Benefits of shorter cranks

[grldtnr]

Just pondering, before a ordered my current Azub Tri-tris, I did consider speccing shorter cranks, but the option wasn't available with the gearing set up I chose, a single chainring via a Sturmey 3 spd/ deralliuer set up.
I have always ridden standard cranks on all my other bikes, but read something about shorter cranks for longer people being more efficient, strangely I thought it should be the other way round?
Anyway, rather than go through the expense of getting new cranks, I thought I might have my current chainset shortened by an engineer friend, there's kiddy crank shorteners ,but I rather not go that route, as it would effectively increase the crank width.
Are there benefits to say going from the standard 170mm to something like 140/150 mm?

 

[carpiste]

It would appear there are benefits to shorter cranks but it`s a minefield. Longer cranks ( more leverage) just seem to mean more wear and tear on the joints so the manufacturers seem to have come up with a "optimum" or standard length to suit all. They don`t suit everyone but the costs to get it perfect for individual riders would be prohibitive.
The article below is well worth a look.
https://www.bikeradar.com/advice/sizing-and-fit/what-is-the-best-crank-length-for-cycling/

 

[Scoosh]

Longer cranks ( more leverage) just seem to mean more wear and tear on the joints ...

I know quite a few 'bent riders go for shorter cranks, for exactly this reason – to reduce the risk of overloading their knees.
On an upright bike, the maximum force that can be applied to the cranks is (slightly simplified) the rider's maximum weight when standing on the pedals, plus a bit more when pulling the bars up slightly. This protects the knees.
On a 'bent, the rider is 'fixed' in the seat, so can apply as much force as the legs can manage – but the rider can't 'rise up' to prevent damage to the knees.

This is why 'bent riders all [need to] learn to spin, rather than grind away.

 

[Tigerbiten]

Longer cranks give better leverage for hill climbing with a slow cadence.
Shorter cranks makes it easier to spin along on the flat with high cadence.

So ask yourself how often do I run out of gears down and how badly do I suffer when I do.
If you suffer badly when hill climbing then shorter cranks will only make it worse.
But if you have enough silly low gears that you can climb most/all hills easily then you may well benefit from shorter cranks.

Luck ............

 

[Deleted member 1258]

On the fixed, with 165 cranks and 42 x 17 gearing I find the shorter cranks make descents easier but make no difference elsewhere.

 

[grldtnr]

It's common practice in recumbent scene to fit smaller cranks, it's said to be beneficial, but I am sceptical, if I would find it any easier, having ridden for 50 yrs on standard sized cranks, except when I was a youngster, many ,many years ago!
It's just I can't seem to maintain a comfortable cadence with my current trike gearing. It could be the ratios, normal ratios on the upwrongs is a step and half, or 2 teeth , with a compact triple, 46 -38 - 28, so not under or over geared, yet to figure out the recumbent, but that's without counting a 9 SPD , it's complicated by the SA 3 HUB .
I feel I could do with a lower low,but so far have climbed everything I have come across, I might yet fit a 2nd ring.

 

[grldtnr]

On the fixed, with 165 cranks ans 42 x 17 gearing I find the shorter cranks make descents easier but make no difference elsewhere.

Can you get a fixed wheel recumbent?surely an interesting ride!
Used to ride fixie 17-16 on a flip hub 48 tooth ring, without problems on the 172 mm crank..
I have grown older, but maybe not wiser, still have a fixie in the turbo.

 

[FishFright]

My uprights have a range of lengths with out any issues but on my recumbents I can only use fairly short, 152 - 155, cranks without having knee problems.
In addition it feels a more 'natural' pedalling action with the shorter cranks.

 

[Deleted member 1258]

Can you get a fixed wheel recumbent?surely an interesting ride!
Used to ride fixie 17-16 on a flip hub 48 tooth ring, without problems on the 172 mm crank..
I have grown older, but maybe not wiser, still have a fixie in the turbo.

I've no idea on the recumbent, I suspect a fixed wheel would cause problems starting off and on climbs. On an upright I'm a short arse, 5 foot 6 inch tall with a 29 inch inside leg, which might explain why the shorter crank suits me on the fixed, I've got a 170 crank on my geared bike.

 

[Milzy]

Only benefit is to have the right length for your height. Small frames usually have 170 Medium 172.5 Large 175. Though people riding on the track may like a bit shorter so they don’t catch the boards leaning over.

 

[Deleted member 1258]

Only benefit is to have the right length for your height. Small frames usually have 170 Medium 172.5 Large 175. Though people riding on the track may like a bit shorter so they don’t catch the boards leaning over.

On the fixed, with 165 cranks and 42 x 17 gearing I find the shorter cranks make descents easier but make no difference elsewhere.

 

[Sharky]

If you have square taper cranks, have a search for Sinz expert cranks. They are standard 110 bcd and do a huge range of lengths. I have two pairs (145 & 150) on normal bikes.

 

[a.twiddler]

I haven't had issues with crank length despite being on the wrong side of 5'6". Mostly, I just rode wot I got. A lot of my cycling was done on a bike with 165 cranks because that's what came with my Stronglight chainset. In between I've had mountain bikes with 175 cranks which were noticeably different until I got used to them, then generally 170mm. When I got into recumbents last year my Linear had 170mm cranks and I did wonder about trying different lengths but never got round to it because it didn't cause any issues. In fact I felt that it might have given me an advantage on starting off with that extra leverage on the first pedal stroke.

On riding my upright bike I found that I was actually spinning more than I used to and had developed this despite the Linear's relatively long cranks. Earlier this year I bought a Dawes Low Rider which turned out to be just that tiny bit long for me. I fitted a chain set with 150mm cranks so that I could reach the pedals and couldn't say that I have noticed any real difference. It is so different from the Linear LWB with it being a SWB with a higher bottom bracket that any difference due to crank length is probably insignificant.

Just bought a recumbent Trike with 170mm cranks. I am well within its range of adjustment so unless there are any major crank related issues I will probably stick with them. I have always had a fairly slow cadence despite the recent increase in spinning ability. Perhaps for a person who is a real spinner shorter cranks could prove beneficial. The only way to find out is to try some.

 

[Tigerbiten]

Don't fall for the fallacy that "to spin" you need an ultra high cadence.
For me spinning equals a light pressure between my feet and the pedals no matter my cadence.
So I can spin just as easily going uphill at 60 rpm as I can on the flat at 80 rpm simply because the pressure on the pedals is the same.
What varies is my power output as I need to drop it on hills to stop me overheating.
It's only if I run out of gears down on +25% hills that I'll up the pressure on the pedals and start to grind my way up.
So don't worry about your cadence, spin along at what feels natural while trying to keep a light constant pedal pressure.

Luck ............

 

[zoxed]

Personal I ride only 140 or 155 cranks and feel they are better for my knees.
YMMV!
What is definite is that short cranks can help fix clearance issues, eg heel to wheel on SWB, heel to ground on a low BB trike and heel to derailleur (my case!) on a lowracer.
Also they allow for a small front end for a fairing.