Doesn't anyone tire of opinions on this stuff?

No matter what anyone says or posts, I ride what I ride ... I'm assuming we're all the same in that respct.

In other words, no one care that you tele.

 

Technically shorter cranks could allow for a longer travel dropper so you could end up with the ability to lower your COG more with shorter cranks.

Nope, allowing a longer dropper is a frame specific thing. Most run the longest they can reasonably fit or whatever the bike came with.

Not true. Shorter cranks allow a higher seat but don't require it.

We set seat heights to minimize knee flexiation at the top of a pedal stroke, the bottom really isn't a concern. So if you run cranks that are 10mm shorter you can be +-10mm of your orginal seat height and still be within the same previous maximum knee flexiation.

A lot of people do lift their seats. I personally kept my seat height the same.

Nope. Seat position is set from lowest pedal position. It's not credible that you run a different seat-pedal distances for different crank length. Everyone sets it by leg extension.

This sounds like your "ride without any weight on your hands" claim.

 

Nope, allowing a longer dropper is a frame specific thing. Most run the longest they can reasonably fit or whatever the bike came with.



Nope. Seat position is set from lowest pedal position. It's not credible that you run a different seat-pedal distances for different crank length. Everyone sets it by leg extension.

This sounds like your "ride without any weight on your hands" claim.

Even if you can't run a longer dropper because you didn't free up enough insertion depth with shorter cranks I don't get your higher COG with shorter cranks argument? We're going to drop the saddle regardless of crank length so your higher COG only applies to climbing? Or maybe you ride with a fixed post up your bum?

 

You're not answering my question. How are shorter cranks helping when your pedals are level or near level?

More symmetrical stance.

personally I find I notice a small difference in cornering due to this. I think it somewhat reduces my favoritism of certain directions of turns, which I somewhat believe is rooted in how my body is already oriented. IE, I ride right foot forward, which inherently makes my hips easier to point left, and harder to point right (as my stance is "the opposite direction"). The slightly narrower stance makes switching seem easier.

Might be placebo, I couldn't tell you. But I can tell you I notice the stance is a bit more symmetrical, and I haven't noticed any negatives to the narrower stance that others have mentioned, but have noticed slight positives from the narrower stance.

I primarily do it for pedal clearance though, to be clear.

Shorter cranks require higher seat position. How are you dropping it?

Dropper post .

Actually, one thing I don't see people talking about, is the interaction between saddle height with shorter cranks (as you said, shorter cranks increases the pedaling saddle height), and cockpit height. For bikes with low stack heights, if you ride a really short crank, your pedaling position could end up having a really significant saddle/handlebar drop (might be good or bad, depending).

This might lead people to throw on really tall bars/stems to get their pedaling position how they want it... but could also lead to some weird "less weight on the front tire" situations.

Technically shorter cranks could allow for a longer travel dropper so you could end up with the ability to lower your COG more with shorter cranks.

I have noticed this in my dropper calcs for a few frames. My current frame I went with a 180mm without shimming it, but could have fit a 210mm shimmed down to 190-200mm (depending on actuator weirdness) if I'd gone back to 175mm cranks. I went with the 180mm because I wasn't sure I'd want the 165mm cranks at a the time, and didn't want to have to replace any other parts if that was the case.

 

Can people really tell a difference in 5mm? I've ridden back to back 170 and 175...and I'd be lying if I said that there was some measurable difference. My MTBs currently have 170 cranks and the road 172.5. I think if 170 cranks were not readily available...I'd be fine on a 175. Thats what I was using before the internet told me they were bad.

If rat friend was to come into your garage and swap out your cranks in the middle of the night without you knowing...would you be able to tell a difference on your next ride?

Here is rat friend,

 

Can people really tell a difference in 5mm?

It's the most controversial 5mm in cycling. 170, all good...165, all hell breaks loose

 

Can people really tell a difference in 5mm? I've ridden back to back 170 and 175...and I'd be lying if I said that there was some measurable difference. My MTBs currently have 170 cranks and the road 172.5. I think if 170 cranks were not readily available...I'd be fine on a 175. Thats what I was using before the internet told me they were bad.

If rat friend was to come into your garage and swap out your cranks in the middle of the night without you knowing...would you be able to tell a difference on your next ride?

Here is rat friend,

Can people really tell a difference in 5mm? I've ridden back to back 170 and 175...and I'd be lying if I said that there was some measurable difference. My MTBs currently have 170 cranks and the road 172.5. I think if 170 cranks were not readily available...I'd be fine on a 175. Thats what I was using before the internet told me they were bad.

If rat friend was to come into your garage and swap out your cranks in the middle of the night without you knowing...would you be able to tell a difference on your next ride?

Here is rat friend,

View attachment 2096319

I wouldn’t think 95% of riders ( here we go with 95% of bikers thing again) wouldn’t notice 5mm, but remember, you multiply this by 2, which equals around.39. Now going from 165mm to 175mm, most people would notice a little of 3/4” of an inch.
Now if it helps or hinders, it’s up to each individual.
Over the years, I’ve tried everything from 165mm to 180mm and 175mm was what I settled on, on every bike I own.
I think that the riders using shorter cranks, 155-165mm are doing it more for clearance at the bottom pedal position.

 

Your spinning, your spinning, your spinning...now tech section. You don't need that extra leverage until...you do. Yes, I have cranks at 165 and 175, I absolutely notice the difference. Yeah, think there was a "sweet spot" of BB heights lower than 14" before we were forced to start shortening our cranks significantly.

 

Back in the 1970s and 1980s when racers would commonly race both road and track, they would commonly switch crank lengths (even between different types of velodrome races), and the common wisdom was not to change saddle to BB height
Changing crank lengths is nothing new, is has been happening for at least 150 years now

 

Back in the 1970s and 1980s when racers would commonly race both road and track, they would commonly switch crank lengths (even between different types of velodrome races), and the common wisdom was not to change saddle to BB height

That's odd to me. I def feel a reduction in power if my saddle is 5mm lower than normal. I would raise my saddle if I ran shorter cranks regardless of what's considering correct. That said, anyone who doesn't notice less power with a lower saddle it's a non issue. I'm a bit of princess and the pea I guess. My current frame wont' keep my dropper up long term. It slips a hair every so often. I notice at less than 5mm when I need to raise and crank down the collar again. Yes I've used carbon paste. I guess my frame has shi! tolerances? That happens sometimes.Anyway, I can easily feel 5mm of saddle height. I might not feel it the second I start pedaling, but 10 minutes into a climb I'll feel something isn't right.

 

My trainer bike/ clothes drying device has settings for the seat height each about 1.25" apart and I'm sort of in between them. One height is just a smidge too high, like 3mm. The other height is like 25mm too low.

After spending months on the high setting, I figured I'd drop down to the lower setting and just make up any difference by keeping those heels down (something I already try and do). It took about 3 training sessions before I realized I wasn't just having a really weak day, or even a bad week. No, my ability to hold my standard Z2 training watts was down, and down a lot. And it came down to one single factor: my seat being too low was the sole culprit for my loss in power. Going back to my previous seat position fixed this right up.

It's one of those things that is more subtle on a real bike ride, but really stood out on the trainer.

Which reminds me: In this very thread I believe I mentioned that I could feel a notable drop in my pedaling power when I installed 160mm cranks on my e-bike just last week. I had decided that the improved ground clearance and the motor made up for it but now I realize, I didn't even raise my seat. That could actually be the sole cause of my loss in pedaling power and I'm over here blaming the crank length. I'll check that this weekend.

 

My trainer bike/ clothes drying device has settings for the seat height each about 1.25" apart and I'm sort of in between them. One height is just a smidge too high, like 3mm. The other height is like 25mm too low.

After spending months on the high setting, I figured I'd drop down to the lower setting and just make up any difference by keeping those heels down (something I already try and do). It took about 3 training sessions before I realized I wasn't just having a really weak day, or even a bad week. No, by ability to hold my standard Z2 training watts was down, and down a lot. And it came down to one single factor: my seat being too low was the sole culprit for my loss in power. Going back to my previous seat position fixed this right up.

Which reminds me: In this very thread I believe I mentioned that I could feel a notable drop in my pedaling power when I installed 160mm cranks on my e-bike just last week. I had decided that the improved ground clearance and the motor made up for it but now I realize, I didn't even raise my seat. That could actually be the sole cause of my loss in pedaling power and I'm over here blaming the crank length. I'll check that this weekend.

I've found Dylans videos really interesting for this sort of stuff. Turns out, saddle height does affect power. Way more than crank length.

 

I generally know what saddle height works well for me, and so I've always set my saddle height across different bikes by measuring center of BB to center of saddle, not taking crank length into account (because my cranks have always been 175 mm until relatively recently).

I immediately notice a 5 mm change in saddle height on any given bike (ie, seatpost slips a bit or I mess with something) but I can't feel a 5 mm difference in crank length between bikes. Weird.

I am also very sensitive to fore/aft positioning, so for me it's really setting seatpost extension + saddle position to get the right radius from BB with right effective seat tube angle, not just "height"

 

I believe the advantage of using your quads with knees not bent as much (e.g. "cheat" squats) is a big factor behind how these cranks attain comparable performance, despite the expected drop in performance due to adapting to a significant change in fit. There's promise of even higher potential after adapting.

Similar to how full suspension got more popular, there's the potential gain from getting more pedal strokes in. For road bikes, they mostly suffer clearance when leaned. Imagine these pros sensing the opportunity to pedal sooner after a corner.

For MTB, there's the ability to pedal in tech, going over bumps/ledges that are sized just right to fit between the wheels and create clearance issues. There's also cases of pedaling in G-outs, where surprisingly low obstacles can cause clearance issues due to the suspension compression.

Reduction of pedal strikes is a big deal. Clipping/snagging a pedal on something is an extremely violent event. I'm surprised frames can hold up to these kinds of hits, considering the leverage involved. Even if it survives, I don't doubt that it's worse for the bike than a 5+' huck to flat, basically taking massive amounts of "hit points" off the bike (fatigue life).

 

Similar to how full suspension got more popular, there's the potential gain from getting more pedal strokes in. For road bikes, they mostly suffer clearance when leaned. Imagine these pros sensing the opportunity to pedal sooner after a corner.

Pedal clearance is not as big of a deal for road racers as you might think. If it were, bottom brackets would be higher than they are and they would pedal through all of the corners. Pack dynamics and safety concerns keep that from happening and everybody coasts through the corners.

 

Are you really making that arguement??

I am making the assumptions that you have a basic understanding of physics and cycling dynamics. Am I wrong?

I'm using that obvious fact to disprove your claim that we are only power limited and not force limited.

What is short? What is optimal? Are there definitive studies on this for mountain biking? I don't mean to be pokey or snarky but am genuinely curious.

Don't know. I'm 5'10" with long legs (can't remember inseam) and short cranks absolutely suck for me. I'm not aware of any studies where they've grouped riders by leg length. But I also haven't looked for any.

 

I'm using that obvious fact to disprove your claim that we are only power limited and not force limited.

Ahh, so you actually think that more leverage means more power. If you are an engineer that is very disturbing.

I am assuming that you are running the longest cranks you can find then?

BTW my “claim” is solidly backed by research. Never mind that the best road racer in the world is on 165mm cranks. And guess what the best XC racer in the world has also been rumoured to swapping to 165mm cranks this year.

I suspect that you have done zero research on the effect of crank length and power. If you had you would know there is zero evidence to support the idea that longer cranks result in higher power outputs.

I am not saying that short cranks are magic, probably they would make zero difference to you. But your statements about torque and power are wrong.

 

Ahh, so you actually think that more leverage means more power. If you are an engineer that is very disturbing.

More leverage with the same force and rpm does mean more power. That's a fact

Go ahead and try and twist that by introducing new variables. I know you're going to try. How is your downhill riding without any force on your hands going?

I am assuming that you are running the longest cranks you can find then?

In my configuration yes. I wanted to try 180mm but they were too hard to find.
[/QUOTE]

170-ish crankarm length was chosen arbitrarily over a hundred years ago and everyone pretty much just stuck with that. So I am interested in what is right in scientific terms and what exactly is short.

Only speed limits are chosen arbitrarily. When bikes were fixed gear they tried everything to get an advantage. You can guarantee longer and shorter cranks were tried before lengths settled out.

Remember. Tradition is the answer to questions long forgotten.

 

Only speed limits are chosen arbitrarily. When bikes were fixed gear they tried everything to get an advantage. You can guarantee longer and shorter cranks were tried before lengths settled out.

Remember. Tradition is the answer to questions long forgotten.

Ok so they got that sorted in 1902 for track racing, did that same "science" get applied for mountain biking?

 

Ok so they got that sorted in 1902 for track racing, did that same "science" get applied for mountain biking?

Yes. Because the motive power is the same.

Fixed gear racing wasn't just track. Every bike was like that for a long time. They raced over hundreds of km.

A lot of assumptions in your "Fact" there. And you know it. And yes, I am poking big holes in your arguement.

It is pretty clear to me why you didn't understand what I was saying about riding technique. Remember your fundamental physics, Force and Weight are different.

Physics fundamentals son.

Power = torque x rotating speed.

Torque = force x lever.

Power= force x lever x rotating speed.

Noone mentioned weight except you.

 

Yes. Because the motive power is the same.

Fixed gear racing wasn't just track. Every bike was like that for a long time. They raced over hundreds of km.

Remember when just a short time ago the peloton all rode on 12-21 cassettes and thought shifting to an easier gear made you slower?

 

Remember when just a short time ago the peloton all rode on 12-21 cassettes and thought shifting to an easier gear made you slower?

No I don't remember that. It's not really my thing.

Very good you have a very basic understanding of physics 1. Now actually do some thinking!! You made the incorect assumption that force and angular velocity remain constant when crank length changes.

You can argue with me all you want on this. But if you and do a little bit of research and your will see from studies there is pretty well zero correlation between crank length and power. The only hint of difference is time to peak power is shorter with shorter cranks. There is also some very preliminary research indicating a possibility of improved efficiency.

There you go. Pretending that you get a free force or cadence increase with shorter cranks.

But you don't......

As for our technique discussion. I did mention weight, and I had assummed the way you go on about your Physics knowledge that you would understand exactly what I was talking about. Anybody who has done basic physics knows the difference weight and force.

You're arguing with yourself. No-one but you has even mentioned it.

 

There you go. Pretending that you get a free force or cadence increase with shorter cranks.

But you don't......

Come on.....
Your engineer try actually thinking about the problem.

You get extra force because you have reduced the velocity your foot is moving at. If you can hold 300 watts on a climb you can hold that because that is what aerobic and anerobic system can support. If drop the velocity compent of the P=Fv equation then you can use more Force. This why peoples FTP are same within a certain cadence range.

Having been a Guinea pig for numerous experiements I know that my FTP is pretty constant between 70-95rpm on 170mm cranks. Below 70rpm I don't have the strength endurnace to maintain by FTP and above 95rpm I see a drop in efficiency and the matching lower FTP. But inside that cadance range I can swap force for velocity with gain or loss in my sustainable power.

 

So we all we need to do is look for a 10 mm longer wrench instead of a cheater bar when something is stuck?

 

Just use a shorter wrench and your body will automatically increase force.

Or something.

 

I think it's pretty obvious that although leverage, and therefore torque is reduced when going to shorter cranks (within reason), since the circles the cranks move in are smaller most people naturally increase RPM as the distance covered is the same, and therefore wattage/ power ends up being the same.

That said, there are some body dimension factors in there as well that matter and I absolutely climb my best clipped in on 170mm cranks. Not 175s & most certainly not 165s.

 

I think it's pretty obvious that although leverage, and therefore torque is reduced when going to shorter cranks (within reason), since the circles the cranks move in are smaller most people naturally increase RPM

That's a long way to say "they have to use a lower gear".
Like driving a car with less torque. You need lower gears all the time.

 

Just for fun.

 

Increasing RPM is natural due to the circumference of a circle you spin being less with a shorter crank.

The smaller circle motion more closely mimics walking, hiking, stair climbing, etc., too.

An average stair step is pretty close to 175mm in height, so riding 175s is like climbing stairs 2 steps at a time. Got room to shorten cranks well below 150mm, if the goal is to transfer fitness over to movement on-foot.

 

Increasing RPM is natural due to the circumference of a circle you spin being less with a shorter crank.

The smaller circle motion more closely mimics walking, hiking, stair climbing, etc., too.

So you think you can spin 300rpm if you used 87mm cranks?
Go ahead and show us.

 

"Shorter cranks in the pro peleton", this was the OP's post, so I guess the argument over shorter vs longer in mountain biking seems to be a matter of choice. Road cycling, where cadences are higher, a longer crank probably isn't needed ( for torque) as much as it is needed in some offroad situations, so maybe on the road, if there is a trend towards shorter cranks, I can see it.
For offroad, the clearance issues, maybe, but I'd have to believe that you will lose pedaling efficiency, especially with climbing or technical sections where torque is a must. I don't see many offroad riders turning a 90+ cadence.

 

1:13 roadie clips a pedal while cornering. He was pedaling through corners frequently up until this point, but stops pedaling through corners for most of the rest of the video. He was going 35 mph before and after... the difference is his confidence and the risk pedal strikes pose (speed dropped under 30 during it, too).

With shorter cranks, your max speed increases due to the change in gearing associated with it. Can effectively have the effect of a bigger chainring without the issues of chainstay clearance (and anti-squat decrease for FS).

 

I clipped a pedal on a road bike at speed and flung myself into a hillside, that hurt.

Two bad pedal strikes on mtb, one was an unseen rock, that launched me a ways, minor injuries, but another time I broke a leg, trashed my seat, broke my dropper lever off on my knee, yeah, that sucked.

 

That ain't just a roadie, that's Tom Pidcock. An absolute beast in road (TDF stage win that he won descending just like this), cyclocross (World Champ) AND XC (World Champ). I have nothing to add to this dicussion, I just wanted to make it clear this isn't some random guy, lol! SAFA is no one to scoff at himself.

 

After a few weeks on 165s:







I do not like pedaling short-people circles.


I am forced to pedal short-people circles because of how low the BBs are on modern bikes.

I seriously doubt anyone of the size that would normally use 175 saying that significantly shorter cranks are better. The ONLY way they are better is that they are clipping less stuff, they are worse to me in every other way.

 

I seriously doubt anyone of the size that would normally use 175 saying that significantly shorter cranks are better. The ONLY way they are better is that they are clipping less stuff, they are worse to me in every other way.

I have a friend, who is 6'2 and he absolutely swears by 165mm cranks. And riding with him it has transformed his pedal stroke. He went from having a rough hitched pedal stroke to a smooth efficient pedal stroke. It was remarkable difference.

I am 5'5 with short legs and am pretty neutral about 165mm cranks. I have one bike with them on it and they work well, zero complaints. But I am in no hurry to switch out the cranks on my other bikes. 175mm on the other hand are a struggle for me.

 

How smooth can you make it at 90-100rpm over varied terrain? IME, there are far bigger gains by training to maintain the correct RPM range for max efficiency and delivering that RPM seated, fighting the urge to keep getting out of the saddle (and wasting time and effort).

 

Quite smoothly. This in part why FS bikes are faster than hardtails. On a FS you can just sit and pedal smoothly at the optimal cadence and let the suspension do its thing.

 

Sometimes we laugh at what we don't understand.

 

I do not understand being short.

 

I really want to try shorter than 165 but I have a feeling 165 is the perfect compromise. You get enough leverage for slow cadence power moves while increasing clearance. We really should up BB's rather than down cranks but that's not going to happen. We'll just keep sanitizing trails so low riders can manage.