If you find hills, headwinds or load hauling too hard, you might want an e-bike. But there’s also a cheaper, simpler solution: lower gears.

Gears are there to make cycling easier. They enable you to cycle at speed without spinning your legs like a cartoon character or slowly without struggling to force the pedals around. While you can freewheel when you can’t pedal fast enough, running out of gears going uphill is grim, turning a ride into hard, sweaty work.

Many bikes have gears that everyday cyclists will find too high for hills. Gearing is a technical subject. You can read about how to understand derailleur gears and hub gears but the ‘too long, didn’t read’ version boils down to this: to get lower gears, you need smaller sprockets (called chainrings) at the front and/or larger sprockets at the back on the rear wheel. Larger means more teeth, smaller fewer teeth.

Mountain bikes are designed like this. They have really low gears, suitable for scaling steep slopes off road. For any bike with derailleurs, the aim is therefore to make your existing bike more mountain bike (MTB). This is straightforward if it has a flat handlebar – you can just fit mountain bike components – and more complicated if it has a drop handlebar like a road bike.

You don’t need to be workshop expert, however: any good local bike shop can do this work for you. Point them to this article when you explain what you want to do. You can get the components required through Cyclescheme, making an inexpensive alteration even cheaper.

Singlespeeds and hub gears

Before getting into derailleurs, let’s look at singlespeeds (including fixies) and hub-geared bikes. To change the gearing, you change the rear sprocket and/or the chainring, then adjust the chain length to suit by adding or removing chain links. That’s it.

The biggest rear sprocket you can fit will depend on your bike’s setup. Screw-on sprockets for fixies come in sizes up to 20 teeth. Screw-on freewheel sprockets for singlespeeds that allow coasting go up to 22. Singlespeed sprockets that slide onto a cassette hub intended for multiple gears are also available in sizes up to 22. Hub gear sprockets go up to 25 but the maximum varies by manufacturer and model.

Minimum chainring sizes will depend on the chainset (also known as the crankset). On road-going, single-chainring bikes, you may be unable to fit anything smaller than 38 teeth unless you change the chainset at the same time. It’s impossible to be specific without going into the technicalities of bolt-circle diameters. This is something your bike shop mechanic will understand.

Derailleur setups

Bikes with derailleurs have anything from five to 13 sprockets at the back (on what is known as the cassette) and one to three chainrings at the front. Different shifters have a different number of clicks, corresponding with the number of gears. Different types and brands of shifter move the gear cable a different amount per click, so you can’t randomly mix and match shifters and derailleurs. Broadly speaking, for the gears to work properly, the shifter and derailleur have to be the same. Same manufacturer, same discipline (MTB or road, which basically means flat bar or drop bar) and same ‘speed’ (number of sprockets or chainrings).

Some mix-and-matching is possible. Shimano CUES comes in 9, 10 and 11-speed versions, and with both flat-bar and drop-bar shifters. It’s cross-compatible so you can use an 11-speed CUES shifter with a 9-speed CUES derailleur and cassette – the shifter will just have a couple of redundant clicks. SRAM’s flat-bar and drop-bar shifters are cross-compatible as long as the number of gears matches, so you can run an 11-speed SRAM mountain bike rear derailleur and cassette with an 11-speed SRAM road shifter. Similarly, electronic shifters tend to be cross-compatible between a manufacturer’s road and MTB versions, so long as the number of gears matches.

There are also some accidental compatibilities, where a shifter and derailleur that weren’t designed to work together nevertheless do. And there are workarounds to make MTB components work in a drop-bar setup.

MTB cassette on drop-bar bike

Rear derailleurs have a maximum sprocket size that they’ll work with. You can’t just put a huge 11-51 mountain bike cassette on a road bike. The derailleur will jam against the cassette.

You can sometimes fit a slightly larger cassette – for example, an 11-36 when the derailleur is not meant to work with anything bigger than 34 – by screwing the B-screw in further. Or you can fit a longer B-screw.

To fit a significantly larger cassette, you need a derailleur hanger extender such as the Wolf Tooth RoadLink. This repositions the derailleur and enables you to run an 11-40 cassette on a road bike. You’ll have to lengthen the chain but you keep your existing rear derailleur and shifter, so it’s an inexpensive alteration.

MTB rear derailleur and cassette on drop-bar bike

You can have even lower gears – an 11-51 cassette, for example – by fitting an MTB rear derailleur as well as an MTB cassette. Some road shifters are compatible with MTB derailleurs (see above). Otherwise you’ll need a cable adapter such as a JTek Shiftmate or Wolf Tooth Tanpan.

Inexpensive MTB-compatible shifters

Drop-bar shifters that work with MTB derailleurs are relatively expensive. The cheaper option (if you’re not going with an adapter) is a simpler type of shifter that’s separate from the brake lever instead of integrated with it. Microshift makes thumb-shifters and bar-end shifters that work with most of the common derailleurs, enabling you to run MTB derailleurs, cassettes and chainsets whatever handlebar setup you have.

Different chainrings and more

If your bike has a 1x setup, this is dead easy. You fit a smaller chainring and shorten the chain. You’re limited to the smallest chainring that will fit the chainset – unless you change the chainset itself, which raises issues of bottom bracket compatibility and Q-factor (the width of the pedal tread). Your bike shop can advise here.

With 2x and 3x setups, it’s more complicated. You can fit smaller chainrings but will likely to need a new chainset as well, as the smallest existing chainring will probably be the smallest that will fit (or not far off). Instead of a compact chainset, such as a 50-34, you’ll want a ‘super compact’, such as a 46-30. You’ll need to adjust the position of the front derailleur but it should still shift well enough. You’ll also need to shorten the chain.

If you want to fit significantly smaller, MTB-sized chainrings, you’ll need an MTB chainset and likely an MTB front derailleur. Unless your bike’s drop-bar shifter happens to be compatible with an MTB front derailleur, you’ll also need an appropriate JTek Shiftmate or a new front shifter, such as one of Microshift’s.

So there you have it. Lowering a bike’s gears can be complicated but it’s not expensive – and you’ll thank yourself for doing it every time you ride up a hill!