Our dealer recently upgraded our MY94 wheels to 16 inch (from 15). Along with this came tyres with a lot more tread (and probably generally better grip).

Since the "upgrade" I've noticed the car is a bit more "twitchy". By this I mean when occaisionally going over a manhole or some such small anonmoly in the road the car will want to pull in that direction (usually to the left, but this is probably due to most road imperfections being toward the gutter).

Going through a largish gutter puddle today the pull was very noticable and seemed substantially worse than with the old wheels/tyres.

Is this normal and just a result of the increased grip and turn in. (On normal smooth roads, camber permitting, the car goes straight.)

 

Its possible the alignment is out, it may not have been noticable on the 15's, but changing to the 16's may have made it noticable. I would get the alignment checked and changed to Subaru's standard, or to the FAQ settings. You may find that the 4 corners do not have the same settings, as has been noted by other people.

Hope this helps

 

I've just had a frustrating time getting my MY99 sorted to go straight - it's ok now after battling the dealer who insisted that all cars pull to the left on a left camber road. I could only convince him by driving on a flat car park and showing it pulled left all the time.

If the geometry is correct, the car should go straight even on a shallow cambered road. The car may drift left a little on a steep camber, but this is due to gravity "sliding" the car and not the steering pulling that way (the wheel should stay reasonably straight).

Your new tyres will have a smaller sidewall height and so will flex less than the higher aspect ratio tyres on the 15" wheels, making for more "feel" as road feedback is less damped.

However this will tend to show up any suspension set up problems more than before.

Get your dealer to do a full geometry check and you'll be fine - I was amazed how nice the car feels when it's set up right !