Alignment of Tyres

April 13, 2007 at 9:43 am Leave a comment

A vehicle has to track straight on a road that is crowned, or sloped, or flat. The whole vehicle. On some of these huge road trains, their trailers seemingly have a track of their own, whipping from side to side. Yet the modern B-Doubles traveling the major highways, track quite well.

They bear the fruits of a lot of research into vehicle alignment. The whole set-up has been laser aligned to make the trailer track properly. The settings may be different for vehicles that travel the flat roads from the eastern States to W.A. ; or set so the trailer alignment counteracts the high crown of far N.Q. roads.

The Holden Kingswood, or any rear wheel drive car of that vintage, was not as critical in its alignment as the modern front wheel drive. The rear wheels thrust the car forward on the Kingswood, whereas the front wheels drag the car along in the FWD.

There are three major alignment factors- camber, castor, and toe in ( or out). All affect tyre wear and handling. The settings are decided by the car engineers. For example, a Commodore SS has more negative camber than a Commodore Executive, or the tolerances may be set to the maximum on one, the minimum on the other, to improve one aspect of handling.

But there is a fourth setting. The thrust line and its alignment to the drive are more critical in a front wheel drive. If one REAR wheel is out of alignment, it can make the whole car travel crabwise down the road. You see the car drifting off one way or the other, while the unconscious driver is constantly correcting his steering. Once you become aware of this, it’s amazing how many cars you see tracking like that. So if your car has been clipped over one rear wheel, the mountings have been disturbed, or the car repaired after a smash, ask for a “full four wheel alignment to the thrust line.”

If the front tyres on your car (which has had its alignment checked) still wear unevenly on the outside of one front tyre, and the inside of the other, look to the rear end to see what is making it travel crabwise.

Entry filed under: Balance & Alignment. Tags: , , , , .

Wheels Magazine 2007 tyre review. Queensland Corvette Convention 2007

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