Looking after your tyres pays dividends because under-inflation may cause uneven wear and make them prematurely illegal. To be within the law, a tyre must have more than 1.6mm of tread depth across the central 75 per cent of its width. The penalties for having an illegal tyre on your car are a fine of up to £2,500 and three penalty points for each one. It could also cost you more than that because under-inflated tyres use more fuel and adversely affect your car’s braking and cornering. Using a combined pressure and tread depth (DTG) gauge – or a kit containing both – is the simplest way to keep track of tyres. To find the best way to look after yours, we tried a range of solutions.