Crank Downsize Suggestions?

Posted by Curious_Sugar4447@reddit | ebikes | View on Reddit | 5 comments

Hey guys, I’m currently in the process of building my first e-bike build turning a very old single speed beach cruiser bike into a rear wheel hub 750W powered e-bike.

I’m in the process of removing the parts in order to replace new stuff and overall just make my bike look more fresh and not a decade old, and I came across the idea of replacing the current cranks that I have to something that is smaller?

It’s not a complete necessity for me, but rather, I just wanna know if this is something that could benefit me. Should I choose to go down that path or is it just more of an unnecessary cost?

For reference I’m currently 5’3” and I weigh about 120 pounds. I’m unsure if those statistics have anything to do with how beneficial smaller crank are but maybe it might help :)

Any advice helps thanks :)))

[-]

QUEENSNYLAWYER@reddit

thats a cheapo bike from a department store. the crank arms are not removable/changeable without an angle grinder (don't do this)

suggest you find a better frame as a starting point. sorry.

Curious_Sugar4447@reddit (OP)

I’ll look into the manufacturer to see if there’s a possibility to do anything without damage to the frame. If not I’ll find a different frame. 👍🏾

slowmoE30@reddit

AFAIK the purpose of crank sizing is to match your leg position bottom stroke and top stroke. Too big a crank and your knees are up by your chin (exaggerating) or your legs lock out at the bottom. There are crank size charts to find what is correct for you!

Oo thank you, I will reference those to find my match! ❤️

Neenknits@reddit

Absolutely I’d suggest shorter cranks. Also, you definitely need a new crank set, the whole piece that goes on the frame.

https://www.bikeradar.com/advice/buyers-guides/cranksets

Standard cranks are 170mm I have 160mm, and my other ones on my other trike are 155mm. Both are fine for my right leg, and my left needs 155 or a bit shorter. I have a pedal swing on the left, and I’m not sure what the shorter side measures. (It’s a weird crank shortener that allows full extension, but less knee bend).

That crank set on the frame looks like it’s not strong enough to support the motor. Welded on cranks are generally the cheap kind, so I’d get a whole new crank set and arms the length you need. It’s not that cheap, but better than it breaking mid ride.