Q. The tyres of my one-year-old VW Touran have worn so dramatically on the inside edge that they are now noticeably slanted. My garage checked the wheel alignment and said it was fine. So what else could be causing this?
ES, Thurso, Scotland
A. Your garage did the right thing: with any peculiar tyre wear the first thing to check is the wheel alignment. The mechanic should also have checked for obvious signs of wear or damage to the car’s suspension and steering components — such as bearings and links — although it’s unlikely any will be found on so new a car.
Assuming these causes have been eliminated, the most likely culprit is the speed bump. The most frequent offenders are so-called speed cushions, which, rather than being one solid hump across the whole road, are smaller, slope-sided rectangular humps that cover most of each carriageway. If you drive over one head-on, the tyres are forced to grip the sloping sides at a sharp angle. If you do this often enough — especially if you don’t reduce your speed sufficiently — the result can be the sort of tyre wear you describe.
Assuming you can’t find suitable routes that avoid such speed bumps, cut your speed right down and, provided it’s safe to do so, try to drive with one wheel on the road and the opposite wheel on the hump. This will keep both tyres flat to the surface, so helping to avoid uneven wear.
If you think that any particular humps are the cause of your problem, you can check that they meet the government guidelines. The Highways (Road Humps) Regulations 1999 state that they should be no higher than 100mm. If they are too high it is your local council’s obligation to change them.
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory
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