March 2020

W e have arrived at the fourth final part on the subject of tyres. This month, the focus is on the MOT, regarding tyres and tread depths. I’m hoping the manual hasn’t changed by the time this is published, (the MOT manual is, after all, changing all the time). As I write this, it states that the legal limit for a passenger car with no more than eight seats excluding the drivers seat used on or after 3 January 1933 is 1.6mm around the whole circumference of the tyre across the central three-quarters of the tread area. Therefore, if a car was to come to me for a MOT with one or more of its tyres measuring 1.6mm, I would be forced to pass the car with just advisories on the tyres in question. This is a shame as you wouldn’t want to send a car out of your depot with a tyre on the legal limit and 100% worn, would you? The owner could quite easily travel 100 miles or so in the next few hours and their tyres may very well be then deemed illegal If stopped by the police. “But officer! My car passed its MOT earlier today" may well be their perfidious reply. I suppose all that matters is how the car was presented at the time of test. From a tester’s point of view though, you cannot try and pre-empt what may or may not happen after the test. The car maybe stored in a garage for months at a time for all we know. It may only do 200 miles a year. Regardless of what we think may happen, by following the guidelines and rules set out in the manual you can’t go wrong. As long as the customer in question is made fully aware of the situation and you’ve made the best judgement call you can, then you have done your part and can you sleep at night. Measurements Here are some measurements to get your head around regarding tread wear: 8mm-0% worn; 7mm-16% worn; 6mm-31% worn; 5mm-47% worn; 4mm-63% worn; 3mm- 78% worn; 2mm-94% worn. Obviously 1.6mm would be 100% worn. However, as I mentioned, it still passes an MOT as an advisory. A tyre on 2mm also passes but certainly with advisory notice. Me, I give an advisory notice for a 3mm tyre. To me when something is 78% worn, it’s almost had it. If you were to wear a pair of shoes that were 78% worn, I would think that somewhere along the line someone may advise you to replace them too, as they’d look pretty shabby. The garage I work in receives tyre bookings all the time from cars that have been for an MOT elsewhere, a lot of the time, at a main dealer. For some reason they have advised tyres on 4-5mm tread readings. I’m not sure why, as a 4mm tyre still has some life left in it, and a 5mm tyre certainly shouldn’t be classed as worn. Maybe the testers are overzealous. They should take their tread depth gauge and make sure its calibrated. There was me thinking I was being cautious advising on 3mm! I like to think I’m firm but fair when it comes to testing. I’d like to think others are too. Lastly, don’t forget, the next time you’re out walking in bad conditions and keep falling over, check the tread depth on your shoes, it maybe time to replace them. 24 AFTERMARKET MARCH 2020 TECHNICAL www.aftermarketonline.net TREAD A MILE IN YOUR SHOES? In an appropriate conclusion considering the number of wheels on most cars, Gareth Banks brings his four-part look at tyres to a close with their relation to the MOT BY Gareth Banks CAE AMIMI