I already have a 48V ebike so will be using that battery. Road Bike, 48V, 700C wheels, wants about 21 mph average speed.
I have been reading through the forums and there is a lot of info on the Q100 variants. So Q100 at 201/328 rpm, but Q100H at 260 appears to be the best.
First off, you should fill out your profile. If nothing else, it would give us an idea of the terrain where you will be riding. You have left out much personal info. Since the 2 variants of Q100 you are considering have narrow performance envelopes(nature of mini motor in 700 wheel), those "personables" should sway you one way or the other. That's why there is no "best" motor variant.
1. I have a 9 speed cassette road bike with carbon forks so want to use a rear hub. Is the Q100H is 7 spd freewheel only?
The Q100H is freewheel only. The DNP Enoch is available w/ 11T small gear in versions of 7-speed, 8-speed and 9-speed. W/ the Q100H on 20 Amps, you will likely only use 2 or 3 gears anyhow, but you should keep the number of freewheel speeds close to your bike's system. I have used an 8-speed w/ a 9-speed system and it worked well. Some people hate the DNP, but the last two I have used have been ok, as quiet and smooth as a quslity cassette. They are heavy though.
. The CST require dishing the wheel when building, is that a serious issue....
It can be. Not every bike is built on the same jig and there are variations. On my Rocky Mountain, the dish required was extreme and I never could make the "C" work. On my GT I-Drive, the dish was minimal and everything fell into place. My "gut" feeling is, on most bikes, it is usually not a problem.
"The "C" version has a stator that is 15 to 20 % narrower to make room for the cassette. Whether or not the C uses the higher quality magnets is unknown, but my side by side comparsions indicate the C out-puts 20 to 30% less power than a H.
You have been reading my posts. On paper, it looks like a 30% difference, but in the application, maybe somewhat less. I run a 17 AMP "soft start" controller on the C and a 20 Amper on the H, so that averages things out somewhat. maybe 20% is the real world.
"The 260 rpm Q100H at 48v will most likely be too fast for its power."
What Dave is refering to, is the amount of the powerband that is above the "no-load"(the real World top speed). When there are a lots motor rpms above the speed the motor can reach, the motor is said to be Current limited. When the powerband drops off at the no-load speed, it is said to be RPM limited, it just won't spin any faster. The motor that "drops off" at the "no-load" speed will be the better overall performer, but for a fit rider who can generate real power w/ his legs, there is an advantage to having the power-line extend flat past the no-load point. He can add his leg power to the reachable power band and add a couple of MPH. For me, both the 260 and the 328 on the same batt. and controller in a 26" whl. will top out @ 22 to 23 mph. The 260 is rpm limited and the 328 is power limited. I can't add any speed w/ my legs w/ the 260, but if I pedal like hell, I can add a couple of mph on the 328. But the price payed is the 328 is really lazy in the mid-range and at top speed, it wants the controller to supply max Amps, which can over heat the controller. Put the 328 in a big wheel, and those traits are excerbated. Here, I disagree w/ Dave a bit, as I think the 260H will work well in a 26" wheel for most folks. In a 700 whl, here the rider's abilities come into play as to how well it will work. Here you will see a theme, the big wheels push the Cutes to their limit, which makes the rider's abilities paramount. 328 in 700 is only for Super riders.
I have maybe a half a dozen Cute motors of various speed and configurations. Due to their low cost and ease in swapping motor cores, A rider who isn't sure could order a spare motor only of a different speed to try both.
Also what controller should I buy?
These days, Dave is recommending the "KT" sine waves from PSW Power;
http://www.pswpower.com/peng/pic.asp?ModID=PicS224&TypID=S220052
PSW Power is an off shoot of Elifebike. I use ELB square wave controllers and I like them a lot. They are smooth and quiet.
I have no idea if a guy could order the motor(s) and the controllers from PSW Power and ELB, to make it one order to consoldate shipping cost. It would be interesting to find out.
Bottom line, I would recommend the 201 "C" motor w/ the 17 A sine wave if you want to stay a little closer to the "bicycle experience" But, top speed will be limited to around 22 to 23 mph.
The 260H on 20 Amps would be better for those days when you feel lazy and don't care to pedal hard. It will climb hills better and the top speed would be 23 to 25 mph.
Good luck.