Do Bias Ply Trailer Tires have Stiffer Sidewall than Radial Tires  

I have a few general questions regarding boat trailer tires Currently I have a set of 205/75R14 tires with a load range C, 6 Ply, tubeless, max load of 1760 lbs @ 50 PSI Cold, speed rating M. They are Rainier brand which came pre-mounted to a 14x5.5 rim which says max 2200 lbs on it but no brand or anything I am able to find. Max PSI of the rim is not listed anywhere. I bought these last year to replace the bias ply tires of the same rating which were on it when I bought it. Boat + Engine weighs approximately 2530 lbs. 20 foot Single axle steel trailer rated to carry 3500 lbs I assume is about 675 lbs so without any gear its about 3200 lb total on the tires but so far no issues with several long trips. Im thinking the weight on the tongue takes some of that load off the tires. 1 - Even at 50 PSI the tubeless radial tires appear to be a little flat when parked, like the bottom is bulging out a bit similar to if your car tire pressure was low, this was not the case with the bias tires that were on it 205/75D14 C, BSW. Is this cause for concern? 2 - Starting at 50 PSI cold if I jump on the highway I notice the pressure typically increases about 7-8 PSI and holds without increasing further and they come back down fairly quickly after parking. Is this pretty normal? If the max is 50 PSI cold what would be the approximate upper max PSI? I have a tire pressure monitor so I can watch the PSI and tire temp in real time. Tires appear much more normal less flat at this increased pressure when I reach my destination. 3 - In the interest of safety I am considering upgrading from these load C radial tires to load D radial tires of the same size but I see the max PSI cold is usually 65 for these size of tires. Is there a concern about the wheel or valve stem at that pressure keeping in mind if they are set at 65 PSI cold they will most likely head up and increase in pressure a few PSI? Id rather not change the rims if possible. Thank you very much!

asked by: Ben W

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