As I thought we were beginning to get somewhere, and in order to assist SMD get some help on his problem, I am going to reopen this.
But there are some house rules, and anyone not abiding by them will see (possibly) temporary bans.
I shouldn't have to spell it out, we all understand the behaviour expected, but:
No bickering, fighting or general unpleasantness, and no comments purely to stir someone else. It will not be tolerated at all
Here is what I know from personal experience (not what is written on the internet in irrelevent tests), except the first, which is traditional wisdom:
1) Traditional wisdom states that wider tyres and lower profiles gives a greater
tendency to tramline, all other things equal, but does not necessarily mean a tyre will tramline.
2) Not all tyres (discernably) tramline.
3) On a well set up Omega, Sport Maxx TT 235/45/17 Y94 seems to be the benchmark in stability.
4) On same Omega, Continental SC5 235/40/18 Y94 seem to be at the bottom end of the scale for stability.
5) Four different budget tyres, including a mixture of winter and summer tyres, on the same Omega, does not tramline much.
6) SC3s are variable, depending on manufacturer specific sub models, meaning that a wider, lower profile tyre can be tramline free, and a narrower tyre can tramline.
(I am not mentioning Runway Enduros here, as I have not personally driven a "known" Omega with them on, so although I know that people I respect when it comes to tyres say they are a stable tyre, I have no personal experience, thus unqualified to comment - there has been too much heresay and speculation on this thread, and some people's opinions, without experience, portrayed as fact)
The 2 Omegas I have are set up to the WIM standard, with the exception of the 4 budgets on TBE, which was set at the time to an aggressive fast road setting - although these tyres reacted the same on the Silver Bullet that has always had the WIM standard settings.
Certainly with the Sport Maxx TT and the SC5, swapping between the cars, the tramline moves with the tyres. And going from the 4 different budgets to the SC5, the car went from "fairly stable, but not enough grip in the wet" to "very bad tramlining, and poor grip, esp under braking".
So, we can conclude, pretty convincingly, the issue lies with the tyres in this case (although we know that chassis issues can cause tramlining).
Remember, play nicely, or accept you will see a ban. Or shut up.