170mm vs 175mm Crank - Will I notice much difference?

[Tom B]

Team;

Time has come to replace the crankset, chain and cassette on my everyday commuting / everything weapon.

It has needed doing for a few months and I bought he bits before Christmas. Given the grotty weather I decided to just give up maintaining the old set and run it to oblivion with nothing to lose.

It appears that I have inadvertently clicked the 170mm crank option instead of my usual 175mm crank option - I usually buy the 175mm for no better reason than because that's what I always buy and that's what it came with.

Looking online and being 5'9" it seems 170mm cranks arn't an outrageous choice.

Has anyone any experience of changing crank lengths and how much would or will I notice ?

 

[13 rider]

I doubt you will notice , remember to readjust saddle height .
Some say shorter cranks are better for hip angles and other reasons I can't remember but for everyday cyclist I suspect there will not much difference , I run 172.5 mm cranks for the simple reason that's what came on the bikes

 

[a.twiddler]

I think that if you didn't know about it, you wouldn't notice the difference. I'm not particularly tall, but I rode for years with 165mm cranks as that's what came with the chain set and it didn't stop me doing all the usual things. I think it's more to do with fashion than anything, like elliptical chain rings or L shaped cranks. Something in the 170 ish range, plus or minus a little is what's fitted to most bikes and seems to work for most people. Unless you are unusually short or tall then you might need the extremes at either end to allow you to ride comfortably.

Some recumbent riders find that shorter cranks allow them to spin faster, even down to 150mm. I've tried the shorter cranks, but my first recumbent had 170mm and I find I'm comfortable with that. Sheldon Brown has a chart for height vs preferable crank length but everyone is different. It might be that cyclists just like what they're used to, and anything noticeably longer or shorter feels strange but 5mm is probably neither here nor there. Of course now you know about it, it's human nature to think "what if..." and for some it might spoil their ride. For myself, I would just fit them and enjoy them. Once you've had a few enjoyable rides, you probably won't even give them a thought.

 

[derrick]

Team;

Time has come to replace the crankset, chain and cassette on my everyday commuting / everything weapon.

It has needed doing for a few months and I bought he bits before Christmas. Given the grotty weather I decided to just give up maintaining the old set and run it to oblivion with nothing to lose.

It appears that I have inadvertently clicked the 170mm crank option instead of my usual 175mm crank option - I usually buy the 175mm for no better reason than because that's what I always buy and that's what it came with.

Looking online and being 5'9" it seems 170mm cranks arn't an outrageous choice.

Has anyone any experience of changing crank lengths and how much would or will I notice ?

 

[cougie uk]

I don't think you'll notice.

I noticed a crack in a crank just before I had a sportif to ride so put on what I had. I had 172.5 on the right and 167.5 on the left crank.

Did the sportif and a few months of riding before getting a new crank.

 

[simongt]

When I came to learn about the 'importance of the correct crank length' some years ago, I did wonder how as little as 5mm. could really make any noticeable difference to one's riding. I saw the physics side of leverage, leg length etc. if you're mountain biking or doing a lot of hilly terrain perhaps, but for most riding - ?
However, I did take it onboard enough to accept the advice of cycling guru the late Richard Ballantine and have 170mm. cranks on all my bikes as a reasonable compromise and haven't noticed any drawbacks of said advice.

 

[a.twiddler]

I don't think you'll notice.

I noticed a crack in a crank just before I had a sportif to ride so put on what I had. I had 172.5 on the right and 167.5 on the left crank.

Did the sportif and a few months of riding before getting a new crank.

Another point that very few pick up on is that the vast majority of people have unequal leg length, if only by a few mm. Obviously most riders adapt without noticing and it has no effect on them unless it's such that it affects their walking or gait. Surprising, then, that as part of a bike fit fine tuning isn't applied to making crank length match any disparity there too. Just goes to show that for most riders, within a certain range, crank length isn't as critical as many think, and humans are very adaptable.

 

[cougie uk]

Another point that very few pick up on is that the vast majority of people have unequal leg length, if only by a few mm. Obviously most riders adapt without noticing and it has no effect on them unless it's such that it affects their walking or gait. Surprising, then, that as part of a bike fit fine tuning isn't applied to making crank length match any disparity there too. Just goes to show that for most riders, within a certain range, crank length isn't as critical as many think, and humans are very adaptable.

Exactly and 5mm or so in the scheme of things I'd nothing.
We all adjust our position in the saddle and have different hip knee and ankle extensions. 5mm could even be the Difference between padding in new shorts Vs old.

 

[Milzy]

Wow !!!! Shorter cranks are the way to go if you’re more serious about bike fit. Especially if you’re not tall. At 5’7” I could go as low as 160 which are hard to find. It opens up your hip angles so you can ride in an aero position. No pedal strikes around a track or crit. It just feels harder up hills because you lose torque but if you’ve got a 32t on the back it will still be easy enough. Great for high cadence riding instead of grinding your knees like a big old classics rider.

 

[Jameshow]

Aren't pro cyclists going to smaller cranks irrc?

It will be the next big thing in cycling ...

You heard it here first!!

 

[a.twiddler]

What goes around comes around (and round and round)! Is it the next big thing, or the next small thing?

 

[Fastpedaller]

Wow !!!! Shorter cranks are the way to go if you’re more serious about bike fit. Especially if you’re not tall. At 5’7” I could go as low as 160 which are hard to find. It opens up your hip angles so you can ride in an aero position. No pedal strikes around a track or crit. It just feels harder up hills because you lose torque but if you’ve got a 32t on the back it will still be easy enough. Great for high cadence riding instead of grinding your knees like a big old classics rider.

i used to ride fixed with 150mm cranks - I whacked my (Campag record road) pedal once taking a LH bend during a time trial! I wonder what degree of lean I got to? OP, you won't notice 5mm difference, but I have to say I did notice 20mm difference at first but after a few miles I didn't! When I changed to my bike with 170 cranks it felt like my feet were making huge circles

 

[Venod]

5ft 9in is an ideal size for 170mm cranks in my opinion, assuming your in proportion have not got unusually short or long legs, at 5' 10" I ride 170mm on road and CX bikes, 175mm on MTB, 170 suit a good spinning cadence.

 

[cyberknight]

i prefer 170, 175 feels like im having to pull the crank over more .

 

[Fastpedaller]

i prefer 170, 175 feels like im having to pull the crank over more .

That's what I felt when changing from 150 to 170 (but only for a short while).
It would be interesting to do a lab study on same bikes with different lengths of crank and measuring the rider's power output. My suspicion is that it would make little difference if at all, and of course may change once the rider is accustomed to a particular length. Replicating the conditions is nigh-on impossible. A test the next day on different cranks would be inconclusive, as would changing on the day having already done minutes on one crank and then changing to another. Mike Burrows had some interesting thoughts on crank length. My own thought is that 200mm would be much too long, and 50mm would be much too short - somewhere between these extremes is everyone's ideal crank length