Having read many of the replies on this issue, most seem to be related to the choice of 1 motor or 2 when building a bike, and making choices based on the intended use. I for one have 2 motors, a geared hub and a BBSHD with 46t front and 14/28 rear. I will say I am perfectly happy. This bike was factory made with a single hub motor, so the choices I made were based purely on economics and what I could do myself with a conversion kit. I am 6'0 and 220 lbs, my bike from the facory weighed 78 lbs, and came with a 1000w hub drive. My primary interest in riding is 20-40 miles in the backwoods, on forestry service roads, which involve a lot of 4 plus miles of long steep grades in excess of 6%. It didn't take me long to burnout 2 30a controllers, which in retrospect the simulator predicted after about 2 miles.
After researching this forum on adding another motor, I found a lot of good information (Some good- some bad) and I decided to plunge in and install the BBSHD myself. Having an electrical engineering background helped a lot, though most of what I did previously didn't involve electric motors, but I had the basic concepts. The BBS installation turned out to be a piece of cake, including some cusomized electrical configurations, like kill switches on both motors, left brake kill bbs, right brake kill hub, BBS PAS and Throttle only only with manpower pedal on the hub. My Handlebar and extra bar look like a motorcycle dash with 2 lcd's, phone/nav app, camera, kill swithes, throttles, etc.
So How do I mitigate the potential torque problems many writers claim to exist with the hub casing? The simple answer is don't over torque it. I follow a couple of basic rules: I never use the BBS alone! I aways start up from a stop or very low speed with the hub throttle while in a middle or low gear; I always ride with the hub motor unless I want to go faster than 20 mph and my watts get upward of 700w or so, then I kick in the BBS PAS with the appropriate gear and power level to split the load as evenly as I can. Essentially that is how I also ride the mountains; if I am on a long steep grade I am operating on a 46t/26t BBS PAS, and control throttle on the hub to split the load as much as possible, rarely going over 700-800w on either motor. Checking motor and controller temps after a couple of climbs of 5-6% running for a long period of time the temps are always less that 35-40C barely warm to the touch. I have a 52v 20ah battery running the BBS and a 48V 21ah bat on the hub, I also have a 3rd battery I carry on times that I expect to go on extra long excursions This third bat is fed to a blender with the other 48v battery to the hub which gets most of the use. All batteries have on/off switches and common connectors so I can reconfigure the batteries to the motors if needed. I can ride the mountains for much longer than my body can handle.
So, in conclusion, I will say that this has been a very successful conversion. I have a high level of redunancy, which is very important to me riding alone in the backwoods, and I am able to tackle any and all hills I have attempted in recent months. I do have a 36t front chainwheel, but so far I haven't found any reason to put it on, nor do I see a reason to add more bigger cogs to the rear. I didn't mention that this bike is a fat tire, and I plan to convert an exiting mountain/hybrid bike this winter. This convertion is aluminum frame with 42mm tires. I will probably keep it simple and use the BBSHD and no hub motor. Field testing will determine where I from there.
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