# Crank length for touring



## pigpen (Sep 28, 2005)

This past weekend I took my converted cross bike out for a light weight tour test ride.
Rode 75 miles. Several hills really cooked me. I am at my limit with my rear derailleur so I am thinking a mountain triple might get my gear ratio more exceptable.

The crankset I used this weekend was a 7803 with a cross outer ring. 46/38/30. 
My rear cassette is was a 12/27. Will be replacing with a 12/29.

On my road and cross bikes I run 172.5.
My old MTB - 90's has 177.5 but I think they are too long.
I am about 5'-11" with maybe slightly longer femors.

*So, if I go with the mountain triple, should I go with 170's or 175's.*

BTW I have and want to leave my Campagnolo 11sp. Total chain wrap is 33. I know they are coming out with a triple rear derailleur but I am not sold on needing it.

And who in the heck coined the term light weight touring? I believe I had all my camping gear with food below 25 lbs. With racks and bike the thing weighed a freaking ton. After this jaunt I cannot imagine a fully loaded tour remotely enjoyable.

*Or should I just ditch the entire concept and run Shimano rears with a j-teck?*


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## Kerry Irons (Feb 25, 2002)

*Crank length*



pigpen said:


> On my road and cross bikes I run 172.5. My old MTB - 90's has 177.5 but I think they are too long. I am about 5'-11" with maybe slightly longer femors. So, if I go with the mountain triple, should I go with 170's or 175's.


Crank length is strictly personal. There is no relationship that predicts the "right" crank length for you. The only sure thing is that shorter cranks make it a little easier to spin.


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## wim (Feb 28, 2005)

Kerry Irons said:


> The only sure thing is that shorter cranks make it a little easier to spin.


Agree, and you really can't avoid it if you keep your customary leg speed. _At the exact same leg speed_, the pedal on a shorter crank takes slightly less time to complete one revolution than it would on a longer crank.


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## 0.2HP (Jul 13, 2011)

Shorter crank arms increases the overall gain ratio of the drive train:

Gain Ratios--A New Way to Designate Bicycle Gears

Shorter cranks will not affect the gear ratio (# of teeth on the chain ring divided by the teeth on the sprocket) and therefore will not affect the road speed obtained for a given pedaling cadence (RPM). 

Shorter cranks reduces the amount of pedaling FORCE you are able to apply. Another way to look at it is it reduces the amount of pedaling force you HAVE to apply. 

Going up hill shorter cranks will allow you to keep moving at a slower pedaling cadence than you could with longer cranks (gear ratio, wheel size, weight all the same.) So it is easier to climb but you climb slower. Ain't no such thing as a free lunch.

(And yes, adding 25 pound to the bike will make the up hill way more difficult.)


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