Originally Posted by Ky76Argosy
Questions - sorry, but using your 85% rule, 15% load and safety margin, for 26' trailer GVW 4000# 2 axles: 1) Does GYM ST225/75/15 load range C, max weight 2150#, 50#psi work 2) Does ST205/75/15 load range C, max weight 1820#, 50#psi work, and 3) if no for either why, and 4) Opinion for minimum psi cold for each. Thanks.
If all we have to go on is GVW we have some additional factors to deal with. This is why learning the actual loads on the tires is important. lacking the facts we need to apply some adjustments.
Since we don't know the load balance between your axles we apply the 53/47 load split factor.
Heavy axle carries 53% of 4,000 => 2120
Heavy end of the heavy loaded axle 53% of 2120 =. 1,124
Now we apply the 85% factor.to learn the needed load capacity of the tire
1,124/.85 => 1,322#
A tire that is rated to support at least 1,322# would be OK.
BUT I think you can see how much easier it is if you know the actual tire load.
You still need to confirm you have not exceeded the 2000# rating for each axle.