Those with shortened cranks

DIscuss anything relating to non-standard cycles and their equipment.
Dave W
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Those with shortened cranks

Postby Dave W » 8 Mar 2017, 6:32pm

How short and why?

Also what effect if any do shortened cranks make on performance?

Grarea
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Re: Those with shortened cranks

Postby Grarea » 8 Mar 2017, 6:53pm

I am interested to hear this myself.
I have looked around and I think I will try shorter cranks.
There seems to be very little against it.

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[XAP]Bob
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Re: Those with shortened cranks

Postby [XAP]Bob » 8 Mar 2017, 7:08pm

I was idly thinking about shorter cranks during this evening's commute
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

landsurfer
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Re: Those with shortened cranks

Postby landsurfer » 8 Mar 2017, 7:13pm

I don't think it makes any actual difference but i'm sure I will be put right ...
There are intuitive effects ... moment arm over gear ratio, cadence etc.
But if you need to generate 200W to get up a hill the length of the cranks and ratio's will just change the way the 200W is applied ..... it's still 200W.
It's a bit like ready meals ..... cook it in the oven and it takes 30 mins @ 3kw / hr, in the micro wave 10 minutes at 9kw / hr, ...... its still 1.5KW to get your din dins cooked.
The Road Goes On Forever

fishfright
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Re: Those with shortened cranks

Postby fishfright » 8 Mar 2017, 8:54pm

I went from 175mm on my Trice Classic which felt too long from the off. I swapped them out for some very cheap 155mm's which had a really wide and slightly off centre ( wrong bb?) . I then fitted some 160mm Stronglights that feel fine.

On my VTX I specced the 152mm Lasco's and they were lovely from the off.

Do bear in mind im a rate short ar** at 5' 5"

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[XAP]Bob
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Re: Those with shortened cranks

Postby [XAP]Bob » 8 Mar 2017, 8:57pm

Landsurfer... there's some biomechanics to deal with in here. Lift a kilo next to your body, then do the same work a metre out...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

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531colin
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Re: Those with shortened cranks

Postby 531colin » 8 Mar 2017, 10:01pm

From an engineering point of view, 200W is 200W.
From a biological POV, a 2 foot long crank will use a different range of muscle contraction to a 2 inch crank.
I wonder if its pure chance that the "rise" of a stair is about the same as the length of a bike crank?
i can go up stairs 2 at a time or even 3 at a time, but I wouldn't like to try it all day.
I don't know how far apart ladder rungs are (and its cold and dark) but 1 rung at a time is OK, 2 rungs is a stretch.
The world of recumbents seems to have taken to short cranks just like the world of triathlons has taken to very steep seat tube angles; i can see the point of steep seat tube angles for getting into an aero position, (although i wonder if the benefits of aero really do outweigh the difficulties inherent in the transition from aero on the bike to running.)
if you are making a faired (streamlined) recumbent, then short cranks might fit easier into the fairing, but are the biomechanics of pedalling a recumbent really different to an upwrong? I know you can't "honk" (out of the saddle) but thats infrequent for me these days anyway. i'm a twiddler rather than a windmiller, but i sometimes find myself "forcing the gear" sitting on the back of the saddle, pulling back at the bottom and pushing forward over the top, and pulling at the hoods....if you don't do that on a recumbent, maybe thats a difference, and maybe its just that short cranks are easier to twiddle?

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[XAP]Bob
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Re: Those with shortened cranks

Postby [XAP]Bob » 8 Mar 2017, 10:41pm

I certainly pedal in circles (even if they are rough) I know because of the number of times I've talken cleats off shoes, or pulled plates off pedals.

Whether or not that would change with a shorter crank I have no idea.
Whether or not it's typical dynamics for ipwrong or 'bent I have no idea.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

UpWrong
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Re: Those with shortened cranks

Postby UpWrong » 9 Mar 2017, 12:09am

Why? usually to avoid knee pain by reducing the angle of bend. So if you're not having knee problems then why?

possibly because it can generate more power (same reasons as having short stroke, high rpm internal combustion engines - more fuel intake, better exhaust scavenging, higher efficiency)
better aerodynamics
reduction in leg lift push off height when starting

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NATURAL ANKLING
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Re: Those with shortened cranks

Postby NATURAL ANKLING » 9 Mar 2017, 1:05am

Hi,
[XAP]Bob wrote:I certainly pedal in circles (even if they are rough) I know because of the number of times I've talken cleats off shoes, or pulled plates off pedals.

Whether or not that would change with a shorter crank I have no idea.
Whether or not it's typical dynamics for ipwrong or 'bent I have no idea.

Tell us what size you use on a laid back?
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UpWrong
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Re: Those with shortened cranks

Postby UpWrong » 9 Mar 2017, 7:17am

I have 148 mm cranks on my Paseo, courtesy of Mike Burrows. ICE and HP-Velotechnic offer either 152 or 155mm crank options I think. Some people are comfortable with standard crands on low bottom bracket machines (e.g. long wheelbase) but beneft from short cranks on high bottom bracket machines.

EDIT: article by Mike Burrows on short cranks here, http://www.bhpc.org.uk/short-and-sweet-a-discussion-on-crank-length-by-mike-burrows.aspx
and http://www.bikefix.co.uk/right-crank-length
or http://www.zoxed.eu/short_cranks.html

BrownBear
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Re: Those with shortened cranks

Postby BrownBear » 9 Mar 2017, 10:14am

On a High Racer other advantages are minimising heel overlap and improving line of sight. For those reasons I got the shortest standard cranks (165) for my Corsa build; barely discernable from previous 175s on a Strada. If I get to do a similar build (my CA2 :-), I'd get some 175s cut down to 155, or maybe 150.

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[XAP]Bob
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Re: Those with shortened cranks

Postby [XAP]Bob » 9 Mar 2017, 10:25am

NATURAL ANKLING wrote:Hi,
[XAP]Bob wrote:I certainly pedal in circles (even if they are rough) I know because of the number of times I've talken cleats off shoes, or pulled plates off pedals.

Whether or not that would change with a shorter crank I have no idea.
Whether or not it's typical dynamics for ipwrong or 'bent I have no idea.

Tell us what size you use on a laid back?

That would be telling :)
They are all default - 170 IIRC
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

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squeaker
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Re: Those with shortened cranks

Postby squeaker » 9 Mar 2017, 10:28am

152 and 155mm on different machines. Knees much happier (but they also don't like big 'Q' factors). YMMV ;)

PS: WAW came with 147's but have changed to 155's for a bit more torque (bottom gear issues on road cranks with 74mm PCD inner: MTB cranks have too high a 'Q' factor for me, not to mention foot clearance inside the shell).
"42"

swscotland bentrider
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Re: Those with shortened cranks

Postby swscotland bentrider » 9 Mar 2017, 3:17pm

Using 165's for the first time on my Gaucho 28 high racer. Really haven't noticed much difference except improved heel clearance. I normally ride 170's on both my recumbent and conventional bikes.