Tire wear is an alignment or ride height issue, not wheel bearings. There's two angles that can cause edge wear. If you find that wear on just one tire, it can only be caused by "camber". Camber is the tilt in or out on top when viewed from in front of the car. Too much positive camber makes that tire run on the outer edge. Positive camber means it's tipped out on top.
Total toe has to do with the direction the two tires are steering. Toe-in is when the fronts of the tires are closer together than the rears of the tires. A little toe-in is desirable, but too much makes both tires scrub sideways as they go down the road. Total toe always affects both tires equally.
Things get a little more complicated though. For my story to be true, all the other alignment angles have to be in specs. THEN, excessive camber will cause edge wear, depending on which way that wheel is leaning, but camber can be off the same amount on both wheels.
At first incorrect total toe will cause tire wear but as it gets worse it can cause an irritating steering wander. It won't cause a shimmy but it can aggravate it. Worn rack and pinion bushings won't cause a shimmy either, as you found out, but they can fail to lessen the severity of that shimmy. Those new, stiffer bushings are fighting the shimmy, but as you noticed, the actual cause hasn't been corrected yet. Less obvious causes of a shimmy are a bent wheel, rust or debris stuck between a wheel and brake rotor after a recent service, or between the brake rotor and hub, a warped brake rotor, and a worn inner cv joint.
When you have edge wear on both tires, the only way to know if it's a camber or toe problem is to look at the numbers on the alignment computer. I suspect the alignment wasn't set correctly or the car's suspension has sagged from age. Incorrect ride height causes the suspension parts to go through different geometrical changes as it goes up and down over bumps. That will cause tire wear even when the numbers look good on the alignment computer.
Wednesday, November 6th, 2013 AT 8:32 PM