165 is the tyre width in millimetres, 40 is the aspect ratio (sidewall height as a percentage of the width), and R16 means radial construction for a 16 inch wheel. With a 40 profile, the sidewall is very short, so the tyre will look low and feel more direct, but it is also less forgiving over potholes and kerbs.
Fitment depends on the size listed on your door placard or handbook, plus your wheel width and suspension clearance. This size is often used with aftermarket 16 inch wheels on modified small cars, so confirm the exact size on your current tyre sidewall and check there is no rubbing on arches, springs or inner liners before ordering.
They can be used on some wider rims, but you must stay within the tyre manufacturer’s approved rim width range for that exact model. Going too wide creates an aggressive stretched fitment that can reduce rim protection and change the way the tyre seats and flexes, so always check the spec sheet and keep your insurer informed if the setup differs from standard.
Use the pressure shown on your vehicle’s placard as the starting point, as it is set for your car’s axle loads. Because the sidewall is short, underinflation can increase the risk of rim damage and uneven wear, so check pressures cold at least monthly and after any big temperature change.
Availability can be limited because 165/40 R16 is a specialist, low-profile size, so many ranges focus on summer patterns. If you need year-round grip, check current stock for all-season options first, and if choice is tight consider a second wheel set with a more common winter-friendly size, making sure overall rolling diameter, load index and speed rating remain suitable for your car.
