I can’t find Iconic tyres online. Is it a typo (e.g. for Invovic)?

That aside if these are from the very budget end of the market, they are likely to have compromises compared to mainstream makes. That might include balance issues and whether they give good handling and braking.

As for perishing I had minor inter-tread cracks on Michelins last year and I put that down to two successive hot summers and sitting on the drive when COVID restrictions limited use. I wonder if perishing is going to be more common even on premium tyres if we get more hot summers.

If Iconic do exist hopefully some backroomer can comment more specifically.

I once had a vibration which was due to a 'flat spot' or 'out of round' condition which didn't show up as unbalance.

Try jacking wheels up and spinning, such an out of round of a few millimeters will be visible.

Thanks for clarifying. These are Chinese tyres whose main attraction seems to be cheapness. I can’t find any professional reviews.

Opinions differ on Chinese tyres. I’m just an amateur tyre user and play safe by buying recognised, well reviewed makes. That’s not to say all Chinese tyres are bad,

Back to the original vibration issue, it’s likely down to the new tyres if the previous ones were OK. However there are other potential causes of vibration. It might be worth getting a good indie to check the car rather than a tyre fitter. Even if that throws up another cause I would budget for a new set of mainstream tyres but maybe I’m over-cautious. Thousands of cars run around on them without incident.