# Crank arm length in conjuction to saddle height



## loneclimber (Feb 2, 2011)

Good morning to you all!

I am converting from a 172.5 to a 170 crank. How much to I need to adjust the height of my saddle and any other adjustment.

Any constructive answers will be appreciated.


----------



## chase196126 (Jan 4, 2008)

You would lower your seat by 2.5mm, and push your saddle backwards by roughly 1mm


----------



## loneclimber (Feb 2, 2011)

Thank you!



chase196126 said:


> You would lower your seat by 2.5mm, and push your saddle backwards by roughly 1mm


----------



## Cableguy (Jun 6, 2010)

chase196126 said:


> You would lower your seat by 2.5mm, and push your saddle backwards by roughly 1mm


I don't have any experience with doing this, but intuitively if his crank arms are 2.5mm shorter wouldn't that mean his leg will extend 2.5mm less on the downstroke and he'll want to *raise* his saddle so his leg is extended the same as before?


----------



## loneclimber (Feb 2, 2011)

Thanks for the advice! I'm assuming you are in the Bissel Pro Team. How is the road to turning Pro? That's one goal I need to check off my list no matter what age I am.



chase196126 said:


> You would lower your seat by 2.5mm, and push your saddle backwards by roughly 1mm


----------



## cxwrench (Nov 9, 2004)

Cableguy said:


> I don't have any experience with doing this, but intuitively if his crank arms are 2.5mm shorter wouldn't that mean his leg will extend 2.5mm less on the downstroke and he'll want to *raise* his saddle so his leg is extended the same as before?


yeah, it should be *raised* 2.5mm, not lowered.


----------



## chase196126 (Jan 4, 2008)

Aaaaaand now I look like a jack ass . Sorry, it should be RAISED! And your seat will need to go forward roughly 1 mm. I had my opposite hat on today. Thanks for catching that guys

Getting to be a pro is a hard, but rewarding, life choice. Feel free to PM me and i can tell you more or answer any questions


----------



## Alex_Simmons/RST (Jan 12, 2008)

chase196126 said:


> Aaaaaand now I look like a jack ass . Sorry, it should be RAISED! And your seat will need to go forward roughly 1 mm. I had my opposite hat on today. Thanks for catching that guys
> 
> Getting to be a pro is a hard, but rewarding, life choice. Feel free to PM me and i can tell you more or answer any questions


While the crank length has changed by X mm, you might find the adjustment to saddle height need only be a fraction of that (e.g. half or two thirds), so I would experiment to see what feels right. Going 100% might feel right too.


----------

