Posted by Alan Bowes on March 09, 1998 at 14:02:45:
In Reply to: Re: LAV tires on an M-37 posted by Alan Bowes on March 09, 1998 at 13:46:31:
Just a postscript on the subject of axle breakage and how it might be affected by a taller tire.
Generally speaking, the point at which the tire tread breaks loose and begins to slip on the pavement is analogous to a circuit breaker in an electrical circuit. You can keep increasing torque on an axle shaft until either the tire tread slips on the pavement, or the shaft twists/breaks. One or the other will happen if you keep increasing torque on the axle shaft.
The problem with using a taller tire is twofold:
First, there tends to be more traction, which is like raising the amperage rating on a circuit breaker. Greater traction means that you can put more torque on the axle shaft before the tire breaks loose.
Second, the increased "arm" (due to the larger tire diameter), means that you will be able to put even more torque on the axle shaft before the tire tread slips on the pavement.
As long as you never apply that much torque to the axle, you're fine. In normal driving, this may not happen very often. However, there are occasions in normal driving that can create a high-stress situation. For example, if the tire is spinning on a patch of sand, then suddenly bites clean pavement, it can put a lot of stress on the axle. Also, if a vehicle is heavily loaded, it will increase the amount of torque that you can put on an axle before the tread slips on the pavement.
For that matter, just going from a bias-ply to a radial can increase the traction on dry pavement, but it doesn't increase the "arm" unless the tire diameter is larger. Doing both (radial and larger diameter) may have a significant effect.