Originally Posted by IntruderF350
I have a family member who just bought a 93 HR that needs tires
can he replace them with the 245/70R/19.5 in place of the old 8R/19.5 tires? When mounted theres only like 3/4 to 1 inch between the rear tires. what can he do to make them work?
That doesn't sound good. I don't have any technically supported figures but based on my coach I would want to see approx. 3" between duals.
Going to the tire specification table for the size in question might show the minimum dual-spacing. You'd need to subtract the width of one tire from that number, and measure between equivalent points on the two tires to get a rough estimate.
For example measure from the outer-most rib of the outer tire to the outer-most rib of the inner tire. Subtracting that distance from the Minimum dual spacing gives an indication of the gap between the tires.
There are other ways to get better estimates, but this should help.
Also, you need to pay attention to Revolutions per Mile since large differences between old and new tires will show up on the speedometer and odometer.