Among the most important components on any road vehicle are the tyres that support it. These are the points that actually come into contact with the road surface – and the quality of that contact has significant performance and safety implications.
One key feature of tyres is that they wear out over time. Every time you apply to brakes, you’re taking a small amount of rubber and leaving it on the road. In fact, this process of erosion occurs even if you’re driving in a straight line at a constant speed.
Tyre wear changes the behaviour of the tyre. It will prevent the tyre from distributing standing water away from the bottom of the vehicle, since it will make the treads shallower. This puts you at increased risk of aquaplaning – the phenomenon that will turn your car into an uncontrollable hovercraft.
But does tyre wear matter all that much? And is it worth shopping for a replacement before you hit that legal minimum?
Does it really matter?
Research from the Royal Society for the Prevention of Accidents indicates that stopping distances actually start to increase when the tread depth reaches around 4mm. The distance also varies according to the quality of the road surface. On hot rolled asphalt, there’s no difference in stopping distance between a tread depth of 4mm and above. If you’re on smooth concrete, you’ll get falloff well below that.
Specifically, the stopping distance rises by 36.8% at the legal minimum on hot rolled asphalt, and 44.6% on smooth concrete. Consequently, the organisation recommends that tyres be changed when the treads hit 3mm.
Obviously, it’s better to substitute a quality tyre from a reputable manufacturer. You’ll find continental tyres available online.
What are the legal limits on tyre wear?
In the UK, a legal minimum for tyre tread depth is enforced: it’s 1.6mm. As we’ve seen, this should be considered a minimum rather than a target. By replacing early, you’ll not only make the vehicle safer: you’ll also improve your fuel efficiency, too. This saving is often enough to offset the cost of the replacement tyres.
The depth of the tread isn’t the only thing we should be paying attention to. The degree to which your tyres are inflated also matters. Consult the vehicle’s manual, or an online database, for recommended pressures, usually expressed in Pounds per Square Inch. Note that if the vehicle is loaded, you’ll benefit from a little bit of extra pressure.
Penalties for illegal tread depth
If the safety data doesn’t persuade you, then it’s worth considering the potential legal penalties for being caught with bald tyres. You could be fined up to £2,500, given three penalty points per tyre, and banned from driving. Given this, there’s a strong case to be made for making regular checks.