You’ve got a damaged tyre and it’s not repairable. To avoid making a bad situation any worse, you wonder if it’s possible to replace just that tyre and not the other three too. Well, you might be in luck. ‘Might be’ is, of course, the crucial qualifier, as it’s not always possible to replace only one tyre. It’s all determined by the tread.
There’s only one hand-print size of rubber per tyre connecting you to the road. To keep you safe, not only does the tread need to be deep enough, it also needs to be consistent across all four tyres. Tread usually starts out at a depth of 8-10mm. Once it wears to 3mm, the tyre can no longer adequately disperse water. Instead, water will slip between the rubber and the road and the vehicle will aquaplane. At 1.6mm of tread, the tyre is no longer roadworthy.
The tread must also be consistent across all four tyres. If they cannot equally disperse water and grip the road to the same degree, handling, acceleration and braking will be compromised. If the discrepancy of tread depth across all the tyres isn’t too great, your vehicle should still perform adequately, but it’s best to have this checked by a professional who knows the limits.
Good question. This is knowledge all car owners should have, as your tyre’s tread depth is a very good indication of how safe you are on the road (as well as those around you). There are two ways of checking your tyre’s tread depth.
All tyres come with indicator bars, which are little bumps of rubber that sit within the tread at a depth of 1.6mm. Once the walls of the tread are level with these bumps, it means the tread is also at 1.6mm, and the tyre is no longer roadworthy. Of course, this method doesn’t tell you how much tread remains if it still sits above the indicator bars.
To determine that, use a treadwear gauge, which very simply measures the depth of your tread in millimetres, letting you know with certainty how much life is left in your tyres. For more information, have a look at our blog on checking tread depth.
Yes, you can. However, never mix tread patterns or have big discrepancies in tread depth across the same axle; the handling and safety will be seriously compromised, particularly when cornering and braking.
It might. New tyres have a larger overall diameter than older tyres because they are yet to lose any tread. If you replace just one tyre on a 4WD, the older tyres will spin faster than the new one, which has the potential to engage the all-wheel-drive system when it isn’t necessary, potentially causing damage. Because of this, manufacturers of 4WDs recommend that all four tyres be replaced at the same time.