ST205/75R15 Radial Trailer Tires for Vintage Travel Trailer to Replace 7.00-15 LT Tires

Question:

I just bought a fixer upper 1959 Travel trailer Wt./wheels 3120 with 7.00-15 LT tires. I am shying from buying new 7.00-15s because of the expense of them. I am trying to read through your FAQs on what to use instead which has been helpful but I am still unsure. My question is if I can get the Contender ST205/75R15 Radial mounted on the wheels instead? If this does work, are there any special considerations to look in to first? Any other recommendations? Thank you and sorry to have to ask you the same question youve probably been asked 100 times!

asked by: Danielle

Expert Reply:

We're glad to help you with new tires for your trailer restoration project and good for you for keeping an oldie but goodie on the road.

Tire sizes 7.00-15LT and ST205/75-15 will both fit on certain wheel sizes. Those compatible wheel sizes are 15 x 5, 15 x 5-1/2 and 15 x 6. When you measure your wheels you want to measure from bead seat to bead seat, NOT from edge to edge. Please refer to the photo to see how to measure your wheel's bead seat width.

In tire size ST205/75-15 we have both bias ply and radial tires (either can mount on your rims) and three different weight load ranges. You can see all on the page I linked for you.

Radial tires flex more and maintain better ground contact; they also run cooler than bias ply tires. Bias ply tires have stiffer sidewalls that make them desirable for off-road use. For mostly highway and paved road use radials are the better option.

You will want to confirm the trailer's gross vehicle weight rating (GVWR), the most it can ever weigh, and choose a set of tires with the appropriate load range rating for that weight plus some safety margin. For instance, Provider # TR20515D is a load range D tire that can handle 2150-lbs at 65-psi pressure. For a trailer with GVWR of 3500-lbs, for example, a pair of these would give you a good weight safety margin of 800-lbs. The tire you referenced, # AM10256, handles up to 2540-lbs.

The other consideration is speed rating. Tire # AM10256 is rated to 65-mph but the Provider # TR20515D has a speed rating M, meaning it is good to 81-mph. You want to choose a tire that has a speed rating to match your typical driving habits.

The main things that cause issues with trailer tires are incorrect inflation, overloading and driving too fast. Trailer tires should always be inflated to their maximum COLD psi pressure noted on the sidewall; and they should naturally be operated within their weight and speed ratings.

The other way to protect your tire investment is a set of covers like # 290-3953 which will block most of the damaging UV rays that can cause deterioration.