Ok, so here's the backstory on this first. 4 years ago, i set out to build a very comfortable, light, very fast full suspension downhill bike with a large range. I achieved every goal with that build - 40mph continuous with 60mph burst speed available, enough range to cross county lines and back, and supreme comfort over potholed pavement.
The sticking point
was every 26" bicycle tire on the market. Our streets are littered with goatheads for half of the year, which are approx 10mm long. I tried every single "flat proof" tire on the market and every single one failed. I tried tire liners. I tried slime & stans no tubes. $400 of tires and tire accessories later, i decided to give up. The thickest tire i found, a schwalbe marathon plus, only had 7mm of total rubber..
Instead of range anxiety, i developed tire anxiety. I would get a flat tube every other ride without fail, as i'd be picking up a few goatheads per mile, and eventually one would strike at the right angle, regardless of various experiments with an ideal tire pressure..
So, knowing that some scooter/motorcycle tires have 10mm or more of rubber, i set out to build a bike with 20" wheels and mount a 16" scooter tire to it. 17" and 18" motorcycle wheel builds just come out being far too heavy.
First try.. a Downtube 9FS. I sweet talked the owner of Downtube into selling me a demo unit after finding nothing but praise for the bike on the internet.
Upon opening the box, i was impressed by the dimensions of the bike. The wheelbase is similar to a large size frame, and with some adjustment, fit me pretty well. It appeared to be nicely overbuilt and i was pretty excited about finally having one of these.
Also, the bike looks like it easily accommodated 2.25-2.5 moped tires, and it had a standard 135mm rear dropout, so it is perfect for a hub motor setup!
The first ride was pretty revealing. The front suspension only compressed about half as far as the manufacturer claimed ( 40mm versus 20mm real travel ) and was basically useless as it'd bottom out and clunk on the smallest bump, regardless of the preload setting. The rear suspension is a very short spring, but was much more useful.
There was the usual flex in the handlebars that you'll find on nearly every folding bike on the market. The folding mechanism in the center was very solid. The real problem is the rear swingarm - i could feel flex in it as i pedaled or changed gears. This was the real deal breaker with this frame. I decided to put the ebike up on eBay.
Second attempt.. after looking at every minivelo on the market, i decided to try a Sundeal V2 out because of it's dimensions and the fact that it had a chromoly frame with standard rear dropouts. I figured that fitting a front suspension and a suspension seat post would be good enough, since scooter/moto tires provide a suspension of their own.
Truth is that this bike is much smaller than it appears and is advertised - way too small for me. The headtube is also a 1 inch threaded :/. The biggest deal breaker here though is the brakes and tire fitment. They put the tube the brake caliper mounts to very close to the tiny 1 inch tires, which rules out the possibility of fitting a wider caliper and thus a wider tire.
In addition, the headset came ungreased, and was partially cross threaded upon arrival. The box it came in had been stapled shut twice, so maybe this bike was a return at one point? but still.. totally unacceptable for a manufacturer to ship a bike in this state..
Off to eBay she goes.
So.. third try's a charm, right? Being inspired by Recumpence's Cannondale Hooligan build, i found a used Hooligan on eBay for an eye watering $800, but was desperate to get this build going, so i paid the cash..
Dimensions are a little bit small for me, but doable with handlebar adjustments and maybe an aftermarket lean-back seat post.
The frame is SUPER sturdy and built like a tough little BMX bike.. big plus!
The bike came with 20 x 2.35 tires and would easily take a 16 x 2.5 scooter tire, so that is a win.
I had read the specs completely on this bike and was certain that it had standard 135mm QR dropouts.
Nope. It has a 12mm axle flat rear dropout... something i have never seen or heard of on a bike.. the rear dropout area does not allow for you to bolt on an external plate or plate + shim to remedy this easily. So a rear hub motor is out.
The bottom bracket is an odd size and the bike came with some kind of eccentric bottom bracket adapter to fit a standard size bottom bracket. Probably not a good situation for bolting a mid drive on.
Front fork is a super sturdy lefty fork. On these bikes, they have a proprietary headset and so it would require an aftermarket adapter to fit a standard 1 1/8 fork. So yes.. you could theoretically go for a front hub motor, but we all know the problems that come with a suspension fork and a hub motor..
It's almost as if the bike was built with preventing ebike conversion in mind..
( unless you have a CNC shop at your beck and call! )
OK, what about other minivelos on the market that can accommodate suspension? there's the wildly expensive airnimal rhino, but looking at the frame, i suspect it will be flexy around the rear like the downtube. Rear dropouts might be designed around the IGH hub and thus be an odd size to fit a hub motor.. that option is out as well.
I was at interbike this year and saw this little beauty.. full suspension.. fits a tall adult.. light.. electric.. ticks all the boxes. Except nearly every part is proprietary 'cept for the pedals and grips. No DIY on this baby without a CNC shop.
So what have we learned here? well, if you're 6 feet tall.. forget these 20" wheel bikes as a whole.
I have decided that the only feasible way to go is weld a 2-3 inch dropout extension on a hardtail chromoly mountain bike. Far easier than playing with the dumpster-worthy stuff on the market.
So there ya go.. a cautionary tale for others looking to go this route. Hopefully i save some others some pain, suffering, and money..