Hello;
I have discovered that in my bike (a long 55cm road frame) I ride 170mm crankarms. I have asked to friends that ride on triple crankset and also have this lenght. How can I know if this lenght is fitted to me? Should I measure my legs? or is a factor that is not so important? Do you think that I will notice any difference if in my next bike ride 172,5mm?? is a very litle difference;
so, how I can calculate my apropiate lenght??

thank you!

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flat transitioner shimanoist

There is no rule to determine crank length depending on you leg length. I have a 90cm inseam, I've been using 175mm for years, this season I want to improve my cadence so I changed to 172,5mm, I can now ride at higher cadences more comfortably. I don't know if it's because of the crank length or it's just psychological fact.
Before buying try to borrow a set and do 2-3 rides to test them.

Heres a general rule of crank sizes, for all around riding.

If your inseam is 79cm or less 170mm
80-84 cm is 172.5
85+ is 175.

Longer cranks are good for steady efforts, time trials, hill climbs etc.

Shorter cranks are good for high cadence efforts, such as sprinting and some track events.

However if you have knee problems you need to be careful about going to long on crank arm length.

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I see he changed it again

my inseam is 94 cm and i ride 180mm.

i tried 175, 177,5 and 180mm. and with 180 i felt like having much more power.

well, very high cadences ain´t as easy as before, but i often go for lower cadences like jan ullrich who also rides 177,5 or 180mm

I first started riding with 170s, but I was quickly advided to move to 180s. I have a 93cm inseam, and a F/T of 1.21.

Many have told me that you cannot spin on 180s yet, as many of them are much shorter than I and as such their knee angle change is greater than mine.

Once I had trained myself to the longer cranks, I was able to exceed 190rpm on the track. Now having ridden them for ~10 years I can't spin as fast on shorter cranks as I can on the 180s as I am looking for the extra up/down or foward/back and my pedal stroke gets very choppy.

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Success is how far you you bounce back up after being knocked down

They say longer cranks are for endurance riders and shorter cranks are for strength riders. To obtain the same amount of power with a longer crank you dont have to push as hard, however you have to push longer! Hence why candence is slower!

However cadence, is the RPM(the amount your leg goes around in circles per min) It IS NOT THE SPEED OF YOUR LEGS!!! Meaning you can have a slower RPM with longer cranks but your legs could move faster then someone having a higher RPM! A longer crank means you have more ground to cover!!! but at a less effort!

I would like to hear your oppinion. I just slipped a bit from budjet and ordered Race Face Candence cranks. Longest ones are 175mm as most of my bikes..but my mtb single speed has 180mm XTR's...And they feel funny for start. But not long.And in hills that +5mm feel like nitrogen oxside on Honda Civic..or tuned turbo on RS Octavia. And my "historic racer" has 170mm and they feel afful.

I would like to think that 177.5mm would be nice for me for TT? I have inseam 91cm and my avg cadense is ~95, sometimes 100 on TT.

But 177.5mm are bit rare. No Truvativ etc just 175mm or 180. (No Shimano, please.)

I would have 180mm Mavic cranks from friend but I must try those. Would this idea work, ride some near max interwalls like 400-500W on Tacx Basic trainer, rest for a day+change for 180mm and try again???

I have no Powertap...or adjustable lenght SRM's etc. handy analysing tools.

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Samu @ www.signature.fi

Samu, the testing we did at the shop a couple of years ago with a number of taller riders who were used to different crank lengths.

Results
Riders used to 170s on 180s = +12w
Riders used to 175s on 180s = +7w
Riders used to 180s on 170s = -8w

This was based in multipul crank swaps at a constant heart rate (once drift was taken ito account) and was consistant from day to day.

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Success is how far you you bounce back up after being knocked down

great quote. I use 185mm and love them.

I´ve been thinking about going 177,5 or 180 myself as I have an inseam of 91 cm. As far as I can see the only carbon crankset is Stronglight pulsion in 177,5. If you wanna go 180 I can only find Campy alu, DA (not for campy bikes), Stronglight Impact (heavy) and Tune bigfoot (retrocool but not the lightest).

Can anyone supply other suggestions?

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Sic transit gloria mundi

Truvatiw has also 177.5 and 180mm cranks. I would get Rouler's in same price as Race Face...but I "feel" at this moment that 177.5mm would be best for me for TT. I must call to importer, was thinking that they carry only 175 and 180mm but may be they can order them form me.

http://www.sram.com/_media/pdf/truvativ ... ouleur.pdf

I think I must do that call and try 180mm on trainer and think more then.

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Samu @ www.signature.fi

my inseam is 88cm so i want to switch from 172.5 to 175 but
my shoes size is 41/42 hence - short foot.

how short foot taken into acount in cranck lenght ???