What governs whether a bike gets pedal assist up to 20 vs. 28 mph?

[Andrea Bozoki]

I just purchased a Surface 604 Colt, which I'm really enjoying. I chose it over a Juiced CrossCurrent because I liked the more refined styling (integrated bike computer/lights; fenders and rear rack). I'm puzzled by why the Surface only gives PAS up to 20 mph while the CC would go up to 28, even though they both use a Bafang rear-mounted geared drive hub system and the Surface has a seemingly more powerful 500W motor to the CC's 350W. Is it just a matter of the software being run by the computer, or is there a hardware difference somewhere that I'm missing? More to the point, if I wanted, is there a way to override the 20 mph PAS limit on my Surface?

 

[James Alderson]

As far as I understand it, its purely software. But, that doesn't meant you can stretch a 20 mph bike to 28 without actual firmware that supports it. There are dongles and such out there that will do it for you and many would argue it won't hurt anything, but I wouldn't do it myself.

 

[scrambler]

It is most likely limited by software so it would follow the requirement of a Class 1 (or 2) E-bike. Read the article below to learn more about these.
https://electricbikereview.com/guides/electric-bike-classes/

The first thing is to ask the manufacturer if here is a way to lift the limitation. Some will allow it and give you the details on how to change the programming.

If not, the limitation is often triggered by a speed sensor that is somewhere on the rear wheel and frame. If so, some ways around the limitation can be to deactivate the sensor (you wont see your speed anymore), or mount some gizmo that changes the reading of the speed (your speed will be inaccurate).

read more on E-bike Tuning below
http://ebike-mtb.com/en/back-issue-e-bike-tuning/
https://www.ebiketuning.com/

 

[JRA]

There is no computer as you envision on an e bike, there is a controller and a battery management system that can be manipulated via software that resides in a computer that links to the controller either via bluetooth or a cable. Most manufacturers have proprietary software solutions for their products and your best response to your query will be from Surface itself.

 

[rich c]

A lot of manufacturers engineer a class 3 or 28mph bike differently than a class 1 or 2. Brakes, tires, and even material choices in high stress areas. In my model year Haibike XDURO Trekking S RX, you get a steel suspension fork instead of aluminum as an example. Top speed achieved on my Haibike XDURO Full Seven S RX shows as 41.8mph on the display. At that speed, I prefer to ride a bike that is fully designed for speed. You might check on the forum on http://www.pedelecs.co.uk or endless-sphere.com
Two sites that draw a wider European participation. On pedelecs, there is endless discussion of hacking from 20 to 28. As a note, I hardly ever ride at 24-28+mph, but do often find myself riding up to 22mph. Feels like it really takes a big increase in energy to push me through the air above 23mph, but the riding position on both my bikes is more upright than a true road bike.