Did you know that if your tyres are under-inflated by 10 per cent, their life will be cut by the same amount? Yet most drivers don’t check their pressures often enough – so products that give at-a-glance warnings are booming.

Usually, these replace the valve cap, and alert you to any psi loss via coloured inserts; green means everything is OK, while red (and sometimes yellow before it) indicates the pressure has dropped. But some of the kits are based on conventional gauges.

We set out to see if such devices really can help you take better care of your tyres.

The test

Using a wheel and tyre with three valves, we checked the cap alerts while monitoring the slowly released pressure with a digital gauge.

Ideally, we wanted to be able to spot even a small pressure loss.