Crank length.

[Evilbofh]

I have been using 172.5mm 30.39.50 cranks on my winter bike. with a 12-25 cassette.
My summer bike has 172.5 53.39 and a 12-26 cassette.

I am building a new bike to be a mid point to the above 2 bike.
I have been offered very cheap group set with 170mm 53/39 (or 34) cranks with a 12-27 cassette. (2009 years model) alternative 170,0 34-50 / 11-26

How much difference is there between the cranks? How would this effect my ride..

I understand I will have to adjust my saddle hight to accommodate for the smaller crank length?

I am 175cm. If that help to give an answer..

/E

 

[gman0482]

Measure your inseam (in cm) and multiply it by 2.16. That should give you the length of the cranks in (mm).

-OR-

170 mm/ inseam 80 cm or less
172.5 mm/ inseam 81 - 86 cm
175 mm/ inseam 87 cm or above

-Greg

 

[Peter@vecchios]

I have been using 172.5mm 30.39.50 cranks on my winter bike. with a 12-25 cassette.
My summer bike has 172.5 53.39 and a 12-26 cassette.

I am building a new bike to be a mid point to the above 2 bike.
I have been offered very cheap group set with 170mm 53/39 (or 34) cranks with a 12-27 cassette. (2009 years model) alternative 170,0 34-50 / 11-26

How much difference is there between the cranks? How would this effect my ride..

I understand I will have to adjust my saddle hight to accommodate for the smaller crank length?

I am 175cm. If that help to give an answer..

/E

Put three people in a room and ask about crank length, get 4 answers. It depends on SO much. No simple formulas will give you an answer as to whether or not 2.5mm will be noticeable or significant. If you are concerned, get the 170s, sell 'em and buy a 172.5 but it makes very little difference. I had a customer who brought her DeRosa in for service and one crank arm was 2.5mm longer than the other. Been riding that way for 5-6 years and she didn't even know it.

BTW-using the mentioned formula I should be riding 180s..I use 172.5, have for decades. I'm 6 feet tall, normal inseam(33 inches) but shortish femurs.

 

[gman0482]

I do agree with Peter it ultimately comes down to more than a formula and how you feel. I just put that out there in general for you to compare. I am 197cm (6'4") and had 170 on my 1st bike, and now I have 175 and it's a huge difference to me.

 

[Peter@vecchios]

I do agree with Peter it ultimately comes down to more than a formula and how you feel. I just put that out there in general for you to compare. I am 197cm (6'4") and had 170 on my 1st bike, and now I have 175 and it's a huge difference to me.

Fair enough, thanks for the 'edit'.

 

[Evilbofh]

Thanks I will give it a try...

There is always ebay otherwise...

/E

 

[Akadat]

Crank length is part of the overall gear ratio. Shorter cranks = taller gearing and conversely allows for faster spinning of the pedals.

Ground clearance of the pedals and leg length are factors.

It sure comes down to 'try it and see'.