I have a Carry-On utility trailer (2990 lb GVRW).

It uses a ST205/75D15C tire. I notice Walmart and others sell a spare tire labeled ST205/75R15D with rim for $86.99 or ST205/75D-15 with rim for between $75 and $97 and others as well.

My question is what is the R vs D mean. I only want it as spare. When new tires are required I will buy a decent set for regular use.

It seems prices vary widely. Since I only want it as spare I was assuming the cheapest might be OK. I planed on getting it via Internet purchase or the Walmart route.

Any comments?

 

just seems to be construction type R=radial or D=bias they both can be used on trailers but seems radial is probably more common. would probably use whatever matches your existing trailer tires.

 

To be honest I though bias tires were a thing of the past. Never connected the dots. I suppose for spare bias will do the job.

 

I like my spare tire to be the same as the others on the trailer. That way if you use it you can just leave it in place as the new daily use tire. But, given the chance I'd be upgrading to radials.

 

I agree with liking to keep the spare the same as what are on the trailer, but my preference for trailer tires is bias ply. I have read, for whatever that's worth, that bias ply tend to have less sway, but think that how the trailer is configured and loaded has a whole lot more to do with sway than what tires are under it, and there are obviously a whole lot of trailers running the roads on radials, so don't know how significant that by itself is. From a personal perspective, I always check tire pressure on the trailers before leaving, but, particularly on a long trip, give them a visual check periodically, just like checking ratchet straps, etc., and have noticed that a simple visual check can be a bit deceiving sometimes with radials if everything isn't setting on a flat plane. Lastly, I think that bias tires are a little easier to back on soft ground because they stand more upright. And of course, any of these reasons vary by individual usage, and may or may not be relevant, so it still goes back to personal preference.

 

Regardless of being a radial or bias ply tire the main consideration is the weight carrying ability of the tire which is stamped on every tire.
it is possible when buying bargain tires for a trailer that they will not meet the rating of the trailer or load you are carrying.
It is also one of the first things highway inspectors look at if you are ever inspected.

 

In my opinion,

The D means that the tire is an oblique bias-ply form and the R means that the tire is a spiral tire production. Behind the size and type, there are load limits for tires.