Pneumatic tires are also used on dirt and gravel surfaces and soft yards. They provide slightly better traction than solid pneumatic tires, but they are susceptible to flats because they hold air. They are also about half the cost of solid pneumatic tires.
Rubber Tire Replacement
For optimum performance, we recommend that rubber tires be replaced when approximately 30% of the available rubber tread is used.
How to measure your tires:
To assist you in deciding when to change the tire we suggest you use the following formula:
OD = Original outside diameter of tire
ID = Inside diameter of tire
X = Maximum recommend wear
Y = OD at which tire should be changed
Formula to obtain maximum wear:
X = [(OD - ID) + 2] x .30
Y= 00 - X
Example: 18 x 6 x 12 1/8
X = [(18 - 12 1/8) + 2] X .30 = .881
Y = 18 - .881 = 17.12
Conclusion - Tire should be changed when the OD is reduced to 17.12