The Stovebolt Site Forums The Shop Area General Truck Talk Question about tire ply's

I have been researching tire options for my 1/2 ton.. I have searched old threads on this form trying to dig up answers but have only confused myself more at this point..
Currently I am running 225/75R15 steel belted radials. The overall diameter of the tires according to my tape measure is 27".. I have heard that taller narrower tires are the best tires to run on the stock 15" rims for these 1/2 tons.. Plus they seem to look cooler to..
Anyway, Firestone and B F Goodrich have a 820-15 tires with an overall
diameter of 29.56" and a tread width of 5.40"... They are calling them two ply polyester tires.. (don't know what that means?)
I read an old thread on this forum that 8 ply tires on these 1/2 tons may make it ride a little rougher..
What I'm shooting for is a quality steel belted radial that is narrow and tall and doesn't cost a fortune.. But I am not privy to the lingo about tires and what to look for.. The above mentioned tires didn't say if they were radials or steel belted either.. So I'm not sure what I'm doing.. I understand the difference between bias tires and radials.. After researching them I have decided that for my application, radials are the best choice.. Now it's just a matter of making sure I buy the best choice for performance, longevity, durability, esthetics and economy.. Seems like a lot to ask for huh?
Anyone want to through in their 2 cents?

First I'm no tire expert, but most of what you ask is general.

Over all diameter does not need to be that precise. If it does need to be precise, find the factory size for you truck. The original tire was bias ply, and radials are just not the same. The BFG 820 sound like a large tire IIRC.

There are two factors (and probably more), the side wall height, and the number of plys. The shorter the side wall height the harsher the ride and the more plys, stiffer the side wall. You don't need a lot of plys, if you don't haul heavy loads and the roads you drive are with out pot holes.

When I buy tires I usually buy tread width to match rim width. I want my sidewalls to be vertical. Radials are the best tire for mpg.


Larry

Depending on whaether you're looking at P rated/P rated XL or LT rated tires as to what the ply ratings are. The size will determine what ply ratings are available. Unfortunatly, tall and narrow is somewhat of a rare bird in the tire world these days, especially in a 15" radial.
First, I suppose some explaination of ply ratings is in order. You mention the 8.20-15s from Firestone and BF Goodrich that are 2 ply. In this case, those are the old bias ply tires. The ply rating is simply the number of fabric plys (originally cotton, later polyester and even fiberglareinforced polyester) that the tire had. More plys=stronger/heaveir load rated tire. In todays tires, the "ply rating" is really more of a "ply equivalent", as the tire itself may not actually have the same number of plys as the bias equivalent.
Now, on the ratings. The 2 ply tires mentioned are not for truck use, strictly passenger. For the most part, trucks use at least a 4 ply tire on 1/2 tons, with 6 ply optional. Depending on year, heavier trucks can get into 10 and 12 ply tires, depending on size. Whith todays tires, the lower ratings are enerally taken care of in the P-Metric tires, with a P rating being 3-4 ply, depending on size (larger tires tend ot be 4 ply). There is also a 5 ply, which is the P-XL, almost always a 235/75/15, though there are some P rated light truck tires in 16" and 17" that are coming in XL ratings, too. The LT tires use a different rating system, though still based on ply equivelent ratings, they use a letter system to designate the rating, called "load range" in tire terms. For light truck tires, for the most part you will see "C"-"G" ranges, "A" and "B" are used mainly for light trailer use, and the "B" rated truck tire is obsolete, havng been replaced with the heavier P/XL tires. The low end "C" range is a 6 ply tire, with each letter after being 2 plys higher rating. Most light trucks stop at "E", the heaveir range tires start getting into 1 1/2 ton trucks and also 19.5s.
Now for what you have. With a 15" rim, while there are many choices, tall and narrow are not really one of them. 235/75/15 is about the largest available without going into floatation sizes, which start really getting into wider tires in addition to taller. If you want tall and narrow, you're alomost going to have to go to a 16" rim, using either a 215/85/16 or 235/85/16.
<y personal suggestion, go with the 235/75/15, preferrably in a P/XL or LT range C. That will handle the load of a truck without loosing the ride quality, and you will still be able to use it to haul stuff in needed. If you don't mind a little stiffer steering, a 30x9.50x15 C range floatation tire would be another choice. That will get you a bit taller tire than the 235/75/15, but not really get too wide. Go for a highway type tread, I'm partial to Michelin LTX/MS myself. ALso, you want to make sure you have the proper wheel to handle the stesses of not only a radial tire, but also the give proper support to the tire. A 7" rim is fine for the 235s, an 8" is better for the 30x9.50.

Thanks longbox55 and LGriffin..
I appreciate you guys taking the time to give me the breakdown.. I'm learning as I am going.. In the past 6 months I've learned more about mechanics and old cars and trucks than I ever thought I would.. It seems like you almost have to if you wanna be using an old truck as a daily driver.. So far I regret nothing and I am enjoying myself very much..
As far as the rim sizes, I was actually looking for a 16" 6 lug rims at one point.. But I couldn't seem to find anything in new production that looked stock enough except for some steel rally wheels i found.. But the width of the rim is what I wasn't sure about.. I think the stock steelies I have on there now are no more than 6" inches wide.. Of corse I really wouldn't be able to tell unless I remove the tire and measure it.. But near guesstimate is 6"..
I looked for 16"X6" Rally steel wheels but couldn't find any.. Any suggestions? Maybe I just have to go with a 16"X7" Rally?
I may end up just running the 235/75R15's and calling it quits.. My R&P is plenty tall now (3.07).. But those tall thin tires look so RAD..!!
It seems I could throw the bias plys which are cheap and and lots of options available.. But I know the radials are the way to go for performance and fuel economy..
So longbox55, you think maybe my rims are a tad to narrow at 6" for those 30x9.50x15 C range Michelin LTX/MS floatation tires?

Yes, a 6" would be too narrow. What would happen is you would get severe wandering due to a lack of sidewall support. You could get away with 7" rims if you can't find 8", though. You will find in the long run, radials will win hands down. Longer life, better ride and handling over the bias plys. Also, bias tires have really gone up on price the last few years, especially in sizes and load capacities that these trucks need.
BTW, If you wan't to see what the Michelins look like, clink on my signature below, it will take you to pix of my turck, which has them on it.

Nice tires Bill.. And your truck is awesome.. It's the same color as mine.. So those rims on there are the 8" rims??

Yes. 15x8 Blazer Ralleys, they were a std Chevy/GMC 4x4 truck wheels offered from '73-'87 ('91 on Blazer/Jimmy and Suburban). Kelsey-hayes still makes them new, which is were I got mine from. They fit perfectly, no rubbing, and the handling is great.

Sweet.. They are handsome.. A little wider looking than I was hoping for but still a sharp looking tire and wheel... Also, as a matter of interest I was wondering if I could get the traditional half moon hubcaps on there as oppose to the pop through caps you have on yours?

These wheels don't really have a provision for moon caps, but I suppose clips could be added to them. There are holes for the original screws for the factory caps that one might be able to use to attach clips to. The caps I'm running are from a '94-'98 1/2 ton 4x4, the actually have the black plastic "nuts" that screw on over the lug nuts, just like the late model GMs do. It was really kind of a fluke, as I managed to find the special lugnuts I needed at a swap meet. Normally, those nuts are only available in 14mm thread, but I found a vendor that had them in 1/2-20 std. I'm not really certain of a source for those lug nuts, though.

Cool Bill.. thanks for the info.. definitely gonna get a close up look at those in my search.. they are real sharp looking..
Have to find out about the moon caps and look at some other rims.. I know the 16" steel rally's you can put the moon caps on..

AH, I think I see which wheel you might be thinking of. The whel you've looked at is the Corvette style Rally (5 slot), where mine are the Blazer Ralley (10 slot). The Blazer ralley is designed to use a bolt on cap, where the Corvette Rally (or Disk Brake Wheel as used on Chevy SS models) was designed to use a pop on cap. The Corvette style Rally can be used with the moon cap, and is also available in 15". There are several companies that make them now, along with a variant usually referred to as a "Smoothie". That one is basically the 'Vette rally without the slots.

Yeah, I think your right Bill.. I can't for the life of me find the web link now.. They were 16" X 7" if memory serves and they were 5 slots with option finishes, chrome, flat black and something else.. Also , you could use them on drum brake types of axles.. Does that sound right to you? I seem to remember reading that they worked on both disk or drums.. perhaps I was seeing things? It has been a while since I saw that web page..