I have 175mm cranks on my road bike and a fitteer reckopns I need 172.5mm. Should I shell out for the new cranks?
A real basic guide I have always hear is 6’ and above = 175-180, 5’10" and below is 172.5, 5’7" and below is 170
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Part of that depends on your style, as well. In general:
Long(er) cranks: masher
Short(er) cranks: spinner
Rotor cranks: eliminate the dead spot
Power cranks: learn to pedal efficiently
Compact cranks: Spinners, clydes, and non-natural born climbers
Carbon cranks: People with WAY more money than I have.
Old cranks: half the Slowtwitch population 
thanks very much
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At 6’6" I used 170 -172 mm for years as a boy , just used 175 - 180 these last 10 yrs. I do notice the 180s help climbing but , but for beach riding / non racing ,its hard to notice any BIG difference.
I have 175mm cranks on my road bike and a fitteer reckopns I need 172.5mm. Should I shell out for the new cranks?
I’ll bet 10 bucks in a blind test you won’t be able to tell the difference. Take a look at a quarter of a cm on a ruler and tell me that’s worth a new crankset.
I’d say watch your wallet with this guy.
I would try Leonard Zinn’s formula based off of your inseam. For example-- 32 inch inseam. 32 x 2.54 (convert to mm) x .21 or .216. This yields a range from 170-175. If you are in that range I would not put out the cash for a new crankset.
Most cranks only come in about three lengths (170,172.5, 175) because to make more is not economical for the manufacturers. If you need longer or shorter than this then plan on paying a ton of money because they will be hard to find.
I doubt very much that I would pay for cranks that are only 2.5 different.
Chad
Khai,
Powercranks should be on the “People with WAY more money than I have” category. Regular cranks on the “learn to pedal efficiently”.
With that formula I need a 202.9 mm crank set ,not 180 , please no too short jokes.
Therein lies the problem with available cranks and their lengths. Where do you get a 200 mm crankset? Only Leonard Zinn makes them for about $350. With the price of carbon and one-piece cranks driving the cash output up into the stratosphere, the $350 doesn’t sound so bad.
I am going to go from 180s (34 ½ inch inseam), to 190s this winter when I have the time to adapt a little. I liked moving from 175s to 180s and suspect the longer cranks will be even better.
Chad
Powercranks should be on the “People with WAY more money than I have” category. Regular cranks on the “learn to pedal efficiently”.
Have you ever used PowerCranks? Every time I see someone make this ridiculous statement I must laugh. Unless you have twice as much time to train so you can pedal around one-legged, then you really are not going to get very far trying to duplicate the motion of powercranks.
Not that I will disagree that they are expensive, but this forum doesn’t strike me as a group of penny-pinchers, by and large, so that particular problem shouldn’t be the issue that everyone makes of it. Whether it really makes you faster or not has been argued to death on this forum, but saying you can duplicate pedaling efficiency just by “trying harder” is simply silly. Come try my 180mm PCs for a few minutes and tell me its the same.
Chad
Hey, cool sig!
Nobody can answer a question like that for you. Are you infinitely wealthy? Then go ahead and buy them. Can’t affort a cup of rice for dinner, probably shouldn’t buy them. Paid $300 for a fit, probably may as well take his advice…it all depends on you.
I disagree that there won’t be any noticable difference though. I went from 172.5 to 180s and really liked them for climbing, it is somewhat a personal preference. I ride 175’s now.
Excellent question, but one that does not have a simple answer. I would say that paying a lot of money for 2.5 mm crank length difference is probably not worth it because, depending on your leg length, you probably need MUCH longer or MUCH shorter cranks. The problem is that about 95% of what you hear from people (even quite experienced riders) about crank lengths is a pile of crock and unsubstantiated by any decent physiological research. Probably the item that restrains crank length the most is bicycle design and manufacturer convenience. If you want to read something VERY interesting about crank length that does a very good job explaining these variables, go to this site and read all the expanatory links and assumptions and then decide for yourself. Also, measure your legs, put the no. in the easy formula there and be surprised by the result:
http://www.nettally.com/palmk/crankset.html
Also, a question: I travel to and stay in Sydney a fair amount. Any decent tri clubs in the area? Or any good masters swim teams? I stay near Coogee Beach. Thanks.
I wonder what a 148mm crank would be like
jaretj
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I’ll bet 10 bucks in a blind test you won’t be able to tell the difference. Take a look at a quarter of a cm on a ruler and tell me that’s worth a new crankset.
A quarter of a centimeter in length translates into a half a centimeter in diameter of the pedal stroke. You can feel it.
I could not agree with you more Greg. Crank length studies are lacking in many ways and have resulted in unsubstantiated findings. Too small of a sample size, sample used (I saw one sample that was using boys that never cycle), too few studies, improper analysis of findings.
I have 3 cranks at home. 170mm, 172.5mm and 180mm. I ride my road/race bike with the 180mm. I have to say that I do notice a significant difference. Although I cannot back up my findings with data, I will say that it is noticeably easier to spin with the 172.5mm’s. However, the 180mm are fantastic when I am in great cycle shape and able to cycle steady state with good power output for a minimum of an hour with little fatigue - that’s where they shine and the poweroutput is significantly more There is little forgiveness with the 180mm’s - when I am in poor shape the bicycle ride feels like sh$t.
I am not convinced that there is enough study to say that the Zinn formula is the best way of determining crank length. I have also heard many notible cyclists (Steve Larsen included) refer to Greg LeMonds formula.
Greg / ORD wrote
I am not convinced that there is enough study to say that the Zinn formula is the best way of determining crank length. I have also heard many notible cyclists (Steve Larsen included) refer to Greg LeMonds formula.
I would think that Zinn's numbers would be best for taller bikes ( since that what he builds ) and LeMonds the other end. Unless someone was a world class climber ,I don't see the point in riding cranks longer, than the rules of thumb ,lists for an average rider. Beside sales volume, of <u>over</u> 180 mm cranks , some frames , it gets close to ground contact problems ,there is a lawyer in there some place. I may try to lenghten a cheap lower price campy crank . to my recommened size of 202 mm , which may feel odd for a few miles.
I’m surprised that nobody has brought this up http://www.computrainer.com/varicrank.asp
“RacerMate announces the introduction of the VariCrank TM Adjustable Length Crank. With the availability of accurate electronic bicycle ergometers like the CompuTrainerTM and Velotron™ ergometer/trainers which measure wattage and heartrate and analyze pedal stroke (SpinScan TM), it is now possible to isolate and measure the effect of crank length on an individual’s cycling performance.”
Sorry, I don’t know anything about it, I just saw it when I went to the c-trainer site to download updated software.
I agree that it looks like a pretty worthwhile product. I would love to try it but it would not make sense to buy the unit. I think, due to the price tag, it is best for a cycling club where the purchase price could be shared amongst many users.
big fan of the Palm site…Zinn points to it too as supporting info for his general approach, I believe.
I tried 172.5’s for a year with spinning in mind, but went back to 175’s this year (in no small part because that’s the LOW end of where the Zinn/Palm formulae would put me) and have never been happier…road, tri, TT, whatever. always on the lookout for “cheap” (ha ha ha) splined 177.5 and 180 sets on eBay for experimentation purposes.
170’s I can pick out of a test blindfolded, drunk, and half asleep. feels like running in a damn gerbil wheel.
Carl - 5’9" ~32.5" inseam