduction in speed) would be a detectable advantage (or even disadvantage) except in one or two very isolated cases.

So I guess it boils down to personal preference, unless you're very very good, and fine tuning to this tiny degree will matter to you. (I tend to work on the basis that around 10% is a significant change of crank length.)

[jagur]

Originally posted by TonyMelton
I suppose the 145s would give more leverage and stability but would hit the ground more easily during sharp turns. Is this trade-off an acceptable one?

not for me,i hated the 145's.i like to do tricks other than hopping around like a pogo stick and every time i made a slight turn SPANK! went a pedal on the ground.

i just bought a new trialz uni with the KH 140's and the 5mm differance is noticeable in tight turns.i think 145mm is to long so that being said,i'll take anything shorter.even if it is only 5mm shorter.

[TonyMelton]

Originally posted by Rowan
G'day Tony,
I was thinking about getting a Suzue hub to put in a 20" and get a wheel built to resurrect it, but after hearing your plans to upgrade from the Suzue I am not so sure.

My guess is that all the parts contribute to the weight and if you have strong material for everything it is bound to weigh more than a whimpy setup.

Rowan - the Suzue hubs I've got on my unicycles so far have been plenty strong enough for me. My only reason for upgrading my trials uni is that it is very difficult to get strong enough short square taper cranks for the sort of riding I do.

This weight reduction thing comes from my XC mountain biker days. MTBers love to ditch heavy components off their bikes and replace them with lighter ones (and boast about it to their riding mates!). I guess with a unicycle there is less choice in components and fewer of them! One thing I was considering was changing the standard wheelset for an Alex DX32 + Monty tyre. Though I don't really know if this will make any significant difference.


Tony

[andrew_carter]

I guess you could always use 145mm cranks with narrower pedals...then they wouldn't hit the ground as much.

Andrew

[jagur]

Originally posted by andrew_carter
I guess you could always use 145mm cranks with narrower pedals...then they wouldn't hit the ground as much.

i thought and did search for smaller pedals for the very same thought,but even that is pointless.145mm is to long for anything that involves turning sharply.

i dont have a pic but if you put a 145mm Profile crank arm in the 6 O'clock position (pointing at the ground) the pedal is a little less than 5 inches from the gound on a Monty wheel

[Sofa]

Originally posted by jagur


i dont have a pic but if you put a 145mm Profile crank arm in the 6 O'clock position (pointing at the ground) the pedal is a little less than 5 inches from the gound on a Monty wheel

I suppose in this day of 1 out of 3 people having a digital camera, someone wouldn't mind striking this pose for us not in the know?