So no hub motor love huh?
I ride a front hub motor converted cargo bike. I pedal myself most of the time but the 60th to 80th hills, the steepest, I use the assist heavily. I carry 60 lb supplies out the uphill leg. I like that a geared hub motor doesn't drag power off. Also when the rain shorts out the throttle, about once a year, I don't have to call a tow truck. I just pedal to destination & use a hair dryer. With the motor on the front the bike has the 3x8 speeds it came with, from 1:1 to 4.7:1 ratios. I've worn out one hub motor ($221), burnt another one out in the rain ($740) that had the pins too close together. I'm on the 3rd motor ($39) in ~8000 miles. No waiting for parts, I've had a spare in the garage since the 2nd year. Making new mounts for different controllers is most of the 2 or 3 afternoons it takes to convert from one to the other.
I had a rear DD motor for a few months, but it wouldn't let me have more than 7 speeds on its rear freewheel. I could never find one in stock that went from 32 to 11 teeth. Best I could get was 28 to 14. Wasn't low enough to pedal 330 lb gross up 15% grade without assist, and wasn't high enough to assist the motor over 18 mph. Besides the front shifter wore out and would only select 2 of the 3 front speeds from the 18th month on. I didn't figure that out until the 3rd year, then the exact replacement shifter wasn't available. I ended up buying a shifter that pulled up instead of down and had to spend a couple of days making a converter block to relocate the cable. The DD motor used vast amounts of watt hours lugging up hills, it really wasn't competent at that. The DD motor also dragged power off like being in 2 speeds higher than I really was. The hub motor I liked the best was a Mac12t, but I can't buy a replacement. The $740 one I bought from Luna had a harness suitable for the ASI controller it came with, and the pins were too close together to withstand the rain. Water burnt a pin into the harness, making both motor & controller unusable. New motor is a bafang 500 w, wimpy but cheap since it was a uber rental fleet takeoff.
Your goal of 25 mph is not within the realm of an electric bicycle, not for any distance. You need a gasoline scooter for that. 25 peak is achievable, but it burns up the watthours very fast. Exception, head down flat back road bikes orbea & cannondale will allow 25 mph if the rider puts in most of the effort. Those motors are only 250 w. Most stores will not sell even a 48 v hub motor anymore, much less a 52. The geared hubs will burn a winding if you try to ride it up 1000' in an hour, and most purchasers in CA, OR, WA, bought the bike just for that purpose. The big US seller of geared hubs, ebikeling.com no longer carries the 48 v ones only 36. My 48 v ebikeling motor was fine at my speeds, since we have rolling hills in S. Indiana, not mountains. I wore out the gears on the ebikeling one in ~4500 miles.
Happy shopping & riding.
A three speed is going out today, I hope, and a single speed tandem coaster brake beach cruiser is coming in for a three-speed coaster electric conversion. He wants to use it to beer garden hop with a lady friend without getting busted driving a car. Bikes are a different as riders.
