More fun with tires :-)

I suspect a mistype.

PR (Ply Rating) and LR (Load Range) are directly linked with no deviation. The way to tell which is the mistype is to look at the max pressure. As a general rule, LR C have a max pressure of 50 psi, LR D = 65 psi, and LR E = 80 psi (Please note that some sizes have exceptions to this "rule".)

I was suspecting a "mistype" in the ad... but I see in others that even carlisle appear to have "multiple rating" for the 14 in size (and others) with both C and D. Is this the "new direction" especially at the 14 inch size which seemed to not have many options left in recent times?

The ply rating is meaningless nowadays. Archaic terminology.

CapriRacer is one of our tire engineers and certainly one to answer your questions.
However a 14" C and D load range ST tire is nothing new or a new direction as you call it.
We've had C and D load range ST tires since the ST tires first became available for light weight trailers (all types) many years ago.

Actually the tire industry still use "ply rating" terminology in their mfg and dealer adds usually such wording as say a 6 ply rated load C tire. Six ply rated doesn't mean six actual plies.

Kanata Ontario? If you need tires now the Maxxis 8008s are on sale (25 percent off) from the manufacturer. They have good reviews and seem to be well liked on the forums. Order online from Maxxis Canada and they ship to your door for free.

thanks for the info and comments... I will look thru the listing with the guidance that has been provided here as my tires are getting "there".

When I purchased Carlisle's for my trailer a few years ago, their ST Radial Trail was available in C and in D load range. I bought the D load range and have been happy with that decision.

I moved to Ds also, westend. The additional capacity is comforting.

As stated ply rating is not often used. The load rating is the most common. With the used of steel and various plastic compositions it seem the "ply" number were phased out.

My tires are rated C at 50 psi and D at 65 psi. At 50 psi they are rated 140 lbs. more than the 7000 lbs. max axle rating; at 65 psi they are more than 1000 lbs. over the axel rating. However they definitely transfer more shock to the TT at 65 psi.

Since the scales tell me that my 7000 lbs. axle pair are only carrying 5600 lbs. when I am loaded for the road, the C rating would be fine but the D rating was only $20.00 more per tire.

I bought the TT used and put over 15,000 miles in three years on the original C rated tires. I changed them because they were 7 years old. I had the D rated tires two months and hit a road hazard that bent the rim, shredded a tire and broke a spring.

Road hazards have very little respect for tire ratings or price. :)

A little background on the term "Ply Rating".

Way back when, tires were mostly made of cotton thread (and were bias tires) - and pretty standardized thread size and breaking strength. In those days, a tire's strength could be gauged by the number of plies it had.

When synethic fibers came along - notably nylon - the tire could be built with fewer plies and retain the same strength - hence the term "Ply Rating" (PR). Nylon came in a number of strengths and one could build a tire with different number of plies at the same strength. In other words, not only were there fewer plies than with cotton, but a different number of nylon plies depending on how the tire was engineered.

It didn't take very long for people to be confused between ply and PR, so the tire manufacturers created the term "Load Range" and used letters. This occurred in the 1960's. However, many people had a hard time moving on and kept using PR - and kept being confused when the number of plies didn't match the PR number.

So when radial tires were introduced and steel wire became the common belt material, the connection between the number of plies and the PR became even more remote. As an example, over the road truck tires (18 wheeler variety) the common construction is 1 steel body ply and 2 steel belts with perhaps a protector (non-working) belt or 2 (frequently steel as well!)

In the ST and LT tire lineup, the common construction is 2 polyester body plies with 2 steel belts with perhaps a nylon cap ply (or 2).

When tire engineers talk about tire strength, they are referring to the body plies in radial tires. The belts stiffen the tread area, and don't affect the strength of the sidewall. So while an LT tire may have 6 tread plies (2+2+2), it's the sidewall that determines its Load Range - and because of the variety of fibers available, a LR C can have the same number of plies as a LR F.