There have been a few posts recently about bike sizes.
While normal bikes typically come in a range of frame sizes - 5 being typical - most electric bikes come in just one size. Some, notably the Khalkoff range, do have a range of sizes.
In the old days - ie when life was simple and crossbars were horizontal - frame size, as measured from bottom bracket to top of seat tube, was a reasonable universal guide to bike size. Nowadays, frame size is pretty much useless for comparing between different models of bike. The advent of compact frames with sloping crossbars, and longer seat-posts means that people often ride a frame that is a smaller size than a traditional one. Furthermore, people have started measuring frame size to different places, such as to the crossbar, or to the place where a notional horizontal crossbar would be if it existed. Comparing frame size between, say a Khalkoff, a Torq and a Wisper is therefore pretty much impossible.
Electric bike manufacturers can get away with just one size because today's longer seat posts give much more flexibility, and also many electric bike riders are happy to accept a less well optimised riding position than a pedal-only cyclist.
So, how do you know if a bike will be the right size for you (or what size you need in, say, a Khalkoff)? The only true answer is that you can't know properly without trying it.
However there are two measurements which are more useful than frame size in giving some clue. Unfortunately I have never seen an e-bike supplier publish them. They are:
1. Standover height. This is the distance from the crossbar at the point where you would stand over the bike to the ground (obviously it only applies to diamond frames). Standing astride the frame you should have at least an inch of clearance - but more is fine.
2. Length of top tube. This is actually the most important measurement and it determines whether you can reach the handlebars comfortably. If the bike is too long you are likely to get back pain from leaning too far over. If it is too short it will be uncomfortable to pedal properly and harder to control the steering. There is some adjustment possible through moving the saddle back or forward, or possibly by changing the stem.
If you get these two measurements right, the rest should follow easily.
The next thing is to get the seat the right height. To pedal efficiently, your leg should be almost but not quite straight at the bottom of the pedal stroke. NB some people like to have their seat lower in order to feel safer, which is fine. There's usually lots of adjustment potential here. If you need even more height, it is usually possible to get longer seat posts - or some people have dispensed with suspension seat posts to get the seat an extra inch or so lower.
You then need to get the handlebars at the right height. This is mainly determined not by any measurement of your body, but by how hard you intend to push down on the pedals! If you intend to pootle along gently, you need your handlebars high up to avoid wrist pain from your weght being supported by your hands. On the other hand if you want to pedal hard, lower handlebars are better to allow a more efficient body position; your hands and feet will be ok because if you are pedalling hard, most of your weight is being supported by your feet. Indeed if you really sprint you are likely to find yourself pulling the handlebars up - not leaning down on them.
The challenge is that on many bikes, handlebar height adjustment is hard. It's easiest wiht conventional quill stems, but they are going out of fashion. Modern threadless 'Ahead' stems typically have very limited height adjustment. With adjustable stems (as found on the Wisper and Ezee bikes) the handlebars can be raised a little, but this makes them nearer, which may not be ideal.
To sum up, it's not straightforward to get the size of a bike right, and next to impossible without trying the bike and understanding how you want to use it. Most bikes have a good bit of tolerance and potential for adjustment - but if you are very tall or short, there may be some bike models that are just not going to fit you properly.
While normal bikes typically come in a range of frame sizes - 5 being typical - most electric bikes come in just one size. Some, notably the Khalkoff range, do have a range of sizes.
In the old days - ie when life was simple and crossbars were horizontal - frame size, as measured from bottom bracket to top of seat tube, was a reasonable universal guide to bike size. Nowadays, frame size is pretty much useless for comparing between different models of bike. The advent of compact frames with sloping crossbars, and longer seat-posts means that people often ride a frame that is a smaller size than a traditional one. Furthermore, people have started measuring frame size to different places, such as to the crossbar, or to the place where a notional horizontal crossbar would be if it existed. Comparing frame size between, say a Khalkoff, a Torq and a Wisper is therefore pretty much impossible.
Electric bike manufacturers can get away with just one size because today's longer seat posts give much more flexibility, and also many electric bike riders are happy to accept a less well optimised riding position than a pedal-only cyclist.
So, how do you know if a bike will be the right size for you (or what size you need in, say, a Khalkoff)? The only true answer is that you can't know properly without trying it.
However there are two measurements which are more useful than frame size in giving some clue. Unfortunately I have never seen an e-bike supplier publish them. They are:
1. Standover height. This is the distance from the crossbar at the point where you would stand over the bike to the ground (obviously it only applies to diamond frames). Standing astride the frame you should have at least an inch of clearance - but more is fine.
2. Length of top tube. This is actually the most important measurement and it determines whether you can reach the handlebars comfortably. If the bike is too long you are likely to get back pain from leaning too far over. If it is too short it will be uncomfortable to pedal properly and harder to control the steering. There is some adjustment possible through moving the saddle back or forward, or possibly by changing the stem.
If you get these two measurements right, the rest should follow easily.
The next thing is to get the seat the right height. To pedal efficiently, your leg should be almost but not quite straight at the bottom of the pedal stroke. NB some people like to have their seat lower in order to feel safer, which is fine. There's usually lots of adjustment potential here. If you need even more height, it is usually possible to get longer seat posts - or some people have dispensed with suspension seat posts to get the seat an extra inch or so lower.
You then need to get the handlebars at the right height. This is mainly determined not by any measurement of your body, but by how hard you intend to push down on the pedals! If you intend to pootle along gently, you need your handlebars high up to avoid wrist pain from your weght being supported by your hands. On the other hand if you want to pedal hard, lower handlebars are better to allow a more efficient body position; your hands and feet will be ok because if you are pedalling hard, most of your weight is being supported by your feet. Indeed if you really sprint you are likely to find yourself pulling the handlebars up - not leaning down on them.
The challenge is that on many bikes, handlebar height adjustment is hard. It's easiest wiht conventional quill stems, but they are going out of fashion. Modern threadless 'Ahead' stems typically have very limited height adjustment. With adjustable stems (as found on the Wisper and Ezee bikes) the handlebars can be raised a little, but this makes them nearer, which may not be ideal.
To sum up, it's not straightforward to get the size of a bike right, and next to impossible without trying the bike and understanding how you want to use it. Most bikes have a good bit of tolerance and potential for adjustment - but if you are very tall or short, there may be some bike models that are just not going to fit you properly.
