Looking for advice on picking a frame

A place to discuss the repair, design, and customization of the bicycle itself, not the powertrain ( battery, controller, motor, etc ).
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beekman001   1 µW

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Looking for advice on picking a frame

Post by beekman001 » May 28 2021 4:15pm

The local bike stores are backed up months on bike availability so I'm looking at picking up an enduro-style frame to use initially as an unpowered bike and then add a motor later. It looks like the size of the rear suspension seriously affects the ride height and maybe bottom bracket positioning.
suspension-diagram.jpg
Suspension examples
suspension-diagram.jpg (40.26 KiB) Viewed 278 times
I've also noticed that the frames seem to vary in where they place the bottom bracket falling into one of three categories as below.

- bottom bracket on the body, in front of the swingarm mount
on-body.jpg
Bottom Bracket on the body
on-body.jpg (68.48 KiB) Viewed 278 times
- bottom bracket on the swingarm, in a bracket below the arm
on-swingarm.jpg
Bottom Bracket on the swingarm
on-swingarm.jpg (16.73 KiB) Viewed 278 times
- bottom bracket on the swingarm, inline between the body bracket and the shock bracket
under-body.jpg
Bottom Bracket under the swingarm
under-body.jpg (26.97 KiB) Viewed 278 times

While I've assembled a bike before, its mostly been from a 'kit' that a friend put together for me. So I'm a little hazy on how these options will affect both the placement of the pedals and where I could place a mid-mount/coaxial motor.

I'm short (5'6" / 1.67m) so I expect I'll want a lower ride height. I suspect that when I do install a motor, I'll want to use a mid-drive rather than hub motor as one core purpose is hauling. Other than that I'm open to suggestions or alternatives.

I'd love to hear suggestions on:
suspension
breaks
wheels & tires
handlebars & front forks

RunForTheHills   100 W

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Re: Looking for advice on picking a frame

Post by RunForTheHills » May 28 2021 4:36pm

I don't think you will like riding on that frame unpowered. If you want a mid-drive, you might be better off waiting until you can afford the motor kit also and look at frames built for an Ultra motor.

beekman001   1 µW

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Re: Looking for advice on picking a frame

Post by beekman001 » May 29 2021 7:00pm

I definitely looked into ultra frames. I'm just not super sure I want to be locked into a single motor option or even a motor out of the gate. I do hear you about the weight of the frame though. You dont happen to be aware of like a bottom bracket mount which would let me use a bafang ultra frame w/o the motor do you?

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Chalo   100 GW

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Re: Looking for advice on picking a frame

Post by Chalo » May 29 2021 7:10pm

beekman001 wrote:
May 28 2021 4:15pm
I'm looking at picking up an enduro-style frame to use initially as an unpowered bike and then add a motor later.
That might be good for a laugh, but if you do it you'll quickly find out why there were never any bikes like that until people decided to cheat regulations designed for real electric assist bicycles.

Suitcase bikes like that were never intended to be pedaled. They're just weak, small motorcycles that couldn't pass a legitimate vehicle inspection, with make-believe pedals on them.

See also fat-tire folding e-bikes. Only motor power makes them tolerable, and even then they suck.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

RunForTheHills   100 W

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Re: Looking for advice on picking a frame

Post by RunForTheHills » May 29 2021 7:48pm

beekman001 wrote:
May 29 2021 7:00pm
I definitely looked into ultra frames. I'm just not super sure I want to be locked into a single motor option or even a motor out of the gate. I do hear you about the weight of the frame though. You dont happen to be aware of like a bottom bracket mount which would let me use a bafang ultra frame w/o the motor do you?
I am haven't heard of a bottom bracket mount for Ultra frames. There are not a lot of mid-drive motor options outside of Bafang and the TSDZ2. The Ultra motors offer a torque sensor, which the BBSxx motors do not. Bosch doesn't offer DIY motors. If it doesn't work out, you could just sell the frame later. Bafang Ultra ebikes are very popular right now.

markz   100 GW

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Re: Looking for advice on picking a frame

Post by markz » May 29 2021 9:23pm

Buy a used major brand name bicycle and you won't have what happened to John Bozi.
Those brand name bicycles (ex: Specialized) spend tons of money to make their bicycles last a long long time, sure its only engineered for human leg power, but its still better engineering when motors are installed then those Enduro style suitcase ebike frames.
Find a frame with a suitable area in the triangle for a battery and whatever frame geometry you want if your going for a mid drive.
Keep in mind the other factors like thru-axles (hub motors), tapered steering tubes, bottom bracket style (mid drive) and of course availability of parts.


viewtopic.php?f=51&t=112030#p1658777
broken 76 qulbix swingarm
John Bozi wrote:
May 29 2021 8:31pm
broken swingarm.jpg
Just happened doing 5kmh. I put some weight on the suspension prior to attempting to lift the front up before a speed bump.
Walked home in shame :oops
The frame is about 3 years old. With signs of rust there. Not sure what failed first, the bolt or swingarm part.
beekman001 wrote:
May 28 2021 4:15pm
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HK12K   100 kW

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Re: Looking for advice on picking a frame

Post by HK12K » May 30 2021 2:57pm

A bolt let go on Bonzi's bike which is what destroyed his swingarm. A frame by any other manufacturer would have likely suffered the same fate, if not worse. Qulbix frames are of high quality and are extremely durable, though the knockoffs not so much.

"Suitcase" style bikes make great ebikes because of the integrated battery box. That's their biggest allure. They give you plenty of space to hide and protect the sensitive bits from damage, environment, and can be an added barrier against simple theft of components. They also look pretty cool, though the pedal-purists might disagree.

They absolutely suck to pedal unpowered however due to weight and oftentimes width and general geometry. Much like how trying to use a dedicated downhill or dirt jump bike as a pedal powered commuter would suck. Pedaling a Dutch bike through the mountains of BC would suck too, and they're apparently gods gift to cycling. Point being, if you have the wrong tool for the job you're going to have a bad time.

Pedaling most any fully laden ebike unpowered Is a chore, but we don't generally build them to ride unpowered. That's kind of the entire point. One thing I will say though is that doing so will absolutely make you a stronger cyclist.

People spend upwards of ten grand on pedal bikes, counting grams the whole while. That same bike would disintegrate if electrified. Great to pedal, but the wrong tool if adding batteries and motors.

Choose wisely.

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