Understanding frames for a 20" bike

[Stylesheets]

This is my first post. What a forum you guys have here. I've spent the last two weeks reading and reading. I own a eZip 750 but alas the SLA battery has refused to maintain enough charge for me to commute to work. IInstead of upgrading to a lithium battery I decided to ditch the scooter and embark on building an eBike.

I've considered mountain bikes frames. Because I'm of small stature at 5'3" 120lbs I feel like I'm a good candidate for a BMX 20" type frame. After considering a BMX frame I saw a few posts converting cheap NEXT bikes from walmart. I like the stature of a BMX frame but would like a little bit of suspension to help with some of the minor bumps in the road. I like the low center of gravity, agility, and for someone of my size my posture wouldn't really cause me pain over my short commute. My commute is 3 miles on a flat bike trail away from car traffic. Yes, I could just use my regular bike and pedal but what's the fun in that?

I've read other posts of people who discourage using the NEXT bikes. They're cheaply made, have horrible components, and lack the triangle in the frame to mount a battery. In my opinion these are all problems that can be mitigated. The frame itself is steel which means the drop outs are stronger than any aluminum frame with a thicker gauge. Also, it has a full suspension, albeit with less than par components. However, I don't plan on pedaling. Weight is not of a concern to me and neither is the quality of the crankset or derailers. I'd be replacing the rims, tires, brake levers, brake pads, the pedals, replacing the seat, and perhaps the cranks.

My question is, is a walmart NEXT steal bike frame a decent choice considering my needs and travel distance? They're only $35 on craigslist. What I'm looking for a small suspension frame to rear mount a 20" hub. I'm considering the Magic pie 3 kit 20" rear mount kit. Thank you for your time.

 

[Chalo]

NEXTs, Roadmasters, Magnas, Ozones, etc. are the dregs of the sorry cesspool that is department store bikes. You could easily spend $200 trying to fix one of those bikes and still not have reliable transportation to show for it.

If you start with a bike like that, you had better enjoy working on it, and not care whether it works right.

Hold out for a real bike.

 

[bowlofsalad]

How fast do you plan on going? What voltage is your pack going to be and how much will it weigh?

Balance and the middle of the frame triangle for battery mounting are two details that I see as big pros to upright bicycles. No triangle and being forced to mount the battery on the rear sounds like a disadvantage to me. Where you place the battery is a fairly important detail, especially if you aren't a very experienced rider. I would definitely seek out a frame with a suitably sized middle triangle for the battery if I had to use upright as the foundation for an ebike. The rest of the details are kind of irrelevant sounding and hard to talk about. If you want 20" wheels, why not? Nothing wrong with that.

If you aren't planning on going very fast, accelerating much, or going up any hills or anything ever, you could probably go with a pretty small pack size for your short trips. Making the need to have a middle of the frame mount irrelevant. Having about 10 pounds on a rack might be acceptable, if you were going for something heavier I'd probably still recommend a triangle mount.

I cannot speak about the quality or integrity of any specific bike.

 

[Stylesheets]

It will go no more than 15mph with a max range of 8 miles. I'm not sure how much it weighs but I'm assuming no more than 25lbs including hub and batt pack. I consider myself a very experienced rider.

I think both of you make valid points. Thank you.

 

[Anthony King]

At that speed I don't see suspension as a great need. Large pneumatic tires will give you plenty of suspension. Cheap suspension systems will give you exactly what you pay for.

Large tires that are not overinflated will offer a good ride at 15mph. There is a misconception that overinflated tires are faster. People confuse rolling resistance (which does not measure suspension losses) with tire speed. The lower suspension losses of tires inflated properly (about 15% tire drop when loaded) increase comfort and speed.

 

[Drunkskunk]

Stear clear of Next BSOs. There are a few BSO type bikes sold at MallWort that might be usable if you're on a budget, but none of them have Next painted on the side. They are badly designed, badly made, with parts that will fail if used. Their primary function is to look neat under the tree at Christmas, and then be recycled.

And the suspension is essentially a pogo stick with wheels. They have no shocks, they just have shock shaped objects with springs. No dampening, no rebound control. If you have ever seen a car try to go down the road with blown shocks, you'll have an idea what the bike will be like.

Bouncy

Bouncy

Bouncy


If you are on a tight budget, try a garage sale. you'll get better prices than craigslist. You might find a Trek 800 for $50, or an old Specalized Rockhopper. Both are good bikes, and are common enough to be found cheap.

 

[-dg]

If you are on a tight budget, try a garage sale. you'll get better prices than craigslist. You might find a Trek 800 for $50, or an old Specalized Rockhopper. Both are good bikes, and are common enough to be found cheap.

What he said. Even here in the SF bay area where used bikes are expensive you can find 800 and 900 series steel Treks from the 90s for around $100 in good working order, even on Craigslist if you have some patience. The 900 series are really nice old bikes. I pickup up a 950 for $80 that needed only a good scrubbing and a new chain, and a 930 for $100 that needed nothing except a wipe down.

Old road bikes cost serious money around here, not even particularly nice ones are $300, because old road bikes have become "vintage". But old mountain bikes are merely "obsolete" and fine old steel lugged US built Treks sell for next to nothing. Which is great for us as these are ideal for electrification.

 

[Stylesheets]

You all are making a lot of sense. I'm convinced my idea was a bad one and for all of the reasons you mentioned. I now realize the shocks aren't shocks but merely shiny springs like DrunkSkunk mentioned.

Because I'm not traveling very fast or very far, somewhat under inflated tires will provide me the comfort I need going over small bumps at 15mph, like Anthony King said.

Also, DG makes a good point that in the bay area there are a ton of used old mountain bikes with decent shocks for as much as a brand new NEXT. I'm sure I could find a really nice one at a swap meet. However, sometimes I feel that the really nice bikes at the swap meet in San Jose on sale for $50 are stolen

I'll do my due diligence and rethink the frame I should use. Thank you all for your guidance.

 

[amberwolf]

You might also check out your local Freecycle.org mailing lists. Around here, old bicycles are offered for free periodically on them. They always need work, but since you wouldn't be buying the bike, you can instead spend the money on the fixit parts.

(or get several over time and combine their good bits).

 

[bowlofsalad]

You all are making a lot of sense. I'm convinced my idea was a bad one and for all of the reasons you mentioned. I now realize the shocks aren't shocks but merely shiny springs like DrunkSkunk mentioned.

Because I'm not traveling very fast or very far, somewhat under inflated tires will provide me the comfort I need going over small bumps at 15mph, like Anthony King said.

You are close to understanding. Not all suspension parts are equal, some are great, some are not.

Just having any tire inflated to a lower PSI will make a difference in the softness of the ride. But if you really want to go this route, very fat or wide tires, at least 2", are the way to go. The wider the tire, the better it is for rolling resistance and comfort. At 15mph, the aerodynamics drag isn't as big of a deal. Just find some 2"+ wide tires like big apples, hookworms, marathon, big apple plus and so on, and you'll be riding soft.