How to Select Size, Load Rating and Speed Rating for Special Trailer Tires on Pontoon Boat Trailer

Question:

been looking around for a pontoon trailer and noticed alot of manufacturers offer 12 inc tires as standard. a marina owner showed me a trailer with 10.5 tires does it make a big difference. i am not doing long hauls on weekends but heard that 12 inc make driving more stable but i also read here on this site that 10 are good for long hauls. i wanted 12 but got 10.5 should i be concerned. and insist on 12. thank you

asked by: Willie M

Helpful Expert Reply:

12-inch trailer tires are in much wider use than 10-inch tires but the tire size in itself is not really what matters, apart from them fitting properly inside the fenders or wheel wells. What is most important in selecting trailer wheels/tires is having ones with the appropriate weight load range rating for the actual loaded weight of the trailer with the boat, and having tires that are rated for your typical driving speed. Some trailer tires are rated only to 65-mph but others can be rated for the higher speeds that are likely for trips on the interstate.

First, determine what the total weight of the trailer loaded with the boat will be and include things like gas tanks, sporting gear and anything else that will be in the boat and on the trailer. Once you know this total weight divide by the number of tires on the trailer, as in 2 for a single axle or 4 for a tandem axle.

A pontoon trailer typically weighs about 1200-lbs; most pontoon boats weigh about 2200-lbs including the motor. So if we use a total of 3500-lbs for our example of a loaded tandem axle trailer this means that each of the 4 wheels/tires must be able to handle at least 875-lbs. Naturally you want to use wheels/tires that are rated for more weight than this in order to have a safety margin.

In the 12-inch size ST145/80-12 we have Kenda wheel/tire item # AM31202. This is a galvanized 5-lug wheel fitted with a Load Range D radial tire. This product has a weight capacity of 1220-lbs which for our example means that it would provide an excellent safety margin for weight capacity. This wheel/tire is rated for 65-mph.

In comparison, the Taskmaster 4.80R12 Radial Trailer Tire and Wheel # TA98RR has a Load Range C weight rating of 990-lbs but it offers a higher speed rating of 81-mph.

The main things to do with ANY trailer tire are to maintain the maximum COLD psi tire pressure which is noted on the sidewall; operate them within their rated speed; and operate them within their rated weight capacity. Doing these three things consistently will help avoid the excess heat that is the single worst thing for a trailer tire. The wrong inflation pressure (too high or too low), driving too fast or putting too much weight on the tire all cause excess heat which is the condition that is most likely to lead to a failure.

I linked two helpful articles on tires that will give you additional information but please feel free to reply if you have any further questions.