CRANK LENGTH SELECTION

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CRANK LENGTH SELECTION

Postby mauriceandgrandad » 20 Jun 2011, 09:37

Here is a starting point for crank length selection.

Rider Inseam /Crank Arm Length
20" 140 mm
21" 145 mm
22" 150 mm
23" 155 mm
24" 160 mm
25" 162 mm
26" 166 mm
27" 171 mm
28" 175 mm
29" 177 mm
30" 180 mm
31" 182 mm
32" 185 mm
33" 185 mm
34" + 190 mm

One size up or down may be appropriate.

For the very young Sinz do cranksets in 5mm increments down to 115mm.
Last edited by mauriceandgrandad on 24 Jun 2011, 21:23, edited 1 time in total.
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Re: CRANK LENGTH SELECTION

Postby krautrocks » 20 Jun 2011, 12:35

This and the "frame size-thread" are likely two of the most valuable threads ever @ BMX Talk.

If bloody n00bs, oldfarts & parents would actually read and use the info provided, a lot would change for the better on here.


Well done Ian! :lol:
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Re: CRANK LENGTH SELECTION

Postby grinna » 24 Jun 2011, 19:58

SINZ GO DOWN TO 115MM
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Re: CRANK LENGTH SELECTION

Postby mauriceandgrandad » 24 Jun 2011, 21:21

grinna wrote:SINZ GO DOWN TO 115MM


Even better, thanks! I've edited it.
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Re: CRANK LENGTH SELECTION

Postby r2d2 » 12 Jul 2011, 23:31

Gr8 start Ian, thanks!! Looks like Profile better get Billy a signature limited edition 200mm set done then :wink:
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Re: CRANK LENGTH SELECTION

Postby mauriceandgrandad » 13 Jul 2011, 15:43

r2d2 wrote:Gr8 start Ian, thanks!! Looks like Profile better get Billy a signature limited edition 200mm set done then :wink:


And a 52T chainring?
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Re: CRANK LENGTH SELECTION

Postby Smartihawk » 19 Feb 2012, 22:10

Guidelines don't always work out in real life though, that's the problem.

I'm 5"8.75, (98kg) with a 30" leg and a 170mm crank is just about right for me. I think 175mm is 'the norm' isn't it? It's what you get on stock bikes off the shelf isn't it?

I remember once I had a custom 26" Supercross big BMX built for me with 180mm Profile cranks, and I almost couldn't ride it. I was blowing windmills with my legs, almost chewing on my knees. The circle created by a 180mm crank going round, is way bigger than a circle created by a 170mm crank going round.... You got to remember that each mm gained is gained on BOTH sides of the cranks. Your feet will be spaced apart an extra 2cm if you rode a 180mm crank instead of a 170mm one.

Also...... LONGER CRANKS = MORE ACCELERATION . It might be ever so slight, but still, a longer crank arm provides more leverage on the BB fulcrum, and in effect is 'easier' to fire the back wheel up.
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Re: CRANK LENGTH SELECTION

Postby toddgreen » 28 Feb 2012, 13:01

Would shorter cranks be better for clipped in riders?
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Re: CRANK LENGTH SELECTION

Postby ManchesterTrev » 10 Jan 2013, 20:14

According to the Pro BMX Skills Book, use the Zinn method ( Inseam in mm x 0.216 ) then add 5mm to enhance acceleration......... this has me using 170mm cranks. Im 5'8" with short legs, so Im going with that!
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Re: CRANK LENGTH SELECTION

Postby EllyGant » 12 Jul 2013, 11:07

Hi

I have found this really interesting. My son is on 155mm cranks and by these sums should be 165mm with 170mm (with the added 5mm for accelaration) - he's 8 but has really long legs. I was thinking of going up to 160mm, so he's not going up too much, but other parents reckon he should be fine on 155mm.
At home the only bike of our he doesn't like riding is my identiti with 180mm cranks, but he can ride it fine. His fave is the Onza which has 160mm cranks.

Is 160mm too long, will it make his riding go 'choppy'???
:shock:
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Re: CRANK LENGTH SELECTION

Postby Liifebehindbars » 30 Nov 2013, 21:34

Hi, I'm looking to build a custom bike up and I'm looking at cranks, just verifying what crank length I should be riding? (I'm 1.50cm)
Cheers :D
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