Initially I wasn't sure how to replace the roller wheels on my Brompton with larger Rollerblade style wheels. There are some kits online but they are expensive.

You follow this recipe at your own risk. Not my fault if you break the bike, break yourself or blow up the universe.

The roller wheels are just bolted to the bike, nothing fancy, just standard righty tighty, lefty loosey on both sides. I think I was expecting something more complex.

If you don't have a rear rack adding wheels that are too large will make the bike a slightly wobbly in the folded position which is why I went with 60mm.  The bike is still fairly stable when folded but can also be rolled along train station platforms and the like. 

The wheels and bolts I used are as described below:

• 1 pair of 60mm dia replacement wheels for a roller suitcase
• 1 pair of M6 40mm bolts with button heads

It's very simple to bolt these on.  The bolt holds the bushing in the center of the wheel bearing so it's ok to do it up tight, it won't affect how the wheel rolls.  Probably should add some thread locker just to ensure it can't come undone, or at least remember to check the bolts are tight once in a while. 

Button head screw caps have a low profile so they are less likely to snag or get snagged on stuff.
With bolts/screws M6 is the diameter and 40 is the length of the threaded part.

The suitcase wheels are probably better than rollerblade wheels since they are actually designed for this, but also you can buy them in pairs, not packs of 6. 

 I got an e-bike!  I used to be a keen cyclist, but I'm lazy and unfit.  CV19 seemed like a great excuse to get back out on a bike, especially if a battery could take some of the slog out of it.  I knew I wanted a basic exploring/hybrid type bike rather than an mountain bike and I didn't want to spend a huge amount of money.  Then there were stock issues, many bike stores have pictures of machines on their websites that they don't have in stock.  I didn't want to order something and then wait 3 months...   
Halfords have a family of bikes that all use the same tech, you just need to pick the flavor you like, I went for their urban commuting model called the Subway, which is sort of a cross between a fixie and a hybrid touring bike in appearance.  You could also describe it as an old school mountain bike with bmx tires. 

It's powered by a Suntour HESC system.  That's a geared rear motor system which is street legal.  250W and pedal assist cuts about at 25kph (16mph).  It doesn't have a hand throttle, which means it also doesn't need to have e-bike specific brake levers.  The crank contains cadence and torque sensors which combined with some software result in natural feeling riding experience for the most part. 

So what's it like to ride?
Well it's a lot like riding a bike honestly, but with a couple of foibles you quickly adapt to.  The first foible is that there is a bit of lag between the crank moving and the motor starting.  I'd guess this is around half a second. Same thing with the motor stopping.  This is actually fine for hill starts, you just have to trust the motor is going to kick in as you reach the bottom of your pedal stroke.   Where this can bite you is turning the bike around.  If you aren't expecting it at low speeds, having the motor kick in while manoevering can be bit disconcerting.  It's something that you quickly adapt to.  The motor makes a hum/whine while its operating so you get a useful audio cue as well as feeling the power. The other issue is the speed limiter. It really does limit your speed.  16mph takes about half the effort that 17mph does, so if you wanted a fast bike, this probably isn't it, unless you have the lungs and legs for it.

Batteries
The bike uses a 36v 8.7Ah 313Wh battery and they claim a 60 mile range.  But that range probably involves a small rider who lives somewhere flat and likes to use Eco mode.  What I found was that my range is probably a bit less than half that.  I'm about 240lbs and Wales has hills. Still 30 miles is a good couple of hours pedalling so can't really complain.  Overall I feel that the balance between range and power is pretty good.  I mean if the motor had more power, then the batteries would drain faster.

I'm scared of punctures
The motor is in the rear wheel.  There isn't a quick release for the backwheel.  Removing the back wheel involves disconnecting some electrics and cutting some cable ties as well as the usual stuff. It's not something I want to try for the first time at the side of the road.  At some point when I'm feeling brave I'm going to change out the tires for some puncture proof ones and maybe I'll put slime in the inner tubes. 

I wasn't sure if it had enough gears
It has gone up every hill I've found so far.  Don't get me wrong, I still have to pedal and I'm still a mess at the top but it goes up 1:10 gradients that I would normally have to walk up.


Rest of the bike
I'd budgeted for a better bike, I was kind of expecting this thing to feel cheap which is part of the reason I didn't get a model with cheap suspension, but its actually very solid, the frame is crazy stiff, the welds and paint look top notch. The hydraulic disk brakes work well.  The rear mech is a bit chintzy but easy to upgrade.  I was half expecting it to feel like the cheapest bike possible with a motor thrown on it considering the price. 
The only changes I made so far was to change the ergonomic bar grips out for some round ones and to add an adjustable stem to raise the bars about an inch.  Apart from that its fine, even the saddle is alright.

​Summary
I love it. It feels like riding a bike, BUT WITH BIONIC LEGS. I would definitely like to try one with a more powerful mid drive motor when lockdown ends and the mountain bike parks and trials are open.  I'll probably rent a modern full suspension MTB and see how I like it.  Hey you never know, if I ride the one I have enough, I might even be fit by then. 

Update: Feb23
I just noticed this post still gets lots of views so here's an update.  Bike has now successfully completed 115 rides and is still going strong.  I did get fitter and get a normal bike, but I still like to ride the Subway in winter when there isn't a lot of time to go for a long bike ride.   I think the e-bike marketers are missing a trick by not telling customers that a bike like this is a great way to get back into cycling. 
I did briefly have an issue where I was getting rear wheel punctures caused by cheap rim tape and a bit of swarf on the inner wheel rim.  I filed the sharp bit of metal down and replaced the rim tape with a heavier version.  At the same time I fitted slime puncture proof inner tubes for peace of mind.  
I also fitted swept back touring bars because I find them more comfortable than mtb bars. 

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