A size chart written for a nineteen-pound road bike tells you almost nothing useful about a pedal-assist bike that weighs fifty-five pounds with the battery in. The numbers are the same numbers, standover height, reach, stack, effective top tube, but the consequences change once the machine is heavy enough that you cannot save it with a shrug when it starts to tip. Fit on an e-bike is partly about pedaling comfort and mostly about control at the two moments the bike is least stable, which are the moment you get on and the moment you stop.
Standover stops being a comfort measurement and becomes a dismount plan
On a light bike, standover clearance is a courtesy. You want an inch or two so you are not straddling the top tube painfully when you stop, and beyond that it barely registers. On a heavy bike, standover is the difference between a stop you control and a stop where the bike leans past the point you can hold it. Fifty-five pounds falling away from you at ten degrees is a strain; at twenty degrees it is going down and taking your knee or your ankle with it. That is why riders who never thought about standover on a road bike suddenly care about three inches of it.
The second-order effect is that standover clearance interacts with where the battery sits. A downtube battery raises the effective top tube on some frames and thickens the tube you have to clear on almost all of them, so two bikes with identical published standover can feel different between your legs at a stop light. Check it with your shoes on, on the surface you actually ride, not on a showroom floor that is flatter than any street.
Reach is where the weight of the front end shows up
Reach, the horizontal distance from the bottom bracket to the head tube, decides how much of your weight sits over the front wheel and how much leverage you have on the bars. A hub-drive bike with a rear motor and a rear rack is already tail-heavy, and a long reach that stretches you forward can mask that on smooth pavement while making low-speed steering feel vague. A short reach with a tall, swept bar puts you upright, which is comfortable and gives excellent visibility in traffic, but it also lightens the front wheel enough that loose gravel and wet paint lines start to matter. Neither is wrong. They are different bikes to ride, and the only way to tell which one suits you is to ride both at walking speed.
Careful readers check reach by looking at their elbows. Slightly bent, shoulders relaxed, wrists straight: that is a fit that will still work on mile twenty. Locked arms mean the reach is long for you, and a shorter stem is a twenty-dollar fix rather than a reason to reject the frame.
Low-step and step-through are handling decisions wearing a marketing label
Manufacturers have sorted step-through frames into women's catalogs for a century, and the habit survived into pedal assist, where it makes even less sense than it did before. A step-through frame does three things: it lets you mount without lifting a leg over a heavy bike, it lets you put both feet flat on the ground without dismounting, and it lowers the center of gravity of the frame itself. Those are useful to a commuter carrying a laptop bag, a rider with a hip replacement, a parent loading a child seat, and anyone who has to stop and start twenty times on a two-mile trip. The tradeoff, a less rigid front triangle, is handled in current frames with larger-diameter tubing and a reinforced downtube, which is why well-built step-throughs no longer flex noticeably under a strong rider.
Read the geometry table rather than the catalog category. A low-step frame with a 44-centimeter reach and a slack head angle is the same bike whichever page it appears on, and the Consumer Product Safety Commission, which oversees bicycle safety requirements for bikes sold in the United States, does not recognize a gendered frame either.
What to check on the test ride
Ride it at four miles an hour in a parking lot and try to hold a straight line, because that is where a bad fit announces itself. Mount and dismount five times from the curb side. Stop hard from twelve miles an hour and notice whether you can get a foot down without hopping. Turn around in the width of a residential street. Then lift the front wheel over an imaginary curb, and lift the whole bike a few inches, since you will do that in a bike room or a car rack eventually.
Ask to ride the size above and the size below, even when the chart is emphatic. The chart is a starting point built from averages, and your inseam, your torso, and your shoulder width are not averages. Fifteen minutes of low-speed work will tell you more than any table.