Due to road camber, the toe-out condition resulting from a worn idler would tend to cause a drift to the right (in the USA, anyway, no pun intended). This would require a compensating steer to the left, scrubbing the inside of the driver's side tire. Worn idler bushings could also cause vibration, and most noticeably - road wander and imprecise steering.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7