Crank length

secretsam

I typically ride 170mm through choice, but by chance have a good-as-new pair of 172.5mm cranks. I'm in the process of building up n+1 (see various posts dotted around) - would I really notice that 2.5mm (insert predictable jokes... )?

rick_chasey

So went the other way to 165 and I noticed that it felt easier to spin and harder to mash.

It also stopped some of my back pain I had, so I’d go for yes it’s noticeable.

Then again there are plenty of stories of pros not noticing the wrong and different crank lengths.

So maybe it’s psychosomatic

First.Aspect

It is subtle, but you can tell the difference. The jury is out as to whether it actually makes any difference to speed, once you are used to it.

What RC has observed is effectively lowering his saddle by 5 mm, thereby reducing how much his pelvis rocks (that's an educated guess).

rick_chasey

Possibly - I thought it was more just being made to spin more as I still get the pain if I really mash it.

It is noticeably more comfortable in the drops

secretsam

Rick, did you adjust your saddle?

MattFalle

MF uses 170, 172.5 and 175 for the past 30 years and hasn't noticed any difference at all ever.

First.Aspect

MattFalle said:

MF uses 170, 172.5 and 175 for the past 30 years and hasn't noticed any difference at all ever.

Some people are more proprioceptive than others.

MattFalle

that as maybe, but there is always a window to be opened.

veronese68

I've also used 170, 172.5 & 175 without noticing the difference, across different bikes and changing cranks. I probably adjusted the seat height after changing but it was a long time ago.

First.Aspect

Terrain makes a difference. The bikes I've ridden with 170 mm cranks were in very hilly areas. I definitely noticed the difference the steeper the pitch.

secretsam

It's a CX so there might be a small issue with clearance, etc.

rick_chasey

secretsam said:

Rick, did you adjust your saddle?

Yes but it's 5mm so I honestly couldn't notice the difference there.

rick_chasey

First.Aspect said:

Terrain makes a difference. The bikes I've ridden with 170 mm cranks were in very hilly areas. I definitely noticed the difference the steeper the pitch.

As in, easier to mash when it's super steep?

First.Aspect

secretsam said:

It's a CX so there might be a small issue with clearance, etc.

Heel clearance wrt chain stay? Wouldn't that be within range of cleat adjustment?

secretsam

First.Aspect said:

secretsam said:

It's a CX so there might be a small issue with clearance, etc.

Heel clearance wrt chain stay? Wouldn't that be within range of cleat adjustment?

Nope, the mash thing per Rick

rick_chasey

veronese68 said:

I've also used 170, 172.5 & 175 without noticing the difference, across different bikes and changing cranks. I probably adjusted the seat height after changing but it was a long time ago.

Isn't that because you mainly ride either hung over or drunk? :P

ibr17xvii

I have 172.5 on one bike, 175 on another & TBH I can't tell the difference.

Always used 175 so when I got 172.5 I had a little bit of extra faffing with saddle height but apart from that no problems.

lesfirth

I have used 165,170 and 172.5. Set saddle height and I can not tell any difference.
However I cant tell if my wheels roll well or spin up quick , if my tyres have stiff side walls or if my frame is super stiff,... the list goes on . I would never get a job as a bike journalist.

veronese68

rick_chasey said:

veronese68 said:

I've also used 170, 172.5 & 175 without noticing the difference, across different bikes and changing cranks. I probably adjusted the seat height after changing but it was a long time ago.

Isn't that because you mainly ride either hung over or drunk? :P

Harsh 😂

DeVlaeminck

I reckon I notice the difference - 2.5m isn't much though - it wouldn't stop me buying a bike and if the OP already has the longer cranks why not give them a go.

secretsam

I actually got them swapped on my last bike. Just picked up a pair of 170mm cranks with rings on Fleabay, so matter resolved!

Anyone want some 172.5mm Tiagra cranks? 🤣

rick_chasey

I've got a whole 52/39 170mm Ultegra crankset if anyone's looking for one...

Used but decent nick.

darkhairedlord

If you have little legs you will notice it more. A lanky streak is going be more comfortable on 165mm than a shortarse on 175mm.

secretsam

darkhairedlord said:

If you have little legs you will notice it more. A lanky streak is going be more comfortable on 165mm than a shortarse on 175mm.

I have tiny, tiny legs (relative to my height). But a shortarse?!?! Harrumph

davidof

lesfirth said:

I have used 165,170 and 172.5. Set saddle height and I can not tell any difference.
However I cant tell if my wheels roll well or spin up quick , if my tyres have stiff side walls or if my frame is super stiff,... the list goes on . I would never get a job as a bike journalist.

excellent.

I live in the mountains and have bikes with different crank lengths, can't tell the difference either if the saddle is set right.

amrushton

there are threads on that internet you can look at. Phil Burt prob has the best few mins. https://www.youtube.com/watch?v=79okJ8Lyj0E