h0ward

I think spoke length is measured to inside of the elbow, which is different from above by only 1mm typically. Your picture looks like 2 cross to me, large hubs are often 1 cross. You can see the difference if you play around with the spoke calculator mentioned above. If you put in the relevant data you should be able to confirm your 200mm spoke length. This is a good start for understanding what is needed to re-lace a wheel. Ideally a spoke should be just shy of protruding from the nipple, (not always possible). At least with a large hub you won't have to remove the cassette (or freewheel) to replace spokes. Maybe you need to keep a spare spoke handy in case of further problems? One broken spoke can stress the next and so on. Check spoke tension without tools by squeezing two together by hand between cross and rim and comparing around the rim, and comparing with a known good rim with similar pattern etc. You're going to need to do this when you replace your broken spokes. Remember that spoke tension on a dished wheel differs from drive side to non-drive side slightly, (or disc side to non-disc side at the front, possibly). If you do re-lace take lots of pics and allow quite a bit of time, if it's your first. Read Sheldon Brown's guide (as you progress), and allow for the fact that electric motor hubs are sometimes laced with spokes leaving on one side of spoking flange instead of alternating, witness marks on the hub will give a clue after disassembly. These details can be seen on the spoke calc graphics quite well, I think. My opinion is wheel building whilst a challenge can be quite rewarding. Are 2mm = 14g spokes thick enough, for these hubs? Any opinions, either way, anybody?

Thanks, BornAgainCyclist, and d8veh, and m1santhrope, Detailed answers, great! The BMS battery with integrated controller looks really neat, especially with the waterproof connector, I reckon a very good solution. Only downside is shipping cost, probably not more than UK all-in, unless it develops a fault and needs returning. BMS seem to have a good reputation. Still undecided exactly which motor to choose, as I am quite light I favour the 36V (with 48V battery). I shall make an effort to assess my present speed, and work from that: 20+ mph (36V motor & 26" wheel) would be more than adequate, but 19mph (48V) a tad slow, but closer to legal. Thanks for the clarification regarding controller choice, all makes sense now. Drawing 17A from the battery at max PAS setting might be a good compromise for me (headroom), who knows, I may lend the bike out occasionally. I suspect that I'll be happy with any of the combinations in reality, in any case a different controller later would be cheap enough. I did read some of the other Q128 threads. I am more than happy that I have enough info now. I hope that the answers might benefit m1santhrope (OP), and others as well. If/when complete, I'll post some details. Great forum!!!

d8veh, I am intending to convert a 26" wheel bike using your recommended combination (36V Q128c motor & 48V battery), thanks. What are the pros and cons of a 20A vs 17A (or other) controller, please? I shall be commuting, 15 mile round trip, mostly flat, sometimes with a significant head wind, but no stops. I am reasonably fit, so really just need pedal assistance, generally to around 20 mph. I am more interested in battery range and longevity than all out speed, whilst cutting a few minutes off my present journey time. Occasionally I would like to travel further, on more varied (hilly) terrain, and sometimes a little faster, all up weight 90kg. I don't think that I shall need to use the full 20A at 48V, so would a 17A (or even lower-rated) controller be more suitable,? In essence I guess I want the system optimised for efficiency and reliability, if poss. I am happy with your recommended motor, more robust, and powerful than the Q100, if a little heavier, I understand? Battery I shall source in UK due, in part to the shipping costs from China. The Eclipse units at 48V 12Ah look good, is the standard/supplied charger ok in your opinion, or worth an upgrade (expensive though)? Torque arms from BMS too. I have a rim, and know about spoke length and wheel building. OP, sorry if I am hi-jacking your post, but my requirements seem similar to yours (despite the smaller wheels), D8veh can probably advise if the 36V or 48V version of the motor goes better with the 29er wheels. I too am keen to convert rather than buy finished bike (more fun). Sorry if I am repeating questions already answered, but I couldn't find them. As a newbie, I have read quite a few posts here (and elsewhere), and have found the info invaluable and enlightening, thanks to all!