This is a mixture of classic bike wisdom combined with the present day realities of eBike maintenance. How when and why to shift:
Start in the lowest gear possible, like a manual transmission car.
As you increase speed, upshift into harder gears, but always stay in a gear that is 1 step lower than what feels “hard”.
When riding uphill or into the wind, downshift 2 steps lower than what feels “hard”.
When coming to a stop, downshift to the lowest gear possible.
If using a derailleur, take care to gently apply a firm but smooth pedal stroke while shifting to ensure the chain makes enough rotations to climb up to the next gear.
If using a derailleur, when shifting under load (at low speed, or heading uphill) take extra care to downshift into an easy gear as early as possible, to prevent strain on the derailleur and chain.
When using a derailleur, if it’s not possible to downshift in time before approaching a hill, or other “pedalling under load” scenario, you can still use your shifter, however in this scenario you MUST continue pedalling gently, while still pedalling firmly enough to make at least 1 full rotation of the cranks, to help ease the chain up to an easier gear. It is possible to shift under load without taking care to “walk the chain up to the next gear” but when shifting under load and pedalling in a hard and punchy style, as opposed to firm, gentle and smooth, these are situations when your derailleur is prone to breaking, or your chain, or both.
When using an internally geared hub, you essentially apply the same practice in reverse. With an internally geared hub, you cannot shift while pedalling, whether you are pedalling under load or pedalling at a smooth cadence appropriate for your current speed.
With an internally geared hub, you must pause your pedal stroke as you shift. With an Enviolo hub, if you do not pause your pedal stroke while shifting, you may very wheel damage some of the components. With a Shimano hub, pedalling while shifting is less likely to damage the components, but the hub will stay in the same gear and will not shift until your pedal stroke is paused.
With an internally geared hub, just like a derailleur system, it is still critically important to use easy gears.
#1 use the easiest gear possible when taking off from a stop
#2 downshift always whenever the pedal pressure feels hard, or takes a lot of force to turn the pedals
#3 downshift always whenever coming to a stop or quick decelerating
#4 downshift always whenever approaching a hill.
-The right time to upshift into a harder gear is when you have gained enough momentum and speed to make that harder gear you are shifting into now feel “light”. In other words, you shouldn’t ever upshift until after gaining a little speed.
Taking off from 0-2mph, then upshift
Increasing speed from 2-5mph, then upshift
Increasing speed from 5-10mph, upshift some more
Increasing speed from 10-15mph, upshift some more, and feel it out, and downshift back into the easy gears if it feels hard
Increasing speed from 15-20mph, upshift some more, and feel it out, and downshift back into the easy gears if it feels hard
Why shouldn’t I use more of the hard gears more often?
Using a harder gear than is necessary for the terrain and current speed, traffic, etc. has a number of negative consequences:
#1 rider energy — it is a scientific fact, that the easy gears on a bicycle provide more mechanical leverage than the hard gears. What this means is if you think the hard gears “feel more natural”, that is our natural tendency, since we are used to walking, not cycling, by nature. However, over time, and across longer distances, it becomes painfully clear that anybody, regardless of fitness level, can maintain riding a bike or ebike for a exponentially longer period of time without needing to stop to rest when properly downshifting to prevent expending more energy than is needed to move the bike. This is especially apparent when riding uphill or into the wind (or at the end of a really long work day).
#2 component stress — chains, belts, sprockets, hub bearings, motor bearings, cranks, pedals, wheels and even tires are all part of the drive system on a bike. When a rider prioritizes downshifting as opposed to upshifting (AKA using the light gears as opposed to the heavy gears) they are decreasing the stress on all of these components — the chain/belt, sprockets, hub and motor bearings, cranks and pedals, wheels and tires. When a rider prioritizes upshifting as opposed to downshifting (AKA using the heavy gears preferentially, and neglecting the light gears) a number of unplanned-for-stresses begin to show themselves:
-chains and belts will stretch or fray earlier than the expected interval, since they are not designed for the torque that is put down by the rider when pedalling hard in the wrong gear
-sprockets similarly will wear down their teeth too early if riding in too hard a gear
-a rear hub may fail outright if the stress from the motor, plus staying in a hard gear all the time is too much. We have seen this happen many times both on derailleur bikes and internal gear hub bikes
-motor bearings may develop play early on and require service or replacement if riding in too hard of a gear for too long
-rear wheels will experience extra torsional stress and as a result will need to be tensioned and trued more often than a bike that is experiencing the full use of its gear range, not just the harder end.
-even tires will show a reduction in life if the rider is incorrectly only using the harder end of the gear range, because the tires will be getting shaved down by the pavement on each heavy pedal rotation. When the torque on the pedals is lighter, the tires grip, instead of slip or scrape.
Upshift = Go to harder gear (which is the smaller gear)
-the derailleur is moving downwards and releasing cable [low stress]
-Nexus Shimano IGH hub is pulling cable and loading up the spring-loaded shifting mechanism [high stress])
-Alfine Shimano IGH hub is releasing cable and unloading the spring-loaded shifting mechanism [low stress])
-Enviolo and Rohloff hubs use two cables, instead of a spring-loaded shifting mechanism–upshifting and downshifting mechanically operate with about the same amount of stress, but improper upshifting will still stress and gradually wear out an Enviolo hub. Less likely with a Rohloff.)
Downshift = Go to lighter gear (which is the larger gear
-the derailleur is moving up and pulling cable [high stress]
-Nexus Shimano IGH hub is releasing cable and unloading the spring-loaded shifting mechanism [low stress]
-Alfine Shimano IGH hub is pulling cable and loading the spring-loaded shifting mechanism [high stress]
-Enviolo and Rohloff hubs use two cables, instead of a spring-loaded shifting mechanism–upshifting and downshifting mechanically operate with about the same amount of stress, but downshifting is a lot less stressful because you are taking strain off of the entire drivetrain and bike)
There’s more to it, but that’s a good start. And remember, OIL YOUR CHAIN!