Clas C and tires
I have been doing online research for the purchase of a new to us RV. A Class C is high on my list. Probably an E450 from about 2000 to 2004. I really want a dinette, sofa and a chair. That would mean...
Forum Discussion
All Class C LT 225/75R-14 tires must pass the NHTSA FMVSS 139 test. You can view the tests here:
https://www.nhtsa.gov/DOT/NHTSA/Vehicle%20Safety/Test%20Procedures/Associated%20Files/TP-139-03.pdf
For example, endurance test (page 40) on our LT tires uses a pressure of 59.5 psi then is run at 85% of max load for 4 hours, followed by 90% max load for 6 hours, followed by 100% max load for 24 hours, for a total of 35 hours run, at a speed of 75 mph.
This is immediately followed by a low-inflation test for 90 minutes at 46.4 psi with 100% load and 75 mph.
Tires are not run to failure so there is no information on how much design margin each tire has. For that reason we run fully steel cased commercial grade tires that we know have plenty of design margin.
Shorter motorhomes can likely safely use standard LT tires since they are not anywhere near approaching the maximum load rating of the tires.
Longer heavy motorhome owners may want to consider one of the many commercial grade tires.
In any case tire manufactures recommend all tires older than 10 years be replaced regardless of condition.
https://www.nhtsa.gov/DOT/NHTSA/Vehicle%20Safety/Test%20Procedures/Associated%20Files/TP-139-03.pdf
For example, endurance test (page 40) on our LT tires uses a pressure of 59.5 psi then is run at 85% of max load for 4 hours, followed by 90% max load for 6 hours, followed by 100% max load for 24 hours, for a total of 35 hours run, at a speed of 75 mph.
This is immediately followed by a low-inflation test for 90 minutes at 46.4 psi with 100% load and 75 mph.
Tires are not run to failure so there is no information on how much design margin each tire has. For that reason we run fully steel cased commercial grade tires that we know have plenty of design margin.
Shorter motorhomes can likely safely use standard LT tires since they are not anywhere near approaching the maximum load rating of the tires.
Longer heavy motorhome owners may want to consider one of the many commercial grade tires.
In any case tire manufactures recommend all tires older than 10 years be replaced regardless of condition.
