Posted by Alan Bowes on March 09, 1998 at 13:46:31:
In Reply to: LAV tires on an M-37 posted by JR on March 07, 1998 at 17:27:53:
Do you happen to know what the outside tire diameter is? As I recall, the stock NDTs are about 35.2 inches in diameter.
Anyway, here are a few thoughts on the pros and cons of using taller tires:
Good things:
- Slightly higher effective gearing will raise top speed and might produce a slight mileage improvement.
- Longer footprint and reduced angle of attack means slightly better traction compared with a smaller diameter tire of the same type.
- More ground clearance (if that is important to you).
- Looks (if you like the looks better).
Negative things:
- Slightly more braking effort required.
- Somewhat reduced acceleration.
- More stress on axle shafts.
- More stress on steering knuckle components.
- Higher roll center and CG.
With a taller tire, you are increasing the "arm" length at the end of the axle shafts (the distance from the center of the shaft to the tread). This means that greater torque must be applied to the axle shaft to produce the same amount of acceleration. Whether it would be enough to significantly increase the liklihood of shaft failure is another question.
Braking is affected in a similar manner, since more braking friction would have to be applied to produce the same amount of deceleration. Again, this may not be a great amount, but you would probably notice it.
All in all, the taller tires should work OK if there is not a radical change in diameter, but keep in mind that you can't cheat physics. The above effects are quite real.
You could probably put the taller tires on and they would work fine for years and years. The only time you might have a problem is when you encounter a high-stress "borderline" condition where the extra stress (or the higher roll center, etc.) is just enough to put you over the edge and break something or cause a roll-over that might otherwise not have happened. It really depends on how and where you drive.
Would I do it? Well, I think I'm going to remain non-committal on this.
Have fun,
Alan