Andre - always good to hear your thoughts on this subject. I'm looking at the Sunstar iBike S03 kit. Doesn't seem to difficult to fit myself.
Thanks for that, Ian. I took a look. Interesting about the torque sensing of the Japanese Sunstar. The best the Chinese offer is "torque simulation", which to me sounds like the computer's best guess of the lowest common denominator circumstances of a cyclist somewhere else, bever where you live.
That Sunstar is a rather pricey kit, though, and the battery is on top of that.
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I was looking at the much more commonplace, cruder, Bafang BBS01 kit at BMS Battery
http://www.bmsbattery.com/89-central-motor but a few considerations stopped me ordering it either from them or from a British dealer
http://www.wooshbikes.co.uk/?cdkit offering a reasonable price on the same kit :
1. My current setup serves faithful and unobtrusively and has only about 3000km of wear on it; years of service left in it. So replacing it merely for technical interest would be an expensive luxury.
2. There have been reports of central motors not playing nice with rear wheel gearing, especially on tarmac (as opposed to off road) bikes. I can quite believe this. I've gone to enormous trouble and expense to build an extremely low maintenance bike, and particularly don't want a new motor to start chewing Rohloff sprockets, with all the known difficulties of removing them. (Ironically, I started looking at the new motor kit while looking for a present for myself to celebrate being in so much better health that I could start bending over the bike again...)
3. What I actually want is more torque. Notice I don't say I need more torque. I have plenty for my purposes (I cycle and the motor fills in) and hills; I just want more. Central motors don't yet have the torque, watt for watt, of hub motors. I in fact already have the highest torque of any street-legal motor in my QSWXK, so to get more torque from a mid motor, I'd have to go up to 350 or more probably 500W.
4. I'm an old Porsche racer. I don't notice any problem with roadholding or handling from having the motor on the bike in the front. I reckon my Big Apples can handle twice that power before a central motor's better balance will become desireable enough to make any sacrifice for it. (My Big Apples have well over 7000km on them, about 3000 of those on the motor, and the motor has not caused any accelerated wear, in fact the front tyre is in better condition than the rear, indicating that the front can handle much more power.)
5. The torquier motor in the same range as the SWXK is the BPM, which comes in front or rear configurations, but is intended only for offroad use, starting at 350W. Some call the the SWXK the "little BPM" for its torque, but in fact there used to be a 250W BPM and Bafang withdrew it because it interfered with the sales of newer models.
That's just too many considerations to come to a decision, so I shelved the choice until midmotors grow more torque, and some way to control it, particularly at gear changes, at a reasonable price. That probably means torque-sensing and responding to it in a controlled manner.
It looks like you had much more luck, or skill, in narrowing your requirements down to an actual choice. Congratulations.
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I can't tell how easy or difficult your chosen kit would be to fit. But if if you're buying it locally or anyway from a British dealer, get a completion guarantee in the form, "Okay, you say it is easy to fit, and I have experience of working on bikes, so, if I can't fit it, you guarantee to complete the job, free of charge." I know a fellow whose business selling extremely expensive hi-fi kits was built on that promise, and Velleman, the famous Belgian electronic kit vendor, for years gave that guarantee on their more expensive kits, and probably still does. I was amazed when the Velleman MD told me how rarely they have to meet their promise.
