Mr tyre manufacturer will go away and try altering compound and tread pattern until it works. Usually. I have known them give up, tho.
On 18's - I usually buy a set before each track-day and then finish them off on the road. Cheapest, always. On the couple that I've had that tramlined, I've always found it to be the car and not the tyres.
since these ao1 where fitted, I think the rear wb bushes have failed, and the steering idler was replaced.
I could pick out the differences with the steering idler before and after. Slight steering play and a creak.
But I can't feel any difference with the rear wb bushes. ...another creak has developed so i need to check them again. But they where fine when ao1 where fitted because I checked while the car was jacked at the tyre fitters.
So, as I've made that about as clear as mud;
No tram lining.
Mo came off with worn in/outside edges and plenty of tread in the middle.
Rear bushes checked, and fine, while jacked at tyre fitters.
Ao1 went on, drove it away from the tyre fitters, instant tram lining.
Creak and slight play in idler, replaced, slightly better steering, tramlining no change.
Different creak developed, might be rear wb bushes, tramlining is same.
Conclude, mo don't tram line, ao1 do. Why?
Not tread pattern, it's exactly the same.
Don't think it's compound, grip and wear is very similar Afaict.
It's the narrower ao1 (235wide) the plays up so its not to do with width.
Mo where on both sets of sport stars in et30 and 38. No tramlining, it's not the et.
It's not the car as the before and after tyre change was night and day.
Ao1 pressures tried between 28 psi to 35. No affect on tramlining, just harsher ride.
IMO, it's the construction of the tyre, unless anyone else can think of another aspect that we could eliminate. ...?