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 Post subject: Crank arm length
PostPosted: Tue Apr 09, 2013 10:32 pm 
Old School Hero
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Joined: Tue Jan 08, 2013 8:47 pm
Posts: 199
Location: Barrrkshire
What is the reason behind different length crank arms 170, 175, 180mm etc
Was told a long time ago longer legs suit longer arms, is that all there is to it?

Enlighten me please :oops:


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 Post subject: Re: Crank arm length
PostPosted: Tue Apr 09, 2013 11:07 pm 
Old School Grand Master
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Joined: Fri May 01, 2009 7:11 pm
Posts: 8479
Location: Fircombe.
You've got it!


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 Post subject: Re: Crank arm length
PostPosted: Tue Apr 09, 2013 11:12 pm 
Old School Grand Master
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Joined: Sun Aug 21, 2011 11:57 pm
Posts: 4074
Location: Antwerp, Belgium
There's also the torque vs RPM thing to think about.

Longer arms will give you more leverage, increasing your torque. Very useful for MTB-ing. Shorter arms will be more suited to a higher cadence, which is ideal for riding on the road or on rollers.


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 Post subject: Re: Crank arm length
PostPosted: Wed Apr 10, 2013 7:46 am 
Old School Hero
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Joined: Tue Jan 08, 2013 8:47 pm
Posts: 199
Location: Barrrkshire
Due to my freakishly long legs I will be heading for some 180mm just seen then

Thanks


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 Post subject: Re: Crank arm length
PostPosted: Wed Apr 10, 2013 8:18 am 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 8212
Location: New Forest, UK
Raging_Bulls wrote:
There's also the torque vs RPM thing to think about.

Longer arms will give you more leverage, increasing your torque. Very useful for MTB-ing. Shorter arms will be more suited to a higher cadence, which is ideal for riding on the road or on rollers.


This argument is always trotted out - however there is also chainring size to consider. If you have difficulty turning the crank then fit a smaller chainring!
The torque is only at the BB shaft - in reality what matters is the tirque at the rear hub, which is affected by the gears.

You need the right length for your legs - too long and you over-articulate the knee, which is inefficient and also increases the risk of injury. Too short is inefficient also.


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 Post subject: Re: Crank arm length
PostPosted: Wed Apr 10, 2013 8:32 am 
Old School Grand Master
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Joined: Tue Oct 19, 2010 9:55 am
Posts: 7058
Location: The land of Lea & Perrins
If in doubt, get 175s ;)


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 Post subject: Re: Crank arm length
PostPosted: Wed Apr 10, 2013 11:06 am 
BoTM Winner / Gold Trader / Rider
BoTM Winner / Gold Trader / Rider
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Joined: Tue Oct 14, 2008 7:37 pm
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Location: Groningen, Netherlands
Barneyballbags wrote:
If in doubt, get 175s ;)


Or 177,5! :wink:


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 Post subject: Re: Crank arm length
PostPosted: Wed Apr 10, 2013 10:34 pm 
retrobike rider
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Joined: Tue Mar 17, 2009 3:55 pm
Posts: 4309
Location: In trubble'fsumthin r'uther....North Warwickshire
i go from 165 on a road bike to 175 on some mtbs........with plenty in the middle.......remember its not what sits between the legs that matters, its whats inside them.......just get out and ride!..... :wink: :D


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 Post subject: Re: Crank arm length
PostPosted: Wed Apr 10, 2013 11:10 pm 
Old School Grand Master
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Joined: Sun Aug 21, 2011 11:57 pm
Posts: 4074
Location: Antwerp, Belgium
feetabix wrote:
remember its not what sits between the legs that matters


That's what she said.




:lol:


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 Post subject: Re: Crank arm length
PostPosted: Thu Apr 11, 2013 11:56 am 
Retro Guru
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Joined: Mon Feb 07, 2011 1:14 am
Posts: 1871
Location: Kuranda DH circa 1991
180s are bloody hard to turn over. even very tall people struggle. 175s are great for MTB. 170s if you are short or female. 165s or so if you are a downhiller on a long travel bike and want to avoid pedal strikes.


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