# Benefits of shorter cranks



## grldtnr (8 Nov 2021)

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?


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## carpiste (8 Nov 2021)

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/


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## Scoosh (8 Nov 2021)

carpiste said:


> 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.


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## Tigerbiten (8 Nov 2021)

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 ............


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## dave r (8 Nov 2021)

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


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## grldtnr (8 Nov 2021)

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.


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## grldtnr (8 Nov 2021)

dave r said:


> 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.


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## FishFright (8 Nov 2021)

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.


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## dave r (8 Nov 2021)

grldtnr said:


> 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.


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## Milzy (8 Nov 2021)

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.


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## dave r (8 Nov 2021)

Milzy said:


> 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.





dave r said:


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


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## Sharky (8 Nov 2021)

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.


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## a.twiddler (8 Nov 2021)

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.


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## Tigerbiten (8 Nov 2021)

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 ............


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## zoxed (9 Nov 2021)

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.


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## GrandadPig (19 Nov 2021)

As a bit of a numpty, I have nothing to add to the replies. However, on my “new to me” Anthrotech trike I seem to suffer from heel strike, where the heels of my SPD shoes hit the tarmac. Reading the replies above, I guess shorter cranks would solve this issue?

thanks

Steve


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## zoxed (19 Nov 2021)

> suffer from heel strike, where the heels of my SPD shoes hit the tarmac. Reading the replies above, I guess shorter cranks would solve this issue?
Yes, short cranks would solve that. But also you may want to Google about midfoot cleat position, which may also fix it - I haven't tried it but some people swear by it!


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## a.twiddler (19 Nov 2021)

GrandadPig said:


> As a bit of a numpty, I have nothing to add to the replies. However, on my “new to me” Anthrotech trike I seem to suffer from heel strike, where the heels of my SPD shoes hit the tarmac. Reading the replies above, I guess shorter cranks would solve this issue?
> 
> thanks
> 
> Steve


Blimey! How big are your feet? From my recollection, at least for the models that I have seen photos of, the Anthrotec is fairly high off the ground, Being somewhat of a twinkletoes myself I don't have much in the way of heel strike problems even on my SWB front wheel. Up to now I haven't needed to use clips as my feet just seem to stay put. Do your heels make contact on level tarmac or is it just if the surface is uneven?


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## simongt (21 Nov 2021)

A lot of bikes, particularily MTBs, come with 175mm cranks as 'standard' regardless of the size of the frame. The percieved 'rule of thumb' was the shorter your legs, in theory, the shorter the cranks should be. However, ride what suits you best. For road bikes, I believe it's 170mm as 'standard', MTBs, 175mm to give more leverage on the uphill bits. The GLW at 1.63m. tall prefers 165mm. cranks on all her bikes if they are available.


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## Sharky (21 Nov 2021)

simongt said:


> 175mm to give more leverage


Crank length is just one variable in the gearing/leverage system on the bike.

Wheel size, chain wheel and sprockets as well as crank length make up the gearing. 
Sheldon Brown gives a good explanation.


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## Arellcat (22 Nov 2021)

Tigerbiten said:


> 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.
> If you suffer badly when hill climbing then shorter cranks will only make it worse.



As Sharky alluded to above, in respect of the entire drivetrain, these statements feel like they ought to be common sense, but they are not so much wrong as economical with the truth.

You can climb hills with whatever crank length you like, because you also select a gear ratio that matches your power output, and your cranks are, as a first approximation, designed for your leg length (and everyone else's leg length). This is why children's bikes come with short cranks and adult bikes come with long(er) cranks. Most adults are five or six feet tall which is why, with some allowance for greater or lesser bending of the legs because people can adapt, cranks have ended up at about 170mm.

You could fit a larger or smaller back wheel for climbing hills and it would have the same effect as changing gear. The difference between short and long cranks, once force at the pedal is accounted for through the drivetrain, is the rotational distance covered by your feet, and the amount of flexion incurred by your knees and hips. A smaller foot distance suits a higher cadence because short cranks reduce the linear travel of the mass of your legs, once your muscles are acclimatised to the higher cadence, otherwise your slow twitch fibres are firing too often and will tire. Power is torque times speed, so for the same power you can reduce the torque through your gearing and speed up your cadence, which is something every cyclist with gears will know about. But there is also a limit to what is comfortable and efficient to spin faster – foot distance coupled with leg length and leg mass; consider what 200mm cranks at 100rpm would feel like compared with 150mm at 100rpm. This is why shorter cranks geared correctly are better for you.


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## Tigerbiten (23 Nov 2021)

Arellcat said:


> As Sharky alluded to above, in respect of the entire drivetrain, these statements feel like they ought to be common sense, but they are not so much wrong as economical with the truth.
> 
> You can climb hills with whatever crank length you like, because you also select a gear ratio that matches your power output, and your cranks are, as a first approximation, designed for your leg length (and everyone else's leg length). This is why children's bikes come with short cranks and adult bikes come with long(er) cranks. Most adults are five or six feet tall which is why, with some allowance for greater or lesser bending of the legs because people can adapt, cranks have ended up at about 170mm.
> 
> You could fit a larger or smaller back wheel for climbing hills and it would have the same effect as changing gear. The difference between short and long cranks, once force at the pedal is accounted for through the drivetrain, is the rotational distance covered by your feet, and the amount of flexion incurred by your knees and hips. A smaller foot distance suits a higher cadence because short cranks reduce the linear travel of the mass of your legs, once your muscles are acclimatised to the higher cadence, otherwise your slow twitch fibres are firing too often and will tire. Power is torque times speed, so for the same power you can reduce the torque through your gearing and speed up your cadence, which is something every cyclist with gears will know about. But there is also a limit to what is comfortable and efficient to spin faster – foot distance coupled with leg length and leg mass; consider what 200mm cranks at 100rpm would feel like compared with 150mm at 100rpm. This is why shorter cranks geared correctly are better for you.


I agree.
If you don't run out of gears down then shorter cranks may well give you an overall bio-mechanical advantage.
The better you can spin, keep a light constant pressure on the pedal no matter what your cadence is, then the better they will suit that style of riding.
But it's more normal to run out of gears down on hills and you end up grinding your way up.
Now it's a question does the bio-mechanical advantage of shorter cranks on the flat outweigh the straight up mechanical disadvantage of them on the hills.
The 170-175 crank length was standardized in an era where you did run out of gears down.
Now with ultra low gears due to sub compact doubles/dinner plate sprockets you don't run out of gears as often on hills so I wonder if the next best thing for your bike will be shorter cranks ......... 

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


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## recumbentpanda (25 Nov 2021)

I’ve posted on this before in various boards, (and after this I’ll probably give up! 🤪) but:

To me, discussions of the leverage of short vs long cranks always miss two essential parts of the system: the tibia and the femur.

Try this thoughtexperiment (not for real kids, cos it might fall on you!): You have manoeuvred a heavy chest of drawers into place against a wall, but there are still a few inches to go. So you lie on your back on the floor with your feet against the base of it and shove. Which will be easier: starting with knees bent at an acute angle, or with your butt further out and knees just a few inches above the floor?

To save you taking the risk I have tried it myself and it is definitely the latter.

Coming back to bikes, the biggest effect of varying crank length is to vary the knee angle during the push phase of pedal rotation. (The precise effect will vary depending on your upper and lower leg dimensions.) This is why, despite many sages advising to the contrary, changing bottom end gearing to accommodate the supposed lesser leverage of shorter cranks is rarely necessary. While taken as a stand-alone component, a shorter crank certainly has less leverage, for a significant number of cyclists the short crank will increase the leverage of the leg bones and muscles to a greater extent than any loss at the crank itself.

This leads to the admittedly counter-intuitive situation that shortening the cranks increases leverage -in the system as a whole.

I have always changed my recumbents to 155 cranks. It has never required a change in low end gearing


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## grldtnr (25 Nov 2021)

recumbentpanda said:


> I’ve posted on this before in various boards, (and after this I’ll probably give up! 🤪) but:
> 
> To me, discussions of the leverage of short vs long cranks always miss two essential parts of the system: the tibia and the femur.
> 
> ...


So, what your saying is shorter cranks work best for recumbenteers, my lower limbs seem of a similar propertion , ( my shin bone, connected to my knee bone, connected to my thigh bone, connected to my hip bone,.......

Shorter cranks make in spin easier, therefore in theory, makes it easier to pedal, but for most efficient you should have longer cranks.

Having posted this thread ,it behoves me to change to shorter cranks, I'll get some engineer, and see how it is !


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## recumbentpanda (27 Nov 2021)

No need to engineer . . . If you are able to buy. BMX riders have long used cranks of a variety of lengths, and some BMX manufacturers make five bolt spider square taper cranks. Alternatively, if you don’t want to build up your own chain set, Sugino make very nice old school touring doubles and triples in a range of crank lengths.


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## grldtnr (27 Nov 2021)

recumbentpanda said:


> No need to engineer . . . If you are able to buy. BMX riders have long used cranks of a variety of lengths, and some BMX manufacturers make five bolt spider square taper cranks. Alternatively, if you don’t want to build up your own chain set, Sugino make very nice old school touring doubles and triples in a range of crank lengths.


Slight problem ,the AZUB is hollow/external bearings on it , further complicated by a single ring & 3 SPD hub 9 gear rear hub, not insurmountable, but costly to change if it isn't right for me.
But fortunately I have a spare recumbent, an Optima Rider trike ,same gearing config, but it does have a double up front, that does have taper axle tho', but I don't find it as comfortable as the AZUB.


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## Sharky (27 Nov 2021)

recumbentpanda said:


> BMX riders have long used cranks of a variety of lengths, and some BMX manufacturers make five bolt spider square taper cranks


SINZ expert cranks can be got for about £50 and are standard 110, square taper and as short as you want. I've got these on two of my bikes.


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## fatjel (29 Nov 2021)

When I first built the Bachetta Giro it had 175 crank arms because I bought them without checking the size. 
The first couple of months I rode it a lot and my knees did hurt. 
Reading stuff online seemed to suggest shorter crank arms would help so i bought a 165 crankset
It didn't feel different if I'm honest , 
My knee problem was caused , I think, by me pushing against the seat to help climbing
As I became more used to recumbenting it got better
I do think the shorter cranks gave my knees very slightly better clearance on the bars


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## grldtnr (29 Nov 2021)

Sharky said:


> SINZ expert cranks can be got for about £50 and are standard 110, square taper and as short as you want. I've got these on two of my bikes.


Might get a smaller ring to give a lower ratio, but I don't want all the fuss of another changer,the extra ring won't lower bottom gear by much, I will just grab the chain tube to flip it over, it's what I do with the Optima trike, is no bovver.


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## GrandadPig (29 Nov 2021)

a.twiddler said:


> Blimey! How big are your feet? From my recollection, at least for the models that I have seen photos of, the Anthrotec is fairly high off the ground, Being somewhat of a twinkletoes myself I don't have much in the way of heel strike problems even on my SWB front wheel. Up to now I haven't needed to use clips as my feet just seem to stay put. Do your heels make contact on level tarmac or is it just if the surface is uneven?


You know the okd saying about men with big feet 😂. it’s not true by the way😢

seriously, I am a standard uk size 8. But if I angle my foot vertically then I can hit the floor. My previous trike, also an Anthrotech did not do this. Commuted to work everyday summer and winter with no issues. Now thinking perhaps this one has longer cranks, I’ll measure them.


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## a.twiddler (29 Nov 2021)

grldtnr said:


> Might get a smaller ring to give a lower ratio, but I don't want all the fuss of another changer,the extra ring won't lower bottom gear by much, I will just grab the chain tube to flip it over, it's what I do with the Optima trike, is no bovver.


I went through a lot of faff after fitting a triple ring on my Lowrider. Fitting the rings was no problem but working out how to fix a front derailleur post without welding led to some head scratching. I managed to jury rig something up with a length of seat pin, an "L" shaped bracket, various nuts and bolts and a hose clip. It ain't pretty, but it works. I have probably been overthinking all this as there are chain tubes close at hand - I could probably have got by by just changing by hand. 

Now I have got the Sinner trike with a double chainwheel and no derailleur post It's the same thing -with a bit of practice I could probably just push and pull the chain tubes to move the chain about. The chain tubes would keep the hands fairly clean. Tskl! we're all just so spoiled with all our fancy levers to hand everywhere these days. 

My Linear came with a triple on the front and no front changer or even chain tubes. I suppose on encountering a big hill you were expected to heave the chain onto a suitable sprocket, wipe your hands on a passing kitten and proceed manfully on your way. I fitted a post and front changer eventually, as there's never a kitten about when you need one.


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## a.twiddler (29 Nov 2021)

GrandadPig said:


> You know the okd saying about men with big feet 😂. it’s not true by the way😢
> 
> seriously, I am a standard uk size 8. But if I angle my foot vertically then I can hit the floor. My previous trike, also an Anthrotech did not do this. Commuted to work everyday summer and winter with no issues. Now thinking perhaps this one has longer cranks, I’ll measure them.


I suppose that on reflection, it doesn't take much of a change in clearances before heels start making contact with things. Maybe a change in tyre make or size added to a difference in crank length could do it.


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