[phillyg]

You should not have to replace Sailuns at 15,000 miles. Is the wear excessive on the other three tires? It sounds you have a bent spindle or something else going on with that axle, so I'd have that checked first and replace only the bad tire if the others check out..

WRT the plies, tires used to be reported as "x" plies, but materials improvements now allow less than, say 14 plies, with only 12 plies "rated" as 14PR. The Hercules tire is getting good reviews here and on other RV sites.