(long time lurker, first time c/bikewrench poster)
I have a Bikonit MD750 ebike that currently wears its stock wheels with its third set of tires. The front is a 26" wheel (ETRTO 100-559) with 203mm brake rotors and 15x150mm thru-axle. The rear is also 26" (ETRTO 100-559) with 203mm brake rotors ans 12x197mm thru-axle. Both tires are 26x4.0, inflated to the max 30 PSI (~200 kPA), with a measured outside diameter of 74cm. On the rear is a 9-speed SRAM cassette and its matching HG-style splined freehub.
My problem: I use this ebike as a fast (40-45 kph, 25-28 MPH) inter-city cruiser on paved roads, rather than off-road as the manufacturer might have intended. The long stretches of road shoulder I ride on have all manner of debris, and the wide tires are constantly hitting things. In 1400 km (~860 miles), I've had four rear-wheel flats (with two in the span of 12 hours!), presumably from both sharp objects and pinch flats due to hitting protrusions at speed. These tires are also a drag, since under human power only, I can barely hold 20 kph (13 mph) but on my acoustic bike with 700x32 tires, I'm closer to 28-32 kph (17-20 mph). At higher speeds under electric power, this drag can only get worse. The original tires were Kenda Juggernauts (too loud on pavement), and the second set were Origin8 Supercells (too easily punctured above 32 kph (20 mph)). So I'd like to change to narrower tires, which also implies narrower rims.
Preliminary research: Since the weight of this ebike is around 40 kg (88 lbs), I know I cannot run narrow tires -- like the aformentioned 700x32 -- since it might concentrate the wheel forces on too little of contact area. Also, I want to keep the tire widths manageable when taking public transport: the buses and trains here have a tire width limit of ~2.5 inch (64 mm), and I will retain the stock wheels for mounting any tires wider than this. Two different references suggest that 23mm rims might be my sweet spot, giving me a range of possible tire widths to later purchase, from about 1.5" to 2.4".
For wheel diameter, I would prefer to retain or exceed the existing 74mm outside diameter, since it's not clear if I can easily reprogram this ebike's computer to acknowledge a different wheel circumference. A smaller outside diameter would cause the speed governor to engage prematurely, whereas a larger diameter is limited primarily by the frame around the rear wheel. By my measurements, this frame has clearance for an absolute maximum rear-wheel outside diameter of 82 cm. This reference indicates that a 29" wheel has a rough outside diameter of 29" (73.6mm), give or take. One size smaller is the 27.5" wheel, with a slightly smaller outside diameter of 27.5" (69.8mm).
Since my goal is to equate or exceed the existing 74cm outside diameter, I'm inclined toward a 29" wheelset. There may also be operational efficiencies, since a 29" wheel and my acoustic bike's 700C wheels have identical ETRTO diameters of 622mm. For example, I could possibly stock a single size of 700C spare tubes at home. Also, within mountain biking, there seems to be a trend of seasonally switching between fatbike wheels and 29" or 29"+ wheels, so I don't feel my desire is out-of-place.
Finally, I wish to leave the 9-speed shifter alone, so that I can swap between this new wheelset and the stock wheelset at-will. This means the new rear wheel must also be compatible with 9-speed HG-style cassettes. This compatibility chart indicates that if the new hub is Shimano 8/9/10 or SRAM 9/10 speed compatible, then I'm set. And if the new hub is Shimano 11/12 or SRAM 11 speed compatible, then I can use a 1.85mm spacer with my existing 9-speed HG cassette, which should be easy enough to find.
What I've found so far: With a search criteria for a 29" wheelset with 150mm front and 197mm rear, with a 23mm inner rim and HG-style splines, I've found very few results that aren't custom builds. The first (and least expensive) wheelset is from Bikesdirect.com but it doesn't actually exist in stock, and its 29mm rim width is more than desired. The next from Biktrix is significantly wider, at 60mm rim width. The third and fourth are from Ican and Fyxation, at 50mm and 40mm respectively, and both wheelsets run into $700 territory.
Of those four, two use Novatec D201SB-15/D202SB hubs, one uses Fyxation's own hub, and one is unspecified. All appear to support 15x150mm thru-axle in the front and 12x197mm thru-axle in the rear. Other search efforts showed that a bit more variety exists if I went with a 27.5" wheelset, but I'm trying to keep to the criteria from earlier.
Hub variety: While researching 150/197mm hubs, it seems that various brands are relabeled, of varying quality. It seems Framed and Novatec are the same, Pub is made by Bitex, and DT Swiss is generally well-liked but expensive. I'm led to believe DT Swiss is on the higher end of the market, while Novatec and Pub are entry-level, with sporadic reports of years of life or months before failure. Certainly, on eBay, Pub and Framed sell for $40-60 while DT Swiss seems to be $300-400.
I need help: First of all, thank you for reading this far. What I would like is to know whether I'm so far off the mark that I need to start over, or if this is a mostly solid criteria and it's just that no ready-made wheelsets for my use-case are available and that I should build or commission my own wheelset. To guide toward an answer, I wrote out some questions:
- Are there alternatives I haven't considered for reducing punctures on an off-road style ebike currently wearing fatbike wheels?
- Is a 29" wheelset right for my bike?
- Is there some reason I shouldn't pair a 23mm rim width with 15x150mm/12x197mm hubs?
- With no experience building or specifying wheelsets, should I first build a cheap custom wheelset as a beta version, then later commission a "good for lifetime", YOLO, high-quality wheelset as the final goal? Or should I cut straight to the chase?
- Are there other -- ideally less than $1k -- wheelsets that I didn't find from my search efforts?
- Is 12x197mm thru-axle really that rare? Is it rare because I'm looking for such a narrow rim? Or because I'm making a grand tourer out of an off-roader?
- Is wheel-building difficult to do at home? Sheldon Brown makes it sound straighforward, although there was a post here earlier about computing spoke lengths.
- What 29" tires might be well-suited for speed, lower rolling resistance, reasonably high air pressure, and debris resistance on an ebike?
Any and all advice would be greatly appreciated. Thank you!