Is it OK to change tire size on duallies?

Question from RVer on a forum

“I need six new tires for a 2004 38-foot Dutch Star on a Spartan chassis. Michelin tire models and sizing have me totally confused. Current Michelin size is 275/80R22.5. Dealers claim this Michelin size is interchangeable to 295/75R22.5 from brands that don’t offer the original size. They tell me there will be no ill effects on the drive line or instrumentation.” 

 My response:
I was concerned with this possibly incorrect information. In this case, the two sizes have the same load capacities, so that was not my concern.

Some folks replied to the original question on the forum by suggesting he use this tire size website or similar websites to learn about tire sizes. I did have a little problem with using such a “tire size” site, as the information is aimed at car applications and does not include special information regarding dual-tire applications. Also, the resulting numbers may or may not match published industry standards.

I pointed out my concern about the Minimum Dual Spacing (MDS), which is a published dimension in industry standards and has been covered previously in this blog.

Some folks reported that they have changed tire sizes and had no problems, implying that any change might be OK

I provided this graphic to help people understand what this dimension is:

As you can see, the wheel offset and even wheel thickness can have an effect on this spacing. I also pointed out this example: 275s have an MDS of 12.24, and 295s have an MDS of 13.19.

Let's assume that with your wheels and with the 275s you have a physical 1.00" clearance down at the bulge in the sidewall near the road. So if you don't change wheels and put wider 295s on the new, clearance will be 1.00 - ( 13.19 - 12.24) or 1.00-0.95 or a final clearance of 0.05", which is clearly too small.

I hope that those considering changing tire size consider not only the load capacity, which is very important, but also the dimensions.

 

Problems with small trailer tires.

 Roger, back in March 2024 I bought a Bear Track Aluminum Trailer to tow my new-to-me Harley Trike. The bed is 10', trike fits great, trailer weight 400 lbs and I love it. But not so happy about the tires. For one thing, I just found that when I bought the trailer, the tires were already over 2 years old, date stamp is "0822". Anyway, we did a short trip in Apr 2024, all was fine. Then a big trip in Oct 2024 and about 80 miles from home we had a flat. A puncture, so not the tire's fault. But then in March 2025 I took the trailer back to where we bought it, because one side the wheel wiggled. They said the bearing needed tightened. They did that under warranty, but also told me the tire on the other side had a broken belt. They got that replaced under warranty as well. Then just last week, returning home from a 5 day trip, the other tire a belt broke while on the road and the tire went immediately flat. So now, all 3 tires, only the patched tire (now the spare) is even usable.

So my question is, what brand do people recommend most for trailer tires and where can I get some that were made very recently. The ones that came with the trailer are MasterTrack UN203 Branded, Size: ST175/80R13, other numbering: 6PR 91/87M Load Range C, rated at 1360 lbs (single) I think that means one tire on each side. So the Trike weight 1200 lbs and the trailer 400 lbs. So that should be 1600 lbs total or only 800 lbs exerted onto each tire. Well below the limit indicated.

Also this tire says Plies: Tread Polyester 1 + Steel 2 Sidewall Polyester 1

I am willing to spend more for a better brand, higher Load Range, whatever it takes.

 

My answer..............

Based on the numbers in your post, I'm not sure why you are having "broken belt" problems. That term is kind of a catch-all, so without seeing the tire and lacking a few pictures of the "Broken Belts", I am doing a little "shooting in the dark, but here goes.

 

An 0822 date tire should not be having belt problems at that light a load. However if the dealer was willing and able to change one tire under warranty at 3 years old and the second tire also having some issue at 3-1/2 years, it is not unreasonable for you to "shop around".

IMO an  ST175/80R13 LR-C when only loaded to 50% of its "rated load" in your type of service should be good for 4+ years assuming it is always fully inflated to 50 psi.

I would suggest you check with etrailer.com as they have both radial and bias tires in LR-D in your size. Even though the etrailer tires are LR-D you can get 1,360# load capacity at 50 psi as long as you keep them inflated to that level.