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Bex · 08-06-2012, 07:50 AM

I need to get 6 tires for our 97 6.5 TD Silverado duallie. Problemis that the tire shop want me to buy e rated tires and not the SL which I believe is Standard Load. He says to go with the E because its 10ply and has a high load rating. Looking at the tires, and these are the ones, what would you buy? We don't haul heavy loads with the duallie and we pull a 26 ft Argosy so tongue weight would be in the mid 600's for Lbs.
Here are the tires:
245/75R16 111/S
245/75R16 111S
245/75R16 120/116Q

They are all light truck tires. The 111/s load rating, as far as I can tell gives me 2400Lbs per tire or the first two and 2800/3100 for the last. Am I missing a point here or is the Guy just playing safe or up-selling me? Only thing I can come up with is that the load ratings might reduce for a duallie but even if they did, I would still be within range wouldn't I?

Any info, as ever, gratefully received.
I will be getting the tires later today as they are all on sale but the purchase of 6 can make $240.00 of difference on the purchase!

Bex

Phoenix · 08-06-2012, 11:05 AM

Not sure where you are shopping for tires; but for comparison, check Tire Rack - Your performance experts for tires and wheels.

On this site, the difference between SL (passenger car, 2271 pounds @ 44 psi) and E rated (light truck, 3042 pounds @ 80 psi) is $10 only per tire. With a curb weight of between 5,000 and 6,000+ pounds, and using your truck as a tow vehicle, I'd definitely get the E rated LT tires.

In addition, Michelin and BFGoodrich frequently offer $70 off per set, which would more than offset the $60 difference in cost. And, if this rebate is currently unavailable, it should be coming back soon, with Labor Day approaching.

If you were using your dually as a daily driver and never towed with it, you could buy the passenger car tires. However, for a tow vehicle, I don't understand why you don't want to install LT tires.

Note: Costco has pretty good prices and fills tires with dry nitrogen for free. Alternately, Discount Tire matches nearly all competitors, including on-line Internet prices, and they fix flats for free, even if you bought the tires somewhere else.

Bex · 08-06-2012, 11:44 AM

The tires I referenced are all LT tires.
I am in Canada and shipping is cost prohibitive.
Canadian Tire is where I am getting the best prices on the tires I referenced.
Original Spec for the truck is 225/75/R16 D so if I go that route I can get tires with a load rating of 1984Lbs each which is in line with the GAWR on the vehicle which is 7500Lbs these tires are 118.49 each. In contrast, the tire the shop manager has put forward are 149.99 each. Difference of 189.00 (I see I made an error in above posting)

SteveH · 08-06-2012, 12:01 PM

Tire shops will always sell you the type tires your vehicle manufacturer specs for that vehicle, and in your case to get to the capacity of the one ton duelly, I'm sure the "E" rated tires are needed.

Now if you want to reduce that capacity, that's another thing, but the tire dealer may be concerned about his liability, and I know they would be here.

Bex · 08-06-2012, 03:04 PM

As I said, the previous owner changed tires. Original spec called for 225/75/R15 load D. Thats whats causing my confusion. I know he used to transport horses so might have needed the additional loading. As the tongue weight is only about 650/680 lbs at most, I think the original spec'd tires will be OK. I understand they would have a liability issue but I am only buying them, not having them fitted. I will get my regular shop to do that for me.
I guess I could have worded my original post differently.
If my GAWR is 7500lbs, what minimum tire load rating do I need for a duallie?

SteveH · 08-06-2012, 03:07 PM

Another thing I think you'll find is the tire dealers are concerned with selling the tires they actually have in stock, and that might be his "deal".

Bex · 08-06-2012, 03:17 PM

SteveH. I very good and valid point.

r carl · 08-06-2012, 05:03 PM

It appears you should go with load range D tires.

Bex · 08-06-2012, 06:56 PM

Finally found an explanation I can understand for load ratings, as they relate to Passenger vehicles and light trucks:
Tire Load Range Explained | eHow.com
So now I am (fairly) confident I am OK with the lower priced, D rated tires at 65psi (assuming the ehow article is correct!)

rumrunner · 08-06-2012, 07:21 PM

There should be a placard on the drivers side door post or frame with the original mfg recommendations as to size and load rate of the tires. Do not use the current tires for reference- who knows what the PO was thinking.
Most if not all dually trucks in current production require load range E tires. If you downgrade the tire specs you will probably have trouble with your insurance company in the event of an accident and most major tire chains will not warranty down graded tires. Too many things can go wrong here, heat build-up, decreased load capacity, excessive suspension sway, etc.
tim

Bex · 08-07-2012, 06:10 AM

Tim; thats the cause of my confusion! Mine is a '97 and the drivers door placard says 225/75/R16 D
With mods (most of which I have) the truck is capable of towing/hauling much more but is rated low for various reasons (most to do with over heating)
My concern was that the tires I was looking at were SL rated which is the designation for "standard load" and I thought that meant max 35psi pressure but that actually means standard load for the rating so for the tires I am looking at its up to 65 psi for the max standard load of 1984lbs per tire which I think is plenty for my daily use and Argosy towing.

Bex

Phoenix · 08-07-2012, 10:13 AM

"...the tires I was looking at were SL rated which is the designation for "standard load" and I thought that meant max 35psi pressure but that actually means standard load for the rating so for the tires I am looking at its up to 65 psi for the max standard load of 1984lbs per tire which I think is plenty for my daily use and Argosy towing."

=============

"SL" does mean "standard load". See explanation below. If you have a dually pickup, you really need load range "D" or "E" tires. And, since the "E" rated tires are only a couple of dollars more; I would personally buy the "E's".

Hopefully not, but the false economy of buying downgraded tires for your tow vehicle to save a couple of bucks may make you the lead story on the 10 PM news. It just doesn't make sense to put your tow vehicle, Airstream and family in jeopardy.

What Does a Load Range of SL on a Truck Tire Mean? | eHow.com

Just another opinion, to be taken with a grain of salt...

Bex · 08-07-2012, 03:44 PM

Phoenix:
In answer to your previous comment, these are not passenger tires they are light truck "Standard Load" tires. I would not put passenger tires on the truck.
I would certainly not put my family in jeopardy, as has been said, the PO of the vehicle went non standard E rated tires for the truck. He obviously had a reason for doing this. They are overkill for the truck (and how we use it) and towing my trailer, really, they are. 3000+ lbs loading each tire is more than my truck is rated for (by nearly double). Its not a few dollars more in savings, its $31.50 per tire which is quite a lot for me and the E rated tires are not rated as high for Mileage, grip, speed or durability, just loading, so I think the decision is made.
I was trying to find the actual tire rating for the truck. I have now done this and they are 225/75 R16 Load rated D and thats what I have decided to put back on the truck.
Thanks for the input everyone, I am out to buy tires right now!

Bex

rumrunner · 08-07-2012, 06:44 PM

Bex, sounds like you got the right information and made the correct choice. If the placard says D load then D load it is! Might be overkill for the towing that you do now but who knows what might happen in the future? You can certainly reduce the tire pressure slightly under non towing conditions to improve the ride quality and tire longevity. check with your tire mfg for recommendations -or if you want to stir things up again just ask here

tim

Bex · 08-08-2012, 06:54 AM

Tim: Who knew the tire rating was as easy as looking at the tag sitting on the end of the door? Not me, thats for sure! In my continuing search for answers, I found this:
Tire size calculator
And also some info from dieselplace forum suggests that a taller tire will be less stable, not that I think that will be noticeable with the two tires I am comparing, especially as one is likely stiffer than the other.
Thought I would post the link as other might find it useful.

Bex

Bex · 08-08-2012, 02:47 PM

Tim, I'm not finished yet!
Looks like we were pretty much all right.
The SL rated tire cannot be put on my truck even though they can take the loading. Because the truck calls for D rated, thats what HAS to go on it, legally. The designation is something called Euro Metric and is making its way across the pond to North America and is in light of many trucks being used more as passenger vehicles and less for load carrying and towing. Euro Metric tires of the same size give a better ride quality at the expense of load carrying capability.
I also just came across why I think the PO put 245/75/16's on the truck. If I read this right: Gearing Up for Taller Tires! · Superlift · www.superlift.com
Its to give more towing capability by effectively changing the gear ratio by having a larger tire. The expense is fuel economy. So by putting the stock tires back, I should be able to gain in MPG (and every little helps) Funnily enough, I can only get an E rated 225/75/16, no D's so I am back to paying more for the tires, but not as much as the 245/75/16 that are currently on there.
Wow, what a saga.
Now all I have to do is change my order

Thanks everybody for the awesome conversation, I really appreciate it!

Bex

Phoenix · 08-08-2012, 03:22 PM

Just a quick note; 245/75's are larger in diameter than 225/75's. So, by switching from 245's to 225's, you will be putting smaller diameter tires on your truck. This will effectively increase your numerical gear ratio, with a resultant increase in engine RPM at any given speed. The end result could be slightly lower gas mileage.

For example, if you are currently getting 12 mpg on 245/75x16 tires, switching to 225/75x16 tires will increase your engine RPM'S by around 4% and may result in a decrease in fuel economy by about the same percentage, to around 11.5 mpg. However, the slightly lower gear ratio will improve climbing power on hills and engine braking on long downgrades.

Bex · 08-08-2012, 06:04 PM

Thanks Phoenix. I don't begin to understand that stuff but do check MPG's, so real world test will tell me whats happening. I obviously read the article the opposite to what you have explained

rumrunner · 08-08-2012, 06:08 PM

You really know how to do your research Bex. As for going to the E rated tires you are really not giving up anything except possibly a few more dollars as long as you inflate properly. Phoenix makes a good point about the 245/75R16 tires being taller in diameter than the 225/75R16 but another consideration is the aspect ratio. the 75 number in the middle of the tire size is known as an aspect ratio and defined as the ratio of height to width when mounted on a rim of known standard size. what this means in the real world is that the tire is 75% as tall rim to tread as it is wide at its widest point-not across the tread. this means that the 245 tire is both taller and wider than the 225 resulting in greater rolling friction. Having sold tires and repaired vehicles for 18 years I can say with some authority that going to a larger tire does not always equate to greater mileage. In fact in many cases owners are greatly surprised to find that they burn more fuel to produce the rpms necessary. Sometimes it works and sometimes not.
sometimes its easier to just go with the flow

tim

slowmover · 08-09-2012, 06:02 AM

Taller tires tend to mean greater rolling resistance, so mpg increases are not likely but for those who don't do anything but highway. They also increase the load on the wheel bearings and brakes are less effective.

Stock sizing and load index really is the way to go.

Note, also, that the dual rear wheel loadings are not the same, per tire, as with single wheel. They are downrated, each, somewhat (though the total is obviously higher; the GAWR).

.