[Closed] Crank Length - Does size matter?

I've been considering 165 long as I too have regular / short legs but not overly sure I'd notice the difference

imho, crank length is as important as frame size.

Unfortunately, the difference between 165 and 175 is only 6%, that's about the same difference as between an 18" frame, and a 19".

So lots of people can't really tell much difference between 165 and 175, and extend this to the conclusion that crank length doesn't matter.

(and then wonder why their knees/hips hurt)

fwiw, if i were you, at 5'9", i'd get the 165's.

(i'm 6'2", my knees prefer 165 to 175)

imagine a world where a frame manufacturer only made 18" frames, and 19", and presented that choice as a 'full range', that's the world of cranks.

Most of the research says that as long as they aren't too long it pretty much doesn't matter how short they are within reason (from a biomechnical standpoint). Too long will probably hurt your knees, as they will be too bent at TDC. And the range of movement will be too much.

Some people don't like them from a stability/feel point of view, but that's a different issue.

I've used a wide range, 165 through to a brief experiment on 180s (that hurt) and whilst i can feel the difference, it made almost exactly no difference to performance at all.

170 would be the longest I would ride, 165 would be cool too if you can get it in the cranks you want. I don't fully understand why anyone runs 175 cranks!

I don't fully understand why anyone runs 175 cranks!

I'm on 180s for everything. It's easy to understand 😆

I can't see how having a longer crank isn't beneficial as it gives more leverage Shirley?

I rode a mates bike the other day with 165's (I have 175's mainly because I've never thought about trying shorter)and I was sure it felt harder to climb because of the little baby revolutions of the cranks.

Given the same gear and same incline, would it not prove harder to push the shorter crank?

My new bike came with 170s on and I can't tell the difference, 6 1 on a lg bike

165 to try and avoid rock strikes.

Initially I fitted 165's in place of a pair of 175's because of pedal strikes. I found that I got less pedal strikes funnily enough but also was able to pedal through rough sections too. I'd also hazard a guess that the shorter crank had me spinning more leading to less fatigue and stress on the knees. I'd say the biomechanical aspect is more relevant to road biking than mtb'in.

Btw if anyone knows of any 165 cranks with 2 rings let me know!

XT 2x10s come in 165s. I have a couple sets in stock from last years line up if you wanted some.

kayak23 - Member

Given the same gear and same incline, would it not prove harder to push the shorter crank?

If you reduce your model of a bicycle crank to a lever horizontal to the ground, yes.

But consider 2 things:

1) you can change gear.

2) you've got to turn that lever through a circle, which might well prove uncomfortable* with too-long cranks.

(*especially past tdc)

(* like climbing steps that are just a bit too high)

I have 165s on the FS, for pedal strikes mainly
175 on the fat/29er
172.5 on the road bike - used to have 180s (well, they were cheap 😳 ), couldn't tell any important difference between any of the above, even the extremes ridden back to back

So WHY are cranks available in different lengths?

I run 185s, but I've no idea where I will ever get any new ones if and when I need them. In other vaguely comparable power sports, we are told that a full range of movement is important. I used to row, and rowing short was a serious fault. Constraining everyones' feet to move in the same tiny little circles can't be sensible really. 185 is not long relative to my leg length, compared to 170 or even 165 for an average height cyclist. Eg my wife rides 170s cos that's what all her bikes came with, and she's a full foot shorter than me (actually 13").

Having the same size cranks for all makes as much sense as having the same size frame.

yes go for 170s at least. i'm the same size and they feel different and better for proper mtb. to the point where i actually considered starting a Wanted thread to swap all mine to 170. it's asubtle differnce mind. also did notice more clearance, which seems slightly daft for only 5mm but i would say i noticed.

another issue however may be if you have other bikes still with another length which you ride regularly too. may contribute to knee problems is my suspision. only a subtle difference can make all the difference

I can't see how having a longer crank isn't beneficial as it gives more leverage Shirley?

Ground clearance depends on BB height. My MTB tandems have such a high BB I don't find it a problem - I'm much more likely to smash my stoker's feet on a rock than my own 🙂

MTB tandems have such a high BB I don't find it a problem