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What is the tread depth of new tyres ? I have some Continental Ecocontacts and I'm interested in the amount of wear since new.
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So 20k miles in my 306 has worn the rears by just under 1mm, and the fronts by just over 2mm.
This give a potential of approx. 50k mileage on the fronts assuming replacement at 2mm
What is the legal limit - 2mm ??
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1.6mm, although i wouldn't like to be driving with less than 2mm in the wet!
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and tyres will wear faster the older they get (the diameter will decrease as they wear) so you may be slightly over estimating.
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Taking tyre assumtions to be, say 100 wide and 500 outer diameter when new, that gives a surface area on the tyre as
3.141*100*500 = 157050mm^2.
Loosing 10mm of tread gives
3.141*100*480 = 150786mm^2.
That's quite a big difference, bigger than I though it would be. In terms of revs per km, this gives 636 for full tread, and 663 for 10mm less tread. Therefore tread wear would increase about 5%.
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So we need to reduce the 50k figure by nothing with new tyres and 5% with old tyres, so average of 2.5%, so reducing 50K by 2.5% gives just under 49K, so not much difference there really.
Think we've gone a *little* too far with this approximation?
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willsimm
I'm not sure that's the case - in fact it may be the other way round. The deeper tread of new tyres is more flexible, so tends to move more on the road, causing a greater wear rate. That's why buffed down tyres are used in motor sport which requires road tyres. The wear rate will tend to reduce as the thinner tread is less flexible. I'm sure the older contingent will remember the original Michelin X tyres, which seem to last for ever once they got down to about 2 or 3 mm.
Regards
John S
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But do all tyres start with the same amount of tread? My (hazy) impression is that tyres don't come with as much tread as they used to. I have an ancient(1954) pair of 16" tyres on an old trailer and they have about 1/2", virtually unworn.
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Most new tyres I have bought since 1980 have started with 8mm. Tyres on a front-wheel drive car wear 3 times faster on the front, as a rule of thumb.
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I well remember the old Michy X tyres. Considering all of the slipping and sliding they did it's a wonder they lasted 5mins. But they did, and the 15 inch ones on a Citroen 2CV they might well outlast the rest of the car.
I recently saw a couple of nearly new tyres as fitted to the front of a Bedford Movano, after one emergency stop - motorway with locked wheels - nearly 4mm of tread was worn from the 'footprint' of one tyre, the other had patchy wear patterns around it. Both had to be replaced after the event.
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