The short answer
Shift to an easier gear just before the road starts to climb, while you still have speed and the pedals are lightly loaded. It is much easier on you and your bike than waiting until you are slowing down and pushing hard.
Why early is easier
When you ride onto a hill, your speed starts to drop and the pedals get heavier. If you wait until that happens to change gear, two things work against you.
First, the chain is under strong tension. A shift under heavy pressure often crunches, hesitates or skips, because the chain has to move sideways while being pulled hard. Second, if the shift is slow or goes wrong, you lose more speed, which makes the hill harder still. By then you are often in a gear that is too hard, so you may stall or have to stand up and grind.
If you change gear before the slope, none of that applies. The pedals are light, the chain moves cleanly, and by the time the road rises you are already turning at a comfortable rhythm. The idea of a steady rhythm is explained in pedalling cadence.
How to judge the moment
You are looking for the point just before your effort rises. A few cues help:
- Look ahead. Notice where the road begins to tilt. Trees, buildings and the shape of the horizon often show the rise early.
- Watch the road surface. A change in the angle of the road ahead or a long straight line up the hill tells you what is coming.
- Feel the bike. The first sign of a gradient is often a slight slowing. If you feel that, shift now, not later.
- Use what you know. If you ride a regular route, you will learn where each rise starts.
As a rough rule, shift a few moments before the slope, then make any further adjustments as the effort changes. Because every bike, rider and hill is different, use your own judgement rather than a fixed distance.
How many gears?
It depends on the hill. For a gentle rise, one or two easier gears may do. For a long or steep climb, you might drop several, one step at a time, as the slope bites. A good trick is to choose a gear that feels slightly too easy at the base, because the effort tends to build as you go. You can always shift up if you have more in reserve. The best gears for climbing are covered in climbing gears.
When making several changes, ease the pedal pressure for each one and let the chain settle before the next. The method is in the article on smooth shifting.
Front or rear first?
If the climb needs a lot of change, you may want to use the front shift to the smaller ring before the hill, since this makes a large change in effort. Doing it early, while pedal pressure is low, avoids the clunk of shifting a big gear under load. Then use the rear gears to fine-tune. Whether you need the front shift at all depends on your bike and the hill.
If you are late
Everyone is sometimes caught out. If you are already on the slope in a hard gear:
- Ease the pressure on the pedals as much as you safely can, without stopping.
- Shift one gear at a time, giving the chain a moment to catch.
- Stay seated if you can, and keep your weight steady.
- If the chain will not move, you may need to stop, shift in a safe place, and start again in an easier gear.
Do not push hard through a crunching shift; it can make the situation worse. If your gears often struggle to change under load, have the drivetrain looked at by a shop, because worn or poorly adjusted parts make late shifts harder.
Rolling and repeated hills
On roads with many short rises, the same idea applies but with smaller adjustments. You change a gear or two before each rise and use the descent in between to build speed. Details are in the article on rolling terrain shifting.
Descents and the other side
The reverse also applies. As you crest and start to descend, you will want to move up to a harder gear so your legs are not spinning uselessly. Remember to keep your hands near the brakes, as steep descents can bring speed up fast, and keep control above all else. More about riding downhill appears in descending basics.
A short practice
Pick a quiet, gentle hill with little traffic, and wear a helmet. Ride it three times: once changing gear halfway up, once changing a few moments before the slope, and once changing just a little earlier than that. Notice how each feels. Most riders find the early shifts quieter and less tiring.
Results vary with fitness and terrain, so use this as a guide, not a rule. If anything on the bike feels wrong, a bike shop can help.