Crank Arm Length and Rider Height
This is a spillover from an earlier thread - it was suggested that I raise this as a separate topic since there seems to be a decent amount of interest.
My initial post was about sourcing a compact crank overseas but included a reference to crank arm length. I know this topic has been revisited ad nausem in the Wiki and the forums (not to mention ST, etc.) but I found it very interesting to learn that some of the taller EN riders (6 ft+) are using 170mm long cranks with their 50/34. My P2 was originally spec'd with 172.5 mm cranks so my inclination was to stick to this length when I order my compact for no other reason than that's the only thing I've ever used... Given that I'm only 5'7 it was suggested by some of my vertically gifted and far more experienced teammates that I likely wouldn't want to go any longer than 170 mm and should perhaps consider 165's. Ego aside (ahem..), I'm here to learn and just want to make the best decision on this point.
Soooo, if you are using a compact crank, how tall are you and what size crank do you roll with? Did you drop down from a longer length crank to your current set-up? What do you think you've gained or lost from making the move? Did the move throw off your bike fitting significantly? Obviously I'm most interested in hearing the experiences of those in my general height range so I can add this information into the mix when I make my decision, but welcome all input since it was the experiences of those in the Valley of the Six-Footers that really got me thinking about this.
Thanks in advance.
Comments
As I mentioned in the other thread I have 170 mm cranks on both my tri bike and my new road bike. I am 6' tall and have an 32" inseam. I think inseam is likely as important as height for the discussion. Not sure how ego would play into it at all, its kinda like buying shoes that are the correct size. Shorter cranks will let you have a slightly more open hip angle on a tri bike which is a good thing. You will likely not notice the difference at all. I certainly can't feel the difference between the 170's and tne 172.5's on my other road bike. Its 2.5 millimeters, not much.
Also crank size has no bearing on the size of the chainrings, meaning compact v standard cranks have no bearing on the discussion.
If you have a good fit and are comfortable on your bike there is no reason to run out and buy shorter cranks. If you are buying new ones, it is something to consider. You LBS, depending on who they are, is not really the place to get into this type of discussion. They will likely be clueless about it.
I agree with Chris, your LBS is generally not the place to get great bike related advice... as ass backwards as that sounds. It's a different story if that shop has a real good fitter on staff though. They would be able to advise you on the little nuances.
I'm going to switch from my existing afraid-it's-going-to-die-at-anytime Ergomo to a new Quarq/Joule combo when I get back from Spain, for use on both my tri and road bike. Also, I'll be getting a new tri bike this year.
I don't have any problem with 172.5mm, as I don't know any difference, but just wanted to know if there was any benefit to shorter (170mm) crank arms.
Bottom line is I use 175s and maybe Thor or Macca can notice the difference in the 2.5mm one way or the other, but not me. Bike geo, setup, cleat position, improved pedal stroke are the focus. It's not a game of mechanical millimeters at this level...er, my level.
I am 5'11", I ride 165mm crankarms on a compact Sram Red. That's as short as they readily come, aside from bmx cranks.
I think you should go shorter, and worst case, there is always a market for 165 cranksets, as they are hard to come across.
But it from PBK or Wiggle, that's where I bought mine from.
You'll end up doing a bit of cassette tweaking as you can get into a tighter cluster w/ the compact up front, but it will also take a bit of trial & error to find the best combo, as the shorter arms alter your gear inches & also necessitate a bit of a cassette swap.
I find it much more comfortable on the TT bike. I can get lower & not have hip restriction at top-dead-center. Short is the way to go.
People <~5'6" ride 170mm <br /> ~5'7" - 6'1" ish ride 172.5mm
>6'2" ride 175mm
165mm cranks are becoming more popular for triathletes and TT'ers, due to the hip angle stuff mentioned. At some point in the next couple months I need to drop some $$ on my tri bike and will likely get 165mm cranks. My hip flexors and hips are ludicrous tight so I think this would help me...
Before ToC I ordered a bunch of bike stuff for the tri bike (been hanging in the garage, untouched, for 3yrs), include 165mm cranks. Looking forward to putting it all together and trying it out!