KramesJamer

I am 47, 6'-1" and 195lbs. I have raced on and off since I was 20 including a season in Europe. I am a CAT 1 on the road and a CAT 2 on the track. For all my years of riding, I rode 175mm (on road bike, on TT bike, on cross bike, on mountain bike). I went back to doing the Pursuit and Kilo on the track in 2012 after 20 years off the track and had a set of 180mm Zipp Vuma Chrono cranks. I got bronze in the pursuit (3k in 3:42) and 4th in the Kilo (1:08.797).

Last year after hearing so much about the benefits of short cranks, and primarily influenced by the Martin study of peak power at 220/195/170/145/120, I went cold turkey and went 145mm on ALL my bikes. I have been on them for 13 months now.

My observations: my peak power is down 250W on average and 400W from my all time high. My standing starts in the pursuit and kilo are embarrassingly slow. I had decent success in criteriums and mass start track races, winning a half dozen or so, but it wasn't from sprinting, it was from overall fitness. I did have a PR in the 3K pursuit at Carson Velodrome of 3:41.

I am struggling with wanting to stay on the 145mm given how I see the leverage and peak power down so much. I want to get an adjustable crank for my road bike and track bike to go out and do real world field experiments to see power numbers. I am tempted to leave 145mm on my TT bike and my Pursuit bike as aerodynamics are the premium, to go between 170mm and 175mm for for criteriums, road races, and mass start track races, and to go 180, or maybe even 190mm for the Kilo (where the start and leverage is most important) and mass starts.

Thoughts on that logic?

I am leaning towards getting a Power Cranks adjustable crank (from 145mm - 182.5mm) that you can put in dual mode (locking out that both arms rotate independently) and then I can do out on the road and take notes about power output.

Any other feedback?

Leisesturm

The fastest way up a flight of stairs is on your toes! I suspect most people in a hurry, take the stairs on their toes until they fatigue and then switch to a flat foot position. Most of the scholarly discussions here on crank length concern racing cyclists and these individuals are highly motivated towards efficiency (i.e. in a hurry) and results. Your mistake is discounting the effects of physiology and psychology in what you assume is a strictly mechanical system. Shorter cranks may result in an increased cadence. They may not. And longer cranks may result in a slower cadence, and they may not.

I submit that a highly motivated racer on 170mm cranks is going to attempt to turn those cranks as fast as he possibly can. An equally motivated racer on 100mm cranks will be doing the same thing, and possibly in the same gear inch. Possibly. But the physics will be against the shorter cranks. With enough talent (drugs?) just about anything can be done, but... 170/175mm cranks are not illegal, drugs are. Talent is randomly distributed through the population, 170/175mm cranks are as close as your grocers freezer. Can you say no brainer boys and girls...

Leisesturm

Anthony... why do you continually imply that there is some international agenda against shorter riders? Maybe there is a reason that a short bike comes with 165mm cranks! Maybe that is, in fact, the best length for a HUMAN rider, regardless of size, to achieve good results over a variety of terrain and road speeds! Maybe, Anthony, maybe, you are wrong!! Can I suggest, kindly, that you attempt to be a little more objective? There is no inter/national conspiracy to harm short people, or limit their performance on bicycles. At 5'1" plus you are a minority among adult male riders, you know that right? So? Why do you imagine that short people specifically are shortchanged by the bicycle manufacturers? I don't imagine super tall riders have all that much choice either. Leonard Zinn has established himself as a resource for super tall riders, and Georgina Terry has established herself as a resource for shorter than average cyclists, male or female and ... "what if that's as good as it gets?" -Jack Nicholson. As mentioned in another post Mark Stronich shortens brand name cranks to customer specifications. TA, Stronglight and others offer a wide variety of crank lengths, and you yourself have managed to obtain custom frames, bikes, wheels, cranks, and etc. to aid in whatever quest of bicycle adaptation you seem to be on. Why are you still grousing?!

Leisesturm

Hey, if you want to spend $1,000 on cranks to find out what the other poster found out with two pairs of short cranks, go for it! Myself, I am thankful that posters like him are generous enough to share their experiences so that we don't all have to reinvent the wheel.

McBTC

Probably true that the stair analogy has it's limitations (doing stars is very literally a pedestrian activity-- the gradient is totally different from cycling and foot speeds at a relatively high cadence over many miles does not play much of a factor).

Nevertheless, the last paragraph from what I said earlier that you didn't quote is what some can expect in real world bicycling situations (especially when not focusing on extremes and considering what I believe is a more common situation where many of us may be spinning in the 70s but would perform better overall spinning in the 80s, which can be accomplished easily and very naturally by going to shorter cranks): If you couple an increase in cadence with a higher gear (which is what the studies indicate may come naturally from an optimal foot-speed), the only result possible is an increase in power.

KramesJamer

I understand your comment, but my whole post was specific to the question of if different crank lengths apply, or are more advantageous to different events (staying in an aerodynamic position and shorter cranks vs. standing sprints or standing starts and longer cranks). I don't want to spend $1,000 on a set of adjustable cranks, but at this point, I don't know of a better way to answer the question.

Carbonfiberboy 

Great! That sounds very interesting. Let us know what you find out. I'd also be curious about your success with the unlocked PCs. The few reviews I've read seem to indicate that those with very good circular pedal strokes do not benefit, but those who hammer the downstroke do.

Leisesturm

The question may be unanswerable. In any case, it appears you would be in a good position to answer it for yoursef because you appear to have experience with a much wider range of crank lengths than the average bear. What have you learned? If still no conclusion what do you think would be different now? I've just saved you $1,000.

AnthonyG

The fundamental question here is, Why does it bug you( a tall rider), SOO much that a short rider wants to use short cranks?

Seriously.

I've stated several times in this thread that its not so much a conspiracy as it is a convergence of interests and biases that leads to a serious limit on choices in bike design.

Number one is, Manufacturing economics (I'd like a dollar for every time I have stated this in this thread).Less variety makes items cheaper to manufacture. More variety makes items more expensive to manufacture.

Number two. A natural human bias that seeks to find he ONE right answer which renders all other answers as wrong.

Both reasons are likely to be burning you up inside to be honest which leaves you unable to leave the question alone.

Anthony

AnthonyG

As a proponent of Short cranks for SHORT people I would have NEVER put a 6' 1" rider on 145mm cranks. Never.

As such the fact that you performed poorly on short cranks is NOT evidence supporting the case that SHORT riders don't do better with short cranks.

Anthony

McBTC

It would make no sense to say that 'short' engines should have shorter crankshafts than 'tall' engines. The crankshaft length in a car engine is only a part of the story when it comes to generating power.

I suspect the same goes for humans and there seems to be a growing body of research that challenges conventional notions about the most efficient crank length. I do not know of any studies that support the idea that taller riders are able to generate more power than others simply because they have longer legs that make them better able to equip their bikes with longer cranks that then allows them to produce more power.

If we're looking to maximize watts, at any given cadence, only the size of the gear matters. At any given gear, only the cadence matters. Accordingly, it seems to me that overall, cadence and gearing matter most when it comes to producing power and varying leg lengths may have relatively little to do with it.

AnthonyG

Actually, it does make sense to say that short(small) engines have short crankshafts, and tall (large) engines have tall crankshafts. That's just the way it works.

Is there a reason why long legged riders shouldn't use short cranks like short legged riders?

Yes there is.

The femur is a REVERSE lever. Short legged riders have MORE force at the knee than a long legged rider. A long legged rider, NEEDS a longer lever to be able to push down on the cranks as hard as a short legged rider can.

You need to MATCH crank length, to leg length.

Long cranks don't work for everyone. Short cranks don't work for everyone.

If cranks are too long then the rider has a LOT of torque at 9-3 but struggle to get through 12-6. If cranks are too short then there is a lack of torque at 9-3 even though its dead easy to get through 12-6.

I don't think that there is ONE crank length only that suits ONE leg length. There is a range that works yet the range that works for a short legged rider is shorter, than the range that works for a long legged rider.

Anthony

KramesJamer

The thing is... I didn't perform poorly in general. I set a new PR in the pursuit and I won several crits and mass start track races. What was poor, was peak power and standing starts... hence my desire to explore different lengths for different events. I still think at this point that the benefits of a shorter crank (more open hip angle and better aerodynamics) makes sense for all riders sizes in AERODYNAMIC events, but not ones where leverage is important.

AnthonyG

Yes, hence my case that aerodynamics and comfort are the correct arbiters for crank length. Not power.

I suspect that someone who is 6'1" is going to be as aerodynamic as the can be and have open hip angles with 165mm cranks. No more benefit for someone that tall to go down to 145mm cranks. They will only start suffering from lack of leverage.

A typical 5'"4" rider however would be much better off with 145-150mm cranks.

Anthony

Leisesturm

A 6'1" cyclist is NEVER going to be as aero as a 5'4" one, no matter what crank size s/he uses. A short cyclist on long cranks can still be quite aero. They have shorter bones, the longer cranks will NOT impact their aero ability comfort. If anything, a short cyclist can use longer cranks than a taller rider for the same degree of 'comfort'. But whether they should or not depends on what they need to do with the bike. You're so stubborn about this its pathetic It's really going to hurt when it finally sinks in that you have been wrong about this for so long.

The human interface with cranks is complex. Complex beyond belief. You completely discount the many articulations. Ankle flexion is capable of inputting considerable power into the drive-train independent of the power input by the quadriceps. I will say it again, a plumber does not choose wrenches based on the size of his hands. He chooses a wrench based on the amount of torque he needs!

A short cyclist can use 170mm cranks to very good effect if they want to. If they don't, fine. It's their choice. A tall cyclist can use short cranks, its their choice. I don't know if it is in this thread or the other one but the Penny Farthing bicycle with the adjustable cranks. The adjustment is there so a shorter cyclist can ride it. In 1860 the bigger the wheel you could fit over the faster you went. Cyclists bought the biggest wheels they could straddle. They used the LONGEST cranks they could straddle. Shorter cranks were a compromise necessary to reach the pedals of a 66" tall front wheel! When safety bicycle were invented, the longest practical cranks were fitted that would not strike the ground when turning. It remains that way to this day.

AnthonyG

Leisesturm. YOUR stubbornness is out of control. Simply calling ME stubborn doesn't take away from you being stubborn.

Seriously Leisesturm. I have asked you before. I will ask you again. Why on earth is a 6' plus person arguing so vehemently about how a bicycle should be designed for a 5' range person?

Really. Please disclose your interests in this argument. I want to know.

I most certainly would NOT put a tall rider on 145mm cranks. That's someone else's argument. I'm calling for a greater size range of parts to be available for different sized people.

How/Why are you arguing against this.

I AM 5'1". I've stated this many times. I HAVE ridden bikes with 165/170mm cranks. I DO ride bikes with 125/135mm cranks. I just COULDN'T ride in the drops in an Aero position with 165mm cranks. I CAN ride in the drops in an Aero position with 125/135mm cranks so this isn't just theory to me.

I cant get away from the idea that you have an undisclosed interest in this argument and you don't really care in the slightest what works for short people.

You just intend to stubbornly argue your case regardless.

Anthony

Leisesturm

it's all about the power... or should be. I mean... we are talking about racing right? Not just tooling around the park for fun... right?


The leverage is in the crank, not the cyclist. A cyclist any cyclist is going to be down on leverage with 145mm cranks. That's like saying a plumber with smaller hands and shorter arms can get more leverage with a 6" wrench than a plumber with bigger hands and longer arms.


Why? Not if they have to be competitive against riders using 170mm cranks.



I am 5'10".


I am participating in a discussion, same as you are, or anyone else active in the thread.



I would not put a tall rider on 145mm cranks either. That would be throwing away a God given advantage. There is a reason crew coaches go looking for 6'+ oarsmen. If it was like you suppose they could simply give 5'1" oarsmen proportionately sized oars and turn them loose on the water. Uh... no... bigger and stronger means just that.


Because I can.


I am not convinced you couldn't get in the drops with the longer cranks if you dropped the Twinkies from your diet. That is the bigger determinant of how low you can go than what length crank you are turning.


Everything is not a conspiracy. Everyone does not have an agenda. I hate to break it to you, you may be short but you need to be a whole lot shorter before it is a cause celebre. You are an adult I presume. I don't have any small children, but maybe you do, maybe someone else in this thread has young children. Really young children. Like four or five years old. Like two years old. What length cranks are on a two year olds tricycle?? What length cranks are on an 8 year olds 20"?? Why does a 5'1" adult obsess about crank length??

You just intend to stubbornly argue your case regardless.[/QUOTE]


Nope. I have a life. No doubt I've missed a whole lot of your threads about the travails of being a SHORT cyclist and how there aren't cranks that fit, bikes that fit, etc. and I call BS big time because its all out there. If you want it, its out there. I don't know why cranks need to be available in 2.5mm increments (but they are) and bicycles in 5mm increments to make YOU happy. As you say it would make everything more expensive and that would be fine with you because you have a supply of U.S. Mint blank currency stock and a printing press, but I don't. I'm ok with a somewhat limited selection of sizes of some things given the wide adjustability of the things that matter. YMMV

Leisesturm

In engines perhaps, but not in people. That is way oversimplifying a complex interaction. People don't produce enough power to waste any of it in trying to overcome inefficient crank ratios.


You do not, and luckily so, because no one knows what the exact formula is. To wit:



Absolutely true, I wouldn't quite agree that the range is any smaller for the shorter rider, it is just shifted downward. Maybe the best analogy I can offer is the human voice, the singing human voice. The average untrained human can sing pitches over about a 3 octave range. A bass will start about 4 or 5 notes (that's all) lower than a tenor and run out of quality about 4 or 5 notes lower than a tenor at the top end. In other words there are only about 4 notes at the very bottom of the voice that a tenor can't sing, but a bass can! In still other words, there is a HUGE overlap in the ranges of a bass and a tenor and one might be tempted to just call them both 'male voices' and be done with it.

I believe there is a huge overlap in the range of cranks an adult cyclist can utilize, and the only requisite is practice and training. A 6'1" human can learn to play a violin (145mm cranks), but a double bass (185mm cranks) is probably a better choice. A 5'1" human can learn to play a double bass, but a violin is probably a better choice. There is, however, this: violinists are a dime a dozen. A 5'1" violinist who learns to play the cello (170mm cranks) has way more employment options :-)

CliffordK

Interesting thoughts about stairs. I find the fastest way up the stairs is to take them 2 or 3 steps at a time. Taking them 1 step at a time (quickly) and it feels like I'm really churning the legs and going nowhere.

Not really... or at least not in practical bicycle design. The bottom bracket height can be adjusted in the bike manufacture, So, it would be easy enough to raise the bottom bracket to fit 400mm cranks if you wished.

The actual limit may be the body. For an upright body position, I'd imagine the cranks could be quite long. For a low racing position, the longer the cranks, the lower the seat (good in theory). But, also the longer the cranks, the more likely to impact the stomach (bad, depending on how much extra stomach one is packing around).

Leverage with cranks is complex.
Leverage increases linearly with crank length.
But, the crank circle also increases linearly with crank length.
Thus, one gets more leverage, but has to move the legs through more distance, and power to effort is very similar.

Interesting comments. Training, of course, is one factor involved with improved average speed.

My guess is that "leverage" may come into play with rapid starts, especially those first few crank strokes until you get up to speed. Perhaps also with sprinting. After that, it is all about maintaining power at speed.

Now, the question with body dynamics is interesting, and will be hard to answer. It may be that some bodies are better adapted to longer or shorter cranks, and there is a cadence/leverage trade-off.

If you went with square taper cranks, it would be easy enough, and relatively cheap to buy 3 or 4 sizes from 145 to 180mm, and just experiment. You might be able to take some chunkier cranks and drill and tap them for multiple sizes too.

You may well find different peak points with cadence, aerodynamics, and peak power, and average power, and not necessarily all in the same cranks. It would, of course, be confounded by training. So, if you train with 145 mm cranks, you might perform poorly initially with 180mm cranks, or visa-versa.

BTW: There is a set of 140/180 powercranks on E-Bay right now.

AnthonyG

Liesesturm,

I don't accept that you don't have a personal interest in this discussion. I'm guessing that you have sold bikes and/or have coached riders. Your interest is that you aren't ready to admit that what you have advised in the past is wrong.

Where to start. You have power wrong and this has already been discussed but you still get power wrong.

Power = torque x rpm.

High torque engines are usually reserved for trucks and vehicles pulling loads. High powered engines usually do high RPM at the expense of high torque.

Now this doesn't necessarily apply directly to cyclists in ALL cases yet in many cases it DOES work. Anyway, what's needed is to balance torque vs RPM to suit each rider.

Your wrench example does NOT apply to cycling. Wrenches are ALL torque. NO RPM.

For every person that states that they have more power with long cranks there is another that gets more power with short cranks. I'm calling it a DRAW, therefore power is off the table in this comparison.

How a cyclist gets power to the cranks is complicated, yes, and you have it wrong.

A cyclist with short legs has MORE torque at the knee than a long legged rider.

Think about it. This is where you are going wrong.

Anthony

Carbonfiberboy 

No. A rider with stronger legs has more torque than a rider with weaker legs. Strength has a much greater variation than femur length. I have a 6'5" riding buddy who has literally ripped the pedals off his cranks. He's quite a rider, a PBP ancien. He of course rides 180 cranks, very short for him. He has a custom bike but it didn't occur to him to have it made with a higher BB and custom cranks.

Not my buddy, but you get the idea:

AnthonyG

Guys, if we want to have a serious discussion here, then we need to be Scientific.

I have stated numerous times that two riders with the same muscle strength, one short legs, one long legs, the rider with the short legs has more torque at the knee. The long legged rider will have more speed at the knee. The fulcrum for your leg is the hip and the femur is quite a long lever.

A short legged guy could have quite a bit LESS muscle mass but still have as much torque at the knee as the really muscular guy, and then since the shorter guy is lighter, that's another advantage for cycling.

Comparing two riders with the same muscle strength but different leg length.

The short rider has MORE torque at the knee and therefore can exert the same torque into the drivetrain with a shorter crank arm.

The long legged rider has LESS torque at the knee and therefore needs a longer crank arm to exert the same torque into the drivetrain.

Just increasing the lever length is NOT always an advantage because you get to the point where the leg angles needed to move the lever through 360 degrees are outside the range that a human leg can deliver good torque, and, when considering cycling, the greater range of motion makes it impossible to adopt an aerodynamic tuck.

So. There is an ideal RANGE of crank length that suit a particular leg length. The ideal crank length for a short legged rider is SHORTER than the ideal crank length range for a taller rider and the shorter rider is NOT disadvantaged by the shorter crank arm because given the same leg strength they have more torque at the knee than the longer legged rider.

Anthony

PepeM

I am not that short, but my knees would hit my stomach when I was using 175mm cranks. That was not very comfortable.

Then gears were invented.

Many time trialists trade some of their power at threshold for a more aerodynamic position. It is not all about power.


Another situation where gears are not involved. Not a good analogy at all.

Leisesturm

Is the answer really to shorten the crank? Or is it maybe to raise the stack height and accept a little aero penalty? Maybe lose some gut, if that is the issue. Maybe raise the seat and accept a little more open knee angle? I mean the solutions are myriad depending on what the exact issue for the knee strike is. Shortening crank is a legitimate one but introduces its own penalties.



No. Gears were invented at the exact same time that the change was made to a "safety" configuration. It may only have been one speed but it was still a gear and it could be modified to suit. The bottom bracket height however was not so easily changed. The goal of "most" would still be to use the largest gear practical and the longest practical set of cranks to spin it efficiently.



Rowing is actually a perfect analogy. An oar is a gear, just like a chainwheel/sprocket combination is a gear. The inboard portion of the oars length is the 'crank'. Oars are sold in any length and inboard/outboard ratio a sculler wants to use to suit their intrinsics in training, but for Federation competition, rules are made and enforced. An eight man boat can have rowers ranging from 5'8" to 6'4" and they will all have to use the exact same length of oar. It will be optimal for some, efficient for most, but sub-optimal for quite a few. Furthermore, a 6'1" woman (common in that sport) has to row in a women's Federated boat, with much shorter oars than she would find if she were allowed to row a mens boat.

Ideally cranks would be adjustable on the fly. Even with "gears", depending on what your need for torque is in a given moment a longer or shorter crank might be useful. Shorter crank for spinning a small gear at high rpm for acceleration/hills. Longer crank for mashing very high gear without blowing up your knees to eat up miles on a long touring day. Railroad locomotives used to be built with varying size wheels and that size would determine their top speed. However, being built for a high top speed came with the penalty of poor acceleration and load pulling ability. 170mm cranks are a compromise for everyone, and it's hard to say when and where to start changing crank lengths based on height. Formulas are great but I am not sure how useful they are if you come out needing 153mm cranks. Good luck finding some.

McBTC

Analogies can be interesting but also misleading... for example, the crank length based on automobile efficiency has some credence an yet Formula One engines maximize power by increasing rpms.

Another interesting analogy that reaches a logical limit is that, like in a car engine, your knees are like pistons in an engine-- moving them faster increases power. The problem is, with a long stroke the knees are traveling a greater distance per rpm so they're moving much faster but you cannot lighten your knees like you can lighten the weight of a piston.

The 8-man crew analogy also has it's problems: it isn't just a matter of oar-length. Skulls are designed to make use of seats that travel and longer legs allow for greater seat travel. Additionally, racing skulls travel on a smooth, flat surface in a straight line. Change the course dynamics a bit and shorter boats with less seat travel -- allowing for better utilization of higher rpms to increase power -- might make more sense.