Does anyone have information on the effect of longer crank arms for climbing or time trialing? I have long legs and am wondering if I might benefit from longer cranks.
Some people prefer longer cranks as they provide a little better leverage. But studies have shown no differences in performance with different crank lengths. If you just want a different feeling, go ahead and try them, but do not expect any performance gains.
Man, this is one of the great debates… Personally, in my opinion, I view crank length as a “fit tool” and feel there is an appropriate crank length for a given femoral/tibial ratio. The variable that throws a wrench in the works of this may be pedalling style, specifically, cadence. I think everyone has thier own “best” or most efficient cadence. The trick is finding the appropriate crank length for your body dimensions and pedalling styke, acknowledging that that these factors can be dynamic (i.e., ever changing).
Having said all this I’ll relate an anecdote:
When I started racing triathlon back in 1982 my bike had the cranks it came with: 170mm. I used them in about 20 triathlons. A guy whose opinion I trusted said, “You should use 172.5mm cranks. You’ll go faster.” I switched and I did go faster a little for a few reasons, mostly becasue I was just getttng better at the sport.
A few years later I started winning local time trials and then our USCF State Championship and our Road Race. I had switched to 175mm cranks by then. I figured if 172.5mm cranks were good, 175mm would be better. They were. So, I went to 177.5mm cranks. Oops. Point of diminishing return: It totally screwed up my position. To make matters worse, some guy named Boone Lennon invented these things called aerodynamic handlebars that screwed up my position even worse. So I went back to 175mm cranks and that was good. I was trying to get used to those aerobars though and wasn’t 100% sold on them. I met some weird guy who seemed way too enthusisastic but had a lot of interesting ideas named Dan Empfield. He was selling this new thing called a “triathlon wetsuit” and I bought a few. He told me, “Hey, I have this bike called a Superform that is specifically made for those aerobars. I’ll send you one…” He did and the whole thing came together.
So, there is a “best” or at least “better” crank length for you, you just have to find it. An experienced triathlon bike fitter can help, so can doing some tests on a Computrainer.
Good luck!
I have posted this before and gotten many negative reviews but here goes. At one time I had three sets of Ultegra cranks, 170, 172.5, & 175. Just for fun I picked a 6 mile ride with two hills near my home. I put all of the cranks in a pile and randomly put them on the bike and made a loop. So sometimes I even had different lengths on each side. After about 7 or 8 loops I had no idea which cranks were on the bike and could not tell the difference. The last time I posted this a man told me “I must be an amateur”. I am 56, have been competing for 20 years, have several trophies and ride about 5000 miles a year.
Aloha,
Larry
After about 7 or 8 loops I had no idea which cranks were on the bike and could not tell the difference. The last time I posted this a man told me “I must be an amateur”. I am 56, have been competing for 20 years, have several trophies and ride about 5000 miles a year.
And the controlled studies done by actual researchers (not the one goofy test done by Lennard Zinn) back you up 100%. Within the “normal” range of choices, there is no difference. Our bodies can adapt to damn near any crank length in the 165 - 180 range. People should self-select what feels best and ride that length.
Whenever somebody writes a post about how they changed lengths and got better/stronger/faster, it is probably true. They have self-selected what feels right and it allows them to ride harder and more comfortably. But, there is no formula; never has been, never will be. If one’s current cranks feel normal, there is zero need to change.
i’ve played around a bit with crank length. in and of itself, i haven’t found big differences.
until… i did one legged drills. then i found that longer crank lengths required more flexibility. a very flexible athlete may be able to use very long cranks, but the mortal athlete may find it difficult to start getting the pedal over the top after a tiring period vs shorter cranks.
i suspect i did not find this using both legs because the other foot on the downstroke was doing the work to get the other foot through those few degrees. this would show up in performance, but unfortunately, in this sport there are so many variables it gets difficult to adjust only one variable while keeping everything else constant, and record meaningful data.
when i figgered what my max length was without tiring out my hip flexors too soon doing one legged drills, i sized down 1, and that’s worked pretty well.
I basically agree with Julian, with a slight twist…I always tried to go to longer and longer cranks, hoping to get a bit more leverage, but always felt like I couldn’t get “on top of” the pedal when I was on a crank longer than 170. Most bikes that come in my size have 175’s. I always tried to ride them for a while, struggled with them especially when tired, and would return to 170s.
Then, I trained on PC’s. Couple of things happened…I can now ride 175’s easily without feeling like I’m not clearing the top. I also ride at slower cadences than before. I THINK that a rider with a faster cadence may be served better with cranks that aren’t on the long side of what is calculated for them based on their femur-tibial ratio or whatever method is used. And that slower cadence riders MIGHT be able to ride better on cranks that are on the longer end of standard for their femur-tibia ratio, if everything else were similar between the two riders.
Maybe the reason so many tests seem to be inconclusive on which crank-length is best when based on a body measurement ratio, is that simple ratios don’t take into consideration an individual’s various muscle strengths and weaknesses, flexibility, preponderance of fast or slow twitch muscles, and maybe some other varibles. Pre-PC training, I think my hip flexors just weren’t working enough to get the rising leg over the top , and I could feel the weight of the rising leg requiring energy from the driving down leg in to get the rising leg over the top. Now, I’ve overcome that specific weakness. Who knows…maybe I can ride even longer cranks now…but, would that be better? I don’t know.
Which brings one back to what Julian said…you sort of have to go by feel. But, if you haven’t ridden long enough to “feel” what is right for you, a good fitter should be able to get you started in a decent direction, by using some sort of a formula, and then adjusting from that initial length as best as they can determine.
Allow me to throw another consideration into the mix…
How has your riding postion evolved or changed (i.e. hip angle open/closed, steep vs shallow, getting more/less ‘low’ on the bike) through your history of changes in crank length and before and after PC’s? Could your earlier difficulty with longer crank lengths have as much to do with trying to get ‘low’ on a bike with a lot of saddle setback?
Wow, what a debate… Coming from a porfessional cycling (road and velodrome) and over 30 year of coaching, this issue does not look that tricky… Yes, you have to find an individually most comfortable ratio. The longer the cranks - the more effort (stronger legs) they would require. Your acceleration - is also a function of cranks length - the shorter (170, or even 167.5) - the better for initial acceleration (sprint, for example). The combination of cranks and gear may determine your race strategy. However, regardless of cranks, you will stay in your “comfort cadence” zone. So, technically speaking, the longer the cranks - the more distance you may cover for one rotation. The question is always - at what cost?
Assuming that tirahtlon distance is always about long distance time-trial, the longer cranks may be more for energy efficiency, however more demanding from muscle strenth point of view. I would debate, that run after using longer cranks may be more painfull. It may be an interesting study…
Coach Sergei
I found out that my form cycling uphill completely changed according to crank arm lenght:
175: Standing most of the time
170: Sitting & spinning most of the time
172,5: 50/50
.
I see your point, and it’s a good one. Actually, pre-PC, I was on a 78 degree tt bike and just couldn’t seem to get over the top with 175’s. Now, I ride a either a 74 degree road with 172.5 PC’s or a 76 degree TT bike with 175’s and never feel like I’m not clearing the top. Being forced to pull up really makes those muscles work much better. I remember when I first started PCing, I had to almost sit down in the shower to wash my feet…because my hip flexors and hamstrings were just too cooked to pick my foot up where I could reach it. Going up steps was slow, too. After just a few weeks, I was surprised at how long I could raise my leg with my knee above my waist and just hold it there…I could do it for minutes instead of 30 seconds. It just goes to show that there are things other than femur/tibia ratio that may determine the optimum crankarm length for an individual at a specific time in their current condition. Change their fitness, strength, or flexibility, and a different crankarm length may be better…at least for a while!
I think what many people overlook is that the choice in cranklengths available to the average individual in the real world is basically nonexistent.
The range of manufactured cranks is about 165 mm to 180 mm–that is a small 8 % range. However, we may discover that for the range of decent adult bicycle riders (smaller women to larger men), Big Surprise!, leg length varies FAR more than 8 %. If you assume that SOME KIND of proportional relationship exists between crank length and leg length, then the range of 165 mm to 180 mm cranks typically will fit folks with inseams ranging from 30 inches to 33 inches. If you are more or less than that, you are simply out of luck (unless you have custom crankarms made for you).
Much of what the bicycle industry and, sadly, the coaching and fitting contingent feeds us on this topic is a bit of crock, tradition, and manufacturing inertia, but that is difficult for anyone to admit. As others may have mentioned, there is a very interesting website (www.nettally.com/palmk/crankset.html) that challenges many of the hallowed ‘truths’ of the crankarm length mythology.
And mythology it is becuse there simply have NOT been ANY truly excellent studies on this topic that used a LARGE no. of untrained male and female individuals (trained cyclists will generally ride best on the cranks that their legs have adapted to) on a truly WIDE range of crank lengths (i.e., far beyond the range of 165 to 180 mm) on a WIDE range of workloads.
Why? A truly decent unbiased study like this would cost quite a bit of money (but in any case a lot cheaper than 1 blackhawk helicoter or an F-16). I must agree with other posters here that an individual trying to detect big performance or “feel” differences with crank length differences of 2.5 mm to 5.0 mm borders on the impossible.
From the website listed above, I quote: "…the crank length formula presented here results in considerably different recommended crank lengths than those customarily fitted to bicycles for sale or recommended by cycling coaches and experts. At this point, I’ll provide some possible explanations for the status quo, in hopes of shedding some light on the situation. As mentioned elsewhere, the use of significantly longer cranksets needs to be accompanied by framesets with a smaller drop – raising the BB higher off the ground to maintain cornering clearance. This may not sound like a big deal, but it is. Framesets and cranksets are typically made by different companies. Therefore, a crankset maker cannot sell a long crank because there’s no frames designed to use it, and a frame maker cannot sell a frame with a high BB because there’s no cranks available to use with it.
If consumer demand warranted it, these problems would be fairly easy to overcome. However, to quote Bob Morris: “There cannot be a demand until there is a supply.” If the consumers are unaware of the advantages of properly-sized cranksets, it’s unlikely the manufacturers are gonna hear any demand to change their ways. In the past, the problems were even worse. Up until a couple of decades back, all high-quality bicycles were made with butted tubing brazed into cast or forged lugs. Often, the lugs and tubes were made by different companies and assembled into a frame by a third company. When the BB height is to be changed, the angles at which the seat tube, down tube, and chainstays attach to the BB must change. This requires a different lug forging for each BB height. Since the use of crank lengths according to this formula would require significantly different BB heights for each frame size, different forgings for the BB shell will be required for every frame size. While this might be reasonable today, in decades past it would have been considered an outrageous expense – and clearly unwarranted if buyers were not demanding it.
The same problems existed in crankset manufacturing. In this day of computer-controlled machining and advanced aluminum forging processes, the production of different length cranks would not really be that big a deal. But in the past, making a high-quality forged aluminum crankset with integral spider in several significantly different lengths would have been considered prohibitively expensive. Aside from the manufacturing and market issues, the various cycling team coaches seem to have done their part to ruin the reputation of differing crank lengths. Coaches seem to regard variations in crank length as a “speed secret” rather than good bicycle fit. There have been a few scare stories of coaches who have forced their riders to use cranksets that were too long for them, resulting in damaged knees, shortened careers, etc.
For the most part, coaches don’t appear to have put any more thought into proper crank sizing than anyone else. If a rider from some other team did well with a long crank, they’ll try it with their riders – regardless of size. And if someone blames knee problems or poor performance on the use of a long crank, they will never again consider long cranks – even for their tall riders. Such is the way tradition is developed; it has its place, but it needs to be tempered with some sound engineering practice as well…"
Kind of makes you think, doesn’t it?