crank arm length?

Discuss light weight issues concerning road bikes & parts.
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apricotwalnut
Posts: 36
Joined: Fri Aug 04, 2017 3:49 pm

by apricotwalnut

My inseam is 74~75cm.
I have used 170mm for two years, and i haven't been feeling nervous.
by the way, I'm going to change it to 165mm or 167.5mm.
is it good for me or i have to keep 170mm?

by Weenie


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LouisN
Posts: 2319
Joined: Mon Feb 19, 2007 3:44 am
Location: Canada

by LouisN

Any of the three is fine.
Choose the one that feels better.
I have identical twins with both 73 mm inseam. One uses a 165 mm, the other a 170 mm.
If you put your "numbers" in a crank lenght chart, you might end up with a suggested lenght of 155-160 mm ;) .

Louis :)

apricotwalnut
Posts: 36
Joined: Fri Aug 04, 2017 3:49 pm

by apricotwalnut

LouisN wrote:
Sun Mar 04, 2018 3:39 pm
Any of the three is fine.
Choose the one that feels better.
I have identical twins with both 73 mm inseam. One uses a 165 mm, the other a 170 mm.
If you put your "numbers" in a crank lenght chart, you might end up with a suggested lenght of 155-160 mm ;) .

Louis :)
Thanks, it means that if i follow the crank length chart, shorter is better. but it doesn't matter^^

mattr
Posts: 3456
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Too short can feel odd, but you usually adjust to the oddness. If not you've gone too short.
Too long can make a mess of knee joints which takes a long time to recover from. If it gets really bad, you may end up permanently broken.

Power output will be unaffected.

Geoff
Posts: 5093
Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

So personal. Unfortunately, you can only really tell by trying it out yourself. In my experience, you will know almost right away if the change will work for you, or not.

morganb
Posts: 484
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

I've got slightly longer legs and prefer 150-155mm. I didn't realize how much more natural proportional cranks felt until I had joint problems that caused me to seek shorter cranks for pain relief. The adaptation period was very short for me coming from "normal" length cranks and now anything over 160 feels awkward.

pdlpsher1
Posts: 1412
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

Where do you find a 150mm crank? I’d think most cranks start at 165mm.


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LouisN
Posts: 2319
Joined: Mon Feb 19, 2007 3:44 am
Location: Canada

by LouisN

Rotor.

Louis :)

Jereb
Posts: 3
Joined: Mon Jan 15, 2018 9:16 am

by Jereb

pdlpsher1 wrote:
Mon Mar 05, 2018 2:51 am
Where do you find a 150mm crank? I’d think most cranks start at 165mm.


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Hi

http://www.bikesmithdesign.com/Short_Cranks/

mattr
Posts: 3456
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

morganb wrote:
Sun Mar 04, 2018 7:06 pm
The adaptation period was very short for me coming from "normal" length cranks and now anything over 160 feels awkward.
I first found the first pain related issue on my turbo bike (long periods sat in one position) which had 172.5.
Switched to 165.
Adaption time. About 10 seconds.
Didn't realise how many other biomechanical issues longer cranks had been causing. Even if they weren't actually painful.

Downsides, ~10 bikes which now need shorter cranks. :/

Anyone got any 165/167.5 shimano compatible cranks for sale?

morganb
Posts: 484
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

mattr wrote:
Mon Mar 05, 2018 8:45 am
morganb wrote:
Sun Mar 04, 2018 7:06 pm
The adaptation period was very short for me coming from "normal" length cranks and now anything over 160 feels awkward.
I first found the first pain related issue on my turbo bike (long periods sat in one position) which had 172.5.
Switched to 165.
Adaption time. About 10 seconds.
Didn't realise how many other biomechanical issues longer cranks had been causing. Even if they weren't actually painful.

Downsides, ~10 bikes which now need shorter cranks. :/

Anyone got any 165/167.5 shimano compatible cranks for sale?
I have 7 bikes all of which are now on short cranks. I have two pairs of 165 left to see if they would be adequate but I needed shorter. They are BB30 and 386 though if you didn't need a 24mm spindle.

parleez1
Posts: 28
Joined: Wed May 26, 2004 8:57 pm
Location: Boston, MAssachusetts

by parleez1

I have 7 bikes all of which are now on short cranks. I have two pairs of 165 left to see if they would be adequate but I needed shorter. They are BB30 and 386 though if you didn't need a 24mm spindle.
[/quote]

I'm looking for a Cannondale Hollowgram SiSl2 with 165mm crank arms, do you have a set?
Thanks

mattr
Posts: 3456
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Thanks for the offer, but i'm on 24mm spindle across the board.........

cyclenutnz
Posts: 762
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Location: Cambridge, New Zealand
Contact:

by cyclenutnz

Fitted husband and wife pro triathletes today. He is 192cm and she is around 160cm.
Calculated that shifting her to 145mm cranks still meant they were proportionally slightly longer than his 170s. Made a massive difference to her knee tracking and hip tension.
Anyone with inseam less than 75cm is not well served by the common crank sizes.
http://www.speedtheory.co.nz
http://www.velogicfit.com - 3D Motion Capture and Frame Finder Software

by Weenie


Hexsense
Posts: 340
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

Inseam 79cm. Using 165mm. I don't really consider this short. It's just about right size actually.

One thing to note is you'll have reduced torque leverage (by ~3%). But not reduced power.
Power=Torque x rotation speed.
torque is down but you get back with smaller circle which make same linear foot speed translate to higher cadence automatically. This give you back all the power (providing you are not in torque limit situation like climb up mountain and run out of gear). And you'll still gain some more with improved biomechanical efficiency of your leg moving in smaller more comfortable range.

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