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? Tyre wall distortion

Tyre wall distortion 2nd photo

  • 1
    I know this might not be important for you nor any experts reading this post but would you be so kind as to draw a red circle around the affected area? Since I am not a tire expert I would like to more easily see what the issue is so that I can properly identify hazards on my own vehicles. Thank you! – MonkeyZeus Sep 21 '16 at 19:01

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.

  • Thanks for your prompt response. Yep - they're still the original tyres that came with the car. I feared that might be the case. I might take the car to get looked at later. If I do need new tyres I doubt I'll get runflats, they seem to be more trouble and expense than they're worth! – Feanor Sep 21 '16 at 10:10
  • My uncle has them on his 5 series and I'm sure he'd been through around five or six of them. The majority failed in the sidewall. – Steve Matthews Sep 21 '16 at 11:52
  • It's not just BMW run-flats that do that. My grandmother had a Honda Accord with run-flats that did a very similar thing. Then she discovered the big problem with them: when you scrape against a curb, they blow out and the run-flat part doesn't help, because run-flat is really designed for tread punctures, not sidewall damage. – Moshe Katz Sep 21 '16 at 12:35
  • I've noticed with mine the most obvious symptom of sidewall failure is a remarkable amount of noise from the tire at very low speeds. I was hearing a squeak which I could not pinpoint and it turned out to be a bad sidewall on one of my runflats. I damaged another one two weeks later and a similar sound started once again. Needless to say with the mileage I run (and my love of good tires) I've decided to abandon the runflats and risk needing a tow... – Lathejockey81 Sep 22 '16 at 4:11

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.

  • Ask someone at TÜV or Dekra if they would send someone home with that damage or let them drive another 2 years. – PlasmaHH Sep 21 '16 at 13:05

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.

  • Indeed, but they're 4 years old so I was hoping to get at least another year out of them :) – Feanor Sep 21 '16 at 11:04

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.

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