Quote:
Originally Posted by Bob Carriere
Another factoid...... just got a hold of two new 1940 Chevrolet and Maple Leaf parts book and in the listings.....although only one size hub/adapter of 4 1/4 inch is listed they have four different offset rims sizes ranging from 4 1/8 to 5 1/4 offsets on the rim center parts....all in 20 inches.... So GM played with the track width by varying the offset of the wheels and the greater offset seems to be on the larger truck axles....series 15 to 18 had the wide offset....... they were not to concerned with the overloading of the bearings.
Bob C
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Ford explained the problem well in their Service Bulletins. Different capacity trucks were fitted with different tire sizes for their weight capacities. This resulted in different tire diameters, but still with the same steering geometry. This would cause tire wear issues on the front tires because the centreline of the kingpin axis should intersect the centreline of the tire contact patch on the road. By using wheels with different offsets with particular tire sizes, this geometry could be corrected and irregular tire wear eliminated.
It should be noted that tires would scrub out and become unserviceable much quicker than wheel bearings would fail from being overloaded or not in line with the tire centre.
This geometry will be a more critical issue in determining your wheel offset than exposing some brake drum.