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 Post subject: Re:
PostPosted: Sun Nov 19, 2017 12:28 pm 
Retro Guru

Joined: Sat Oct 10, 2009 12:31 pm
Posts: 253
165mm was also the traditional length for British bikes with cottered cranks, or 6 1/2" was (165.1mm).


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 Post subject: Re:
PostPosted: Mon Nov 20, 2017 12:49 am 
Retro Guru
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Joined: Thu May 20, 2010 9:03 am
Posts: 2149
Location: Bodmin,Cornwall.
I am of the ride any length you get given but I've just been given a set of TA's nice cranks.The left is 170 the right 165.Just not quite brave enough to try it.


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PostPosted: Mon Nov 20, 2017 10:15 am 
Old School Grand Master

Joined: Mon Feb 11, 2008 9:42 am
Posts: 3116
legrandefromage wrote:
I have an inside leg of 33 inches

What should I expect?
Once you are used to it (5 mins) nothing.
I'm running a 32" inside leg at the moment, no opportunity to upgrade at all......

ScillySuffolk wrote:
Crank length, like Q-factor, falls within the gamut of self-selectable criteria that you are (unconsciously) capable of adjusting for: ie ride what you have/like/want and ignore anyone who tells you otherwise.
Not quite true. Too long can give long term issues with knee damage.
You set saddle height to BDC, so you need enough knee/ankle/hip motion to get over TDC, too long cranks will encroach on that. And it's (usually) the knee that goes.

You can go as short as you want, until it feels weird!

I'm currently just starting the process of moving to shorter cranks across the board. 165 was massively more comfortable than 170 on the road bike, and still not sure what i should do with regards the MTBs and CX bikes..... shorter is pretty much a given, just how much!


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PostPosted: Mon Nov 20, 2017 11:10 am 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 9208
Location: New Forest, UK
Absolutely agree with mattr - I once did a tour on 175s (usually ride 170) and I had knee pain all the time. I recently swapped from 175 on my singlespeed to 170 and it's amazing how much smoother my pedalling is.

Match crank length to suit leg length.


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 Post subject: Re:
PostPosted: Mon Nov 20, 2017 12:58 pm 
Retro Guru

Joined: Wed Dec 10, 2008 9:19 am
Posts: 2384
Location: Sheffield, top city
I can tell the difference between 170/172.5/175 .... not had 165's since I had a cottered chainset in the 80's

if I lived in a flat area, I'd go for shorter cranks and rev like hell. I currently use 172.5 on all bikes except the pub clunker
My weakness is hills and as I ride in the Peak district and am asthmatic i've never been able to climb with a fast cadence, so I tend to churn a bigger gear (and I have Rik-van-looy style thighs so the knees don't take the strain).

longer cranks will give you far better acceleration, but will be hard on stamina as you're moving a bigger circle (pedalling further). Short cranks will let you sustain a speed for longer, but will feel like you can't power through a short hill.

Horses for courses - experiment and see what works - there is no formula to account for a whole host of physical differences.


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PostPosted: Tue Dec 26, 2017 6:51 am 
Dirt Disciple
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Joined: Sat Dec 23, 2017 5:49 am
Posts: 14
Location: Comberton
If you are usually using 170/ 175mm then you should try 5mm higher from 165 which will be suitable for your leg and can be got more power.
When you change the crank from 170 to 165 it can be hurt for your legs and body. So, think first before the change.


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PostPosted: Fri Feb 09, 2018 12:03 pm 
Gold Trader
Gold Trader
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Joined: Sat Jul 29, 2006 11:14 pm
Posts: 4084
Location: Somerset
Peter Keen wrote an interesting article about this a few years ago and reckons everyone is on too longs cranks.

He went as far as to advocate 140mm cranks for shorter people and a maximum of about 170mm.

Damned if I can find it now.


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PostPosted: Fri Feb 09, 2018 12:12 pm 
r.B.o.T.M. & P.o.T.M. Winner
r.B.o.T.M. & P.o.T.M. Winner
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Joined: Thu Nov 22, 2007 10:51 am
Posts: 2678
Location: Camel Land
Since 78 I've used 177.5's & feel comfortable with them. Tried shorter & long but began feeling pain around the knees etc so just stuck with my chosen length as it's what I'm comfortable with. Ride with what your comfortable with by listening to your body :)


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 Post subject: Re:
PostPosted: Fri Feb 16, 2018 11:37 am 
Retro Guru
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Joined: Thu Aug 27, 2009 12:47 am
Posts: 601
Location: The South Coast's Premier Dump
Crank length does affect the flexion of the knee independently of saddle height. Longer cranks mean the distance between each foot is greater so even if you compensated to provide the correct leg extension at BDC, the other foot is sitting higher than normal and the knee is bent further than usual. I have 170's on my road bikes and 175 on the MTB. I do have knee issues that are exacerbated by the MTB but I am sceptical as to the reason being the increased crank length. I believe it is more due to the offset of the triple crank.


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PostPosted: Fri Feb 16, 2018 2:00 pm 
Old School Grand Master

Joined: Mon Feb 11, 2008 9:42 am
Posts: 3116
Yes, i don't like bandy legged Q-Factors either.......

I try my best to optimise it (too narrow is uncomfortable as well. But not as bad.)


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