I want 180mm cranks on my Ebike.

uart
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Re: I want 180mm cranks on my Ebike.

Postby uart » Mon Feb 26, 2018 11:18 am

leovendramini wrote:In my mental image,only the 2 bottom holes are necessary as there would be only one lengthening option.70mm would be total length and comp. riders would have no use for it as their cranks are dedicated anyway.These would be for the non pro who just wants some extra mechanical advantage.Had the design in fig 2 dispensed with all those options it could have been a success.Thanks for the post.

That's going to be some pretty coarse adjustment though. I think that incredibly few riders would want anything even remotely like the thing pictured bolted onto their cranks. :)

As for "extra mechanical advantage", that's what gears are for. You can use either a smaller chainring or larger rear sprockets to get greater mechanical advantage. Having the optimal length cranks for your height (or more specifically your leg length) can increase your bio mechanical efficiency, but it's not really about mechanical advantage (as that can more easily be obtained in other ways).

Longer cranks put your knee joints though a greater range of angles. Up to a point that's ok, but you can definitely go too far and then you lose both comfort and efficiency. It really isn't just as simple as the larger the better.

RobertL
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Re: I want 180mm cranks on my Ebike.

Postby RobertL » Mon Feb 26, 2018 5:18 pm

There's a US website called Tall Life that has some information on bike cranks. Try here: https://tall.life/proportional-bike-cra ... ll-people/

I stumbled upon that site by accident some time ago. The one thing that I learned from it is that I am not actually "tall".

I am 190cm, which puts me right at what I'd call the tall end of "average" and I can buy regular things in a large or extra-large size. The guys on that site have to buy all sorts of specialised oversized things to make life easier.
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baabaa
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Re: I want 180mm cranks on my Ebike.

Postby baabaa » Mon Feb 26, 2018 5:53 pm

uart wrote:Longer cranks put your knee joints though a greater range of angles. Up to a point that's ok, but you can definitely go too far and then you lose both comfort and efficiency. It really isn't just as simple as the larger the better.

Sorry but that is just technical brouhaha, the same is true for shorter. If not everyone would be on 165 mm cranks (or less). Why do people have to make something as simple as riding one type of bike or equipment vs another into a drill-down of how clever they think they are in mechanical systems?
Do people really care that much they they are riding the absolute perfect bike?

uart
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Re: I want 180mm cranks on my Ebike.

Postby uart » Mon Feb 26, 2018 6:11 pm

baabaa wrote:
uart wrote:Longer cranks put your knee joints though a greater range of angles. Up to a point that's ok, but you can definitely go too far and then you lose both comfort and efficiency. It really isn't just as simple as the larger the better.

Sorry but that is just technical brouhaha, the same is true for shorter.
Yes, cranks can be too short as well. Then the range of muscle extension is reduced, which can reduce the overall bio mechanical efficiency. I believe that I already said that.

I'm really not sure what your point is. Perhaps you are unable to understand that saying: "increasing the crank length can increase efficiency" also implies that reducing the length can reduce that efficiency.
Last edited by uart on Tue Feb 27, 2018 1:28 pm, edited 1 time in total.

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baabaa
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Re: I want 180mm cranks on my Ebike.

Postby baabaa » Mon Feb 26, 2018 7:22 pm

So on tar or pea gravel, the velodrome track, in black mud, riding up the Alps, downhill mountain biking, on 24in wheels or a 29er, cargo bike, with a fat bike in the sand, on what-ever the people who deliver food ride (insert what other type of bikes come to mind...................)??
What difference does it make if I understand or not, as I said it is pointless technical brouhaha and hardly helps anyone riding a bike to think that what they are doing or the equipment is wrong or right ‘cause, it, just, don’t, matter.

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