I have 170’s on both my race bike and my CX bike, but I’ve ended up with 175mm cranks on my training bike.
At 5’8″ 170mm’ seem the norm. Whilst I’m not suffering at all with the 175mm’s I feel a little sluggish climbing whilst seated and strong climbing out of the saddle. Is this in my head or is that the difference between the two sizes coming into play?

Thinking of selling on and fitting 170’s

Some people are more sensitive to the difference than others. Since going from 175 to 170, I can’t ride 175 any more.

at 172cm tall Graham Obree reckons you should be on 165’s…

(9.5% of your height, as a rule of thumb)

I am 5’10” and found 170mm cranks make an appreciable difference for me on both road and MTB some time ago.

Seated your using your leg muscles more, stood you’re using more of your body weight to lever the cranks, hence the different sensation between stood and seated climbing, length of the levers will always affect how efficiently your body can Use the, longer won’t work better for everyone.

Use what you find most comfortable…

I definitely notice the difference I went from 175 to 170 back to 175.

Surly it’s to do with inseam length… I’m 5.11 and a bit (182cm) but I have a 34 inch inseam which is on the rather long side.

I’m 5ft 6, 32″ inside leg and run 165mm middleburns on the Tripster, I think I have 170mm middleburns on the hummer.

Surly it’s to do with inseam length

I’d guess it is femur length more than anything but that is getting a bit specific

I certainly notice a difference between 170’s and 175’s and would sell the 175’s in an instant

5ft 10 here with 30.5 IL, cranks range from 165 on track bike, 172.5 on road and 175 mtb. The track ones took their toll on my hypermobile knees initially but all good now and can’t really tell them apart.

I’m 6ft (34″ inseam) and got a bike built to my measurements, and it was specced with 172.5mm cranks, which I now use on all bikes except the MTBs which are running 175s for extra leverage.

Myth Busting & Tips from Team Sky’s Head Physio

Great link macavity!

Good info there. The reason I went for shorter cranks was because my knees hurt on 175 but not on 170 after advice from a physio.

From what the sky chap is saying, sounds like I’ve made the change for exactly the right reasons.

I’m guessing there may be more than 5mm in the cranks that’s different between the training bike and the other road bike?

Also…

Onzadog – Member

Some people are more sensitive to the difference hype/nosnense than others

Al, read my post above your last few ne before dismissing someone else’s opinion so glibly.

Which one?

What about sky guy’s opinion?:

There is no “correct” crank length, as there is no appreciable difference in power output between 150 – 180mm cranks

More the points about knees being the biggest cause of issue, small changes upsetting knees and all knees having their own biomechanics.

Ah fair enough.

Has your average cadence changed? I recommend the new Garmin cadence pod because it is so easy to swap between bikes.

I ride 165 to 175 and my cadence doesn’t really change (from high) – 105 in yesterday’s race is normal).

I suspect it’s psychosomatic to be honest.

all knees having their own biomechanics.

agreed, especially when knees come attached to legs that range from <28″ to >38″. The belief that 175-165mm cranks is enough choice for everyone is a little daft.

(sorry for mixing units, it’s the curse of my generation)

the difference from 175 to 165 is only 6%, i’m not surprised many people can’t really tell, it’s like the difference between a 58cm frame and a 56.

A friend was visiting a couple of weeks ago and wanted to try out my fatbike and 29er. We took both for a ride and swapped half-way round. She immediately sussed that the 29er had longer cranks (175 vs 170). I can’t say I was really aware of it and had to check the cranks to find out what length they were).

I’m 5’11” with a 32″ inseam and run 175’s on the hardtail and 170’s on the full suss. Can’t tell the difference personally, only reason the susser has shorter cranks is to help with ground clearance.

Did you adjust saddle height when switching to the longer cranks? A bit of extra extension would be very noticeable. Drop your saddle 5mm compared to that with 170s.

I’ve currently got 170mm on the left and 175mm on the right. Both feel the same to me.

http://www.cervelo.com/en/engineering/ask-the-engineers/crank-length.html

https://www.powercranks.com/cld.html

CRANK LENGTH – Which one?