So here is the promised Downtube Nova overview.
When I was buying the bike, I had a lot of trouble finding good reviews and critiques about the bike. A handful of blogs and some bike forums about conversions supplied me with most of what I know about the bike. I figured I would help others by compiling my research because the specs for the bike on downtube are inaccurate or unhelpful. It's now my main get-around bike so I will be racking up some considerable time (for me) on it.
I'll put a comprehensive list at the end of the post, but I want the bulk of the page devoted to my feelings about the bike and what I think rather than a clinical listing of cheap parts.
Unboxing and first impressions:
Well, the box was pretty big. They ship the Nova in a folded state with almost everything ready to ride. There is a substantial amount of Styrofoam and cardboard padding, between the box and frame. However, there wasn't enough padding where frame met frame, leading to some paint damage.
There was a lot of unwrapping, but once you get the frame out of the box and wrapping, it looks pretty sweet. On the hinge, there is a black plastic cover to protect the linkage. I tried to unfold it without removing it, and that didn't go so well. It does its job.
Besides the bike, there was a piece of velcro (hook and hoop fastener) to keep the bike folded together, a manual and bad instructions, and a piece of black plastic with 2 clips. One of the clips was broken and it was pretty warped to boot. Anyway, I don't use it and I don't need it.
Doing a quick once over, I went through the bolts, tightening what I could find. I also reseated the wheels in the dropouts; factory ships them out with the wheels about 1/2 a cm out of the drops.
Lifting the bike, you get the feeling it is really light. It isn't that light, but the size and compactness deceives. The tubes have a bit of machine-grit that should be wiped away and the headset is just a little off. The instructions advise aligning the headset, but I found there wasn't a whole lot of adjustment possible.
The handlebar hinge looks pretty sturdy. Although it looks like plastic, the entire hinge is cast aluminium or steel. The only plastic is the twist lever for locking the hinge down.
Components:
The brakes and levers are C-Star branded. As you can see here, calling them passable is being generous. I haven't had a whole lot of trouble with them while riding, they stop the bike well enough and once you set them, they stay aligned okay. I am using the stock pads, and I'm sure a pad upgrade would change things dramatically, but why put good $10 pads on something you could replace for $15-$20. On the other hand, most of the complaints are about wet weather stopping. Well, I live in Portland. Wet weather is pretty much the norm. Maybe I haven't had "really good" disc brakes, but they stop about as well wet as dry so I would have to disagree on that point. These will be the first thing I swap out, for safety if nothing else.
On the stock bike, there are 20" kenda kampaign K177 1.2" tires on 20" 1.5" Rainbow Dino VP-20 rims with schrader holes. The tires are rated fir 45-60 PSI.Out of the box, the wheels are out of true. Lateral true is pretty out of shape but the radial true is something nasty. I'll need to get that looked at.
I checked the spokes and rim tape before I inflated the tube, and everything seemed fine. The kampaigns have a light V-tread which, according to Sheldon Brown, are useless on the road. On the rear wheel is a 7 speed freewheel. More details on that later. 
The shimano shifter is a SIS indexed 7 speed twist grip shifter. Coming from a SRAM trigger type shifter on my Monona, I was a bit disappointed by the shifter. Don't get me wrong, it shifts just fine. it's just that I'm used to the convenience of not twisting my wrists and trying to count/feel out each detent as I shift. That being said, I have had no problems with slippage. When going through 3 or 4 gears at a time, there is the expected chain jerk, but nothing more and I never lose power. Sometimes it is quite violent and my feel can slip off, but it's worse on my Monona so that is neither here nor there.
The derailleur is a short arm mountain bike type D-TZ50D. It bears the tourney series name. It rests about 3"(7.7cm) off the ground, so clearance on tight curves may be a problem. On the other hand, the folding rest stand is also pretty low to the ground, so I wouldn't take this off roading anytime soon. Out of box, the derailluer was a little off to the inside. The included tuning guide is a b&w printout of their webpage, except the webpage has links on how to adjust each step. The printed sheets do not go into detail, so I would suggest just tossing them for this guide on their site.
The rear cog is a Shimano MF-TZ07 14-28 freewheel. Being a freewheel, replacement freewheels that increase gearing to a reasonable range are hard to find. There are some vintage and a few new 11-(30,32,34) hubs on ebay by some Chinese manufacturer. At $30 not including shipping, they are considerably cheaper than buying or building a new 20" cassette wheel.
The cranks are the cheap kind, welded to the sprocket. If you want to upgrade, those'll have to go. They come with a small plastic chain guard on either side of the crank. It's plastic and is in 2 part, sandwiching the sprocket between them. As you can see, they are attached with 5 phillips screws. The bike comes with folding flat pedals. To fold them, you pull out on the round metal centers and fold at the bearing. If you want a cage or strap, you'll want to make sure they don't interfere with the fold. As it is, the gearing leaves a large gap on either side of the performance scale. It cannot handle the steep hills around my school very well in either direction. Uphill, you really have to fight to keep moving. It could be a lot worse, but I wish the largest was a 30 or 32. Downhill, it maxes out at ~18 mph. Beyond that and you are just spinning out. The most I have gone was 25mph, which also happens to be the speed limit for cars on residential streets in the US. At that speed, the bike seems to hold together just fine. Nothing that shouldn't be moving was moving and I didn't notice any rattling or strange noises. It actually handled the downhill speeds a little better than the monona as far as steering and frame flex. I haven't taken it down a really long grade yet so I'll report on that when I do.
Speaking of which. I took off the standard grips and threw on some bar ends. I taped them yesterday (just the bar ends) so we'll see how they help the ride. When my hands are on the ends, I really have no way of getting to the brake levers so I reserve riding on them for uphill and straightaways with good visibility. The inner diameter of the flat bar is typical of cheap flats and is much smaller than an road bike's tube. It makes getting plugs in really hard. All I can advise is to use an excess of appropriately applied force.Frame and other parts:
The stock seat post is a 30.4" OD Alu tube with a black paint job. As some other have complained, the black paint gets rubbed off where you clamp it. Purely aesthetic, but a pain nonetheless. The thickness is about the same size as the dahon seat posts and I suspect they are interchangeable.The stock seat itself is pretty nasty. It's pretty thick foam and you sort of sink in a bit. I think a seat post or seat with suspension would be a good upgrade to help with the rough ride.
When not in use, the seat post can be lowered into the seat tube, which is open at the bottom. When fully lowered and only the reflector on the tube, it stocks out of the bottom by a few inches. Once you add a post-rack or lights or lock holder, you probably won't be lowering it it much. It doesn't do much for the footprint and makes getting it ready to ride all the longer. I usually don't bother folding the handlebars either. Since I added the endbars, the fold is a bit precarious. If space is really at a premium, the lowered seat combined with the folded handles drops the height of the folded bike to about 60cm or about 24". That's shorter than most full sized bike tires.
As you can see, I got the green version. The paint job is pretty smooth without major bubbles or rough spots. It does damage easily though, which is another complain I found online. I'm going to have to get some clear nail polish to touch the damaged spots up and when the rainy season is over, I'll probably wax it. It is an aluminium frame, but I don't want the nice green to start flaking off everywhere.
The warped and broken piece of plastic I mentioned earlier was supposed to go on the little trapezoid underneath the bottom bracket. When folded, the bike is supposed to rest upon the bar, and the little bit of plastic is to keep the paint from getting damaged. Apart from the fact that the stand protector was broken, it looked pretty ugly to boot. Instead, I wrapped some nylon cord around the bottom of the stand like I was whipping the end of a rope. I'm a little worried that it'll trap water, but since the frame is aluminium, rusting isn't too big of an issue I suppose. It looks good though and matches the black components nicely. While folded, the bike balances on the little stand pretty well, but if the front wheel starts to turn out, the bike can tip right over. Whenever I store it folded, I usually turn the front wheel into the rear wheel and that keeps it upright pretty well.As Downtube lists on their product listing, there is a braze-on derailleur mount on the seat tube above the cranks. Under the bottom bracket, there are populated braze-on cable mounts for the rear brake, and the rear derailleur, and an empty braze on set for the front derailleur cables. Good foresight on Downtube's part.
A close look at the forks shows that the rear dropouts can support a disc brake as can be seen here, although it seems like it needs a machined adapter plate. The front fork however does not have the pair of mounts discs seem to need as shown here and I'm not sure about the fork strength.
On the "top tube", there are two braze-ons for a water bottle cage or pump holder. One of the braze-ons seem to have been cross-threaded when it was manufactures and strips any socket screw I try to use. I'm planning on getting a tap and die set in the near future, and when I do, I'll try to re-cut those threads. Until then, the braze-ons are mostly useless. That said, online I read complaints that said the top tube was too close to horizontal to keep bottles from falling out of the cages. It really depends on the type of cage I suppose. There are a lot of images online of people who put cages on the braze-ons, and of those who use handle bar mounted holders.As a heads up, the Nova spec site, http://downtubesg.blogspot.com/, lists the rear hub to be 130mm, standard road bike spacing. However, the rear is actually 135mm, standard mountain bike spacing. I confirmed the original report from here (Post #3).
This was also confirmed by an email from Dr. Yan in 2012
Got a quick reply from Dr. Yan:http://www.bikeforums.net/archive/index.php/t-575616-p-5.html
1) What is the rear spacing of the frame? (126mm / 130mm /135mm)
we have had 130's and 135's the latest ones should be 135's
2) What is the spacing of the front fork? (74mm / 80mm / 100mm)
100
3) What is the width and threading of the bottom bracket?
68x114 (as I recall)
4) What is the head set size? 1” or 1 1/8”
1 1/8"
5) What is the size of the seat post?
550mm (L) 30.4mm (D)
6) Is there touchup paint available for the bikes?
No
7) Are there any geometry specs that can be found? (effective top tube length, etc..)
We do not have them, however it is a Dahon licensed frame, hence you can get the info from them
Ride impressions:
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After going out on the really hilly side streets this Tuesday, I discovered a few things and confirmed a few more. Some people wrote that the handlebars creaked if you lean too much weight into it, and they were right. No matter how tight you make the aluminium hinge, if you bear into it, you get this unpleasant creak. I also confirmed that the gearing is really insufficient to hilly areas. I found myself bottoming out on the smallest gear and spinning out on most of the downhills. The crappy streets I was riding on are a pretty good test and you feel every little crack and pebble. Even if you ride through them on the pedals, you still feel the jolt. If you go off any kind of jump/sidewalk-street joint, the back of the bike bucks and you feel like you'll be thrown forward over the bars.The stock tubes need to be carefully monitored. It has been a little over 2 weeks, and it has already dropped 6 PSI or so. I recently bought new tubes and a single Schwalbe kojack tire for when I upgrade the wheels.
We have seen a lot of rain these past few days and I really need to get fenders at some point. Every night, the bike is dripping wet and splattered with mud.
Upgrade Tree:
Apart from hard to find 20" fenders, the upgrade tree is as follows:
2-New rear wheel build with a 7 speed cassette
3-New front wheel build
4-New derailleur/cassette (8 or 9 sp) and new rear brakes and pads.
I was originally planning on making this an ebike with a middrive or RC motor, but I'll hold off on that until I get to level 2 or 3 on the upgrade tree.
--update--
I just bought some components and tools for upgrades. They should arrive sometime in the next week or two.
- 2 bare 20" Araya Aero rims
- 1 laced 20" Araya Aero wheel
- 100 12mm 14G nipples
- 3 20" rim straps (rim tape alternatives)
- 1 Avid SD5 Linear pull brake
- 1 Avid FR5 brake lever
- A set of brake cables
- a chain breaker
- a 14G spoke wrench
I went to my LBS today and saw that a set of fenders for my 20" wheels are $44, I said like hell. I'll be making some fenders this weekend from some aluminium stock and some steel wire.
