Can anyone please advice me the correct Crank length. I'm 5'6"

[mgarrucho]

At the moment I'm using 170mm crank length for my road bike and 175mm for my MTB. Is that alright or it's better to make both 170mm or 175mm? Thanks!!!

 

[smokeysmoo]

If both bikes were measured and are the correct size then don't worry about it, it's only 5mm.

My fixed has shorter cranks than my road bike, but it's the right size bike for me so I just ride it.

Granted fixed is a little different but the basic principle is the same.

 

[Pauluk]

I'm not an expert but I don't think it will really matter as long as your riding positions are ok. The different crank lengths may just change the overall gear ratio, but this is probably totally different on each of your bikes anyway.

 

[StuAff]

Should you feel the need to change one or the other, 170mm. The longer cranks won't do you any harm, neither would shorter ones for that matter. but the usual train of thought (for conventional bikes, recumbents usually use shorter than normal) is that the taller the rider, the longer the crank. 5ft 10, and on 172.5mm cranks on three of mine (the folder has 170s).

 

[mgarrucho]

Thanks for the reply, The only thing that bothers me is almost all bike that are sold with a small frame have a 170mm crank length. My MTB was not purchase as a whole bike instead was put together piece by piece.

 

[Scilly Suffolk]

There are two schools of thought, which might be characterised as "task-dependent" and "morphology-dependent".

The former asserts that the "correct" length of crank is determined by what you are doing: the extra-leverage of long cranks being best suited to time trials; the reduced stress on your knees from shorter cranks making them a better choice for touring.

The latter finds the "correct" length of crank to be determined by the length of your legs: long legs need long cranks and vice versa.

Personally, I think the former argument holds more water; practically, I doubt you'll notice the difference.

 

[gts]

It may affect your position slightly.
Meaning with a longer crank you may end up raising/ lowering your seat slightly and/ or move it back/ forward.

I'm 5'-8" and use a 170 on my fixed gear and on the road bike (racing bike) I have used both 172.5 and 175

 

[mgarrucho]

Thanks for that guys, you just made me more confident that I should move down to 170mm.

 

[Pauluk]

Thanks for the reply, The only thing that bothers me is almost all bike that are sold with a small frame have a 170mm crank length. My MTB was not purchase as a whole bike instead was put together piece by piece.

I wouldn't worry about a 175 on your MTB. I think MTBs tend to have higher BB cases anyway for greater clearance (not sure but you could measure it from the ground). If you are doing some really serious MTB trails you'll soon find out if its a problem as your pedals may contact boulders a bit more regularly, but its only 5mm.

 

[simon.r]

Sheldon reckons it doesn't make much difference for most people: http://sheldonbrown.com/cranks.html

I use 165mm cranks (and I'm 6'2"), but that's because I have fairly significant knee problems and I find it much more comfortable to use shorter than average cranks.

 

[StuAff]

Seriously, as the others have said, don't worry about it too much. Keep your eye out for a bargain and change it as and when. Or not at all!

 

[02GF74]

If both bikes were measured and are the correct size then don't worry about it, it's only 5mm.

.

It's actaully 10 mm differnce intotal movement.

but as OP has said, most manufacturer's fit 170 mm cranks to S frames and I can't imagine it is some random cnhoice but they do it for a reason.

also 170 mm cranks are less desirable since there is less demand so can be bought for cheaper oin ebay.