Moisture

You have very long legs in proportion to your inseam! does it make it more difficult to get low? Do you prefer a shorter stem because of this?

You made a fantastic point about differently proportioned legs. I didn't even realize. So of course, there are simply so many factors associated with frame fitting as a whole, this causes everything to be so highly opinionated and biased.

WIth my 190mm crank arms, I find that my knee stops at just below fully parallel. I wouldnt want my knee to go any higher than it is now. I realize that this must have something to do with your saddle height, obviously.

I don't know of any formulas regarding tibia length, no.

DaveSSS 

My cycling inseam is 83cm, so 21% is 174.3mm. I switched from 170 to 172.5 many years ago, but couldn't really notice much difference. Recently I was buying two new inexpensive grx cranks and went back to 170mm. I couldn't tell any significant difference. I've thought about trying 175mm, the next time I make a change. I'm old, but I can still spin up to 125 rpm, and cruise at 100-105. When climbing, I use 70-85 rpm.

colnago62

I ride 175mm cranks on the road and 165 on the track. I also ride roughly the same cadence when turning similar gears on both bikes

195cranky

Guess I will chime in here. Not a regular reader or poster. 6' 5". 200 pound clyde. 37 inch inseam. Ride road, gravel and TT. Masters racer. Mostly crits (refer back to height and weight). Decades of riding experience that started young with 6 day a week newspaper delivering riding a Schwinn Stingray in freezing cold, rain, sleet and snow and high summer heat and humidity to getting first 10 speed late 70's and getting more serious about training, riding, and racing. Now 300 mile weeks all year long. So a bit of time put in, seen fads come and go, and have maybe a little bit of experience to write about proportionally correct crank arm length. Again, just based on what I feel.

After reading through the above and seeing arguments made from both sides I am not going to argue anything specifically. I will just write what I have learned and what works for me. What works for me may be different than what works for you. What I feel may be different than what you may feel. And unlike most, this is not theory, all my specifics presented is application and real world.

So here goes. In no particular order other than stream of thought...I feel...

Having a bicycle manufacturer's marketing and/or purchasing department spec out a retail bike in Large or XL frame sizes with 175 mm crank arms is negligence

Seeing and hearing about pro bike fitters never asking what crank arm length being used or what q factor preferred by a taller rider is malpractice

Having an appropriate BB drop to accommodate longer (please note "longer" not "long" cause that is the crux of many arguments posted above) cranks is quite helpful.

I have used 175, 177.5, and 180 cranks. Be like a shorter rider using 145 or 150 cranks or whatever the 21+- % comes out to. 180 always felt and seemed short. Why should a long legged rider who wants to make use of that leverage be penalized so much by being limited in leverage length by not using longer cranks? Did not make sense to me back then nor even more so now.

I now have and use:

BB drops of 60 to 67 depending on frame
Mostly custom frames - ALU, Carbon, Ti, and steel
Road climbing bike - 195 cranks
Road century/fondo bike - 195
Road race bike - 190 mainly to get cornering clearance
Crit race bike - 185 mainly to get more cornering clearance
TT bike 185 - mainly to get over the top easier with old, worn, tight hips
Gravel bikes 190 and 195

I know I get more power with longer cranks
I know I climb better with longer cranks
i know I can climb out of the saddle way better, way more comfortably, and way longer with longer cranks
I know that longer cranks, for me, do not affect cadence whatsoever. I can grind in 60's and spin easy at 110
Many have said they can’t even tell I am using longer cranks since I can sit and spin 90 to 105 smoothly and efficiently. Again, for me cadence not affected
I know that I laugh when someone says or writes longer cranks will make it harder to spin higher cadence
I sprint faster, better, stronger with longer cranks
I have seen max power of 1600 watts. I see 1200 often in crit surges and gap closings. 1200 is a easy sprint number to get at end of hour crit
And I truly wish I could use 195 instead of 185 for crits cause I feel it would be that much more advantageous to me at my size
I laugh when aerodynamics is brought into the equation. As a clyde, one with a flat back on a TT bike who looks over while riding next to a shorter rider and sees that head level is a foot below mine
Please do not bring in faster aero capability is lost with long cranks since a wide clyde, taller clyde, bigger/fatter clyde will never be aero or more aero than somebody pushing way less wind resistance
Please think of that aero concept as a school bus versus a sports car
I do know that with longer cranks my saddle height drops proportionally and when riding next to a same or close height rider I often sit lower than they do. Hey, more aero!
I feel an industry arbitrarily set 180 max length is just that - arbitrary but economically justified by industry
I feel that longer pedal spindles that provide a wider q factor is also very beneficial and important for longer legged riders who may have bigger torsos and thus wider hips
Why use a power robbing narrow stance when a wider stance, for me, puts down more power and is way more comfortable on the hips to have a more natural wider leg width
i feel there is a misconception that the cost for custom alu longer cranks is way too expensive when I get them for less than the wholesale cost of carbon Campy 180 cranks in the past
i feel threaded BB for taller heavier riders is way less problematic coupled with stronger 30 mm crank spindles that come with my custom longer alu cranks made by Tom Slocum at High Sierra Cycle Center has been a great durable set-up
And now cue the longer alu cranks are heavier comments. Trust me, as a clyde - 15 pounds bikes and saving grams are weight weenie concerns and really don’t apply here. Micro percentages of grams or a pound to clyde is miniscule and really only the wallet gets lighter chasing those weight reductions

Lots more to add, but that is what I feel and to have some write that I should not feel that, should only need and use shorter cranks either is not a tall clyde and has not lived my cycling life to really know and be able to tell what positive differences longer cranks have done for my cycling performance, results, health and fun, or that same naysayer has never tried longer cranks.

If you are taller with arms longer than most of the cyclist legs you may ride with, and do not use or have not tried longer cranks arms, you are doing yourself a disservice. That is what I feel I needed to state here.

Signing off,
195Cranky

woodcraft

[QUOTE=195cranky;21992828]Guess I will chime in here.


Thanks for the input! Sounds like some 30" wheels would be helpful.

veganbikes

I saw this thread was originally from way back in 2009 and immediately thought it was going to be Drippy that zombie'd it and gosh was I right.

It is always funny to see people obsessing over some old cheap bike over and over and over again getting the same result but expecting something different. There is so much moisture it has rusted the frame now and created holes. The next thread will be "what is the cheapest way to repair frame holes? can I just use imitation brand duct tape or do I have to pay an extra 52¢ for the real stuff"

Ride whatever cranks you want to ride but don't expect it to always be a good idea. If you really need custom cranks first GO SEE A FITTER (who works in dynamic fitting), then do what the fitter suggests if you so choose. They are professionals who study all this stuff and can view you on the bike and get you into an optimal position and recommend things based on your unique body.

smashndash

I don't see anything even mildly controversial (IMO) here. The bike industry is screwing people big and small with the range of crank lengths currently available. I'd be shocked if someone with a 37" inseam felt like 175mm was the optimal length when someone like me, with a 32" inseam, likes 165mm. I agree that custom cranks aren't enough - frames need to be adapted to those crank lengths. So we really need the importance of crank length to go mainstream. Otherwise people who actually care about the mechanics of their pedal stroke will be forced to use solid aluminum cranks and custom metal frames (assuming you don't want to spend a lot), which puts them at a disadvantage compared to those who are appropriately sized for standard carbon parts.

195cranky

Retail OEM bicycle frame manufacturer's would have a difficult time justifying the additional expense to develop adjustable molds that can be tweaked for BB drop, chain stay width clearance, and toe overlap to accommodate for those small number of buyers who may desire and/or really benefit from using longer cranks. Mainstream drivetrain American, Italian or Japanese manufacturers barely put out 180's and even that length seems to be mystical to the industry at large, fitters in general, and consumers especially. Talk to Rotor, Praxxis, Wheels Manufacturing, FSA, and others in this space and more often than not the response is there just is not enough demand and if there was the minimum numbers to run design and materials through would make for a lot of new old stock collecting unsold inventory dust.

Education and ease of adjustability or ease of parts swapping may make this bridge crossing a future possibility but when most who need don't know how, or why, or where, much less the watt of this issue, longer cranks will remain mystical. Look at LZinn's attempts to educate in theory and have manufactured into application. Comes down to; most people can buy a business suit retail off the rack and it may fit ok to good. Lucky them that they are "standard" sizing. Some may need some minor or even major tailoring for proper fit. Those who don't fit retail, or enjoy and can do custom tailored, get to pick their fabric, colors, style, stitching, pockets, lining, and other variables to thus wear a truly custom made, custom fit, custom tailored product. More often than not, these are the same consumers who are beyond standard sizing and need from a tall perspective longer sleeves, longer body lengths, or longer inseams.

Really no different in the bicycle world. Some can buy retail right off the rack and of course get some minor adjustments made and they are good to go. Lucky them that they fit in the "standard" world. And then some may need longer stems, wider bars, longer reach bars, less drop bars, longer seat posts, wider saddles, or narrower saddles, on and on. So with a little parts swapping they are on the road not too inconvenienced. Taller rider walks into retail and they may have a Large 59 60 or XL 61 63 but often needs to be special ordered. Bike arrives and does the salesman, shop owner, wrench, shop fitter, or an outside fitter even look at the default 175 cranks and then maybe even think, much less offer to go to 177.5 or god forbid the mystical but possibly still too short 180's? Seldom. That is mainstream true to the core. Default and out the door. Enjoy your not long enough sleeved suit and too short of pants that don't even hit the tassels on the loafers.

One of the problems with mainstream, most buyers don't know of the other cycling world out there. The custom frame maker, the wheel builder, or hey... a custom crank maker. The perception of higher cost or more effort to get is real but not always true. Poster above, smashndash is correct with initial statements. Then I read..."will be forced to use solid aluminum cranks" Gulp! Oh the horror! OK, I give up. What pray tell is wrong or not as good as short standard carbon press fit garbage? Let's change that misconception and put high watts through a threaded BB, 30mm spindle (instead of 24), a torqued bolted connection, 5 arm spyder, longer yes heavier solid alu crank arms, and for giggles a solid TT aero plate 53 or 54 chain ring and what do you get? You gets a solid, strong, durable, positive lever arm and system that just cranks! For possibly less cost than too short carbon stuff with a brand name on them. A bit heavier. Yep. But in the percentages compared to body weight and total with bike weight - negligible. 18 or 19 pound bike weight in this space is not an issue. Especially when most clydes could lose 10 to 20 pounds.

Now on to custom metal frames versus overseas slave labor built manipulated plastic tube shaped molded frames. Instead of trying to address..."which puts them at a disadvantage" let me present the advantages as I have experienced many times. I get to speed dial the local or out of state frame builder. I get to talk with them directly about the build flavor and ride feeling desired. So being a clyde, I could stipulate; strong, stiff, solid, durable, and around a 59 60 with this headtube length, that top tube, this angle, that angle, this wheelbase, etc... Frame builder puts his years of experience and knowledge into play and comes back with tube shapes, tube make, tube diameter, tube wall thickness, etc... etc... artistry at it's finest when he welds either alu, steel, or Ti. I throw on some alloy or carbon stems, posts, forks, bars, rails, rims...depending on dampening desired and I end up with custom geometry lengths and angles to my size and weight, custom tubing to handling characteristics desired, and my taste graphics and my palette paint for a one of a kind frame that won't be identified as the 20xx insert any brand name and model here color scheme that is now old and replaced by newer model year colors. The other day heard, "New bike?" I replied, "Nope, just my 11 year old custom built and painted frame." The point of that is, custom bikes seldom identified by model year retail color way. And as for custom frame cost, have paid $1,100 to $3,200 from alu, to steel, to Ti. Do they work? Yep. Do they last? Yep. Do they all fit 185 to 195 cranks? Yep, all made with threaded BB (yep that still works and does not come loose nor creak!)(what a concept!), all made with chain stay clearance for longer cranks, and all with a bit less BB drop to avoid that pesky pegging out. In my size, try to do that with current carbon standard sized plastic machines. Before the comments fly, I do own and ride one new OEM and one Chinese mold private label carbon frames so not just narrow and deep into custom.

Also, follow the money. May as well since it was written (assuming you don't want to spend a lot). Custom frame builder gets paid. Passionate artist making a living. Custom crank maker gets paid. A much needed rare breed from design to finished niche product specialist. Now the eye opener, the OEM money breakdown of who gets paid when say a $8,000 to you gotta be kidding $16,000 retail bicycle is purchased:

OEM Company Owner
CEO
CFO
accountants
lawyers
admin
purchasing
marketing
design
R&D
wharehouse
shipping and receiving
sales
warranty
IT dept
customer reps
Demo vans
Pro race team sponorships
etc

Importer and/or Wholesaler and/or Distributor owner
CEO
CFO
all that staff
Reps

Overseas frame builder company
Owner
CEO
CFO
IT
accountants
lawyers
admin
purchasing
marketing
design
R&D
wharehouse
receiving
sales
warranty
translators
etc

and the actual frame builder
possibly slave labor on slave wages?
possibly unhealthy carbon dust working conditions?
heat molding plastic material that may cost what $50 total?
sander
painter
paint maybe $20
assembly putting on volume discounted purchased parts with 175 crank arms for almost all size ranges
shipping guy wrapping and boxing
box in container
container on ship
ship shipping
unloaded at USA dock
train or truck driver

UPS Fed Ex to LBS

LBS owner
manager
salesperson
mechanic

And finally buying customer with possibly a lighter bike, giddy with new marginal gain aero frame with most of gains lost as soon as a cage and water bottle are installed, and of course a much lighter wallet

In essence, maybe $50 to ok $100 bucks in materials and paint for a retail OEM frame, maybe a couple bucks an hour for frame build labor, the rest of the $$$$ goes to everyone else on the gravy train. Quick review on custom frame, $200 maybe $300 in frame tubing and bits, some for paint, and most of the rest to the frame builder who not only may put their name on their frame but may also put their heart and soul into their passion. Never any regrets in paying a frame builder, a true craftsman, for their time and finished product.

Where were we? Oh yeah...longer cranks. If needed or curious, why deny yourself? There will always be those who say or post that you don't need longer cranks, don't work, not proven, I don't need them at 5'8" so you at 6'4" for sure don't need them, cost too much, too heavy, disadvantaged, can't spin with them, hurts knees, hurts hips, hurts when you peg out, won't work with your frame, saddle will need to be lowered, toe overlap makes bike unrideable, looks funny, not carbon, wrong color, don't need wider q factor, go back to basketball, and the best one of all...175 came with the bike so must be right. All bull! Not one of those should stop the buy-curious from purchasing and trying for themselves.

Good luck and good spin.
195cranky

shelbyfv

Yep. Hope he enjoyed reading all the additional bloviage....

elcruxio

I'm 6'5" with 38" inseam and I have never felt the need to get longer cranks than 175mm. Standard lengths work just fine and I can get lower on the bike if I'm not using all of my range of motion on spinning the cranks.

I haven't seen any plausible evidence why longer cranks would make any difference. They'd change the gear ratio sure, but I can do that by changing chainrings and all that.

I did google longer cranks before when I was curious about them but really I didn't find any evidence why crank length would matter at all. Except when the crank is too long, that's bad. The reality may just as well be that 175mm is optimal for 38" inseam and people 5' tall are riding too long cranks at 165mm.

Q-factor to me is also a nonissue. I've ridden really narrow q-factor cranks (bb30 road crankset that really hugged the frame) and a really wide q-factor (fatbike with 100mm bottom bracket width, outboad bearings and extended width cranks). Comfort wise doesn't make lick of difference but the fastest I've felt was with the narrowest q-factor. This from a wide build and wide pelvis person.

DaveSSS 

With an 83cm cycling inseam, 175mm is barely over 21%, so I bought a new shimano grx 48/31 crankset with 175 arms to try with my sram axs drivetrain. It shifts fine and I haven't noticed a drop in cadence, but it did create some toe overlap. I decided to make no change to my saddle height or fore-aft position, so the additional travel is split between the top and bottom of the stroke. I've only ridden the new setup twice for about 75 miles, so it's too early to draw any conclusions. My small chainring went up 1 tooth from a 30 to a 31, so I didn't gain or lose any leverage for climbing steep grades, compared to my 170mm crank arms. My top gear increased by 2 teeth from 46 to 48. The 48/10 is like a 53/11.

195cranky

So what you are saying basically is, that at 6'5" with a 38" inseam, you use the "standard" 175 default length that probably just came with the bike AND you have NEVER tried longer cranks. Wouldn't your own use be "evidence" enough? Again, wondering why a longer legged person would not want to make use of a longer lever arm? When you are measuring standing vertical leap do you only bend your knees half as much as you can to jump the highest possible? Or would you try to find and use the amount of knee bend in preparation for the jump that would provide the most force and power to get off the ground and jump the highest? Guessing that a bit more knee bend as opposed to less will get you higher off the ground. Doesn't that make you wonder how short crank arms may be penalizing your actual capabilities?

Curious what makes you believe that longer cranks would change gear ratio? Have you tried longer cranks to see if you need to change gear ratios? And if it does, could that possibly be construed as a benefit? I know that with longer cranks I have no issues riding road on 53/39 or 54/42 with 11/25 or 11/27 and have never felt a need to go mid-compact or compact for any climbing gradient. In fact, since I have tried and now use longer cranks I found that I can climb easier, stronger, faster, sit and spin where needed, and out of the saddle much longer with longer cranks. Have you actually tried longer cranks with an open mind or is it just easier to do a google search, find nothing empirical, and then say there is no plausible evidence? The best evidence is actually giving something new and different a try.

And by trying, you may also learn that on a road bike, even with longer cranks, you will still be able to get into the drops and be as low as you want to be with no perceived hindrance to your pedal stroke range. That is what I have found. In fact for road, I use pretty short head tube lengths, slammed stems, and deeper drop bars and can ride comfortably as low as I can while spinning 195's. Try it. You may be surprised. Then again, it may not work for you or for others. Did for me.

As a tall person, if you play tennis would you want to use a junior racquet? A standard adult racquet? Or maybe a larger head and slightly longer racquet? For golf, would you use standard length? Or maybe a bit longer clubs? For skiing, would you use shorter made for a 5'8" skier GS skis or possibly the longest GS skis made to be able to get the turn radius, ski bend, and edge power your longer legs and taller body can produce? And if you are stacked on the ski would you ski with 137 cm long ski poles or 142 cm? Guessing you would probably go with the proportionally better sizing. Why wouldn't you want to at least try to see what may be a better proportional sizing?

And if that is just more bloviating, sorry for trying to open readers minds and not just drink the standard kool-aid.

elcruxio

I gave it a lot of thought and I don't think I'm penalizing my actual capabilities. In fact, I might even be better off with a shorter than 175mm crank. But since I don't want to spend money on cranksets and 175mm isn't causing me issues I'm not going to experiment. Maybe with the next crankset I buy. I'll get to examples further down the post.

A longer lever arm makes it easier to turn the selected gear. But then that lever needs to travel a larger circle and all that. But having a larger lever doesn't actually increase speed, because it does not affect external factors such as wind resistance. It also cannot create energy out of nowhere. With a fixie there could be a point to a longer crank but even that effect can be completely duplicated with gearing and a shorter crank.

Trying something is anecdotal evidence which is generally considered to be the worst type of evidence.

The issue I see with longer cranks and an aero tuck is that longer cranks use up the range of motion that would be otherwise used to bend the pelvis forward. Having the other leg rise higher during the pedal stroke has a negative effect on how well the downstroke leg can extend whilst in a tuck since the pelvis works as a unit. What one leg does has an effect on what other can do. Hence why pistol squats are so difficult.

A lot of these examples aren't applicable because they don't address the main issue of longer cranks which is the use of range of motion. I'll start by pointing out that while it's good to have good mobility and a large range of motion, the utilization of said range of motion should not be the end all motivation of all exercise. For weight training? Sure, that's good form. For aerobic stuff? Not so much unless there's a specific reason. And in my mind there is no such reason in cycling.

The golf example is an interesting one, because counterintuitively a shorter club equates to a longer crank. Why? Larger range of motion use. With a shorter club you need to use a larger range of motion to achieve a swing.

But I think there are better examples. I'll start with an extreme one.

When running, do you want to take short quick strides with just enough bounce to get you along, or do you want to perform a pistol squat with every stride and leap forward as far as you can? The answer is obvious but it highlights the idea that when performing aerobic exercise with the aim of moving steadily in a direction it's typical to use only as much range of motion as is absolutely necessary. Any more is a waste of energy and can potentially lead to injuries.

Another example would be a challenge where you have to squat 100 pounds up and down 50 times. Will you do deep squats or quarter squats? If the aim is to simply go up and down 50 times I'll do the quarter squats, because it's actually easier to generate power when using a smaller range of motion. And since there's no need to create momentum like in box jumps, there's also no point of a long acceleration period.

If we return to cycling with another extreme example. I'm of the opinion that longer cranks can more easily cause injuries. Say you have a bike with 50mm cranks. Will that probably cause injuries? I don't see any mechanic where injuries would be more likely. But if you use 500mm cranks? Injuries are just a matter of course then, because going constantly against one's range of motion or limits of mobility will eventually break stuff. The knee also gets more unstable as flexion increases and instability increases the likelihood of injury. That's the reason why one should not deep squat without excellent heel support. But just the heel flexion increase is a good reason to consider shorter cranks instead of longer

Moisture

195cranky have you tried 200 or 205mm arms before?

195cranky

Have I tried 200 or 205mm cranks?

Well, I googled (and you know everything is now on the internet and the internet is always right) long cranks and did not see any good info, or good data, or plausible evidence, or get anyone else's input who may have spent years on proportionally correct longer crank arms to even consider trying since my bike came with 175 arms and if that is good enough for a 5'8" rider than it must be good for my height.

Oops... sorry. Must have had a brain fart and just wasn't thinking straight when I wrote that.

No, I have not tried 200 or 205. I would love to try just for the sake of seeing what may be construed as long cranks possibly being too long? One of the concerns going past 195 for me is amount of BB drop thus cornering clearance. If there ever was a day when 30 inch road wheels (instead of the 27" that fits well under a 56cm frame but look small dimensionally under a 60cm frame) were to be developed and Large or XL frames coming standard with bigger diameter wheels that would allow for more BB drop yet more clearance height from ground to BB. This geometry and size scope would lend itself for taller riders to possibly have easier access to longer cranks arms. But for the industry to move in that direction with very little to no call for such extreme measures and very little economic feasible marketplace for such sizing it may only be a fantasy. Especially since even at 6'5" I can ride 59 or 60cm custom frames and get geo angles heights drops and wheelbase on 27" with less BB drop to work well with longer seat posts and stems. Point is, a small 5 foot nothing rider rides the exact same wheel diameter on a very small frame that has not a head tube but just a joint as does a 6'6" or taller rider who rides a dinky little wheel diameter in relation to proportion.

Seems like a small light sports car with say 20" wheels and low profile tires will handle better that a pick up truck with 15" wheels. Size wise a certain wheel diameter on smaller frame makes sense and the same wheel size on a larger frame just doesn't seem to make as much sense. But a 29 or 30" wheel with longer spokes and more rim structure would possibly be too heavy and not stiff enough?

Got sidetracked there. Have just enough cornering clearance with 195's and have seen my best power numbers with 195's so in essence have maxed out at a 195 length.

Moisture

195cranky you should be able to spin a bit faster and maybe slightly more smooth with 195.

I think my outboard bearing integrated spindle bottom bracket alone is quite helpful for maintaining a healthy cadence.

My 63.5cm frame (25") has a BB drop of 275mm. Its the absolute lowest I'd want to go with my 190mm crank arms. With an 88cm inseam 190 is the longest id want to go, 21.6% just like you with 205mm cranks. Its be worth a shot if you got the right frame geometry.

I dont go high speeds on my bike most of the time and would consequently prefer smaller wheels. I also prefer thicker tires.

I am so used to lifting an inner pedal around tighter turns. Its well worth the tradeoff though. I've heard of people using 200mm arms with a similar bb drop.

i think it is a proportionally high enough bottom bracket for the majority of reasonable height people who should be riding such a size.

elcruxio

You know you could have worded that a bit more maturely. Just because someone disagrees with you doesn't mean you should become so passive aggressively hostile.

There have been studies on crank length but they seem to suggest that crank length does not really matter all that much. However shorter can many a time be beneficial since while a shorter crank does not reduce power output it does decrease the risk of injury. And going to other way, a longer crank does not increase power output but it does increase knee flexion, closes the hip more and requires more mobility, all of which can predispose one to injury.

Since this is an interesting topic I did some more reading. What I found out was that for example the idea behind the Zinn method of inseam x 2,16 is based on correlation but no causality. Paraphrasing, he looked at some of the most successful cyclists and noticed that their crank lengths compared to their leg lengths suggested a ratio of crank and leg length of inseam x 2,16.

All the cycling superstars he mentions as an inspiration for his proportional crank length ideas are either at or slightly below the average height of the time of their birth. It would in fact seem that many if not most of the most successful cyclists have been either of average height or slightly below. That makes sense as it is easier to gain a high watt/kg number when you're on the small side. Even in my most lean state I would need to crank out an average of 510 watts to get to the level of Chris Froome, who isn't short either. That would be insane.
So using successful cyclists as a basis for crank length is really stretching the correlation and it in no way implies causation as there are so many other factors to explain why said cyclists became so successful in the first place. The simplest answer could just be that around average height there is the largest pool of potential gifted cyclists to pull from so most successful cyclists come from that pool.

I haven't seen a single plausible explanation why using more range of motion would create more power. Jumping is a bad example, because in jumping one needs to create momentum and there using ROM works. However when climbing stairs for example there is no need to add momentum to the momentum required to climb a single stair. Should taller people have houses with taller stairs? I can climb two stairs at a time but my knees will not thank me if I do that exclusively.

Moisture

Do you have a longer inseam and have consequently tried longer than average crank arms? Have you at least tried a couple different sizes which were in proportion to your inseam?

A longer crank arm gives you more leverage over each gear. with each full rotation of your crankset, you are turning the wheel more than you otherwise would be with a shorter crank. As long as your arms aren't TOO long to enjoy the potential benefits, then yes, you CAN get potentially more power with each rotation of the crankset and the larger (or smaller) range of motion is going to change your gearing as well.

The only thing I can agree with would be your comment about shorter crank arms being safer than something which is simply too long. But I get much more stress on my knees using 170mm arms than I do with my 190mm arms.

Until I see some sort of test which explicitly specified that differently proportioned test subjects were used, along with respective inseam and arm length percentages, i think these claims that proportionally longer arms won't help you output more power is complete nonsense.

I'll also state again that this is mostly a factor of fit and finding an arm length which suits your style of cadence. Using different arm lengths to try and change your power output or gearing doesnt make as much sense.

Like I've said before, I've used 165, 170, 175, and 190mm arms with my 88cm inseam. There's absolutely no doubt that I am able to transfer more power to the rear wheel while enjoying a better fit, MUCH smoother spin, and gearing which is far more in line with my cycling needs and abilities.

Koyote

mstateglfr 

Your front chainrings and cogs feel disrespected.

Moisture

I figured I would revisit this thread after trying out 185mm crank arms for the first time yesterday.

First things first, i believe that a lot of the "benefits" i first saw in using longer than average crank arms was with the better quality bottom bracket. One which is smooth and spins well (without spinning too freely) Will make a huge difference with your cadence. Next would be the design of the pedals platform as well as the bearings inside. A wide, low platform with some pegs or straps to for better power transfer throughout the entire pedal stroke is also huge.

. I dont think arm length makes as huge of a difference as I may have initially wagered. Its a matter of preference (considering you have actually tried other lengths for comparison). the percentile range is a good starting point, but different styles of cadence, saddle position, riding style, bottom bracket clearance / frame size etc all play a role as well. I've narrowed it down to mostly a difference in gear inches which is probably the most important difference you can make as long as you stay within a reasonable range.

a general range of 20.6-21.6% seems to be rather accurate. Going less will always be safer than going more, unless we are talking less than 19.5% As far as non standard lengths with my 87.5cm inseam go, I've tried 185mm (21.24%, and 190mm, 21.7%.) .

First impressions, is that there is clearly more of a difference with just 5mm than you might imagine. As I got used to it I noticed the small but otherwise beneficial decrease in gear inches. I was able to consistently maintain slightly more power,.more smoothly, at a higher cadence. Going 190 seemed to spin smoothly and offer great power output when cranking below your optimal cadence, at a very specific RPM which resulted in a marked "dead zone" or lumpy area of the spin when trying to spin at a more efficient cadence. (think cranking back up to your ideal cadence im between shifts) Put effort into the quality/speed of your spin and the slightly shorter arms seemed to really deliver. They definetely felt easier on the knees and a more natural fit for me and the bike as well.

To summarize, as long as you arent going past 21.6% and aren't somewhere below 19.5% or so, im sure what you're running is fine but absolutely wouldn't hurt to experiment if you can do that without too much effort. Please keep in mind that these are just my personal observations and not necessarily something everyone can relate. Im curious to hear opinions from everyone who has actually tried out different lengths, whether your inseam is less,.more or average.

Moisture

Does anyone think that having a torso to inseam ratio + or - the average 45% figure would play a role here as well? I'm at about 46%.

Branko D

Holy thread necro... anyway, a few things.

One, if you don't measure power either directly or indirectly (can be reasonably estimated based on hill climb speed and weight but differences in weather and how hard you went make it a too low resolution tool), then talking about power is pretty silly. How do you know? Talking about feel is all fine and well when we are talking about fit and comfort, but when discussing performance, feel can be completely misleading.

Two, there are studies about effect of crank length on power. In short, unless going for very short or very long cranks (under 150mm, above 200mm) where there is a small (negative) difference compared to mainstream crank lengths, there's no difference in sustainable power between mainstream crank lengths.

Choose cranks based on fit and bike geometry, because a road bike with 200mm cranks - really - how do you intend to pedal in corners?
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If someone claims what everyone is doing is all wrong and has a magic formula which is better, look for proof. When it comes to crank length = xy % of inseam, there's none. Mainstream stuff is mainstream because it works really well.

shelbyfv

PeteHski

I find this summary as good as any on crank length:-

https://bikedynamics.co.uk/FitGuidecranks.htm

There are very few downsides to shorter cranks, but plenty of potential issues going too long. I asked a very experienced fitter recently and he was strongly advocating shorter cranks based on his own experience with customers and recent research. I'm 184 cm tall with an inseam of 88 cm, so most bikes I have come with 175 mm cranks as standard. The fitter I spoke to recommended dropping down to 170 mm cranks for a new build.