Advice for starting out a new conversion (UK)


10 µW
Jul 7, 2021
Hi All

I am going to be moving in the next year or so which will see my commute change from a fairly flat 7 mile ride to a 20 mile trip (each way) with some long hills. I've not done the exact route yet but I am familiar with the roads, the main hill on the way there is a 2 mile 8-10% climb and then a 4 mile 4-5% climb on the way back. Half of the journey is fast roads where I will likely want to be riding 20-25 mph top speed and the other half is stop start city riding.

New commute.PNG

I am a fairly fit 165lb rider but doing that ride daily will take it out of me so I am looking at my options for an e-bike (I am also considering an e-motorbike but that requires a much larger budget). My requirement is bringing the length of the commute down to something reasonable (1hr - 1hr15). I am in the UK so am limited to a 250W motor, though I'm sure nobody will notice if I am being assisted up to my top speed.

I have been reading around the forum and I can't decide to go for a lightweight hub mounted build that is there to increase my speed up the climbs but still leaves me to do a lot of the work or to go for a heavier mid-mount that will have more torque for hills and getting back up to speed from a stop.

I have two bikes that I can use for the project. My current commuter is a modernized 1990s Dawes Galaxy which is a joy to ride. As it is a nippy steel tourer I would be inclined to go for a lightweight front hub motor and small bottle battery which I charge or swap over at work. My main concern is that the narrow front forks limit me to a 25c front tyre due to brake clearance. I have ridden this bike for light touring so it can handle the extra weight, I am just concerned about traction. I could always change the fork to one that could accept a wider tyre (potentially even converting the front brake to disc if I can find a suitable fork – I’ve found a supplier but they are currently out of stock).

Here is a previous incarnation of the bike when I had it in a weird 1x8 bull horn configuration. It has now since been converted to a more conventional drop bar setup.

The other bike is a Specialized AWOL (steel gravel bike) which I have used for long distance touring. It is a heavier frame but also bomb proof as it can reliably handle with 30-50kg of kit on the frame with no issue. I would see this as being a heavier conversion (so mid-mount) with much larger batteries to hold enough charge to do the round trip and give me torque for the hills and getting back up to speed. As it is a gravel bike it can handle wider tyres and has disc brakes which I do prefer.

I’m keen to stick to drop bars on both bikes so it will be just pedal assist to keep things simple. I might look into a hood mounted throttle at some point down the line.

So my main questions are;

Would a lightweight hub motor be suitable for this type of terrain (and the odd detour into the peak district) providing total weight is kept low and I put in some effort on the hills?

Is 25c an okay tyre width for front drive?

What would be the battery requirements for each build?
Change Input to Google Maps top left of graph.
Click your starting destination and your ending destination, then move the route to your desired route.

How much pedaling do you want to do?

Is weight of the total ebike a concern?

How fast do you want to go?

Do you want stealth, thats the best way to go which means a hub motor.

Don't be too concerned about the 250W arbitrary limit, you'll be perfectly fine with a 750-1kw setup. So long as your not doing wheelies, riding up hill with your feet in the air, speeding past walkers, blowing stop signs and red lights.
20 miles each way, 40 miles total on one charge is easy to do with a big enough battery. I'm using a 20ah, 14s, 8p, 18650 cell battery, with your fitness, weight and bikes, you could easily do 30 miles each way. It's an inexpensive battery from Amazon and has never been a problem. It looks like many brands are selling the same batteries. Weight is 12.2 lbs, mounting in the front triangle would be ideal. I'm mounting it in a rear pannier because I'm old and am using a Townie step through.

Aero bars on drop bars would be ideal for this ride, climbing on aero bars works very well as does descending and riding on level ground. A suspension stem and seatpost would tame the bumps, it doesn't take much suspension to take the edge off. I rode that combination with aero bars for a few thousand miles, it works.

The Cycle Analyst Version 3 has an excellent cruise control, it begins after a few seconds at a constant throttle setting, and is user programmable for the duration. Cruise disconnects if throttle is added again, or if the brake levers are tapped. I'd use mountain e-levers, not for braking, but for cruise disconnect. One lever on the aero bars one on the inner part of the bars, next to the stem. Or one could be on the drops. About 95% of my miles are on cruise control, but with good cadence and pedal effort. Shifting while on cruise is no problem at all. Climbing is slower than descending on cruise but descent speed is never run away type speed. On cruise you control your cadence and power output, it's as natural to do as when riding without assist. Throttle is also natural, it blends with your pedal power output, not feeling much like assist, its just that you go faster.

Road bike cruising speed requires a motor with fewer turns of wire, making it a higher speed, higher rpm motor. Direct drive motors are larger and heavier than geared motors but have better heat rejection during long climbs. With your weight and conditioning, either type hub motor, DD or geared should work because will be pedaling at a substantial fraction of total power used.

Front hub motors work very well on dry pavement but they do transmit a lot of shock up through the handle bars and aero bars. Much more than with a non motor front wheel. A rear hub motor on a hard tail transmits more shock than a non hub wheel but a suspension seatpost and a larger tire helps a lot. Lighter geared hubs ride better than DD hubs.

The Dawes is just too fine the way it is. I'd convert the gravel bike to a rear hub motor with a low number of turns. 12T, 10T can give 26 mph but with no reserve speed, 8T would be better.

Power output is a function of how many amps and at what volts a controller can provide to a motor. There's really no 250W motor, push 500 watts through it and it's a 500W motor. Push 80W through it and it's an 80W motor.

A watts example: For 1138 miles my average watts are 128, max watts average is 1426, that's a big spread, but sometimes roadies have to be caught on climbs while sitting upright. Seeing 25 watts and 450 watts is a common thing.

Anyway, electric assist is a perfect match to your planned ride and the bikes you have. Keep us informed on what you are thinking, what you do and how it works out.
The hill won't require a mid drive, on either bike. But a 500w rated rear motor with internal gearing would be a good choice. Invest in some stick on 250 watt labels. The law will only care if you ride like a a--hole.

But first, I always say to a real rider,, Don't ruin your favorite bikes with a motor. You will still want them as is, to do what you always have done with them. Bike plus one is how many bikes you need anyway, right?

So get a good sturdy MTB for your commuter. Or even a decent cruiser/commuter type bike with full fenders but regular . It need not be real expensive, in fact a steel frame can be a plus. But you will want to stick a decent crank on it, decent seat, etc. YOU DO want to have more upright bars, for a convenient throttle, but more importantly if you do 40 miles a day on a bike at decent speeds, you don't have a peloton or chase vehicles clearing the way for you. Those f--kers are out to kill you, as you well know already. Look up and be ready for them. Drop bars are fine out in the country and riding a bit slower, but commuting in town, no.

Put a decent system with rider tunable pas on it, but use a throttle too, especially at those stops.
Thanks for all of the advice so far. After doing some more reading I have decided on the hub drive.

In terms of donor bike I'll go for the Specialized. The relaxed geometry, disc brakes and wider tyres make it more suitable. I very rarely get out on it these days so it will be good for it to see more miles. Given the distance I would be covering I defintely want to keep the drops, they are just more comfotrable and ergonomic than flat bars. I tend to ride fairly upright on the hoods and I have been riding in traffic with them without any issue for years now.

Motor wise I am keen to keep it street legal so 250W is a must, the police aren't ever going to check it but if I am in a crash the insurers would use that fact to put all blame on me.

I'm still undecided between front or rear, Any recommendations for good motors? I'm happy to lace up a wheel myself so just getting the hub is fine. So far I've found either an AKM Q100CST (Rear), AKM Q100SX (Front) or a MXUS XF08 (Rear). The AKMs have a much higher reduction (1:12 vs 1:5) so presumably have better torque on the hills vs top speed