Is this tyre damage a problem?

Question

I just noticed this distortion on my rear left tyre that must have been caused by hitting a pothole or something - there's an even smaller distortion on the front left tyre. It's barely perceptible and I think I only spotted it because of my engineer's eye trained from hours of filing metal flat as an apprentice years ago.

I don't, however, know much about what's safe and what isn't with car tyres and this is bothering me. On the one hand, most other people wouldn't notice this and would carry on driving in blissful ignorance and I've already driven hundreds (maybe more) km at high speed on the motorway and on fairly windy roads. And these R18 255/45 tyres are very expensive at ~£200 a piece. On the other hand a tyre blowout, even with runflats, is something I'd rather avoid.

If you look at the inner line next to the alloy and the outer line just in from where the tread starts you can see the distortion. The surface of the tyre wall is also visibly uneven, if not quite bulging.

What do you all think?

Answer 1

I'm guessing that these are BMW spec runflat tyres? This isn't the first time I've seen such damage. Apparently, because they are intended to be used in an emergency without pressure, the sidewalls are thickened / reinforced. This basically means that they are made from several layers which delaminate with apparent regularity.

You may want to get the expert opinion of a professional tyre tech who can see it first hand but I'm afraid that it's probably a candidate for replacement.

Answer 2

So I just took the car to an independent garage recommended by my wife's aunt here in Germany (we're driving back to UK later in the week). The owner asked if I can feel any vibrations or other problems driving - I can't. He reckons that the material inside has shifted but that the tyres are probably fine to carry on using. He showed me similar, but even less noticeable, slight unevenness on the sides of the other tyres. I asked about their lifetime, since they're four years old but with plenty of tread, and he said that the rubber's in otherwise very good condition and that I should be able to use up the rest of the tread. So all in all very reassuring and I'm very happy not to need to change tyres.

Very impressed with his honesty! Thanks too for all the replies here.

Answer 3

Regardless of damage criticality, tires should be treated as consumables that have a shelf life.

Run-flat or not, if the tires over 5 years old then I would have them replaced regardless.

This is because the tire rubber can and will suffer from degradation through UV exposure, even if the tread is unused.

Answer 4

Yes, replace the affected tire.

Worn rubber like this will start leaking and the whole tire may possibly burst while you are driving. Better safe than sorry.