Tireman9 wrote:
OK based on the lack of data on actual usage I must have mis-interpreted the interest in formulas. So lets go back to the Cliff Notes suggestion
NHIrish wrote:
1. Buy tires of a load rating sufficient to carry the load you have.
2. Allow a safety margin in the tire you choose.
3. Ensure that the valve stem used is appropriate for the pressure rating.
4. Keep your tires inflated to the max pressure rating for the tire.
5. Check said pressure frequently.
6. Don't overload or underinflate.
I will provide a couple of examples on how I would apply this good summary.
Starting with a trailer with loading at LF 2675 RF 2995 LR 2890 RR 2545 and 6000# axles
1. I consult the load tables and find the tires with at least 3000# capacity. ST245/75R16 LR-D or LR-E and ST235/75R16 LR-D or LR-E and ST235/85R16 LR-d or LRE all are rated at 3000# BUT they are ST tires and I admit to driving faster than 65 mph so I need to look at LT type tires which are rated for at least 75 mph per the Speed Symbol marked on the tires. (Note. There are errors on tire company web pages)
2. Also my safety margin is 10psi. I find the LT245/75R16 LR-E will carry 3042# at 80 but with my 10 psi Safety margin I need to look at the 70 psi capacity. I find a LT265/75R16 LR-E is rated at 3000# at 65 psi. Before I get these tires I will need to confirm the rims are rated for at least 3000# and the 75 psi I would run in this application. Wheel inflations are the cold inflation you will be setting the tires at. The original 16 inch rims that came with the ST tires may not be rated for more than 65 psi. You MUST check and get the answer in writing or marked on the wheel. I also need to confirm I have the clearance for the 265 width.
3. New bolt in valves will be part of the purchase.
4. The high inflation shown on the tire will decrease lateral sway and tire loading but will have a slight increase in the potential for impact damage.
5. I will check the inflation before each trip and monthly while parked. To get early warning of a puncture I will also get a Tire Pressure Monitor System and confirm it's accuracy is within +/- 3 psi by using a digital pressure gage as a reference. The chance of both the TPM and the hand gage going bad by the same amount is negligible.
6. I will run across a certified truck scale at least once a year and compare to my reference individual tire load weights to make sure I haven't managed to creep up in loading. If I make any modifications to the RV by adding or moving any component weighing more than 50# I will check individual tire loads. Finally I will have the wheel alignment checked when I apply the new tires & wheels, to avoid irregular wear due to camber(bent axle) or out of spec Toe (impact damage)
I feel that if I do the above and follow the suggested practices I can minimize tire problems and be alerted to air loss due to punctures.
Again someone out of touch with 5th wheel trailers. LT265/75R16 tires call for a wheel that is wider than most available zero offset trailer wheels. If a LT245/75R16E or LT235/85R16E is under rated, then LT235/85R16G is the next logical 16" tire to fit under a 5th wheel. Or move up to 215/75R17.5's. I have only seen two others push the 265's. One said rebuild the trailer make them fit and the other said to run them on a wheel that is narrower than spec. Chris
