Car Advice

Wheel alignment is important but so is radial pull…

Everybody wants a car that tracks straight and doesn’t abuse its tyres, and that’s why wheel alignment is so important.

IT MAY SEEM STRANGE, but your car’s wheels don’t exactly line up straight with the direction of the car. They might be splayed out a bit, known as toe-out, or splayed in, known as toe-in.

And they may not be set to exactly vertical either, usually tipped in a little so they’re leaning inwards. This deviation from the vertically-up position is known as camber.

The differences are tiny, just a degree here or there, but they are important for all sorts of reasons. Handling is one, tyre wear is another, and then there’s braking efficiency and fuel efficiency.

Your manufacturer will have settings for the car’s alignment; camber, caster, toe and more. Almost all the time, you want to keep to these settings which your wheel alignment shop can look up for you. However, there are some rare occasions when you may wish to deviate. For example, my Toyota 86 does a lot of track work so I’ve changed the front toe setting to 0-degrees and reduced the rear toe – I am sacrificing straight-line stability for maneuverability. The differences are tiny, but they are there and noticeable on the track.

You should get your wheels aligned whenever you have new tyres, suspension changes or after a major pothole hit. In fact, last week I was driving my 86 along a temporary road which skirted some housing development. It was dark, wet and I thought I knew the road… until I felt that pothole. Yep, that was a wheel alignment right there. Pity I wasn’t in my Ford Ranger as it would have just laughed it off.

And it’s actually the Ranger I want to talk about, though. I recently replaced all five tyres with Goodyear Wrangler MTRs, and of course had the alignment done. Then over the next day or two I noticed there was a slight pull to the left. That shouldn’t have been the case, or if there was an issue that meant it couldn’t be adjusted out then I should have been informed about it. Sometimes suspension components are bent and that means alignment will never be able to come back within limits, but that’s not the case on my cars.

I presumed the alignment was on spec so it had to be something else. The tyre pressures were all within limits, and anyway it needs to be a significant difference between tyres to create a pull – low tyre pressures increase rolling resistance, and cause a lean into the low-pressure tyre which exaggerates the problem. But my pressures were fine.

Now I have a fairly low opinion of chain tyre shops in general, based on my own experience and that of readers. I could list their sins – selling people tyres that are illegal because they’re too low a load rating for the car, attempting to apply the alignment settings of a 2004 solid-axle Discovery 2 to my fully-independent suspension 2008 Discovery 3. But there are good alignment shops and my usual local one diagnosed the problem in short order. It was radial pull.

Despite mass-production techniques every tyre is built slightly differently. There are tiny variations in weight, distribution of weight, where the steel belts are set and so on. This is why all tyres and wheel combinations are balanced, which is adding tiny weights around the wheel to even it out so it rotates smoothly. As the steel belts inside the tyre are a bit offset the tyre doesn’t inflate quite evenly across its tread width, leading to the pull. This is also known as tyre conicity.

The end result is the drag each tyre creates is slightly different, and even though the wheel alignment may be perfect, that uneven drag can result in a pull to the left or the right. There are special tools to measure the drag on a tyre via a jig, which some alignment shops use, or you can just drive the car, test, swap the tyres from left to right, and see if it pulls in the opposite direction.

The fix is quite easy; if the tyres are new and the problem is bad replace the faulty tyre, or swap the tyres left or right so the pull doesn’t happen, use the faulty tyre as a spare, or put it at the back of the car where the problem is less apparent. But to fix the problem you must first diagnose it, and then know how to fix it. Sadly, that’s where many tyre shops are found wanting, but at least now you know something about it should you find an odd pull to either the left or right with your cars.


Robert Pepper

Robert Pepper