Let’s talk crank arm lengths…

[Monty Dog]

I have a real beef about crank arm lengths on all E-MTBs. Here’s the thing; all E-MTB bike manufacturers stick to the same sized crank arm across all of their frame sizes. You don’t get this in the road biking world, so what’s going on?

It doesn’t take an Einstein to figure out that the correlation between average leg length and body height is going to be high. The road bike design engineers all know that tall riders usually equals long legs whereas short body = short legs; but this simple fact seems to have passed Canyon and other E-MTB design engineers by.

I’m tall, at 6’4” (193cm), and I’ve been riding for a long time (I’m 57). Through trial and error and a professional bike fit, I’ve found that 175mm is perfect for me on my various road bikes. When I bought my (used) Bird hardtail MTB a few years back, it came with 165mm cranks, and I did try to stick with these, because I knew the prevailing wisdom says shorter is better for off-road. But the problem for me was on really long rides, I felt like my leg muscles just weren’t being stretched out enough, and sometimes I’d get cramp.

So I changed to 175mm and never looked back. You feel a subtle difference at first, but for long rides, it’s huge. I do suffer the dreaded pedal strikes - not helped by the long low slack frame geometry - but for me there’s no real option; I just can’t go shorter.

Fast forward to now, and I’m in the market to drop £6k or more on an E-MTB. Being 105kg and less fit than I used to be but never-the-less still enjoying long rides out in the saddle - I really like the sound of the Canyon Spectral:On CF 8 or 9, because of that big 900Wh battery. But hang on - what’s this? 165mm crank arms on ALL frame sizes including XL…?? And no they won’t swap this out.

How can a one-size-fits all approach to crank arms possibly make any sense when you have a range of frame sizes to cater for anywhere between 5’4” in 6’6” in height…? Shimano, SRAM and all the others make a whole range of crank arm lengths, so why not use them?

All of the info I’ve seen out there on webland make the points that different riders have different preferences, and different crank lengths suit different terrains and style of riding, and bike companies can’t possibly predict what each rider will want. All true. To a degree. But this doesn’t change the fact that crank lengths still need to be PROPORTIONATE to leg length.

Another side note; the bottom bracket clearance distance is ALSO exactly the same for each frame size - for every E-MTB I can see out there, not just Canyon. Only makes sense if you believe that everyone - regardless of height - needs the same crank arm length.

And here’s another related point. As well as longer legs, the taller rider is also likely to be heavier. Think about it - a short rider who is (in all likelihood) of shorter leg AND lighter weight AND suited to a shorter crank arm length gets the same bottom bracket clearance as the taller, heavier, longer legged, longer cranked rider.

This is my first post here and quite a rant. I hope that’s OK on this forum. The thing is bike manufacturers need to understand that customers need to believe in their brand if they’re going to part with multiple £1,000’s. And that belief simply won’t hold if the customer sees that they can’t be bothered to properly consider something so very basic.

Question to all you lovely forum members: if I order a Spectral:On CF 8 or 9, and I retro-fit 175mm crank arms, will that be a mistake? Bear in mind I weigh 105kg. What about 172.5mm or 170mm…?

 

[discdigger]

On my regular mtb I run 175 cranks. I bought a used frame from my local store because it ran a 160 mm fork, I was using 140mm and wanted to try something longer. But the bottom bracket was so low, the pedal strikes were unbearable. I switched to 165 mm cranks, but I couldn't get used to them. They didn't give a long enough stroke, I was still bashing pedals. I got rid of the bike, wasted a lot of money.
Rode an emtb for several hours at an mtb festival summer 2022. It was great. Saw a deal on a norco sight, and I'll blame it on the beers, I clicked Buy. So I get it out on the trail and sure enough I'm bashing pedals. I'm kinda bummed, you dont want to fall off in the rocks and you don't want to push a 50+ pound bike thru the rocks either. I have since bought 150 mm cranks and 170mm fork, up from 160mm, Its snowing here now so I may not get to try this setup until spring.
But I saw a guy on utube , that mentioned that the norco sight and the norco range are the same frame. The range has a longer rear shock yoke and has 180mm fork vs 160mm on the sight. Now I wish I had gone with the Range, because that bottom bracket has to be higher.
But I think an ebike is a different animal altogether as far as how you ride them. Now most of your power is from the motor not your legs. You may not need the long leg stroke. I plan to use my ebike for trail maintenance, figuring out new areas and keeping my riding instincts up to par. I'll still be using my regular mtb when I'm riding with the gang.
So my point is, look at the bottom bracket heights of as many bikes as you can, if you ride a lot of rocky terrain it could be important. Get to a big mtb festival and demo some. Or find a local shop that is willing to let you try different size cranks. I would bet larger battery capacity is around the corner for most emtb's. I got mine because I just retired and I plan on doing a lot of riding in 2023, now that I'm not working 50 hours a week.

 

[luna87824]

The last time I road with short crank arms, and I think they were 165s, was when I was when I was 4 years old and they were on my tricycle!

 

[Sherman]

Bottom bracket height is the same for all frame sizes, so longer cranks would mean more pedal strikes. And ebikes have gone for shorter cranks for this reason.

 

[Tepi]

Jos vaihdat lyhyemmät esimerkiksi 165 mm kammet päivitä moottorisi säädöt tälle mitalle.

 

[ALLeighton]

Since the mid-80s I've always had 175mm crankarms on my mountain bikes (I'm 5' 8") until my 2021 Yeti SB130 came with 170s. I was actually looking forward to trying a slightly shorter crankarm length after reading a study from the University of Utah on the subject. I've found that the 170s work perfect for me on my standard MTB.

After purchasing a Trek Rail in 2022 with 165s, I found that I was pedal striking frequently, which is something I rarely (if ever) do on a standard MTB. I believe this can be mostly attributed to the subconscious desire when riding an eMTB to "stay on the power" by pedaling constantly during technical climbs. In fact, last year I hit a rock so hard that I bent a crankarm for the first time. My current Ibis Oso also has 165s and has already experienced a decent share of pedal strikes....to the point that I would probably consider 160s or even 155s if I ever upgraded my crankset or just get tired of striking.

 

[steve_sordy]

I compared a range of bikes that I had owned and wondered why they had different BB heights. But if you subtract 30% sag, take into account crank length and then look where the pedal axis ends up, they were remarkably similar. I started to look at the impact of pedal widths when leaning over, to see where the outer edge ended up, but I got bored at that point.

There appeared to be an industry rule of thumb for pedal clearance at the sag point. My sample was not very wide.

 

[Mikerb]

Firstly there is little point comparing road bike geometry or use to mtb.............and EMTB also brings more differences to mtb.
Designers look to keep centre of gravity low but also have to accomodate a motor where a much smaller profile BB would otherwise be. The crank length...invariably now 165mm........is related to effective BB ( motor on an EMTB) height. Leg fit has far more to do with frame size and dropper post height than crank length.
Assuming you stick to the crank length designed for the bike and rear suspension is set properly, pedal strikes are largely about riding technique. Shorter cranks than standard can help if the terrain you ride dictates that, or any particular bike has a somewhat lower effective BB.............you still need to read the trail however.

You only pedal uphill anyway..............the rest of the time gravity does the job

 

[mark.ai]

I have a real beef about crank arm lengths on all E-MTBs. Here’s the thing; all E-MTB bike manufacturers stick to the same sized crank arm across all of their frame sizes. You don’t get this in the road biking world, so what’s going on?

It doesn’t take an Einstein to figure out that the correlation between average leg length and body height is going to be high. The road bike design engineers all know that tall riders usually equals long legs whereas short body = short legs; but this simple fact seems to have passed Canyon and other E-MTB design engineers by.

I’m tall, at 6’4” (193cm), and I’ve been riding for a long time (I’m 57). Through trial and error and a professional bike fit, I’ve found that 175mm is perfect for me on my various road bikes. When I bought my (used) Bird hardtail MTB a few years back, it came with 165mm cranks, and I did try to stick with these, because I knew the prevailing wisdom says shorter is better for off-road. But the problem for me was on really long rides, I felt like my leg muscles just weren’t being stretched out enough, and sometimes I’d get cramp.

So I changed to 175mm and never looked back. You feel a subtle difference at first, but for long rides, it’s huge. I do suffer the dreaded pedal strikes - not helped by the long low slack frame geometry - but for me there’s no real option; I just can’t go shorter.

Fast forward to now, and I’m in the market to drop £6k or more on an E-MTB. Being 105kg and less fit than I used to be but never-the-less still enjoying long rides out in the saddle - I really like the sound of the Canyon Spectral:On CF 8 or 9, because of that big 900Wh battery. But hang on - what’s this? 165mm crank arms on ALL frame sizes including XL…?? And no they won’t swap this out.

How can a one-size-fits all approach to crank arms possibly make any sense when you have a range of frame sizes to cater for anywhere between 5’4” in 6’6” in height…? Shimano, SRAM and all the others make a whole range of crank arm lengths, so why not use them?

All of the info I’ve seen out there on webland make the points that different riders have different preferences, and different crank lengths suit different terrains and style of riding, and bike companies can’t possibly predict what each rider will want. All true. To a degree. But this doesn’t change the fact that crank lengths still need to be PROPORTIONATE to leg length.

Another side note; the bottom bracket clearance distance is ALSO exactly the same for each frame size - for every E-MTB I can see out there, not just Canyon. Only makes sense if you believe that everyone - regardless of height - needs the same crank arm length.

And here’s another related point. As well as longer legs, the taller rider is also likely to be heavier. Think about it - a short rider who is (in all likelihood) of shorter leg AND lighter weight AND suited to a shorter crank arm length gets the same bottom bracket clearance as the taller, heavier, longer legged, longer cranked rider.

This is my first post here and quite a rant. I hope that’s OK on this forum. The thing is bike manufacturers need to understand that customers need to believe in their brand if they’re going to part with multiple £1,000’s. And that belief simply won’t hold if the customer sees that they can’t be bothered to properly consider something so very basic.

Question to all you lovely forum members: if I order a Spectral:On CF 8 or 9, and I retro-fit 175mm crank arms, will that be a mistake? Bear in mind I weigh 105kg. What about 172.5mm or 170mm…?

Go with whatever crank lengths you like

But I’m surprised you say the shorter cranks weren’t stretching out your muscles. Did you set your saddle height relative to the pedal at the bottom of the stroke? So a higher saddle for shorter cranks. Then the leg stretch should be the same, but the foot & leg don’t raise up quite so high.

I have 170mm cranks on my EMTBs and 175mm on my road bike. I tend to feel it’s slightly easier to keep a higher cadence with the shorter cranks, but otherwise don’t notice much difference.

 

[Monty Dog]

Bottom bracket height is the same for all frame sizes, so longer cranks would mean more pedal strikes. And ebikes have gone for shorter cranks for this reason.

Bottom brackets and crank arm lengths are indeed the same for all frame sizes. Exactly my point. The question is why. Why do taller bigger riders have to put up with either a) unacceptable amount of pedal strikes, or b) unacceptablly mismatched crank arm length?

 

[Monty Dog]

I compared a range of bikes that I had owned and wondered why they had different BB heights. But if you subtract 30% sag, take into account crank length and then look where the pedal axis ends up, they were remarkably similar. I started to look at the impact of pedal widths when leaning over, to see where the outer edge ended up, but I got bored at that point.

There appeared to be an industry rule of thumb for pedal clearance at the sag point. My sample was not very wide.

That’s interesting. All road bike manufacturers do this too. But seemingly nowadays E-MTB bike makers just don’t bother. Short or tall, you get the same BB height and crank length. It’s really frustrating, and I just don’t get it.

 

[Monty Dog]

Firstly there is little point comparing road bike geometry or use to mtb.............and EMTB also brings more differences to mtb.
Designers look to keep centre of gravity low but also have to accomodate a motor where a much smaller profile BB would otherwise be. The crank length...invariably now 165mm........is related to effective BB ( motor on an EMTB) height. Leg fit has far more to do with frame size and dropper post height than crank length.
Assuming you stick to the crank length designed for the bike and rear suspension is set properly, pedal strikes are largely about riding technique. Shorter cranks than standard can help if the terrain you ride dictates that, or any particular bike has a somewhat lower effective BB.............you still need to read the trail however.

You only pedal uphill anyway..............the rest of the time gravity does the job

Thanks for replying, tho not sure I agree. ‘Assuming you stick to crank length designed for the bike’… But they’re designing all frame sizes to have the same crank length, which to my mind is self evidently wrong. ‘Leg fit has more to do with frame size and dropper post size’. Not really - Of course you can fix your saddle height so that the bottom of the pedal stroke feels right, but if the crank is too short, then the top of the stroke won’t be high enough. I‘m tall and I have long legs. My requirements can’t be the same as another rider who is a foot shorter and legs that are 6 inches shorter.

 

[Monty Dog]

Go with whatever crank lengths you like

But I’m surprised you say the shorter cranks weren’t stretching out your muscles. Did you set your saddle height relative to the pedal at the bottom of the stroke? So a higher saddle for shorter cranks. Then the leg stretch should be the same, but the foot & leg don’t raise up quite so high.

I have 170mm cranks on my EMTBs and 175mm on my road bike. I tend to feel it’s slightly easier to keep a higher cadence with the shorter cranks, but otherwise don’t notice much difference.

Yeah, that’s what I mean - the leg raise up wouldn’t be as high. Means you don’t get the full range of muscle use and leverage. Thought experiment - imagine doing a tough 4 hour ride on a bike with cranks that were taken from a kids bike, so your pedals are going round in a tiny 12 inch radius. Ridiculous right? Same principle, but to a different degree….

 

[Monty Dog]

And I’d love to go for the crank lengths that I like, but bike manufacturers don’t allow it; they make the BB height too low for XL frames. All of them. So I’m forced to take the same crank as short riders.
I would really love to get a bike designer guy on this forum who could explain the rational….

 

[kirkbar]

Interesting article I read yesterday about crank length:

Why Shorter Cranks Are Better (According To Science) - Pinkbike

There aren't many win-wins in mountain-biking, but shorter crank arms could be just that.

www.pinkbike.com

 

[rod9301]

Yeah, that’s what I mean - the leg raise up wouldn’t be as high. Means you don’t get the full range of muscle use and leverage. Thought experiment - imagine doing a tough 4 hour ride on a bike with cranks that were taken from a kids bike, so your pedals are going round in a tiny 12 inch radius. Ridiculous right? Same principle, but to a different degree….

Not true at all. I went from 175 to 155, no difference in how tired i was, but huge difference in uphill rocky terrain that i couldn't clear with the longer cranks.

 

[Monty Dog]

Interesting article I read yesterday about crank length:

Why Shorter Cranks Are Better (According To Science) - Pinkbike

There aren't many win-wins in mountain-biking, but shorter crank arms could be just that.

www.pinkbike.com

Nice, thanks. Yeah, that is an interesting read. So the conclusion from bringing all those separate studies together is that overall power and efficiency don’t vary much with different crank lengths. Fair enough.

But….
The article still doesn’t deal with comfort / fatigue / cramp over long 4 hour plus cycle rides. I think if they focussed on that, lhere would be a narrower range of crank lengths suitable for each rider. And if you accept that point, then you’d also have to accept that cranks need to be proportional to height. The article doesn’t reference this at all.

Someone posted that e-bikes are different because a lot (most?) of the power comes from the motor. True, but for me, the point of an e-bike is not to push myself any less - it’s to go faster for longer. When I get my e-MTB, I fully intend to come back from a ride just as knackered.

But jeez, from looking at the comments at the end of the article - those Pink boys are a bit obsessed aren’t they…?

 

[Mikerb]

It obviously depeds to a degree on what sort of mountain biking you do. I mostly drive to the trails so virtually all my riding is offroad and Never have my dropper fully extended. Downhill or on fast single track I am stood on the pedals so actually spend very little time sat in the saddle pedalling.
There is another variable though I think. I changed 165 cranks for 155 cranks on my long travel enduro mtb which has a very low BB. I learnt over time to a void pedal strikes but the change to 155 just meant I had to concentrate less on avoiding pedal strikes and better able to put full strokes in on gnarly climbs ( which I also mostly do stood on the pedals). What I did notice with the shorter cranks however was that I appeared to be a ble excert more power on the cranks whilst getting less leg strain by the end of a ride; I think the reason for this is that the bike in question has a relatively slack seat tube angle so that the BB is further in front of my hips that on bikes with a steeper seat tube, and as a result on that bike a lot of the effort is pushing the cranks over the top of their stroke....rather than pushing down past the top of the stroke. The shorter crank meant that required less effort over time. Obviously that changes once in the ready position up on the pedals so it was mostly when starting the bike off from a standstill.

 

[discdigger]

I think the question isn't, why don't ebike co's spec longer cranks, but when will they make bikes with higher bottom brackets. I assume miranda is making a 150mm crank because they saw a market place need, and they decided to capitalize on it.
Remember the switch from 2x drivetrains to 1x. I thought this is stupid, they don't make big enough rear cassettes for steep climbs. Wolftooth tooth came out with a 40 tooth ring you could add to your shimano cassette, but it was several years before shimano & sram started making cassettes with bigger rings. In the meantime microshift saw the need, they jumped in and made a 10 speed cassette with a whopping 48 tooth ring. Shimano & sram still dont make a 10 speed cassette that big & they only recently started making the 11 speed with a 51 tooth ring. Why, because that wanted you to buy 12 speed stuff.
I think some company will eventually realize that the market want ebikes with higher bottom brackets, so that people will be able to ride the terrain they want, with the components they want.
It just hasn't happened yet.

 

[Monty Dog]

I agree the question isn’t just ‘why don’t ebike co’s spec longer cranks’, but neither do I think it is ‘when will they make bikes with higher bottom brackets’. Not quite, anyway; it’s more nuanced than that.

The real question is, ‘why don’t ebike co’s take a proportional approach?’ So higher bottom brackets AND longer cranks for the biggest frame sizes, to properly cater for the bigger rider. I’m fine with existing low BBs and shorter cranks for smaller frames. It’s the one-size-fits-all approach I don’t get and don’t appreciate.

 

[kirkbar]

Nice, thanks. Yeah, that is an interesting read. So the conclusion from bringing all those separate studies together is that overall power and efficiency don’t vary much with different crank lengths. Fair enough.

But….
The article still doesn’t deal with comfort / fatigue / cramp over long 4 hour plus cycle rides. I think if they focussed on that, lhere would be a narrower range of crank lengths suitable for each rider. And if you accept that point, then you’d also have to accept that cranks need to be proportional to height. The article doesn’t reference this at all.

Someone posted that e-bikes are different because a lot (most?) of the power comes from the motor. True, but for me, the point of an e-bike is not to push myself any less - it’s to go faster for longer. When I get my e-MTB, I fully intend to come back from a ride just as knackered.

But jeez, from looking at the comments at the end of the article - those Pink boys are a bit obsessed aren’t they…?

"Pinkbikers" are the best - they love to go down the rabbit hole!

I was running 172.5 for years on my gravel bike(s) and then went in for professional fitting where they hooked me up to sensors and cameras, etc. They recommended 170mm for my body build 5'8" / 172cm which helped my climbing quite a bit. I rarely get out of the saddle and like to spin up the climbs. It also lowered my saddle. Change one thing and every other parameter must change - it's quite a science!

My biggest concern on an MTB is pedal strike. I ride in VERY rocky terrain on the East Coast and with some of the lower bottom bracket bikes and suspension sag this becomes a very real and dangerous problem.

My eMTB is on it's way (turbo Levo SL) and it has 165mm where as all my "regular" MTBs have 170mm to match my gravel bikes. Should be interesting riding it with the shorter cranks.

 

[jbrown15]

I agree the question isn’t just ‘why don’t ebike co’s spec longer cranks’, but neither do I think it is ‘when will they make bikes with higher bottom brackets’. Not quite, anyway; it’s more nuanced than that.

The real question is, ‘why don’t ebike co’s take a proportional approach?’ So higher bottom brackets AND longer cranks for the biggest frame sizes, to properly cater for the bigger rider. I’m fine with existing low BBs and shorter cranks for smaller frames. It’s the one-size-fits-all approach I don’t get and don’t appreciate.

Well off the top of my head I'd have to think it's not that hard to design a bike to have size specific chainstays. But to design and build a bike around the idea of having higher bottom bracket of larger sizes so someone may or may not run 175mm cranks might be a little over kill. One of the main reasons for longer cranks is to help generate torque/leverage for pedaling. With an ebike the motor helps take care of that, and what ebike motors really like is a high cadence. On the trails shorter cranks help to spin up quicker and provide that higher cadence.

Are you using your ebike for mountain biking or cruising around for hours and hours?

Also what brand of motor do you have? I mean Shimano makes 175mm cranks, but why design a bike to run that long of cranks when probably less than 2% of people would run cranks that long?

 

[ilostmypassword]

I have a real beef about crank arm lengths on all E-MTBs. Here’s the thing; all E-MTB bike manufacturers stick to the same sized crank arm across all of their frame sizes. You don’t get this in the road biking world, so what’s going on?

It doesn’t take an Einstein to figure out that the correlation between average leg length and body height is going to be high. The road bike design engineers all know that tall riders usually equals long legs whereas short body = short legs; but this simple fact seems to have passed Canyon and other E-MTB design engineers by.

I’m tall, at 6’4” (193cm), and I’ve been riding for a long time (I’m 57). Through trial and error and a professional bike fit, I’ve found that 175mm is perfect for me on my various road bikes. When I bought my (used) Bird hardtail MTB a few years back, it came with 165mm cranks, and I did try to stick with these, because I knew the prevailing wisdom says shorter is better for off-road. But the problem for me was on really long rides, I felt like my leg muscles just weren’t being stretched out enough, and sometimes I’d get cramp.

So I changed to 175mm and never looked back. You feel a subtle difference at first, but for long rides, it’s huge. I do suffer the dreaded pedal strikes - not helped by the long low slack frame geometry - but for me there’s no real option; I just can’t go shorter.

Fast forward to now, and I’m in the market to drop £6k or more on an E-MTB. Being 105kg and less fit than I used to be but never-the-less still enjoying long rides out in the saddle - I really like the sound of the Canyon Spectral:On CF 8 or 9, because of that big 900Wh battery. But hang on - what’s this? 165mm crank arms on ALL frame sizes including XL…?? And no they won’t swap this out.

How can a one-size-fits all approach to crank arms possibly make any sense when you have a range of frame sizes to cater for anywhere between 5’4” in 6’6” in height…? Shimano, SRAM and all the others make a whole range of crank arm lengths, so why not use them?

All of the info I’ve seen out there on webland make the points that different riders have different preferences, and different crank lengths suit different terrains and style of riding, and bike companies can’t possibly predict what each rider will want. All true. To a degree. But this doesn’t change the fact that crank lengths still need to be PROPORTIONATE to leg length.

Another side note; the bottom bracket clearance distance is ALSO exactly the same for each frame size - for every E-MTB I can see out there, not just Canyon. Only makes sense if you believe that everyone - regardless of height - needs the same crank arm length.

And here’s another related point. As well as longer legs, the taller rider is also likely to be heavier. Think about it - a short rider who is (in all likelihood) of shorter leg AND lighter weight AND suited to a shorter crank arm length gets the same bottom bracket clearance as the taller, heavier, longer legged, longer cranked rider.

This is my first post here and quite a rant. I hope that’s OK on this forum. The thing is bike manufacturers need to understand that customers need to believe in their brand if they’re going to part with multiple £1,000’s. And that belief simply won’t hold if the customer sees that they can’t be bothered to properly consider something so very basic.

Question to all you lovely forum members: if I order a Spectral:On CF 8 or 9, and I retro-fit 175mm crank arms, will that be a mistake? Bear in mind I weigh 105kg. What about 172.5mm or 170mm…?

Giant offer different sized crank arms on their bikes depending on the size you ride.

 

[Monty Dog]

Well off the top of my head I'd have to think it's not that hard to design a bike to have size specific chainstays. But to design and build a bike around the idea of having higher bottom bracket of larger sizes so someone may or may not run 175mm cranks might be a little over kill. One of the main reasons for longer cranks is to help generate torque/leverage for pedaling. With an ebike the motor helps take care of that, and what ebike motors really like is a high cadence. On the trails shorter cranks help to spin up quicker and provide that higher cadence.

Are you using your ebike for mountain biking or cruising around for hours and hours?

Also what brand of motor do you have? I mean Shimano makes 175mm cranks, but why design a bike to run that long of cranks when probably less than 2% of people would run cranks that long?

Hmmm… 2% overall or 2% of tall riders?

Let’s rephrase the question. Do you think only 2% of XL riders would choose the same length crank as Small riders, if given a choice? And let’s assume pedal strikes are not a factor, which they wouldn’t be if that XL frame came with correspondingly higher BB clearance.

I don’t know the answer either, but I’d hazard a guess at way more than 2%.

As to why all the bike companies do it… I think the real answer is laziness.

They do one-size-fits-all because they can. All their competitor bike companies do it. And when the bike magazines and reviewers do focus on the merits of different crank lengths, they consider a million different factors - but never the simple fact that a rider who is a foot taller than another rider might actually be better off with a longer crank. (Nobody questions the need for different frame sizes).

The topic simply never comes up. Or if it does it gets mixed in with all the other non-size-related factors, and then concludes with, it’s too complicated.

But size isn’t complicated. If you’re bigger, you need bigger. It’s really not that hard…

 

[jbrown15]

Hmmm… 2% overall or 2% of tall riders?

Let’s rephrase the question. Do you think only 2% of XL riders would choose the same length crank as Small riders, if given a choice? And let’s assume pedal strikes are not a factor, which they wouldn’t be if that XL frame came with correspondingly higher BB clearance.

I don’t know the answer either, but I’d hazard a guess at way more than 2%.

As to why all the bike companies do it… I think the real answer is laziness.

They do one-size-fits-all because they can. All their competitor bike companies do it. And when the bike magazines and reviewers do focus on the merits of different crank lengths, they consider a million different factors - but never the simple fact that a rider who is a foot taller than another rider might actually be better off with a longer crank. (Nobody questions the need for different frame sizes).

The topic simply never comes up. Or if it does it gets mixed in with all the other non-size-related factors, and then concludes with, it’s too complicated.

But size isn’t complicated. If you’re bigger, you need bigger. It’s really not that hard…

Laziness? Or a simple equation of knowing there’s no demand for it and not willing to spend a silly amount of money designing front triangle specific sizes to accommodate 175mm cranks when they probably already know people aren’t going to buy them.

If there was a demand to you really think the bike industry would just simply ignore it? The simple fact the some brands offer size specific chainstays indicates they would be willing if there was such a demand. And the fact there isn’t would suggest there just no need to design frames to run 175mm cranks with a high enough bottom bracket that you wouldn’t have to constantly worry about pedal strikes.

I had a Devinci AC that came stock with a 170mm cranks and had a BB height of 357mm, which by most would be considered fairly high. It was insane the amount of pedal strikes I would get, it was almost dangerous at times. I couldn’t even imagine trying to run 175mm cranks. You’d probably need a BB somewhere in the range of 370mm.

 

[Monty Dog]

Are you saying there is also no demand for XL frame sizes for XL riders?

 

[Monty Dog]

Look, unless bike manufacturers take a consistent approach and acknowledge that with different size riders you need different sized frames AND proportional sized cranks, they’re going to be open to criticism. And rightly so.

Flipping this around, would you argue that the smallest riders must only have the same crank lengths as largest?

 

[mtb-steve]

I'm 6'3" and my dad is 6', we both have XL sized Orbea Wild FS which came with 160 cranks, after a bit of idle discussion we both decided to try 165 cranks, and we've both stuck with them.
I found the 160 were just to short, I was spinning and could easily reach a point were the Bosch motor cut the power up a climb, with the 165's I don't do this as often, I do get occasional pedal strikes but most of the time I just half pedal up rocky climbs.
I also have a hard tail Cube with the same Bosch Gen 4 motor and 175 cranks, on the flat I'm usually above the speed limit with next to no effort and last time I rode it I was shocked at how little battery I used and how fast I could go. I know hard tails are more efficient but even with the suspension fully locked on the Wild FS I can't get close to the speed of the Cube and I'm guessing the crank length helps.

 

[jbrown15]

Look, unless bike manufacturers take a consistent approach and acknowledge that with different size riders you need different sized frames AND proportional sized cranks, they’re going to be open to criticism. And rightly so.

Flipping this around, would you argue that the smallest riders must only have the same crank lengths as largest?

I’m not arguing, I’m just simply pointing out that I don’t see a case for what you’re saying. Did talk riders just start coming out of the woodwork now?
There’s been tall riders for as long as there’s been ebikes right? So maybe the bike industry just thought there’s no need to run 175mm cranks on ebikes?

I don’t disagree with someone 5’4” needing different cranks from someone 6’4”. I just can’t see them designing large frames with higher BB with the same model simply to allow you to run 175mm cranks.

 

[mtb-steve]

Laziness? Or a simple equation of knowing there’s no demand for it and not willing to spend a silly amount of money designing front triangle specific sizes to accommodate 175mm cranks when they probably already know people aren’t going to buy them.

They are designing and building a different sized frame anyway, there is no extra work in accounting for longer cranks. It's probably cheaper to order 5000 cranks of the same length than it is to order them in different lengths, and for 90% of customers it'll be fine as the motor compensates.