Although Shengyi advertises 500w max it can easily be rated at 750w with the controller using 15A with the stock 48v battery so in order for this suit to gain traction that would need to be checked.
Rad is ultimately responsible for the motor’s and back them with what appears to be excellent after sale support. Whether Shengyi backs Rad if motors fail running at higher than max rating that is between them.
Rad is a multi million dollar business and this seems to be a play to get some $$ and I don’t see much in that link that will lead to that.
The real challenge with this scenario, is that people buying this ebike on-line, have no idea what they are really getting if they haven't test ridden it, and so until they receive it they wont know if the power is sufficient for their needs. If they then try it out versus a true 750 Watt motor ebike, versus theirs, and find out how comparatively weaker it is they might be disappointed. That said, usually a 350 watt or 500 watt internally geared hub drive is plenty sufficient for most riding situations. So Rad is probably fine getting away with how they rate it. In otherwords, The ebike will work and most won't know the difference. Direct drives like Shengyi builds are rather inexpensive to manufacture in large quantities, so it is a pretty good marketing tactic to simply offer the highest rating allowed on the streets, and then price the ebike rather inexpensively. Its hard to argue that its not a decent ebike for the price they offer.
I have had several of these Rad's in my shop for repairs, and one customer who owned one (Rad City), decided to try out 3 other brands in my shop since he had bought the Rad without ever trying anything else, each with 350 watt, 500 watt, and 750 watt. Every single one of these he tried, he said felt more powerful than his Rad with a "750" watt. He asked me a lot of questions about direct drive versus IG motors, and after that, he said while he felt he got a reasonable price for Rad, he was convinced it was nothing close to a true "750 Watt" motor. (he was however shocked by the power of the 350 watt - interestingly that 350 watt ebike was $100 more than his Rad.) I have also ridden a couple Rad's since then (cargo, city, and fat tire), and they do seem slower to accelerate, and simply don't compare to most 500 watt hub drives that I have ridden. Rad doesn't state the torque, but I have seen on same Shengyi direct drive motors, rating of only 45 nm.
The other difference people will find, is that for the same sized battery (i.e. 48Volt and 14 AH), they will likely get less range using the Rad 750 watt motor, versus what they would with another typical 500 watt IG motor, since on average the 750 watt will draw more kwhr's/mile under the same riding conditions. the Rad's are also fairly heavy ebikes, and that can make a difference too. I was sort of surprised to hear one customer say he only got about 38 miles of range with a 14 AH battery on his Rad City. He said he road with his dad one time, and his dad weighed about 35 lbs more than he does, and his dad was riding a Magnum Ui6, and his dad still had about a 1/3rd of his battery capacity left, when they both went 36 miles, with hills mixed in, and his battery on his Rad completely died. he claimed both were charged overnight and full when they departed. He said he didn't use anything higher than on level 2 assist. His dad road with level 3, since he was not in as good of physical shape. The Ui6 comes with a 13.5 AH battery.
I think many forum commenters have said previously, you shouldn't really go by what is advertised in terms of motor ratings, at least in terms of watt output. Each can be paired with different size controllers, be designed with different torque ratings, and can feel entirely different depending upon the cassette used, drive train and whether direct drive or IG. Personally I doubt Rad has anything to worry about in terms of their ratings.
