crank arms

Shot me later beam, that
Shot me lazer beam,
that best describes how to work a team.
Eg 1 man 1 bike. Yikes seeing the mechanical advantage on hikes,
rolling them hills
to achieve our thrills.
Bike fit comfort is as is per each man,
some prefer torque yet some prefer to spin across land.
Longer arms increase torque but the increase in the knee bend might be too much.
. Too short means no drive, imagine standing on axle, no luck
Hence fit to prefer Watt
And just spin ’em up.

Does anyone here actually

Does anyone here actually understand what happens when you change the length of your crank arms?

It isn’t necessarily about power, or spinning, or any of that.  It’s about making the bike fit your body.  If you have shorter legs, shorter cranks can help.  Remember, when you adjust saddle height you’re doing that to get the correct amount of leg extension at the bottom of the pedal stroke.  But crank length is how you also get the correct amount of extension at the top of the pedal stroke.  If the crank arms are too long, you can still get the correct extension at the bottom of the pedal stroke by lowering your saddle – but then you risk knee pain at the top of the pedal stroke, because your leg is bent too far up into your body, just as you’re using your quads to push down again.

Yes, there is a difference to be had in crank lengths, and it’s a lot to do with ensuring you don’t injure yourself while riding.

 I once bought a new chainset

 I once bought a new chainset and was riding along thinking the bike seemed a bit off. Just couldn’t seem to get away with it. A couple of hundred miles later, by chance, I noticed that one crank arm was 175mm the other 165mm! ​I mainly ride 165mm cranks to replicate my track setup, but one bike has 172.5mm, I wouldn’t notice the difference if I didn’t know  – assuming both sides were the same!

​ I think it comes down to the person though. I’m easy going when it comes to bike fit, some people I know are extremely fussy and notice everything!

Got my vote Wellsprop.
Got my vote Wellsprop. Whatever YOUR comfort prefers. They are near much same. If it didn’t cost me anything I’d try 180 4 4 seasons such that my legs could bend more but it really good cycling with any good cranks. Every person is different

Newave2002 wrote:

so, going from 172.5 to 170 wouldn’t really make a difference. I guessing if I switched from 172.5 to 170 that I would soon forget about it. So with a shorter arm, my trunover would be quicker perhaps, than that of the 172.5 and good for climbing long hills.

Newave2002 wrote:

but will 2.5mm really make a difference?

You *might* notice a slight difference in crank length (I did when I switched from between bikes with 175 and 170mm cranks – but as I said, it’s all in your head really).

There will be absolutely no difference in performance or power. Using a shorter crank will reduce the torque you produce (at the crank), however, that’s irrelevant because the bike has gears anyway to give you a mechanical advantage.

Fundamentally, it comes down to whatever size you want/feel comfortable with. Bradley Wiggins is 6’3″, he had 177.5mm cranks on his TT bike a few years back. He then had 170mm cranks on his later bikes (IIRC, a load of the BC track team switched to short cranks for some reason or another – Ned Boulting was chatting about it when commentating on a race a couple years ago).

BehindTheBikesheds wrote:

BehindTheBikesheds wrote:

Boatsie wrote:

kevvjj wrote:

Get a pen, ruler and paper. Draw a vertical line about 1 cm in height. Now draw another 1cm vertical line exactly 2.5mm to the right of the first. Look at the size of the gap between the two vertical lines and tell yourself you could tell the difference when riding.

You can notice it. Set your seat post at height. Can’t reach pedal if risen 25mm but who cares if lowered 25mm. Really depends upon your range of motion and like Kev indicates; most the time it wouldn’t matter. Longer stroke gives more torque, eg turns wheel using strength Shorter stroke revs easier, eg rhythm development of horsepower. Trucks have long stroke. Race cars have fast stroke. Each develop the equal horsepower yet each horsepower is different . If too easy too pedal then torque it with longer arms or if too fast when spinning, shorten. I’m lost too bro.. I’d use 165-185 and learn with what I’m given. I’d like longer cranks but that’s because I don’t climb, I’m tall cogged and the freewheel freewheels.

25mm is a factor of TEN greater than 2.5mm, you really need to recheck what’s written and how mm/cm are different.

Raising your saddle 2.5mm would not make a difference as to whether you can reach the pedals or not, to suggest so is simply bogus.

the difference in crank length between a 170 to a 172.5 is going to produce such an infintessimally small change in torque that you would not know, it’s in your head.

“Too easy to pedal” is down to the gearing, it’s virtually nada to do with the crank arm length, you even state yourself that you “learn with what I’m given”, you change your gear ratio to whatever you find best for the conditions, the crank length is not relevant to this and is more historical incorrect thinking repeated time and again.

Just typing.. Not much difference until the useable range is breached. Crank is relavent. Truck makes same bHp as race car but truck parts big.. Why? Torque. Both reliant upon weight issues as truck is fare per tare.
Longer cranks will give more torque, more torque means bigger chains to cope with strength.
Maybe some day 3 foot cranks on ratchet from near axle can be used with hub gears and really monster some strength. . As per now, if it’s comfortable, ride it, you won.

I have bikes with 175mm
I have bikes with 175mm cranks and bikes with 170mm no difference to feel. You must set seat height the same to measured from pedal spindle not the centre of crank.