Bias Ply or Radial Truck Tire?

[Kelvin]

This is "Off Topic" but not "Just for Fun"...

Main Questions:
(1) Which type tire is better for a dually truck which carries a load, bias ply or radial?
(2) Are there narrower dually rims that would provide less clearance than standard dually rims?

Details:

I have a 1974 Ford F350 Dually flatbed truck with 7.50x16 bias ply tires that I haul my tractor on. The wheels are not split rims. With the tires filled with the maximum 60 psi pressure, they have about a ¼” clearance between tires when there is no load and they touch each other (usually they barely touch) when my tractor is on the truck.

Additionally, the tires are showing signs of dry rot and leaking from the sidewall.

So, it is time for new tires. But when I get these new tires I want to cure the “tire touching” problem at the same time. I’m convinced that simply buying new 7.5x16 tires will cure the dry rot problem but not the touching problem. Buying new (standard?) rims should cure the problem, assuming that I somehow have some type of narrow rim.

Regarding tires, this is what I have been told so far by various experts(?), and items 3 and 4 disagree with one another. I would like to get a reality check on the information:

(1) 235-85-16 radial tires are the same height as 7.50x16 bias ply tires but are slightly wider, which would make my tire touching problem worse.
(2) 215-85-16 tires are narrower than 7.50x16 bias ply but are also not as tall
(3) Radial tires have a softer sidewall and aren’t as good as bias ply tires for load carrying applications
(4) Radial tires are better than bias ply tires for load carrying applications.

Thanks for any information,
Kelvin

 

[Bird]

Kelvin, I don't know just what kind of wheels you have, but there were some wheels that were made for bias ply tires on which you do not want to put radial tires (the angle of the rim where the tire bead seats against it is different). I do know that you don't want those duals touching each other, of course. And I agree with the guy who says radial tires are better for load carrying applications (look at what you see on the 18-wheelers today), but of course you have to have the right sized radials and the right wheels; width of the wheel is an important factor and I don't know what you have.

 

[cp1969]

I sounds to me like someone has put the wrong wheels on this truck. The tires shouldn't even come close to touching, even under a full load.

As far as carrying the load, 7:50-16's will do it just fine, but you'll probably have a hard time finding them. That's a tube tire and they're getting scarce. It also surprises me that the wheels are not split rim. I didn't know you could use a 7:50-16 on a non-split rim wheel. That's another reason why I think the wheels are wrong.

 

[Kelvin]

Wrong Wheels?:
I get the feeling that the dually wheels that are on there do not have the normal offset, and therefore agree that they are probably the wrong wheels. I have never seen dually wheels that close together. Problem is, how do I go about proving it? I want the tires and wheels to be as safe as possible and will replace the wheels if need be; I just don't want to spend 6x$56.00=$336 just to find the new ones to have the same clearance.

Finding 7.50x16s:
Apparently 7.50x16 tires aren't that hard to come by; my retailer said that he could get them within a week versus the normal same day or next day service.

Tubes:
The 7.50x16 tires that I have are tubeless tires ("Tubeless" is printed on the sidewall) that are mounted without tubes.

<font color=blue>7:50-16's will do it just fine</font color=blue>
If the radial equivalent (235-75R16?) performance, safety, and cost are the same or better than the bias ply, then I believe that I'd prefer going radial.

Kelvin

 

[Kelvin]

Bird,

This is the first that I have heard about different rim designs for radial vs bias ply tires. Is this something that is applicable to all vechicle types, or just some types (such a the big-rigs)?

Kelvin

 

[RobS]

Just a thought Kelvin, do you have any truck/van conversion companies nearby? There's a bunch near us (Elkhart, IN) and they sell brand new "take offs" from the vehicles they convert. Usually steel wheels with brand new tires that they replace with fancy aluminum wheels and spiffier tires. You can usually pick up an entire set for about the cost of the tires. I have seen sets from duallies. If you want some phone numbers, let me know /w3tcompact/icons/smile.gif

 

[Bird]

<font color=blue>applicable to all vechicle types, or just some types</font color=blue>

I really don't know a lot about that, Kelvin; just that my brothers told me about encountering the problem when they were new in the tire business quite a few years ago. If I remember right, the old (probably very old) wheels for bias ply tires had a rim (bead seat) that was almost perfectly vertical while the newer rims have a slight angle. Better check with someone whose knowledge is more up-to-date than mne.

 

[Kelvin]

I have continued my "research" into the subject of which tire type is better for load carrying applications. I was hoping to find something "in writing" from a manufacturer.

Then it hit me...

Every tire that I have seen has a load rating printed on its sidewall. Here are the numbers that I found; it didn't seem to matter which company manufactured the tire:

The maximum load for the 7.50-16LT M&S bias ply tires (Load Range D):
2440 lbs single
2140 lbs dual

The maximum load for the 235-86R16 (Load Range D) radial tire which is supposedly the same height but slightly wider than the 7.50-16:
3042 lbs single
2778 lbs dual

The maximum load for the 215-85R16 (Load Range D) radial tire which is supposedly slightly shorter and narrower than the 7.50-16:
2335 lbs single
2150 lbs dual

Soooo...
It looks like the smaller radial tire has nearly the same load ratings as the 7.50-16 bias ply tire, while a slightly wider radial tire has a fairly significant improvement. At least according to the writing on the (side)wall...

Kelvin

 

[rdln]

Was in same situation last year with my 1979 f350 dually, replaced 7.50-16 bias plys with used LT215/85 R16. Yes they were shorter but didnt care. The set of six cost $150 mounted. I heard that in the early 80's dually wheel offsets became greater to accomadate the radial tire bulge. Can you find and get by with a set of those used tires and keep an eye out for newer rims?

Also, I learned that same size tires with less wear should go on inside rims of dually setup and more wear on outside rims to reduce bearing stress.

Beware!!! after switching from Bias to radial tires you might swear that you are in a new truck!!

 

[Kelvin]

rdln,
I have found a supplier that can get NEW dually rims for under $40 each. I ordered some today. I will probably go with (4) 235-75R16s on the rear since my truck already has that size tire on the front.

It doesn't matter now, but I also found out that they make a 7.50-R16 RADIAL tire. I thought that 7.50-16 only came in a bias-ply tire. Learn something new everyday.

Kelvin