Yes, this. On some tires they do tend to follow road grooves when new.
As a retired mechanic, this is mandatory in the shops to check the front end parts prior to alignment. Whether your mechanic did this we do not know so get another mechanic to look at it.
I’m more inclined to think that your tires are trying to follow the grooves in the road as mentioned. Happens to me too and I drive a Taurus.
Occassionly I heard a “clunk” as I’m driving which I associate with driving in part-time 4 wheel drive on dry pavement. Did my car switch into pt 4WD? That didn’t make sense as my car would oversteer rather than understeer.
Sometimes when there is a large change in engine power like dropping into passing gear or cruise control the car will jerk to the left. I didn’t put the two together until someone said a bad shock will occassionally “clunk” so I went around to the four corners of my car and did the push down test. 3 of the shocks were fine and wouldn’t you know it but the rear left shock was really loose (is that the industry term?). I’m not talking about maybe it is a little worse than the other, slightly, but maybe it’s just me. I mean a blind monkey fucking a cantaloupe would say “Damn, something is wrong here.”
So I am pretty sure the problem is my driver’s side rear suspension so before the snow hits I’m going to replace the rear shocks (planning on having them doing this anyways - just waiting until payday) and have them inspect the other parts as well.
How new is the 4th tire? I know Subaru is pretty clear on mixing old and new tires in a 4WD system but it’s also full time. Even my old Cherokee recommended not mixing and matching as it could cause unusual driving conditions…
this is because the difference in tire diameter can cause accelerated wear on the differentials/couplings in an AWD system, or cause driveline bind-up on a part-time 4WD system. A worn tire of smaller diameter than a new one will cause that wheel to spin slightly faster than the others.
only a month or two difference in the tires.