I am planning on converting my road bike into an electrical one and I can see that I can get average speeds of 35-40kmh. So I am planning on biking long distances at this average speed. Is it safe to do it? What can fail at such high speeds in long run, considering different types of asphalt quality. I know that it depends on the bike manufacturer, but can a generic failure be anticipated?
Stopping distance is definitely something to be aware of. As speed increases, the distance needed to stop increases non-linearly. For illustration, in cars, with 1 sec reaction time:
- 20 km/h = 8m
- 30 km/h = 13m (50% increase in speed, 63% increase in distance)
In other words, it may feel safer than it really is.
Also make sure your conversion has a brake sensor cutoff, you wouldn't want your braking distance increasing because the motor is pushing while you're frantically trying to stop.
Yes - the bike can stand higher speeds fine.
Generally. wear is caused by distance travelled, not the speed it travels.
You might suffer increased wear through increased vibration but this would be very hard to measure and is likely quite small.
On the other hand you might suffer increased damage through accident or sudden pothole, which would have been more avoidable at a lower speed.
Additionally, your bike's braking distance will be increased as velocity increases. So your electric bike requires more defensive riding, anticipation and prediction of what will or could happen. Consider replacing brake pads with really good ones (like kool stop) and consider your tyre tread too.
I rarely mention head protection on SE, but do consider that your momentum is increased by riding an electric assisted bike. That energy has to go somewhere if things go badly, best not through your head.
As you may know kinetic energy is ½mv² where m is mass, v is velocity. You have more mass on the bike with the addition of motor and batteries. A bigger concern is that energy increases with velocity squared.
For 100 Kgs of bike, motor, batteries and rider:
- 10 Km/h: 0.4 Kj
- 20 Km/h: 1.5 Kj
- 30 Km/h: 3.5 Kj
- 40 Km/h: 6.2 Kj
Note that going from 30 to 40 Km/h almost doubles the kinetic energy.
The two things I would be concerned about that have to absorb energy are brakes and wheels.
Brakes obviously have to absorb all the kinetic energy when you need to stop. There are concerns about stopping distance as noted by others. The wear on pads rotors or rims will also be increased. You will also have think about the heat capacity of the brakes. Is repeated stopping from your max speed going to overheat the brakes?
You don't say if you have disc or rim brakes. I personally think I would not have enough confidence in rim brakes for this application. I'd want to fit the beefiest disc brakes possible, preferably a set intended for a downhill mountain bike.
The wheels are going to take more punishment as they roll over bumps at higher speeds. If you have a set of skinny rims with a low spoke count, I'd be looking to upgrade to something strong with a high spoke count (which you would actually need to support strong brakes also).