Legal and safe electric bicycle conversion kits

[johncrossley]

What are the best options for legal and safe electric bicycle conversion kits?

I'm going to get a bike shop to do it for me. So if something goes wrong, they will have to fix it for me. So this is restricting the options I'm looking at. Those are:

Swytch

Electric Bike Conversion Kit - Mountain | Hybrid | Road | Brompton

The Swytch electric bike conversion Kit gets you the best of an eBike, at a fraction of the cost. Turn your bike electric with ease. Order now.

www.swytchbike.com

Boost

Boost - The easy and safe way to electrify your bike.

Electrify your ride! UK designed e-bike conversion system, fitted by your local bike shop.

boostbike.uk

Yose Power

YOSE POWER UK Ebike Battery Conversion Kit DIY Online Shop

Professional manufacturer and seller of electric bikes, electric bicycle batteries, and e-bike conversion kits. The same product, available on Amazon, at a lower price.

www.yosepower.co.uk

I've been quoted £600 including installation for the Yose Power, but I'm attracted to the Boost kit (£699 including installation) because it looks really minimalistic and it doesn't look like an electric bike to a casual thief, whereas the Yose Power has wires all over the place. Swytch is the most well known but has a small range.

 

[erk]

I can recommend Cytronex:

Electric Bike Conversion Kit - Ebike Kits UK - Cytronex

Award-winning electric bike conversion kit, designed & built in the UK. Cytronex fits most bikes, including road, mountain, Brompton & more. Shop online.

www.cytronex.com

Simple to fit (especially if you have bottle cage bosses fitted). On a Brompton the mounting for the front light is rubbish, but I found a way round that).

 

[Ashley Hill]

Just don’t bring them on a train. We’ve just been briefed that conversions are not allowed on trains.

 

[johncrossley]

Just don’t bring them on a train. We’ve just been briefed that conversions are not allowed on trains.

If you take the battery off before boarding that makes it no longer an electric bike.

== Doublepost prevention - post automatically merged: 20 Oct 2025 ==

I can recommend Cytronex:

Electric Bike Conversion Kit - Ebike Kits UK - Cytronex

Award-winning electric bike conversion kit, designed & built in the UK. Cytronex fits most bikes, including road, mountain, Brompton & more. Shop online.

www.cytronex.com

Simple to fit (especially if you have bottle cage bosses fitted). On a Brompton the mounting for the front light is rubbish, but I found a way round that).

What made you choose them?

 

[Harpers Tate]

You might consider: https://skarper.com/

I only used one very briefly and it worked very well. I ended up getting a "proper" EBike.
Advantage: the entire thing clicks on and off the bike, and leaves the bike as just a bike when detached. You could therefore detach it and place it in your backpack before boarding a train with nothing* electric left on the bike.


* except a modified rear brake disc and tiny cadence sensor on the crank.

 

[johncrossley]

* except a modified rear brake disc and tiny cadence sensor on the crank.

Does that mean you have to have disc brakes?

 

[Bletchleyite]

If you take the battery off before boarding that makes it no longer an electric bike.

If too many do that the game of whack-a-mole will continue, such as a ban on lithium ion batteries not fitted to a device over the size of the largest typical power bank, as applies to aircraft. Yes, you could hide it in your bag, but if the staff see you doing so they would have grounds to refuse you.

It's clear what none of us want on trains - the dangerous home-brew type kits - but it's quite hard to define them both legally and in terms of how staff can identify them.

 

[johncrossley]

Just don’t bring them on a train. We’ve just been briefed that conversions are not allowed on trains.

What TOC is that? Nothing on National Rail website about conversions.

 

[Ashley Hill]

What TOC is that? Nothing on National Rail website about conversions.

Apparently its being rolled out nationally and not just at my TOC.

 

[johncrossley]

Apparently its being rolled out nationally and not just at my TOC.

That's not acceptable. On local trains such as London Overground at least you can cycle that distance, but you are screwed if you need to go long distance.

 

[Bletchleyite]

That's not acceptable. On local trains such as London Overground at least you can cycle that distance, but you are screwed if you need to go long distance.

It's better than an outright ban. Conversion kits are typically a compromise anyway - you end up getting things like broken wheels because they aren't designed for the unsprung weight or inadequate braking because that extra weight is again an issue on a bike not designed for it (the batteries and motors really are very heavy), plus often battery capacity is poor, particularly on the conversion kits with the handlebar mounted batteries (which would also affect handling). Best to buy a legal, pre-built e-bike to get the best out of them - if money is an issue the Decathlon offerings are very good for the price.

 

[johncrossley]

It's better than an outright ban. Conversion kits are typically a compromise anyway - you end up getting things like broken wheels because they aren't designed for the unsprung weight or inadequate braking because that extra weight is again an issue on a bike not designed for it (the batteries and motors really are very heavy), plus often battery capacity is poor, particularly on the conversion kits with the handlebar mounted batteries (which would also affect handling). Best to buy a legal, pre-built e-bike to get the best out of them - if money is an issue the Decathlon offerings are very good for the price.

The Boost kit mentioned above only adds an extra 4 kg, making it lighter than most budget e-bikes. Purpose built e-bikes are prone to theft, whereas the Boost bike kit doesn't even look like an e-bike. Increasingly, purpose built e-bikes have the battery built in the bike, making it more vulnerable to theft and cannot be charged without bringing the whole bike indoors.

 

[Ashley Hill]

That's not acceptable. On local trains such as London Overground at least you can cycle that distance, but you are screwed if you need to go long distance.

Dont shoot the messenger.

 

[Bletchleyite]

The Boost kit mentioned above only adds an extra 4 kg, making it lighter than most budget e-bikes.

Then the battery capacity will be useless and the motor underpowered. I would definitely avoid.

Physics say you can't make these things lighter until new battery chemistries and motor technologies are developed (and neither will be cheap).

 

[johncrossley]

Then the battery capacity will be useless and the motor underpowered. I would definitely avoid.

There seems to be lots of happy users on the Facebook group. Some unhappy ones but they aren't complaining about the range. The main complaint is their hill climbing ability on very steep hills. But it would be the same with any hub based system on a purpose built bike. This really only affects elderly people who need a lot of assistance. Crank based e-bikes are best for steep hills but they are very expensive. They have a chain of around 100 bike shops nationwide which do the installations. It seems pretty reputable to me.

Retailers | Find a local shop to fit your Boost Bike conersion kits | Boost Bikes

Find a local bike shop to Boost your bike.

boostbike.uk

 

[Bletchleyite]

That is a very small battery capacity and the range will be on the lowest assist setting which you will not in practice want to use and based around a very light rider (I don't know your weight of course ).

It might be of use to some, but I don't think you will get the best from that kit and remain of the view you would be better buying a dedicated bike designed as an e-bike.

It may be the best of the kits, I suppose, but the kits will never be as good as a proper one.

 

[johncrossley]

That is a very small battery capacity and the range will be on the lowest assist setting which you will not in practice want to use and based around a very light rider (I don't know your weight of course ).

The range is quoted as 50 km and people on the Facebook page seem to be getting at least that. They only have two power settings, Eco and Boost. Many people seem to ride in Eco mode most or all of the time as they find it good enough. Spare batteries are relatively cheap at £229 if that range isn't sufficient and they only weigh about 1 km.

 

[Ashley Hill]

What TOC is that? Nothing on National Rail website about conversions.

Heres a link to GWRs cycling policy. Item 7 refers to ebike conversions. I hope it works.

 

[Harpers Tate]

Does that mean you have to have disc brakes?

I understand not. I think the Skarper modified disc can go on most bike wheels - but you can always check out your specifics. Obviously if you do have discs then the Skarper rotor replaces the conventional one.

EDIT: This from their FB page:

"If you don’t have a disc brake bike, don’t worry! Skarper have developed a rear wheel hub designed for rim brake bikes that can accept a DiskDrive rotor. This means that if you own a rim brake bike and want to breathe new electric life into your bike, you could take your bike to our network of Certified Skarper Installers. They would be able to either rebuild your existing wheel with the Skarper-compatible hub or fit you with a new wheel that is compatible."

 

[johncrossley]

Heres a link to GWRs cycling policy. Item 7 refers to ebike conversions. I hope it works.

It's also on their website

Bringing Your Bike on the Train | Great Western Railway

If you're planning to take your bike on the train, find out everything you need to know before you travel with Great Western Railway.

www.gwr.com

Road legal electric bicycles (also known as E-bikes, including e-folding bikes) can be taken on the train.

These are E-bikes that are pedal-assisted with a motor that generates a maximum continuous rated power output of 250 watts and do not provide electrical assistance when travelling at more than 15.5 mph.

For the safety of yourself and other passengers:

• Electrically modified or adapted E-bikes are not permitted on trains
• Charging of E-bikes is not permitted on trains or at stations
• The battery must not be removed from the bike, unless designed to do so for folding purposes (e.g. a Brompton folding bike)
• E-bikes with a damaged battery cannot be carried
• Spare batteries cannot be carried
• You must use the normal designated cycle storage areas on trains, ensuring the bike does not block entrances, exits or aisleway access for passengers
• Do not lock your bike to any part of the train, in case of the need to remove the bike quickly from the train in an emergency.

The bikes mentioned on this thread are road legal, and it says "Road legal electric bicycles" can be taken on the train.

Why can't you remove the battery from the bike? Leaving it on the bike is surely less safe and increases the risk of theft.

This is quite outrageous, to say the least. The spare battery restriction affects all e-bikes.

 

[Bletchleyite]

Why can't you remove the battery from the bike? Leaving it on the bike is surely less safe and increases the risk of theft.

This is yet another reason why conversion kits are a bad idea. On a properly designed e-bike, the battery is locked to the frame and requires the use of a key to remove it.

FWIW they are often removable - mine is an in-frame one but you can take it out, indeed you have to to charge it!

This is quite outrageous, to say the least. The spare battery restriction affects all e-bikes.

The issue is probably twofold:

1. People taking the battery off and claiming it's not a bodged e-bike any more;
2. The risk of a short circuit on the cheap rubbish (proper ones would have protection) caused by putting the battery in a bag.

Seriously - don't buy a conversion kit, buy a proper one. The conversion kits are full of compromises in ways a bike designed to be an e-bike is not. You will enjoy a much better cycling experience with a proper one, particularly if you don't go for the rock bottom budget end.

(Of course realistically there's no way they can know you've got one in your bag given that bag searches generally don't take place on stations before boarding - there's plenty of other stuff you're not technically supposed to carry that people do, e.g. camping fuels).

 

[JB_B]

I'd also strongly recommend Cytronex - very reliable and excellent after sales service.

 

[johncrossley]

This is yet another reason why conversion kits are a bad idea. On a properly designed e-bike, the battery is locked to the frame and requires the use of a key to remove it.

The Boost battery is locked to the water bottle mount and requires a key to remove it. The Sywtch Air uses a very small battery that is placed on the handlebars and is specifically designed to be carried when not in use. This obviously has a small range. Customers buy it for convenience rather than range.

FWIW they are often removable - mine is an in-frame one but you can take it out, indeed you have to to charge it!

Does it look like you have removed it? So a thief knows the battery isn't there?

 

[Bletchleyite]

The Boost battery is locked to the water bottle mount and requires a key to remove it.

In that case you don't need to remove it!

Does it look like you have removed it? So a thief knows the battery isn't there?

Yes, it leaves a big hole in one side of the frame.

 

[FRob]

Just don’t bring them on a train. We’ve just been briefed that conversions are not allowed on trains.

This seems to be correct. Today (24th October 2025) for the first time ever on my commute a train guard pointed to my e-bike (a Yose conversion) and said that "very soon" all converted e-bikes would not be permitted, at least on GWR trains. The PDF about cycle rules on the GWR website seems to have been updated on the 1st September this year so perhaps that's when this proposed ban actually came into effect as I don't remember seeing it before? Looks like they are about to clamp down in any case. Annoying, as my conversion is a legal one (250W, controller under 15.5 mph, etc, etc...) and was installed with care. Been commuting by train with it since 2021

 

[Ashley Hill]

How many guards remember what a converted E-bike consists of remains to be seen. Until it was explained to me I imagined a conversion looked like a bike with something like a washing machine motor strapped to it.

 

[johncrossley]

This seems to be correct. Today (24th October 2025) for the first time ever on my commute a train guard pointed to my e-bike (a Yose conversion) and said that "very soon" all converted e-bikes would not be permitted, at least on GWR trains. The PDF about cycle rules on the GWR website seems to have been updated on the 1st September this year so perhaps that's when this proposed ban actually came into effect as I don't remember seeing it before? Looks like they are about to clamp down in any case. Annoying, as my conversion is a legal one (250W, controller under 15.5 mph, etc, etc...) and was installed with care. Been commuting by train with it since 2021

And I presume you are happy with how this bike works? So not too heavy, enough range etc.? You must be if you are using it for this long.

I would trust your bike more than many of the cheap imported complete electric bikes we see all the time. There needs to be some kind of certification scheme to show which bikes are legal.

Suppose people who fall foul of this rule now spend £2,000 on a new ebike, only to see a complete ban on ebikes in the future?

 

[FRob]

And I presume you are happy with how this bike works? So not too heavy, enough range etc.? You must be if you are using it for this long.

I would trust your bike more than many of the cheap imported complete electric bikes we see all the time. There needs to be some kind of certification scheme to show which bikes are legal.

Suppose people who fall foul of this rule now spend £2,000 on a new ebike, only to see a complete ban on ebikes in the future?

I am very happy - it's all legal but really gets me up pretty much any hills and has a good range of 30-40 miles. Less in winter and of course depends on the terrain.
I agree we need certification.
I am also concerned that if I have to purchase a "complete" ebike for commuting by train, then in time that might also be banned. I am surprised that the change to regulations regarding converted ebikes on trains hasn't been picked up by the media yet

 

[johncrossley]

I am surprised that the change to regulations regarding converted ebikes on trains hasn't been picked up by the media yet

My guess is they don't want to make a big fuss about this but if something happens they can say that they have advertised it.

 

[FRob]

So just been warned again by a guard on a GWR train that my e-bike conversion is no longer permitted