Ah, yeah maybe 165’s would be a good idea. Haha. See you in August!

---

---

Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

170-175 to 148-153 to 165-172.5

With shorter cranks you generally have less trouble over the top of the stoke. This is the one clear benefit... but only if that is an issue for you. The lower range of motion may be better or worse, the higher cadence usually needed to compensate may be better or worse, aero drag is probably worse unless you get more horizontal... in which case it might improve. Usually it's tiny differences in any case.

I don't think any of the pro male road racers who tried shorter cranks stuck with it, even for TTs. But tri, especially long course, are a different beast.

rruff wrote:

I don't think any of the pro male road racers who tried shorter cranks stuck with it, even for TTs. But tri, especially long course, are a different beast.

You may be onto something here. I believe 6' 4" tall Ganna had 170's for his hour record - a "steady state" effort. I'd be very interested to know what he was using in the recent Tirreno-Addriatico TT.

First I went from 175mm to170mm on my fat bike and can’t say it was better or worse. No problem when on the trails with my friends. The I went from 172.5mm to 165mm on my main road bike mid last year. After the change I had my fastest average ride of the year with the 165mm cranks. Going back? No. Looking to slowly convert other bikes I own as time goes on. For what its worth I’m 6” tall, 155 lbs with a 35.5 inseam and next month will be 66 years old.

I've never done it myself, but I hear that laps on the track are only steady on the macro level, with big fluctuations in resistance through each lap. So, that is another special case.

Evenepoel is one of the shortest TTers and I've seen that he uses 170s on this road bike. His TT cranks may be a little shorter, but it wouldn't be much.

Remco is short, but he's not that short - he's 5'7". He's tiny, though, which (I think) makes him look shorter than he is. Victor Campenaerts is just about an inch taller than Remco, but outweighs him by close to 25 pounds.

My understanding is that Remco running 165 length cranks on the TT bikes. Hard to go shorter with a Shimano sponsorship.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

I'm of the opinion that pros are running 170-175 because that's what was available when they started riding. Short cranks only became widely available in the past few years. Even in this thread there's evidence that the favored (not best, favored) crank length is the one a rider has spent the most time riding. One expects this to hold even more true with riders who have thousands of yearly hours stacked up.


All but the very smallest frames still come with 170mm. This is slowly changing. It's just out of proportion that a 6.5ft rider should run 175's and a 5.5ft rider (18% smaller) should ride 170's (3% smaller).

I think the prevalence of shorter standard cranks will show up as shorter cranks in the pro field in ~10 years.

Paging H20fun.

Absolutely.


This has already begun to happen. Remco dropping down to 165 on his TT bike fairly recently is an example.

This will be the very last thing to change. It's simply not possible for bike manufacturers to spec shorter cranks at scale, and likely won't be for a long time, if ever. The overall percentage of people who actually care about the length of their cranks is a tiny percentage of the consumer base, and the # of those who want <170 is smaller still.


The available data suggests that looking at this as a ratio question is likely misguided. It appears that there is either no effective change in performance - or a slight increase in performance - as crank length decreases, up until the point that the cranks becomes too short, at which point there is a steep (non-linear) decrease in performance. Martin's work suggests that this break point is likely in the range of 140-145mm for most riders.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Does he? His Tarmac was documented with 172.5mm last year and very recently, his Shiv TT was shown with 170cm cranks

He had both on at different points last season. He changed to shorter cranks on road and TT at some point. It's certainly possible he's changed again; he's definitely been working on his position. Current TT position is different from what he was riding as recently as that bike from the UAE Tour, so who knows what he's on now? He's riding with less pad drop on his TT bike than he used to, so increasing crank length correspondingly to match road length wouldn't be unreasonable if it didn't cause problems at top of pedal stroke (which it sure doesn't seem to, whatever length he's on).

FWIW, even if he is on 170s, that's still in the realm of "shorter crank lengths breaking through at the Pro Tour level". It's even noted as such in the video you posted. Up until very recently, a Belgian team like QS would have had him on at least 175 for the TT bike, and probably longer.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Back in the day, us "amateurs" would start off the season's training riding fixed gear, 165mm cranked, track bikes (with added front brake) on the road. When the actual racing started, we were all back on 170 to 175's. Bicycle "fitting" didn't exist, but still, if the short cranks were an advantage, you'd think someone would have noticed. Nobody I know - I mean zero - did!

Oddly enough, I was/am part of this cohort. :)

The available science most strongly supports the conclusion that, for most people, there is little to no performance difference across a range of crank lengths within certain upper and lower bounds. Once those bounds are crossed, the performance decline is almost certainly non linear. A range of 165-175 is almost certainly well within those bounds for most people on a traditional road bike. It almost certainly exceeds the upper bound for a lot of people on a TT/Tri style bike.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

In that same day (until a certain US Postal employee came around) everyone also thought you'd ride at 75rpm and only needed a corncob cassette for everything but L'Alpe d'Huez. I'd wager there's a performance benefit to long cranks if cadence is held below a certain point.

More to your own point, there's definitely a performance advantage to longer cranks if you're stuck with a corncob cassette!

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

I wonder how much ankle to ball of foot length plays into when cranks get too short. I find the natural alingment with ankle at 3 pm with crank arm axle and ball of foot with pedal spidle makes sense until the crank gets so short that you feel "jammed at 3pm"

IME, when this happens it is typically the result of not moving the saddle back in concert with decrease in crank length.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

I don't think you are getting what I am saying. Let's assume you had a crank lenght of 70mm versus 170mm. And your saddle is moved back far enough so that at the 3 o'Clock position your knee and pedal spindle are aligned in the vertical plane. Assuming your left crank is the downstroke crank and the right crank is the upstroke crank. Your right right big toes would literally be in front of your left ankle, meaning you are taking this ridculously small 'steps". You can't apply force when steps are that tiny. You need enough separation between your two psoas muscles on each side for power to be initiated in any way. In the extreme, if the cranks were 2 cm long each you literally cannot apply any power, so it totally makes sense that the cranks have to be long enough to get into a sweet spot of "stride length" to apply power, but not so long as to be "overstriding". Compounding all of this is hip angle because we are "striding" while being bent over. Try to walk with you torso parallel to the ground in the aero position and you will see that you naturally want to take shorter strides than walking upright, but you also don't want to take exceptionally tiny strides either.

Between natural body biomechanics applying force at high frequency hunched over and the dynamics of building a bike between chainstay flare and front wheel overlap, from trial and error, we largely got to what we have...which seems to be a sweet spot somewhere between 170-175mm. I am certain that the size of our feet plays in. I personally measure exactly 170mm from ball of foot to protrusion on my ankle at size EU43. I don't think this is a totally wild coincidence that my foot size that is quite common and my crank length (170) that is insanely common are identical. That length likely "felt right" after a few centuries of bike building trial and error to the bulk of foot sizes riding bikes.

It is probably like doing hamstring curls or leg extensions on the machine in the gym and adjusting level length to tibia length so the pivot point of the machine and knee are aligned and tibia and machine lever are going in line with each other.

It's not exactly controversial to suggest there's a lower bound to crank length below which performance can be expected to decline precipitously. For most people, the data suggests that's in the range of 140-145.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Correct, but you can't think of this as crank length as body proportions are different. 145 for one athlete will create different biomechanical angles than it would for another athlete, even if they're the same overall height. The data is very clear - the driver of crank length is maximum knee flexion. It's certainly not black and white, but the general agreement is anything under 68 degrees (or over 112 degrees should you measure the complimentary angle) necessitates a shorter crank. Alternatively, a flexion angle above 73 degrees seems to be when loss of power occurs, though I believe there's more variability in this number and certainly less data for consensus. I might be inclined to argue for a higher number, but it's athlete dependent.

---

Jim Manton / ERO Sports

 Sure. Don't disagree with any of that. The bound range suggested in the data has (or should have) a high correlation with the range of variance in the morphologies of the population sufficient to capture the likely breakpoint in crank length below which acceptable flexion angles are unlikely to occur without other compromise in the majority of cases.

Edit to add:
It's not a predictive or prescriptive number. For fitting purposes, its just useful to keep in mind that there is a length below which you're likely to encounter performance decreases, but that number is likely lower than most people think.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Which he won by 28 seconds!! This poor quality picture is the best I can find of the bike he used. Hard to tell the crank lengths.

This is a great explanation. I’ve often thought that perhaps because I have a large foot (for a female - I’m a 43) that a longer crank may just suit me better. But I’ve also run up against the knee flexion issue now that I’m pursuing a more aggressive TT position. Putting the 165’s on this weekend and will give it a spin. Literally.

I have found that 155mm works for most people.

Its not really, because it oversimplifies the mechanics to foot length. There are three joints, and levers in play that impact the overall biomechanics: hip, knee, ankle....thigh, shin, foot. Suggesting that foot lengths somehow dominates the equation (to the point of possibly selecting crank solely based on shoe size) is just flat wrong.

The ankle shouldn't flex/dorsiflex much during the pedal stroke. So, with the ankle joint mostly static, the mechanics (and hip/knee angles) are driven by thigh length, and shin length. As described above there are minimum and maximum hip and knee angles that everyone should stay within.

As noted above...I'm 6 ft tall, with a 32" inseam, and a size 44.5 shoe. I ride 150mm cranks, with a professional FIST certified Tri fit (from a fitter who used to write articles for this forum) in an aggressive position.