Load Range D Carlisle Tires

[Pete Dumbleton]

Here's a recent post from Yahoo Scampers:

QUOTE
For what it's worth, I recently bought ST185/80D13 D-rated Carlsles
for my 16' Deluxe from tiresunlimited.com, a supplier referenced in a
KB posting a couple of months ago. The tires arrived in 3 days. 3
tires at $62 each, plus $25 shipping came to $212. Mounting,
balancing, and valve stems added another $20 per tire.

Our local Fleet-Farm store could order them for about the same price.
END QUOTE

I would add that were I doing this, I would be sure to get lug-centric balancing and I would also get the metal valve stems with the higher pressure ratings (Load Range D typically uses up to 65 psi).

[Brian B-P]

I notice that in addition to the load range of "D", these tires also have a construction type of "D", meaning diagonal ply, a.k.a. bias-ply... not radial. Anyone considering these might want to keep that in mind.

[Neil W']

What do you all consider the pro's and con's of "D" bias ply compared to radial. I have recently put 15" D's on my boler. I went with the bias ply as I was wondering about sway and wanted the stronger side walls. I know radials will last longer but I doubt if many of us will ever wear out a tire from miles but will usually replace them from age long before they actually wear out.

[Brian B-P]

I don't know of any advantage to bias-ply tires, and have no reason to expect them to be stronger. A Load Range D bias-ply is stronger than a passenger car tire... but so is a Load Range D tire of any construction.

The bias-ply sidewall may be stiffer, rather than stronger, but I can't imagine how this stiffness might be required for a trailer when it is not required for heavy commercial trucks under much higher loads, or high-performance cars with much greater need for responsiveness.

Radials have replaced bias-plys in essentially every type of vehicle, except where cost is the only significant factor (such as my wheelbarrow). Even tractors and heavy equipment often use radials now, and I doubt that a car has been sold in North America with bias-plys for over 20 years.

Having said that, I'm sure any tire which actually meets the Special Trailer specifications in a suitable load range - radial or bias ply - will operate safely and adequately. And I agree that tire life - in terms of distance traveled - is not important to most of us.

[Neil W']

It was actually the dealer "Kal Tire" who suggested the sidewall would be stiffer than the radials and help with sway. I did say stronger the first post. It sounded reasonable to me because back in the 80's I had a van which I had fixed up, bed. couch etc. all home made with plywood - heavy. I decided I wanted to try the Kevlar tires that Canadian Tire had just come out with. They said they were an excellent tire and would be good for my vehicle as it was only a pleasure vehicle. After changing tires twice in a short time due to sidewall cracking the srervice department decided due to the weight and height of my vehicle I was getting too much side sway. Because they originally recommended the tires when they had to be changed the third time he gave me heavier truck tires at no cost. Problem solved. These memories came back to me and when the dealer suggested it I thought with the height of my 17ft Boler it sounded reasonable and was just wondering if anyone else had experience with it.

[Steve L.]

The strength requirements are a function of the load rating. The bias ply tire will be as strong as a radial ply tire of the same load range. The sidewall stiffness will be higher with a bias ply carcass but I too don't know if that really matters. The only difference I know of is that the rolling resistance will be much higher with the bias ply tire so some or all of the fuel efficiency of our light weight trailers will be lost.

[Brian B-P]

Our trailers are relatively tall and have relatively high tire loads for the tire size. Most commercial vehicles have the same issues, which is why passenger car and commercial tire specifications are different; a light commercial delivery van would be a good example of a motor vehicle with trailer-like demands... and I have not heard of such a vehicle being delivered on bias ply tires for quite a few years.

The van on passenger-car fabric-reinforced radials a couple of decades ago probably needed a light truck or commercial tire (at the time perhaps a bias-ply), and I believe that the same vehicle today would be best served by commercial-service radials.

[ronsmith100]

Pete that guy surely got the tire brand name wrong... no way it could have gotten passed the "K" tire censors! LOL

Brian I have two sets of tires. The 14" Goodyears that came with the my 17' casita and a set of 15" bias ply. There is a great advantage to bias ply on the tire slitting rocky roads I travel frequently. They are far more resistant to knife rocks on all sides. They are also much taller giving me more clearance for ditches and berms.

So I change out depending on where I am going: Bias ply off road, radials highway. But I am not hesitant to take the raidials on some dirt roads or the bias ply out on the highway either... but just occasionally.

Ron

PS the bias ply trailer tire was suggested by every rancher out here ion the Arizona Strip but I am pretty sure 99% of you would not gain much advantage with them.

[Pete Dumbleton]

Ron, I didn't know there was that much difference between the B-P and R tires in that regard.

If it is convenient, I recommend lowering the tire pressures when you are towing on the sharp stuf, and carry a compressor for re-airing when you get back near the highway.

Anyone who doesn't understand this should take two balloons and blow one up hard and one soft, then spend some time slowly poking them with a finger, gradually increasing force and poke-speed. It will quickly become obvious what high speed and high pressures do to air-filled rubber.

[ronsmith100]

Ron, I didn't know there was that much difference between the B-P and R tires in that regard.

If it is convenient, I recommend lowering the tire pressures when you are towing on the sharp stuf, and carry a compressor for re-airing when you get back near the highway.

Anyone who doesn't understand this should take two balloons and blow one up hard and one soft, then spend some time slowly poking them with a finger, gradually increasing force and poke-speed. It will quickly become obvious what high speed and high pressures do to air-filled rubber.

Pete I do take the air out of my tires when I go way way back into the hard road boonies. But I do it (I think) mostly for rivet preservation... to soften the ride.... to keep my casita in one piece. I wish I could give you proof that it worked but I cant. I am going to assume it does though based on reason, not science. The only anecdotal proof I have that this works is that the innards of my trailer appear to be more in order than disorder if I let out the air. But again.. anecdotal. Those Bias ply tires are really really hard and would probably shake my egg apart if I left them at 60 pounds.

Ron

[Brian B-P]

I suspect that much of the difference attributed to bias-ply versus radial construction is actually the result of other aspects of the tires, such as sidewall rubber added specifically for protection (not pressure or load capacity). Of course, in Ron's case, we're also comparing different sizes and brands.

I think that the recommendation of "99% of" any user group often has more to do with what worked for them years (even decades) ago when they settled on their personal standards, rather than the best current choice.

[Steve L.]

(geek moden)

Lowering tire pressure lowers the spring rate of the tire. Impacts to the contents of the trailer are largely a function of how the tire spring rate matches up to the spring rate/damping of whatever suspension you have in the trailer. Changing the pressure can either improve or worsen things depending on your particular trailer.

Lowering the pressure will increase the bulging of the sidewall and will expose it to slightly more contact with "stuff" just to the side of the footprint. As mentioned the lower pressure is slightly more tolerant of penetration by those pokes and prods. Light truck tires (and ST type tires) carry less load per psi of inflation. By definition they are designed to operate with less deflection than the same size passenger car tire so they see less sidewall damage.

As I've mentioned before, the air carries the load. The sidewalls just contain the air. We used basically minor variations of the old boiler formulas to calculate the strength of the sidewall required to contain the air. The higher the pressure the more strength required to contain the air. Once you've determined the required strength, you find that bias tires are a less efficient use of the sidewall cord's strength so there are more and/or stronger cords. So there's more "stuff" in there to resist penetration than for the same size and load range radial tire. (It nets out to the same burst strength.) Because the LT tires need more air for a given load and thus have stronger sidewalls is another reason they are more robust to sidewall damage (in addition to the deflection reasons mentioned above.)

(geek mode: off)