Selecting Replacement Special Trailer Tires for Tandem Axle Boat Trailer

Question:

Looking at trailer tires and was wondering if going to a bigger size would help with towing or do i have to stay with what i have now, the boat weight is 5200lbs and trailer is a load-rite tandem axle , tires are 215/75/14 now and wanted to go to 225/75/14. any info would help ,Thanks.

asked by: Richard H

Expert Reply:

Many trailer wheels will accept more than one tire size. For example, an ST215/75-14 special trailer tire will fit on a 14-inch diameter rim of four different widths: 5-1/2, 6, 6-1/2 and 7-inches. However, we do not offer trailer tires in the wider ST225/75-14 size you mentioned. Similarly, 15-inch trailer tires in size ST225/75-15 will fit on 15-inch rims of several widths: 6, 6-1/2 and 7-inches wide.

What you want to do is make sure the total weight of your loaded tandem-axle boat trailer is matched or exceeded by the combined weight capacity of all four tires. Let's say your 5200-lb boat is on a trailer that weighs 1500-lbs. This makes the total trailer load 6700-lbs in this example. When you divide this weight by the four tires you have a load on each tire of 1675-lbs.

Ideally your tires will have a Load Range rating that gives each one more than this much capacity. Extra capacity = safety margin. In your current tire size ST215/75-14 we offer Load Range C tires like # TTWTR21514 but we also have a Load Range D option too, Taskmaster part # TTWTRTM2157514D that you referenced. This Load Range D tire has a weight rating of 2200-lbs at its rated pressure of 65-psi. Using these LR-D radial tires will enable you to add safety margin to the tires without having to change wheels.

To ensure best performance from any trailer tire always inflate each one to the cold psi pressure rating noted on the tire sidewall. In the case of the Taskmaster # TTWTRTM2157514D this required pressure is 65-psi. It is never appropriate to under- or over-inflate a trailer tire for any reason.

You can expect the longest and most-reliable service life from a trailer tire by always observing its rated pressure, its weight capacity and its speed rating. Some tires can have a higher speed rating than others. The LR-D Taskmaster # TTWTRTM2157514D is rated for highway speeds up to 81-mph, making it an excellent choice for interstate or highway travel.