Changing from 175mm cranks to 165mm

macnab

Has anyone here done this on a road bike. I am 5'5" with a 29" inseam and have decided to try a shorter crank. I have read a lot of conflicting opinion on websites but on the ballance I feel its worth trying. I got a good deal on a Sram Rival compact crankset so I am going to fit it to my commuter. I am just not sure what to expect i.e. better or worse for climbing, better or worse for flat sprints.
Any input?

Beasty

macnab wrote: »

Has anyone here done this on a road bike. I am 5'5" with a 29" inseam and have decided to try a shorter crank. I have read a lot of conflicting opinion on websites but on the ballance I feel its worth trying. I got a good deal on a Sram Rival compact crankset so I am going to fit it to my commuter. I am just not sure what to expect i.e. better or worse for climbing, better or worse for flat sprints.
Any input?

I do it every time I get on my track bike and don't notice any difference. Based on your measurements you may be better suited to the shorter cranks anyway

It does lower your gearing slightly (just under 6%)

macnab

It does lower your gearing slightly (just under 6%)
Does that mean it will make climbs easier, I am still struggling on the tougher climbs like "The Lamb" and am hoping that the shorter cranks might improve this.
I can average over 30km/h for 50km spins with the 175mm cranks so I am OK for fitness.

route66

macnab wrote: »

It does lower your gearing slightly (just under 6%)
Does that mean it will make climbs easier, I am still struggling on the tougher climbs like "The Lamb" and am hoping that the shorter cranks might improve this.
I can average over 30km/h for 50km spins with the 175mm cranks so I am OK for fitness.

Other way around - shorter cranks will give you higher, not lower gearing. Think of the crank as a lever - the longer it is the easier it is to pedal. Your shorter cranks will reduce your knee movements in each rotation and 165 may very well suit your size better than 175. But "The Lamb" will be harder.

Beasty

route66 wrote: »

Other way around - shorter cranks will give you higher, not lower gearing. Think of the crank as a lever - the longer it is the easier it is to pedal. Your shorter cranks will reduce your knee movements in each rotation and 165 may very well suit your size better than 175. But "The Lamb" will be harder.

Sorry, you're right - going to 165 from 175 incraeses gearing by around 6%

nak

Is 165 not a bit short? I'm 5'4, 30 inseam and my cranks are 170mm. I suppose 165mm is fine on the track bike, whatever works.

manwithaplan

nak wrote: »

Is 165 not a bit short?

I would have thought so. It's a big jump from 175 too.

I have 172.5 on my road bikes and 167.5 on my singlespeed (I'm 5' 10"). Wouldn't it be unusual to go below 170 for a road bike?

crosswords

I'm 5'5" with a 29" inseam. I have been running 165mm on my mountain bike for the past 3 years. I was very happy with the set up.

Positives - Great for sprinting, and general pedalling. The shorter cranks lessens the dead spot at the top of the stroke. Much smoother and more fluid stroke.

Negatives - The science says that you will be at a higher VO2 max when climbing on shorter cranks, but I never noticed any extra effort.

I am now back on 170mm this year purely because

a) 170s are cheaper and easier to find, and I want the same length (and position) on all my bikes.

I ride cyclocross and the 170 mm give me extra leverage in the mud.


165mm - I'd say go for it. Especially for the road.

route66

(Far too much!)Crank Information here on the Sheldon Brown website.