What size tyre should I use?
The tyre size is always printed on the tyre sidewall. 700x25 - A 700C size wheel with a 25mm wide tyre for example.
In recent years we have learnt that wider tyres do not necessarily mean a lot less speed, but they can however provide additional comfort and grip. There is a trade off point depending on your preferences though, and your bike frame will have a maximum size clearance and your rims will have a maximum size they can fit.
Typical tyre size per bike type:
Road bikes - 25-28mm
Gravel bikes - 28-50mm
Hybrid bikes - 32-40mm
MTBs - 1.9-2.5 inch
Plus 2.5-3 inch
Fat bike 3.7-5.2 inches
Much comes down to preference, but the following rules apply:
Smoother surface with a desire for speed and low rolling resistance - use a thin, hard tyre.
Rougher/softer surface with a design for control and comfort - use a fat, soft tyre.