the Gruber Assist or now so called VIVAX is a complet different concept from the Bikes you use to build and drive here at endless-sphere...
here at Endless-Sphere you are only happy, with 500Watt, 800Watt, 1000Watt or even (lot) more
well: that all has not much to do with bicycling anymore
a normal, untrained person has about 100-120Watt average Poweroutput (about 80Watt for woman)
so: 100Watt (the Gruber has 200Watt electrical INPUT-Power, but max. 100Watt Outputpower)
so, this 100Watt Outputpower are about doubleing the average poweroutput from untrained people!
consider that for a moment.
for the Bike: i have driven the Gruber Assist 3.15version --> the motorunit weights only 900g (!) (less than an kg !) (2lb or 31,7oz)
and because it has only a maximum of 100Watt outputpower, a very small battery is enough too! for 1 hour FULL POWER the battery weights also less than 1000g (less than 2,2lb / less than 35oz)
AND: because the bike is so light, you don´t need to run the motor all time, you use it only when you need it uphill..
result: you can make a day-drip and this little less than 1kg-Battery is enough
Result: it is possible to build a mountainbike with Gruber-Assist which weights - INKLUDING the Battery AND the driveunit - only 10kg (!)
that are only 22.05lb or 350oz for the whole bike inkluding battery and driveunit !
i drove a Cannondale Caffein with a Gruber Assist 3.15 -- weight was about 14kg inkluding the battery
i have driven BOSCH-Bike, Panasonic-Bikes, Bafang with 800Watt, elfkw, Swiss-drive, BionX, and some more
but this Gruber-Assit was the only bike, i was not possible to say, it was an electric bike when the motor was off..
on all the other bikes you feel the weight in more or less ways..
resulting, that you normaly don´t wana drive them with motor turned off
but the Gruber driveunit is that light, that you don´t feel the weight - so best bicycling-experience so far
so: for the news:
last year the Version 3.15 was introduced..
this version had an 3-stage gearing
(the 100Watt are most likey not because the motor is that weak, but much more torque would kill the little gearings, remember how little space there is inside the tube)
here a sound-example...
also this was already the 3db (50%) quieter version, it was still ... too load in my ears..
her now the new 4.0 version, now called VIVAX:
(they went from 3stage to 2stage-gearing)
on both videos: its a 11% slope which the woman is going up very easily