So yeah, i live in goathead country and have became pretty tired of pulling thorns out of tires and having tubes mutilated after every ride, even with tube liners, puncture proof tires, sealants, etc.
I decided that my next bike would have motorcycle tires, period.
So i went on a quest to find a 20 inch wheeled bike that fit a long legged 6 foot person, which is not an easy task at all.
After spending weeks reading reviews,i decided to buy a Downtube 9FS demo model which was slightly discounted due to various nicks on the paint and whatnot, but said to be low mileage. The dual suspension was a huge selling point, as 20 inch wheels are not exactly known for ride quality.
Based on the reviews i'd seen elsewhere, it seemed to be a solid bike.
+ It fits a tall human like me. The seat has a long range of adjustability, and so do the handlebars.
+ The bike is small but the wheelbase is actually identical to a mid sized bike. It's a little on the twitchy side when a large human rides it, but it's not too bad.
+ The front fork appears to not be a proprietary long stem type, so you could replace it with something better.
+ The handlebars and seat tube do not flex nearly as much as other folding bikes i've ridden do. ( probably due to their large diameter ).
+ The folding mechanisms are pretty solid and stout. I didn't experience any shaking or wobbling due to them.
+ Rear wheel is 135mm and front is 100mm, so this is compatible with standard hub motors.
+ The pedaling position is nice. It puts you a little bit behind the cranks, which i find comfortable.
+ The included bell rings when you hit bumps. OK, it's a cheap bike but this is so annoying that it'd be better without the bell.
+ The front fork appears to have 40mm of travel, but hits a bump stop at 20mm. Basically, it's worthless because you can expect it to clunk/thunk on every major bump / curb drop.
+ The rear spring provides better suspension than the front fork, but is so short that there's no possibility of replacing it with something better.
+ I've had the folding pedals unfold on me more than once and surprise me while riding.
+ The folding mechanism is positioned exactly where pant legs would move as you pedal. This results in various kinds of pants i wear constantly getting caught in the mechanism as i pedal. I would only ride this bike with a lower leg strap, skinny jeans, or shorts.
+ Either the rear swingarm or bottom bracket area is extremely flexy. You can feel it flex as you change gears and turn while pedaling. It's pretty unnerving. And i'm not a super heavy guy, just 180lbs.
+ The rear dropouts do not make adding a hub easy because of their design.
So all in all, i'd put this bike in the 'do not convert' category. It has some unfortunate flex points and does not feel certain under pedal power. These issues will just get worse at higher speeds.