ROAD AND WORKSHOP by Handyman
Page 46
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Check Up on Chassis Alignment
DURING THE LIFE of many vehicles there will have been occasions—both known and unknown—when they have suffered stress and shock to chassis frame and connections. This shock will have been quite strong enough to produce a permanent "set", which though not readily noticeable is enough to interfere with steering geometry and handling generally—and can be the cause of early tyre wear and expense. Many goods vehicles complete their life in this condition; they remain just a fraction out of line, this being noticed only when moving alongside a kerb, or on to a service pit, or when running over clean snow.
There are a number of causes, the obvious one resulting from ditching when loaded, or in attempts made to "tow out" Whilst still loaded. Other causes of misalignment can start from load slip, running too long on a weak spring, and so on. Any of these can produce a twist or set that will affect true running and whether readily measurable or not unnecessary expense is incurred. Larger organizations are, as a rule, well equipped to check and locate any such distortion by means of optical equipment, and the like, Many smaller operators, however, are not so fortunate and miss the significance of this condition. They are prepared to put up with a little out-of-line running on the assumption that this is as far as it goes.
Yet if this misalignment remains unnoticed as much as 20,000 miles can be lost to a set of tyres, with rubber removed and nothing to show for it. Therefore. after being involved in any of the above incidents, or on becoming aware of rapid or odd tyre wear, a check-up on chassis alignment is well worth while. It is quite easy for the layman to carry out, little being required in the way of special equipment or know-how.
The first requirement is a reasonably
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level, smooth floor. Then make up eight plumb lines and suspend these from opposite points on each chassis side, preferably at the centre line of each crossmember. If the chassis is straight and true a cord stretched horizontally along the floor will be in contact with all the
plumb lines at the same time. • In order to locate the area of possible damage with absolute certainty, again make sure that the plumb lines are at the exact centre line of each member, then mark with chalk the point of contact with the floor in each case and move the vehicle away. Now accept the marks of each pair of lines as the corners of rectangles, mark off the diagonals and measure them on the floor. As rectangles must have equal diagonals, a point of distortion will at once be noticeable.