vintageb3

Hi Folks

So...don't laugh, but I have a Decathlon bi-fold folding bike. It was only £100 years ago. I use it when I'm away in my motorhome. I've fitted BMX handlebars and a big seat. Its really comfortable to ride. I bought a mountain bike to swap the kit onto but I can't bring myself to do it. I really love that little folder. Before someone says they are cheap rubbish and not durable, I'm 21 stone and it gets bumped off pavements and the wheels are still round. I'm surprised!

I put a Bafang 350W mid drive kit on it and changed the front sprocket to a 52T from a 48T because the Bafang motor was putting out more power than I could pedal and keep up with! I'm still not quite there...it still has too much power/or I can't pedal at a comfortable cadence with the motor. The little bike has 20" wheels. It has a 14-28, 6 speed Shimano cassette (is that the correct term?) and derailleur on the back wheel. I assume its a cheap poor quality item.

I'd like to fit a better cassette to give me a higher top speed, and also more low gears to help me on hills.

Is it possible to change that Shimano 14-28 for a say a 10-32 or 11-32. Ive seen a 9-32...but I don't think that's required.

It would be great to get this folder the way I want. It gets looks and laughs because it dweeby...but then when I pass them not pedaling...the jaw drops.
If I could just get the cadence on par with the motor output I'd be happy. Oh...and better brakes!

Thanks in advance

Unca_Sam

If it's a mid drive and you can't keep up, I'd say you've maxed your abilities out here. Increasing the cassette will give you more top end speed, but will not change how quickly the cranks turn. That's the mechanical advantage of a bicycle, after all. Can't you just use less throttle?

dedhed

It's probably a 6 speed freewheel, not a cassette. They are not too common under 13T due to inherent design limitations. In addition when they are 13T they are often not lower than 24 T

Bill Kapaun

Most likely Freewheel, but verify first-
https://www.sheldonbrown.com/free-k7.html

dsbrantjr

I think that you should consider improving your brakes before trying to increase your speed to avoid a dangerous situation. If you are going too fast to pedal you are likely going too fast to stop safely.

vintageb3

Thanks for your reply! The Bafang has pedal assist and a throttle. I’m talking about only using assist. If I use throttle only, the speed is way fast enough for that bike. What you’ve said here makes sense. I need yet a bigger crank sprocket.....or bigger wheels. I’m not sure why you don’t get the option of two crank sprockets with a derail on an ebike. Maybe it’s to protect the motor?
I’m actually in Nederland just now and wonder if a step through city bike would suit me. I’d love to get this wee bike right for me though. Thanks!

vintageb3

I did mention that in my OP and this of course would be an upgrade done at the same time as any mods. In fact, that’s on the cards soon anyway.

vintageb3

Thanks for this. I’ve seen MB cassettes at 11-32 etc. I just don’t enough about bike mechanics and terms. Thanks for the information!

Unca_Sam

Bicycle chainrings with more than 53 teeth would be difficult to source, that's as big as they are mass-produced. Now that I understand that you want more top speed, the other poster was right about freewheel limitations. They just don't go lower than 13 teeth. A road freewheel will have the whole cluster grouped lower, with a MTB freewheel only being slightly wider, because the manufacturers want it to shift well.

I'll stand by my earlier comment that the motor belongs on your mountain bike. The only way to increase gear inches after maxing out your chainring and freewheel is with bigger wheels, and your frame will limit the size wheels you can use. Any mountain bike should have brakes capable of keeping you safe at top speeds. Both the common rim brakes on mountain bikes and disc brakes can handle stopping.

You could consider a 700/29er too, if money is no object .

squirtdad

sun race has freewheels for e bikes int thw 11-36 and 11-32 range...... have not idea if they would work in this situation


SunRace | Products

vintageb3

Thanks for this!