'92 Q45 front-end problems with pull and high speed shimmy despite alignment, ba

[kdkrone]

I need to pick the collective brain. I have a 92 Infiniti Q45 with which I refuse to part, but I am having an irritating problem for which I need a consultant.

Here is a synopsis. The car has 103K miles. Front end repairs have included recent rack and pinion replacement and strut replacement. The rest of the front end was carefully inspected and all was OK. I keep the car up to specs and have it aligned regularly (every 6 months at a shop that has its equipment tested monthly; while the fellow who owns the shop where I have work done is a Nissan mechanic, he seems to know my car quite well.. I also have my tires rotated and balanced about every 5000 miles.

Since purchasing Falken Ziex ZE512 unidirectional tires, now about 8,000 miles old, I have noted that the car tracks differently than it used to. On roads that are flat (not crowned), if the surface is very smooth, it will track straight. If the surface is a slightly rough surface, it will pull slightly to the right so that my steering wheel is always turned slightly to the left, which is a little PITA on long trips but tolerable. On a crowned road, the car always pulls slightly to the right following the cant of the road.

The tires were rotated and re-balanced about 2000 miles ago and there is a slight vibration/shimmy above 65-70 MPH, as well as the continued slight pull as I mentioned above. I should also note that my tire is stock (215-65x15).

My questions are: Are unidirectional tires much more sensitive to road surfaces than a more conventional tread design? Was purchasing Falkens a mistake?? (if so, what are decent touring tires for the Q that won' t break the bank?

Any thoughts about the problems I have described with the vibration--is it consistent with a balance issue (even though the tires were balanced about 1500 miles ago) or do other things cause a slight vibration above the usual 50-60MPH when tire balance problmes usually seem to show up?

Is it likely I would solve this problem by changing the tires from Falken's ?? (I did have a set of Yokohama tires that were unidirectional and did not seem to have the tracking problem...)

Feel free to request more info from me.

ThanksKen K

[elwesso]

most commonly rotors are the cause of vibrations around 60 (+/- 10MPH)... They may not feel bad..... At least take the front rotors off and have them resurfaced... probably dont have to take a lot of meat off to get them at 0 runout.

honestly, it sounds like that the car's alignment is too precise... You cant really expect it to go straight on crowned roads... Thats how mine is... You can have them toe it in a little bit more and it should help the tracking a little...