Speed restriction


Just Joined
Jul 12, 2017
Ok, so as a newbie
Am I allowed a stupid question?
Here it is anyway
How is the speed restricted?
I want to start a build but am completely green to this. If a motor is restricted by rpm surely the wheel size makes a big difference? When buying a motor do I need to state wheel size? Sorry if this is a dumb question. Is there any recommendations on literature to read before asking any more dumb questions?
Thanks in advance
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Deleted member 4366

No such thing as a stupid question. It's only the answers that are stupid.

The best place yo get help is here, not from any publications. There's lots of ways to restrict speed. The worst for us is software, because it's difficult to hack. Some use speed limit wires that have to be joined/broken like a switch. Some have a secret or not so secret setting in the LCD. Less common is restriction by the motor speed.

Motor maximum speed depends on voltage, and the battety voltage varies by 30%, so the maximum speed would be significantly different with a charged battery compared with a run-down one. 15.5 mph max speed would become 12 mph.

Motor speed is important, so you need to know what it is. If the supplier gives a number, it's usually maximum rpm at nominal voltage. Bear in mind that a fully-charged battery will be 10% more than nominal, so so will the max rpm be 10% more. Then you need to calculate bike speed from wheel size.

All motors have a max rpm, though you can increase it by stepping up the voltage,so if your 36v motor maxes out at 15 mph (unrestricted), a 48v battery will send it up to 20 mph.

You can't run a 24v 15 mph motor at 100v and expect it to whisk your bike up to 60 mph. A small motor can't handle that much power.
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Esteemed Pedelecer
Aug 7, 2014
West Sx RH
Welcome to the forum Kenton.
Show us a pic of your bike to see that it is suitable.
Then give us an idea of the riding you want to do, lazy, commuting, touring, sporty, terrain, speed, distance and how heavy you are.
We can then point you in the direction of what's available and where to consider buying a kit or the component parts from.
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