Crank length?

[docnjoj]

Our LBS in Daphne, AL has the ability to order various crank lengths in a few days. One guy who works there has has experience with short cranks and reduced knee problems. They can be educated and some actually know stuff. Not all though. These guys build bikes for some of the older Senior Class riders.
otherDoc

my experience with the local is like "opposites day"
In a conversation about knee pain and hip pain, lbs gave the considered opinion that I needed longer crank arms, not shorter.
Needless to say, I didn't agree with that assessment.
For sure, they'll immediately take your order for special parts but they'll actually order said part whenever they feel like it.

Yep those guys are completely wrong since the primary problems leading to knee pain are range of motion (less is better) and reducing pressure by spinning (also reduces knee pain). It is a bit counter-intuitive which is why they said longer is better. As I stated before you gotta gear down and spin to really help. But you know all this stuff. Too bad your LBS doesn't. Maybe "edumacate" them. I'll see if I can find some articles on this that don't only pertain to recumbents.
otherDoc

edit: Here is an article by the guy in the US who re-machines your original cranks.
http://bikesmithdesign.com/Short_Cranks/short_cranks_faqs.html
And her is one by Sheldon Brown
http://sheldonbrown.com/cranks.html

 

[ddk]

https://www.compulsioncycles.com/index.php?route=product/category&path=104
cheap unicycle crank arm sets

 

[docnjoj]

https://www.compulsioncycles.com/index.php?route=product/category&path=104
cheap unicycle crank arm sets

Boy those are inexpensive! Good find.
otherDoc

 

[motomech]

It is an interesting store, but those short crank arms, without spiders, aren't any help to us two-wheeler types.
Having dropped down to 24 inch wheels on my mountain bike, pedal strikes are a real problem.
So I set out researching what my options are and after quite some time, what I have learned is, they are few.
What I wanted was a crankset with at least a double ring and arms in the 150 to 160 mm range.
But the cavit is, my bike, like most mountain bikes, uses an English 73mm shell for the bottom bracket
and that eliminates the entire range Shimano Compact cranksets and once they are tossed out of the equation, there is not much left.
So what I was left with, was leaving my current bottom bracket, a Shimano Octalink and taking a step backwards and going to an old style square taper.
Doing that opens the availability a bunch of BMX arms in pretty much any length desired,
but since I was looking for a "pre-built" ASM w/ chainrings installed that would except my 9-speed chain, I was still looking.
What I finally went with is this;

Sugino XD600 152mm 24-36-50 74/110 7/8spd
http://www.amazon.com/Sugino-XD600-152mm-24-36-50-8spd/dp/B001PRX9FU
The 50T bigring is a plus.
When it arrives, I will come back here and report on how it worked out.

P.S. There was one other option available to me, Cyclesmith does offer a crank arm shortening service, but with shipping, it's about $100,
but more importantly to me, the shortened arms would end up being around 140mm, a little shorter than I wanted.

 

[Jeremy Harris]

https://www.compulsioncycles.com/index.php?route=product/category&path=104
cheap unicycle crank arm sets

Nice find, thanks! The chances are that those cranks would work OK with the Schlumpf or ATS drives, as these need two plain cranks. At that price I'm tempted to risk getting a pair just to experiment with.

 

[ddk]

@motomech
I don't use but single chainrings, as the motor(s) on my trikes do all the real work of climbing hills.
Therefore I only need to gear for my cadence at the fastest speed I wish to mainly cruise at. And for me being a wuss and also wanting the trikes to remain legal that's 20 mph.
Adding a chainring to one of these unicycle cranks appears to be rather simple exercise in welding, either adding a spider or just attaching the chainring directly.
I'm ordering a set of the unicycle crank arms in steel for easy welding.

I actually prefer single-piece cranksets because of their easy-to-change and rightly-priced cranks (about $10 each) ($5 for the bearing sets)
The cranks can be had from 89mm (3.5") on up in 0.5" increments up to 175mm and the rare 180mm. I even have a spider for a one-piece that can take multi-chainrings -although I could see that being limited to only two chainrings because of clearance issues.

My newest trike has a three-piece crankset with a pedelec system installed.
I'd prefer to keep the pedelec that way but the 175mm crank arms are impossible for my knees and hips.
As you've recently discovered there isn't many options for short cranks without getting into the $500 BS.
My take is to either have a spider attached to a unicycle crank or remove and replace the BB shell with for a one-piece crank. If I didn't want to attempt keeping the pedelec intact I would just exchange the 3-piece crank and it's shell for the one-piece version.

 

[ddk]

I ordered cranks from https://www.compulsioncycles.com/ on Monday.
No word on shipping yet.
My LBS said they would redo my crank arms for $20...
-guess I'll have a set of unicycle crank arms to add to my collection of bike parts lol.

 

[ddk]

received the unicycle cranks today
Solid steel so yes, they're heavy.
In fact, a single piece crank weighs (much) less.

-had to do my usual, consisting of an email asking "has it shipped yet?" Then they were shipped the next day.

 

[Lemlux]

I use an Origin-8 triple crankset with 130mm and 74mm BCD. (Currently $41.52 shipped here:

http://www.amazon.com/Origin8-Alloy-Triple-Bicycle-Crank/dp/B002I7MAKG/ref=sr_1_1?ie=UTF8&qid=1351096128&sr=8-1&keywords=origin-8+145mm )

This allowed me to reduce pedal scrape and knee soreness while also allowing me to use a Vuelta 60t large chainring to compensate for the smaller drive wheel diameter. I did have to use a 153mm spindle to keep the 60t from interfering with the chainstay.

A side benefit of the wide spindle was that I was able to widen my triangle bag to 5 1/4" to fit a wider battery without interfering with pedal action.

 

[neptronix]

I am a 30 year old and i have always had one problematic knee. But i also have rather long legs. I thought a 175mm crank was appropriate for my height, but it just lead to discomfort and more pain. The 145mm sinz cranks i had on another bike made it very easy to pedal. I feel like i lost some of my ability to really crank on the pedals, however when i do really push on the 145mm cranks, i never get knee pain as a result.

( 20" wheel with a rather tall tire out back, 26" up front )

Here is my pike's peak race bike with the sinz 145mm cranks installed. The 165mm cranks previously on it would drag on the ground if i took a turn too sharp.. lol..

 

[Chalo]

It is difficult for me to believe the drift of this discussion. Cranks are ancillary to legs. If you have child-sized legs, use child-sized cranks. If not, don't-- unless you have a disability that causes a limitation. Sheldon Brown was a believer in short cranks. But he also had a progressive debilitating disease that eventually robbed him of the ability to ride any bike at all.

170mm cranks are proven to work well for average cycle racers (which is to say, males about 5-1/2 feet tall, in their 20s and 30s). Since I am over 6-1/2 feet tall, I never assumed those cranks were right for me, any more than I believed those little dudes' pants would be right for me. So I got a set of 196mm cranks way back in the late 1980s. They worked well for me, and I put in my longest and fastest rides on them.

Over time, the bicycle components industry has become even less willing to furnish proportional sized cranks in the way that frame makers offer proportional sized frames, but finding unusual items has become easier thanks to our friends on the newfangled Internet. So now most of my bikes have long cranks-- from 185mm for old touring bikes with low bottom brackets to 225mm for my bike with a high bottom bracket.

I feel cramped on my bike that has 170mm cranks, and it takes me a little while to get used to it. But my bikes with 205mm and 225mm cranks feel right even when I've been riding something else. Just for perspective, I got my longest cranks when I was already in my 40s, with crunchy knees from past injuries. So it's not about being young, fit, and resilient.

If you have legs of normal length, and you have normal physical capabilities, then it is reasonable to assume that normal crank length is about right. If you walk with short, shuffling little steps and have a difficult time with normal height stairs, than maybe you should consider shorter cranks. But sub-100mm cranks? Really? Those are for sub-three foot tall people. You cut your mechanical advantage, and more than likely your output, in half by using those, even if you pedal just as hard as ever. Because realistically, you are not going to double your RPM, or even come close to doing that.

Chalo

 

[neptronix]

I'm 6 ft, 250lbs and have rather long legs and i gotta say, anything above 175mm and above is uncomfortable to me.
Different stroke lengths for different folks i guess ..

Another thing that needs to be mentioned is the angle / distance from the seat to the bottom bracket. This can influence pedaling comfort A LOT. You will notice that cruiser bikes have the bottom bracket far forward. This is very comfortable for some reason. Some mountain and road bikes have the seat and bottom bracket distance be 1-2 inches apart. This helps you put more pedal power to the ground, but it is less comfortable.

Shorter cranks won't allow you to put as much power down; but they also i think act as a power limiter for your legs. On my 145mm cranks, i can't manage to hurt my knees.

 

[docnjoj]

Roger that to short cranks for old bad knees. I had serious knee pain at 175 mm and when I put on 150 cranks my knee pain vanished. It is true that you can't put as much force to turn them but by raising cadance from about 60 to 80 or so things work well. You of course need to gear down to do this. We are doing +/-140 miles a week since my wife started working from home and still no knee pain.Now she is using 170 mm cranks and has some pain in one knee. Hmmmm.................
otherDoc

 

[Chalo]

I'm guessing you guys would quickly discover how ineffectual stubby cranks are if you rode pedal-only bikes more often. That's the test of truth. Whatever works best by itself is what works best with power assist, even if the power assist obscures the difference.

Another thing that needs to be mentioned is the angle / distance from the seat to the bottom bracket. This can influence pedaling comfort A LOT. You will notice that cruiser bikes have the bottom bracket far forward. This is very comfortable for some reason. Some mountain and road bikes have the seat and bottom bracket distance be 1-2 inches apart. This helps you put more pedal power to the ground, but it is less comfortable.

Having the saddle forward over the bottom bracket serves two main purposes:

1) It opens up the thigh-to-torso angle so you can get your back lower and flatter without bringing your knees up to your chest, and

2) it makes standing up off the saddle quick and easy, since you're almost there already.

Both these goals are relevant for racers and other sportsmen, but not for most of the rest of us. I like a 70 degree seat angle, and I have bikes with as low as a 60 degree seat angle. A little lower than that and you're in "flat foot" territory, where you can set your saddle for proper leg extension and still get both your feet flat on the ground without getting off the seat. The Electra Townie was the original ancestor of this relatively recent trend.

:

I'll say this much about it: even though it does not offer all the versatility or controllability of a traditional bike layout, it is quite comfortable, quite enjoyable, and way more feasible than a recumbent-- with most of a 'bent's advantages and basically none of its shortcomings.

Chalo

 

[neptronix]

So you ride bikes like that? it would make sense why you are okay with some very long cranksets.

I have owned about 10 bikes in my lifetime, and indeed the ones with the bottom bracket just an inch or two in distance from the seat allows you to really hammer on them, but cruisers are so sedate and easy to pedal, even if you can't go so fast.. i think they're more ideal eBikes than mountain bikes, even though they aerodynamically disadvantage you, whereas mountain bikes and road bikes sorta want to streamline you ( i have super tall handlebars on my trek MTB because of this )

 

[recumbent]

I also have issues with long cranks, i ordered my present recumbent bike with 165mm cranks which I've been riding for a few years, and love them. I can even see myself ordering 160mm next time.

As for "Chalo" and his "Townie" beach bike comparison to a recumbent, your missing the perfectly comfortable seat, the longer wheelbase, and built-in suspension system that most Cr-Mo frames got, especially longer bikes. I know you were just playin round, but they are very different machines.

However a beach bike would be an easy ebike to build, load-up with panniers like i have for batteries.
and your set for many miles of fun and exta room for groceries.

Oops, time for sleep...

 

[Chalo]

So you ride bikes like that? it would make sense why you are okay with some very long cranksets.

No, I don't have any flat foot bikes. They're just an illustration of the laid-back sort of setup you were talking about.

Most of my fleet is old touring bikes with long chainstays and tall frames, but retrofitted with bars other than drop bars. Those bikes tend to have 70 to 72 degree parallel frame angles and bottom brackets about 10-1/2 inches high. Because my frames are so tall (typically 27" or 68cm), the seat sits farther back than normal even though it's at the same angle, and the saddle nose sits about 6" behind the bottom bracket spindle on most of my rides.

My first e-bike was built on a '70s Nishiki touring bike frame in 68cm size. My second e-bike was built on an early '00s Cannondale touring bike frame in size Jumbo (roughly equivalent to 63cm). My third e-bike was built on a Redline 29er MTB in 21" size. The first one used 170mm cranks, because it had a low BB and I didn't know what to expect as to lean angle. The second one had a 185mm crank, because that was as low to the ground as I was comfortable with. And the third used 190mm cranks, because that's what I had sitting around.

The fact is, bike layout (within reason, not counting wheelchair-like atrocities) has almost no effect on ideal crank length, which is pretty much just a function of leg length. Long legs work best with long cranks. Short legs require short cranks. If you're trying to make power with pedals, it behooves you to use the longest cranks that don't cause you any problems or awkwardness in your pedal stroke. In my observation of thousands of customers and other riders over the years, 170mm cranks almost always work without problems for riders down to under 5 feet tall and up into their 70s, as long as they don't have unusual range-of-motion issues. So most folks can actually benefit from longer cranks, not shorter. Physical disabilities represent a wild card, of course.

I think the fascination some folks here have with short cranks is partly corollary to people's fascination with smaller-than-intended wheel sizes (a case of the cart pulling the horse, if you ask me), and partly a by-product of no longer having to produce your own propulsion by means of muscle power. It's the first step towards those useless and ridiculous pedal-shaped appendages on e-scooters.

My own inclination is to have a bicycle first, and electric assist as an auxiliary system. I think it's important that nothing about adding e-power screw up the bike's fundamental virtues in a misguided attempt to improve it.

Chalo

 

[Chalo]

As for "Chalo" and his "Townie" beach bike comparison to a recumbent, your missing the perfectly comfortable seat, the longer wheelbase, and built-in suspension system that most Cr-Mo frames got, especially longer bikes.

A flat foot bike also misses the atrocious handling, lousy stability, abysmal maneuverability, poor-riding small wheels, clumsy off-bike management, transportation and storage difficulties, extravagant expense, abundant extra weight, and inconvenient proprietary parts of a recumbent. To say nothing of the opportunity for injurious leg suck. Riders of normal bikes really miss out on a lot.

To me, it seems a lounge chair and a bike do very different jobs, and it makes sense to have different human interfaces for them. (To be fair, e-bikes do offer the opportunity to lounge and ride simultaneously, if that's what floats your boat.)

However, as to the topic at hand: The impaired riding position of a recumbent bike sometimes works better with shorter-than-normal cranks turned at a higher-than-normal cadence. In addition to accommodating a suboptimal riding position, short cranks can also improve aerodynamics and fit better inside a fairing.

Chalo

 

[ddk]

...
The fact is, bike layout (within reason, not counting wheelchair-like atrocities)

I believe the word you're looking for is "adaptations" rather than "atrocities"

My own inclination is to have a bicycle first, and electric assist as an auxiliary system. I think it's important that nothing about adding e-power screw up the bike's fundamental virtues in a misguided attempt to improve it...

I would hazard a guess that the average forum member here uses "pedal assist" rather than "motor assist"
but I might be wrong...

 

[HAROX]

I would hazard a guess that the average forum member here uses "pedal assist" rather than "motor assist"
but I might be wrong...

I'd think so. That makes it important. Longer cranks always feel better no matter what your size, even when they're too long, they feel better than too short.

 

[neptronix]

I think the fascination some folks here have with short cranks is partly corollary to people's fascination with smaller-than-intended wheel sizes (a case of the cart pulling the horse, if you ask me), and partly a by-product of no longer having to produce your own propulsion by means of muscle power. It's the first step towards those useless and ridiculous pedal-shaped appendages on e-scooters.

Aaahaa.. you have just revealed yourself to be a contrarian, sir.

Hub motors in smaller wheels do not only prove themselves to be more powerful on the butt dyno, but the real dyno you can easily see the effects of running a given amount of copper and magnet faster per MPH by upping the voltage and making the wheel smaller if you check the ebikes.ca simulator.

On the other point;
There seems to be a consensus here that shorter cranks can be better for some people.

https://www.google.com/search?q=sho...&sugexp=chrome,mod=0&sourceid=chrome&ie=UTF-8

If you check google, there seems to be a lot of people saying that shorter cranks are better too.
But no agreement.... so maybe our bodies are just built different? one size does not fit all?

So yeah, neither of the things you mentioned here are particularly specific to ES or ES's collective consciousness.

 

[Chalo]

By small wheels being the "cart pulling the horse", I mean that it is folly to trade away the basic virtues of the bicycle in the attempt to improve it. So if you decide small wheels are what you need, use a bike intended to work with small wheels. And if you use a bike designed for full sized wheels, use the right size and match them with a motor of lower kV, or use a non-hub motor.

An electric bicycle is still a bicycle, and by the same token an electric effed-up bicycle is still an effed-up bicycle. See?

As for cranks, one size doesn't fit all. I said that already. Short folks need short cranks, tall folks need long cranks for best results. But 170mm cranks aren't for average-sized people, they are for racer-sized men. In other words, they are proven to work for short men. Thus they'll suit average sized women, more or less.

I concede that there is less to lose by using short cranks-- all you'll do is limit your performance. Too-long cranks could potentially give you an overuse injury. But that doesn't mean that tall men should handicap themselves with cranks optimized for short men. If you're 6 feet tall, you're 5% to 10% taller than a cycling champion, so there's no good reason to use even shorter cranks than he does, unless you have an impairment.

I understand that electric bikes are attractive to people who do have an impairment, so they are likely to be overrepresented here in this forum. But saying short cranks are better is like saying orthotics for your shoes are better-- they are only better if you suffer a condition that is mitigated by them. Able-bodied people of average or taller height should use cranks of average or greater length. They can get by with shorter ones, but it limits their performance (or, to put it another way, it diminishes the results they get for a given level of effort).

 

[neptronix]

I see what you mean.

One note though - a lower kV motor doesn't change the MPH to RPM factor. So with a hub, you want the tiniest wheel you can get away with, and usually that's a 24" or 20" wheel.

That's why a scooter hub can weigh and cost nearly the same as one of our bike hubs, they spin faster and thus make more power. A rear sprocket or crank driven system does combat this issue, and you could use a 40" wheel if you like if all things are geared right

Oh, and let me spill the beans why shorter cranks are good for me, personally. I am pidgeon-toed on my right leg. This means my knee and my foot are always out of alignment. With the short cranks, i don't get knee pain. I also have a tendency to be in a lower gear than necessary and don't pedal at the best cadence.. in my case, you are right in your theory - i have one knee that is in trouble after an hour of using 175mm cranks, but no trouble using 145 or 165 cranks whatsoever.

 

[John Bozi]

guys ive been searching like crazy,

can't find a way to shorten my mountain bike cranks as they are fluted thinner where I want holes.

can you suggest a product or method?

 

[Chalo]

guys ive been searching like crazy,

can't find a way to shorten my mountain bike cranks as they are fluted thinner where I want holes.

can you suggest a product or method?

Find some inexpensive cranks that aren't fluted.

Maybe buy some BMX racing cranks for child racers that give you the length you're looking for. Like these, for instance.

You can use tandem kidback arm shorteners, but they are expensive and they widen the spacing of your pedals. They are not really intended for riders of adult strength and weight.