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Wheel alignment key to wear

| Friday, Dec. 6, 2013, 10:07 p.m.

Question: I just had new tires installed on my car. The place recommended a wheel alignment and said my new tires would last longer if I had this done. I agreed, then they called me back later and said I need some parts replaced or they couldn't align it. I passed on the work and am now back driving with new tires and no alignment. I'm wondering what to do now. The car doesn't shake and my tires lasted a fair distance. What does an alignment entail, and why can't it be done?

— Holly P.

Answer: Wheel alignment is important for proper tire wear and straight, stable tracking. Older, rear-wheel drive vehicles required only a periodic front wheel alignment (check and/or adjustment), while front-wheel and many all-wheel drive vehicles may have adjustable components in the rear as well. Imagine the human body with very loose knees and/or ankles, or a bent femur or tibia. Your tennis shoes would likely scuff and skid a bit more than planned as you walked.

The three principal front-wheel alignment angles are caster, camber and toe. Adjustable rear suspensions include toe, and possibly camber. Let's look at the front: Visualize a bicycle with two front wheels — parallel to each other, rather than one. Caster is the angle of the bicycle's front fork, viewed from the side — relative to vertical. Most vehicles have a few degrees or more positive caster, similar to a bicycle. If one wheel has less caster than the other, a pull to that side is likely.

Camber is the inward or outward vertical lean of each wheel. Positive camber is out at the top (bow-legged), and negative camber is inward at the top (squatting). Incorrect camber affects tire life as a leaning tire wears more on one side, and can contribute to a pull to one side.

Toe is a measurement of the two wheel's parallelism, as viewed from above and is by far the most critical. Toe-in is pigeon-toed, closer at the front than back, and toe-out is the opposite. Incorrect toe will cause dramatically increased tire wear — usually wearing one side of the tires more than the other, with a feathered tread. If, when rubbing your hand across a tire's tread, it feels smooth one way and rough the other, incorrect toe is likely.

Toe is typically adjustable; caster and camber aren't. Aftermarket kits often allow adjustability.

It sounds like you may have some worn parts, such as ball joints, tie rod ends, control arm bushing, or upper strut mounts. The difference between minor looseness and alignment-altering wear can be a blurry call. Wear or damage is much easier to classify. In the case of safe but worn parts, one might weigh the benefits of optimum handling and tire life versus remaining time of ownership. It's possible to check/adjust static alignment on a vehicle with worn suspension components, but the angles go askew as road forces stretch the worn joints, throwing off actual driving alignment.

Get a second opinion on the suspension parts wear to play it safe. If your tires wore well and there is no pulling, wandering or noises, your parts and alignment may not be that bad.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at under-the-hood@earthlink.net.; he cannot make personal replies.

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