Do you know that tires have a maximum tire speed rating? They do. This isn’t a big deal for passenger, light truck and motorhome tires because they usually have a MPH rating well above typical highway speed limits.
However, nearly all Special Trailer (ST) tires used on RV travel trailers and fifth wheels have a maximum tire speed rating of just 65 MPH.
You can drive faster than 65 MPH but in order to do that, you need to increase your cold inflation by about 10 psi (without exceeding the maximum PSI stamped on the tire) for every 10 mph over 65 that you are going, as well as decrease your load carrying capacity by 10%.
So, for example, a Carlisle ST225/75RR15 Load range E (10 ply) tire, has a load carrying capacity of 2830 lbs at the tire’s maximum 80 psi. But you will have a decreased load carrying capacity of 2,547 lbs to drive at 75 mph.
If you’re maxing out the load rating of your trailer’s tires it’s imperative that you keep your speed at or below 65 MPH. Driving faster will, at the least, shorten the life of the tires and may result in tire failure on the road.
What I’d like to have, and would be willing to pay for, is the full 2830 lbs load carrying capacity of the LRE tires and be able to drive at a more reasonable speed. Tire manufacturers should realize that RVers aren’t pulling 1960’s travel trailers anymore.