When buying a used bike, you first need to decide what type of bicycle you want. The three main types of bikes are road bikes, mountain bikes and hybrid bikes.

Road Bike

Road bikes are designed primarily for riding on paved surfaces and are designed to be fast and efficient, with narrow tyres optimised for speed, drop handlebars for good aerodynamics and higher gearing for maximum top speed. 

Characteristics:

• Drop style handlebars

• Narrow, smooth tyres 

• Higher gearing

• Rigid frame (no suspension)

• 700C size wheels 

Mountain Bike

Mountain bikes are made for riding off-road trails, with tyres optimised for maximum traction on unpaved surfaces, flat handlebars for good control and low range gearing for climbing steep hills. 

Characteristics:

• Wide flat handlebars

• Fat, knobbly tyres

• Low gearing

• Suspension fork + rigid frame (hardtail) or suspension fork + suspension frame (dual/full suspension)

• 29 inch, 27.5 inch or 26 inch size wheels

Hybrid Bike

As the name suggests, hybrid bikes are bikes with a mix of the characteristics of the two former categories. Often, they are also known as ‘commuter’ or ‘urban’ bikes. They typically combine the flat handlebars of mountain bikes with the lighter, rigid frame of a road bike and have smooth, medium width tyres for a balance between speed and comfort. 

Characteristics:

• Flat handlebars

• Rigid frame

• Rigid fork or suspension fork

• Medium width smooth tyres

• 700C size wheels

If you don’t know what to choose, a hybrid bike is a good choice for people just getting into cycling, since they are highly versatile and suitable for most riding conditions. They are also easier to ride than a road bike and much more efficient than a mountain bike when riding on paved surfaces. An added bonus is that they tend to be cheaper than similar grade road and mountain bikes.

An often overlooked aspect by people buying bikes for the first time is sizing. Bikes come in a wide range of sizes, with good sizing being important to ensure a comfortable and more efficient riding experience and to reduce the risk of injury. Hence, it's a good idea to ask about a bike's size if it is not provided in the listing. 

If the bike manufacturer and model is known, it is best to search for the manufacturer’s suggested sizing guide as this will be more accurate than a general size guide. 

A general size chart for road and hybrid bikes can be found here:

Credit: BikeRadar

A general size chart for mountain bikes can be found here: 

Credit BikeRadar

Questions to ask

• How long have you owned the bike?

• When was the last time the bike had a service?

• Are there any parts that are currently not working as they should?

• What size is the frame (if not listed)?

• Good photos are essential to evaluate a bike’s condition, so ask for more photos if few are provided or if photos are unclear

Inspection of bike

• Check for any cracks or large dents in the frame

  • For carbon frames, it is crucial to check for cracks, since these could lead to a catastrophic failure
    

• Look out for excessive rust or corrosion, since this can indicate the bike was left outside and/or poor maintenance

  • A small amount of surface rust on bolts is normal and is to be expected on a well used bike

• Check that the seat post moves freely

  • This will save you the headache of trying to move a seized seat post!

• Check all gears can be shifted into 

• Inspect the wheels for any broken spokes

• Spin the wheels to check if the wheels are true (no excessive wobbling of the wheel when its spinning)

  • A small amount of side-to-side movement is not a major concern, but large movements greater than about 1 cm indicate the wheel is damaged and may need replacement, which will cost upwards of $70 typically

• Check that both the front and rear brakes are working properly