12 Inch Trailer Tire w/ High Load and Speed Rating

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Question:

I need to replace 4.8x12 bias utility trailer tires. I may opt for a tire/wheel combo with radial tires. What is the difference in the numbering system between 5.30R12 and ST145/R12? Is it metric vs SAE? From what I gather off the website, both are suitable replacement options. Also, given your inventory options, why does a load range D radial with greater load carrying capacity compared to a radial with C load have a slower speed rating? I’m looking for the best all around performing tire, but if you want greater hwy speed, one must sacrifice load capacity. In this case, we’re talking about approximately 200 lbs. of load capacity and 65 vs 81 mph speed rating. I understand that with an “M” rating, you can safely recommend the 81 mph speed rating and without it, you must default to 65 mph. However, in the real world based on consumer feedback, is there a significant difference between the two tires and are people experiencing blowouts because they pushed a 65 mph radial tire to 75? I don’t tow any faster than 65-70. My axle capacity is 2,000 lbs. and I will most likely never even come close to towing that weight. However, many consumers will opt for, as I did on my travel trailer, E load over D load tires just for added security and peace of mind even though not necessary. I’m just trying to make the best informed decision for my purchase. Perhaps I’m searching for an answer that is too subjective, but I want to at least eliminate any doubt between the physical properties and limitations of the options when compared head to head. Please advise. I did receive a well appreciated response last night, but I felt it was a bit generic for my needs. Thus, I’m re-enquiring with a bit more detail. It would be great if this message could be addressed by Mike L., as I have dealt with him in the past and he is extremely knowledgeable regarding tires/wheels. Thank you in advance!

asked by: Roger

1

Helpful Expert Reply:

You are correct, the 5.30x12 is the SAE nomenclature, while the 145/80-12 is the closest metric equivalent. The two are approximately the same size with the 5.3x12 being about a tenth of an inch narrower and a quarter of an inch taller than the 145/80-12, so either would be a fine replacement for your current size. I'm not sure which two tires you were comparing to get the size differential but a tire's speed rating can vary between different manufacturers of the same tire size, between load ranges and between a bias ply versus a radial. Long story short, I really couldn't address that without knowing exactly which two tires you were speaking of.

One thing I've found is that trailer tires aren't always speed tested to the point of failure. It's possible that the tire that carries a 65 mph rating is actually capable of carrying a greater rating, but it just wasn't tested for that.

For the highest capacity with the best weight capacity in a 12 inch tire, I'd recommend the Taskmaster # TT53012C. It's a load range C tire with a capacity of 1,050 lbs at 80 psi and carries an M (81mph) speed rating. The combined load capacity of these tires exceeds your trailer's GVWR, so they will work perfectly for you.

The blowout issue is a tricky one. Premature tire failure is caused by excessive heat build-up in the tire over time. This can be caused by a number of things, including failure to observe the speed rating on a consistent basis, continually overloading the tires beyond their load rating or failing to keep the tires fully inflated to the pressure listed on the tire sidewall. Excessive UV exposure can also lead to accelerated deterioration of the tire. As long as you observe those parameters, you should be fine by not using the next highest load rating.

I've linked you to several of our Trailer Wheel and Tire help articles, which have more information than you'll ever want or need about trailer tires.

expert reply by: Mike L

1

12 Inch Trailer Tire w/ High Load and Speed Rating

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