General Advice for Bike Choice When Doing a Conversion

[vfr400]

This advice is for making an electric bike for general transport, like commuting, shopping, leisure rides, etc. I was going to post it in the thread about Aldi bikes, but I thought it might be better on its own.

You can convert just about any bike if you have the resources and the determination. It's surprising how many people come on the forum with all sorts of unusual bikes that they want to convert, mainly because that's the bike they have. Often, they bought an expensive bike then realised that they'd be better off with an electric one. The unusual features often bring some advantage to the bike as it is, but don't really do anything as an electric bike apart from make the conversion more tricky. My first question is always why convert that bike? Used bikes can be obtained relatively cheaply, and in many cases the cost of a donor need not be high in relation to the cost of the conversion.

There's absolutely no point in buying a new bike to convert. You'll wipe out any guarantee, you'll probably be scared to drill any holes or start filing the frame and you'll be more concerned about being able to unconvert it than doing a decent conversion. You can get decent used ones for 1/3 of the price of new, so £150 should get you something pretty decent.

You don't need anything fancy because you have a motor to help you, which will more than compensate for any shortcomings in the rest of the bike. It's an absolute fallacy that you need an expensive bike for durability and reliability. The cheap bikes are very durable and often very suitable for conversion, except those without triangle frames. It's very cheap to upgrade any components that you're not happy with, such as the brakes. You can snag a pair of good hydraulic brakes for about £40 from ebay, which is nothing compared with the cost of conversion and is the best bang-for-buck upgrade you can do to any bike - electric or not.

Things to look out for in a Donor bike:

• For hub-motors, 26" wheels might be best because you get higher torque than the 27.5, 700C and 29" wheels. Onviously, if you're not heavy, you can trade torque for speed with bigger wheels.
• If you're a bloke, a bike with a normal crossbar and triangular frame gives the most battery installation options.
• Choose a bike with disc brakes, which should be upgraded to hydraulics for the better braking required on an electric bike.
• If you want to fit a front motor, choose a bike with steel forks - not the thin ones that you get on the old Raleigh bikes, but some wth a bit of meat in the drop-outs.
• Very old bikes, like BSAs, Raleighs, etc have unusual sized wheels, so you can't buy a ready-made kit. You have to build your own wheel. Their brakes are not up to it anyway, so best avoided.

• For a crank motor conversion, nearly all your focus should be on the bottom bracket. Modern ones bring all sorts of problems, and so does this modern trend for tiny chainwheels, 10 or 11 speed gears and fat tyres, so stick to older convential bikes with normal tyres, gears and bottom brackets.
• You need a conventional tube-type bottom bracket, ideally with the standard BSA/Shimano thread and 68 or 73mm wide. There are versions of the motors with longer shafts for fat bikes, but you're likely to run into other problems.
• Modern MTB bikes with small chainwheels sometimes don't have the clearance for a standard crank motor's reduction gear housing.

 

[Woosh]

choose a lightweight bike with alloy frame, a squarish downtube, air fork, hydraulic brakes.
I like converting Giant bikes. They are good value and easy to work with.
Bike weight is my top consideration.

 

[vidtek]

I'm with Whoosh on this, light-weight is no 1 closely followed by bottom bracket conversion ease. If you are going to go to the effort of doing a conversion, go for a mid-drive as first option, followed by rear wheel hub.

 

[vfr400]

I don't recommend mid drives for riding on the road unless you have special circumstances. All systems work, and different ones have different advantages and disadvantages.

Generally, mid drives require more maintenance to the drive system, are more expensive, less reliable and give a harsher ride than hub-motors. The advantage you get is that they can give both high torque and high speed by using the gears, but there are now legal hubmotors that can give all the torque you need for climbing and a wide spread of power up to the legal limit and a bit more. Mid drives are generally easy to install, but if you think about the long term, why would you want to save an hour's work to compromise thousands of riding hours thereafter.

 

[dwvl]

Bike weight is my top consideration.

Genuine question: why? Is the weight of the bike really a consideration when you're adding a battery and a person to it?

 

[Woosh]

Genuine question: why? Is the weight of the bike really a consideration when you're adding a battery and a person to it?

it's inertia. Less inertia = more responsiveness and you can still ride a lightweight electric bike without power.
My converted Brompton is quite light:

 

[vfr400]

Bike weight is important if you're small, but not if you're big or heavy. Obviously, the less all-up mass, the better, but a saving of 2kg in weight would make less than 2% difference all round when you weigh 100kg.

When you have a non-electric bike, each KG of mass between the rider and the bike makes 1% difference to the effort riding up a hill, so an 80kg rider would see roughly 6% pedal effort difference between a 14kg MTB and an 8kg road bike, which is fairly noticeable, but on an electric bike, you can just turn up the power.

Any mass that can be saved can only give you an advantage. It's simply the lower the better.

 

[vidtek]

@dwvl
I suppose it depends on how you ride your bike. Personally, I like to ride as much as I can with all assist turned off in a vain attempt to get a little fitter. On the controller I have with the Tongsheng mid-drive kit I fitted there is a setting where you can have the display up and so have all the calculations odo etc. but turn off the assist and throttle.

I try to ride as much as possible in this mode so a light bike is essential. I do waver and weaken when there is a headwind or gradient, and I usually have it on for a standing start with the throttle then turn it off. As I am inherently lazy I do tend to slacken off too frequently.....

 

[Ocsid]

Genuine question: why? Is the weight of the bike really a consideration when you're adding a battery and a person to it?

One factor is handling the bike, at low speeds and when not being ridden, and both of these are affected by their centre of gravity, the higher the more negative.

 

[vidtek]

@dwvl
Another issue I forgot to mention is the weight of the bike is very important if you use a bike rack on your vehicle. An electric bike has an extra 2-4kg of weight without battery, if the bike is heavy to begin with it can be an almighty struggle to get it on the rack, be it on the garage wall or the rear of the car. Some days when I'm knackered after my ride I resort to using the ramp that came with my Thule rack, but because it is so light I normally just lift it on the rack.

 

[vfr400]

One factor is handling the bike, at low speeds and when not being ridden, and both of these are affected by their centre of gravity, the higher the more negative.

You need a higher centre of gravity for better handling at speed. It needs to be in the right position for the conditions of your ride. Too low is bad, except at sub 3mph when there's little gyroscopic effect, and to high is also bad. If low was best, every motorbke would have a flat 4 engine and the petrol tank low down. Look at a GP racing bike. They have to figure out how they can get the motor relatively high up. to get the fastest turning. Too low means you have to lean a lot further on corners.

On a bicyclee, the height of the C of G makes virtually no difference compared with the mass of the rider and their seated position. The steering geometry has a much more profound effect on steering and stability.

 

[dwvl]

Thanks all, for your answers.

As a 100Kg (since lockdown - yikes!) bloke, I think a few kilos saved in bike weight would be unnoticeable to me when riding under power. But yes, when cycling unpowered, and especially when lifting the bike, lighter would be easily better

 

[Ocsid]

You need a higher centre of gravity for better handling at speed.

My comment however was very specifically about low speed and when not being ridden.

 

[vidtek]

@dwvl
On my learning curve with e-bikes, I have tried front and rear hub bikes and prefer a mid-drive. Each to his own, and I point out the type of riding you will do on the bike is a major factor in choosing a donor bike.

The easiest fitting is a front hub, I found the ride skittish, you are a big bloke so it may feel better for you. A rear hub is more difficult to fit, but more stable. I found the mid-drive by far the smoothest and most natural and quite easy to fit.

You live in Essex, you could spend a bit of time in your local bike shop there is a charity one in Colchester, Re~Cycle 8, The Grove Estate, Colchester Rd, Colchester CO6 3AJ.

They will have a multitude of donated bikes that can be suitable as a donor bike. I went through my local charity bike shop's stock of "to be done up pile" bikes and chose the lightest I could find. I used that as my donor bike and it's been brilliant. The shop refurbished it completely new chain, cassette, all brakes and all cables, new tyres grips etc. Total cost to me was £220 from memory.

If you do go for a mid-drive kit check the bottom bracket is suitable, clearances are critical. Talk to Andy or Tony at Whoosh, they will be able to talk you through it. There are several kit fitting how-tos on this forum (even one from yours truly), have a look to see what you'll be up against.

The mid-drive Tongsheng kit was £680 from Whoosh including a 48v 15ah battery that I have yet to exhaust on a ride. I charge it every 6-7 outings (7-15 miles each) and it is never less than half full when I charge it.

Best of luck, Tony.

 

[bulldogboab]

@dwvl
On my learning curve with e-bikes, I have tried front and rear hub bikes and prefer a mid-drive. Each to his own, and I point out the type of riding you will do on the bike is a major factor in choosing a donor bike.

The easiest fitting is a front hub, I found the ride skittish, you are a big bloke so it may feel better for you. A rear hub is more difficult to fit, but more stable. I found the mid-drive by far the smoothest and most natural and quite easy to fit.

You live in Essex, you could spend a bit of time in your local bike shop there is a charity one in Colchester, Re~Cycle 8, The Grove Estate, Colchester Rd, Colchester CO6 3AJ.

They will have a multitude of donated bikes that can be suitable as a donor bike. I went through my local charity bike shop's stock of "to be done up pile" bikes and chose the lightest I could find. I used that as my donor bike and it's been brilliant. The shop refurbished it completely new chain, cassette, all brakes and all cables, new tyres grips etc. Total cost to me was £220 from memory.

If you do go for a mid-drive kit check the bottom bracket is suitable, clearances are critical. Talk to Andy or Tony at Whoosh, they will be able to talk you through it. There are several kit fitting how-tos on this forum (even one from yours truly), have a look to see what you'll be up against.

The mid-drive Tongsheng kit was £680 from Whoosh including a 48v 15ah battery that I have yet to exhaust on a ride. I charge it every 6-7 outings (7-15 miles each) and it is never less than half full when I charge it.

Best of luck, Tony.

Hey tony do you know if whoosh have any of these kits available as I’m looking for a kit for my carrera mountain bike? Thanks .

 

[vidtek]

Hey tony do you know if whoosh have any of these kits available as I’m looking for a kit for my carrera mountain bike? Thanks .

Why don't you ask them, Tony from Whoosh is usually lurking around here, he's replied on this thread, the signature has their contact details.

 

[vfr400]

@dwvl

The mid-drive Tongsheng kit was £680 from Whoosh including a 48v 15ah battery that I have yet to exhaust on a ride. I charge it every 6-7 outings (7-15 miles each) and it is never less than half full when I charge it.

If you make statements like that, you have to qualify them and put them into context, otherwise yoy might persuade somebody to get something that's quite unsuitable for them, which will make them very disappointed.

You said that you spend as much time as possible riding your bike with no power and with minimal power. It's not surprising then that you don't have to charge the battery very often. Physics is very simple. The more power you get to help you from the motor, the faster the battery goes down. Riding your bike, one day I could exhaust your battery in about 30 miles. Another week, I could last it out for over 200 miles. It's simply a question of how hard one pedals.

 

[vidtek]

If you make statements like that, you have to qualify them and put them into context, otherwise yoy might persuade somebody to get something that's quite unsuitable for them, which will make them very disappointed.

You said that you spend as much time as possible riding your bike with no power and with minimal power. It's not surprising then that you don't have to charge the battery very often. Physics is very simple. The more power you get to help you from the motor, the faster the battery goes down. Riding your bike, one day I could exhaust your battery in about 30 miles. Another week, I could last it out for over 200 miles. It's simply a question of how hard one pedals.

I thought I made that clear, if it wasn't - thank you for the clarification.

 

[Woosh]

Hey tony do you know if whoosh have any of these kits available as I’m looking for a kit for my carrera mountain bike? Thanks .

We have not much stock to speak of at the moment. I do hope that we'll return to a more normal stock levels in October.

The only battery in stock at the moment is the G30 small bottle 10.5AH made with Samsung cells.
For your Carrera, I would recommend the XF08C kit:
it's in stock.
https://wooshbikes.co.uk/cart/#/product/uid-264-xf08c-g30/xf08c-rear-hub-kit-with-g30-105ah-battery

 

[bulldogboab]

Why don't you ask them, Tony from Whoosh is usually lurking around here, he's replied on this thread, the signature has their contact details.

Yeah

it's inertia. Less inertia = more responsiveness and you can still ride a lightweight electric bike without power.
My converted Brompton is quite light:

it's inertia. Less inertia = more responsiveness and you can still ride a lightweight electric bike without power.
My converted Brompton is quite light:

We have not much stock to speak of at the moment. I do hope that we'll return to a more normal stock levels in October.

The only battery in stock at the moment is the G30 small bottle 10.5AH made with Samsung cells.
For your Carrera, I would recommend the XF08C kit:
it's in stock.
https://wooshbikes.co.uk/cart/#/product/uid-264-xf08c-g30/xf08c-rear-hub-kit-with-g30-105ah-battery

hi mate thanks for reply, was hoping for a stronger bat than the 10.5AH don’t mind waiting for new stock arriving. Also bearing in mind I’m not very mechanical minded is this something I’d be able to fit myself without much hassle. John.