Planning a conversion

Electrically assisted bikes, trikes, etc.
Post Reply
emm0uk
Posts: 1
Joined: 11 May 2022, 10:46am

Planning a conversion

Post by emm0uk »

Hi. Newbie here. I've got a Kona Splice 2014 I've been happily riding for a few years. At 48yrs I could do with some help so I'm planning a conversion. Basically I'm thinking 750w bafang mid drive with a rack/battery/taillight. I know the law says 250w max but I do some off road as well. Is there a controller I can buy or a switch I can fit....i want to restrict the motor to 250w for road use but be able to switch to 750w when off road. Any suggestions? Seems to be lots of different controllers available so presumably one will have a power restriction switch? Hopefully done all measurements OK- 68mm bottom bracket, rack/battery will fit, planning on 44t front sprocket. Any help much appreciated. Thanks
stodd
Posts: 536
Joined: 6 Jun 2018, 10:24am

Re: Planning a conversion

Post by stodd »

emm0uk wrote: 11 May 2022, 11:00am Hi. Newbie here. I've got a Kona Splice 2014 I've been happily riding for a few years. At 48yrs I could do with some help so I'm planning a conversion. Basically I'm thinking 750w bafang mid drive with a rack/battery/taillight. I know the law says 250w max but I do some off road as well. Is there a controller I can buy or a switch I can fit....i want to restrict the motor to 250w for road use but be able to switch to 750w when off road. Any suggestions? Seems to be lots of different controllers available so presumably one will have a power restriction switch? Hopefully done all measurements OK- 68mm bottom bracket, rack/battery will fit, planning on 44t front sprocket. Any help much appreciated. Thanks
Switches with an option to go above nominal 250w are explicitly ruled out somewhere in the legislation. Definition of a switch is pretty vague however; often interpreted as a switch if you can operate while mounted on the bike, but ...???

Over 250w nominal is also illegal off-road in any public space (such as bridleway, canal path, etc); only allowed on private land with no public access and landlord's permission.

Most 250w nominal motors are actually capable of 500 to 750w peak. The chances of being caught with an illegal motor are negligible if riding responsibly and of being prosecuted even less, and pretty small even if riding dangerously with a fragrantly illegal bike. The only significant risk is if you are involved in an accident, in which case the bike might get quite close inspection. In the unlikely event of prosecution the theoretical risks involve destruction of the bike and all that comes with riding a moped uninsured, unregistered, no number plate, etc; fines (surprisingly small), lots of driving licence points, or even loss of licence, +++++ or as correctly pointed out below, by prison.
Last edited by stodd on 12 May 2022, 3:55pm, edited 1 time in total.
saudidave
Posts: 508
Joined: 16 Jan 2009, 12:22am

Re: Planning a conversion

Post by saudidave »

stodd wrote: 11 May 2022, 11:44am Most 250w nominal motors are actually capable of 500 to 750w peak. The chances of being caught with an illegal motor are negligible if riding responsibly and of being prosecuted even less, and pretty small even if riding dangerously with a fragrantly illegal bike. The only significant risk is if you are involved in an accident, in which case the bike might get quite close inspection. In the unlikely event of prosecution the theoretical risks involve destruction of the bike and all that comes with riding a moped uninsured, unregistered, no number plate, etc; fines (surprisingly small), lots of driving licence points, or even loss of licence.
That's all well and good but if you should injure, disable or God forbid kill someone then you are looking at a serious custodial sentence. Much better to buy a lightweight, road legal 125cc trail bike and have some off road fun on that instead. At least if you have an accident the insurance will carry the can, not you.
hemo
Posts: 1169
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Planning a conversion

Post by hemo »

Bosh and Yam push the 250w legal continous rating so probably not worth worring about bar the 750 rating marke on it.
The two I mentioned can push out nearly 800w so they massage the laws and mark them 250w and get away with it.
Dingdong
Posts: 142
Joined: 22 Apr 2022, 4:59pm

Re: Planning a conversion

Post by Dingdong »

hemo wrote: 12 May 2022, 9:23pm Bosh and Yam push the 250w legal continous rating so probably not worth worring about bar the 750 rating marke on it.
The two I mentioned can push out nearly 800w so they massage the laws and mark them 250w and get away with it.
Can you explain in a little more detail how they do that?
Bonzo Banana
Posts: 284
Joined: 5 Feb 2017, 11:58am

Re: Planning a conversion

Post by Bonzo Banana »

Dingdong wrote: 13 May 2022, 5:31am
hemo wrote: 12 May 2022, 9:23pm Bosh and Yam push the 250w legal continous rating so probably not worth worring about bar the 750 rating marke on it.
The two I mentioned can push out nearly 800w so they massage the laws and mark them 250w and get away with it.
Can you explain in a little more detail how they do that?
It seems to be a property of mid-drive motors which are typically much smaller motors that operate at much higher rpm and go through a series of cogs and belts to deliver their high torque. For an e-mountain bike you often need short bursts of high torque to get up steep inclines and then the power lowers again. It feels to me the legislators are far more concerned about the assistance speed of 15.5mph/25km/h than the power output. Bosch being huge and German have maybe influenced the legislators in the EU in how power is determined as they seem to be first to stretch the wattage level of so called legal ebikes. So maybe the EU legislation favours EU companies. Nominal, rated or average Watts is such a vague term for a electric motor and controller that you can interpret it with different methods and come to different figures where as if they said maximum Watts must not exceed 500W then it would be easy to test.

So if you buy a high cost ebike with premium European ebike parts you can be viewed as legal but buy a cheaper Chinese ebike that uses similar power or even less than it can be classed as illegal because they openly state true wattage.

My feeling on the matter is if the ebike has pedals and only assists to around 15.5mph give or take a bit then its practically legal.
Post Reply