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FOBx530 01-23-10 03:57 AM

crank length, building up first multigear, enlighten me please.
building up my first multigear bike.

i was wondering about crank length, my fixie is 165mm, but i notice that multigear bikes are 170 smallest?

i'm not a tall person, only 5'3

the bike i'm building up is going to be 48cm

can you guys recommend me a length? i saw on craigslist a guy is selling shimano 105 groupset used for 100$ w/ crank length of 175mm

can anybody tell me something or enlighten me about what i should do/get?


kayakdiver 01-23-10 07:53 AM

If your comfortable with 165 I would suggest finding one. If you can't then go 170. It's a big jump to 175mm. I'm 7" taller than you and run 170 cranks on all my bikes. I find 175 just not comfortable to me.

DXchulo 01-23-10 09:10 AM

Most road cranks are 170 or 175, but that doesn't necessarily mean those will be the best sizes for you. Fixie cranks tend to be smaller to prevent your pedal from hitting the ground when you corner.

And here's a calculator:

165 road cranks are harder to find, but they're out there. My guess is that a 175 would be too long for you.

jzsoup 01-23-10 02:55 PM

I would recommend 170 for ya. I'm 5'6" and I like 172.5, but have also ridden 170's without objection.

San Rensho 01-23-10 03:03 PM

Crank size is not determined by height, its determined by pedalling style. In general, you use shorter cranks to be able to spin faster. If you mash, then use longer cranks. The reason fixies have 165s is that the immitate track bikes. On the track, spinning is everything and short cranks allow you to achieve a very high cadence that is also very smooth.

Grumpy McTrumpy 01-23-10 03:07 PM

lots of incorrect on this thread

ahsposo 01-23-10 03:11 PM

Originally Posted by jzsoup (Post 10308310)
I would recommend 170 for ya. I'm 5'6" and I like 172.5, but have also ridden 170's without objection.

I agree. My inseam is 29" on a good day. My SS cranks are like 170 and I like the way they spin but my road cranks are 172.5 and I think I get a little more climbing leverage with 'em.

That said check out bikepedia. You can specify a component and details and it will come up with something like:

Randochap 01-23-10 10:25 PM

Originally Posted by Grumpy McTrumpy (Post 10308343)
lots of incorrect on this thread

Give us correct then, Grumpy.

deep_sky 01-23-10 10:31 PM

From what I have been able to gather, how your legs are is what really determines crank length. If you have excessively long femurs in relation to your leg length, then you might be more comfortable with longer cranks. However at 5'3", I don't suspect that you likely have that problem and will want/need 175's. I am 5'8" and while my femurs are longer than would be expected for my height and inseam, I ride 170's and can pedal smoothly. I'd expect you would be happy with 165's or 170's.

thegunner 01-23-10 10:44 PM

i pm'd you, hopefully it helps

TejanoTrackie 01-23-10 10:56 PM

I'm also 5'-3" with a 28" inseam and for 40 years have used 165mm length cranks for both road and track. The only bikes where I use 170mm cranks are my MTBs, where I turn a much lower cadence. There are many road cranks that are available in 165mm length.

Dilberto 01-23-10 11:09 PM

This is what you want...thank me later:

prathmann 01-23-10 11:22 PM

Before you get too concerned about this I'd suggest seeing if you can arrange an extended test ride or borrow someone's bike so you can try out some longer cranks. You may well find that you're just as comfortable with 170, 172.5, or even 175mm ones, in which case you wouldn't have to limit yourself to particular cranks.

I've got a tandem with 165s, a touring bike with 170s, and a road bike with 175mm cranks and they all feel fine. My natural cadence is a little higher on the tandem with the 165s, but I don't have any strong preference for one length over the others.

AnthonyG 01-24-10 07:49 AM

I'm an advocate for crank length being proportional to your inseam. My opinion is that most people are riding with cranks that are too long for them. At a height of 5' 3" I would be staying with 165mm cranks at most unless you have really long legs for your height. What's your actual inseam? Not pant inseam.


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