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-   -   18" wheels, towing and MPG (http://www.ramforumz.com/showthread.php?t=162617)

mean4g 01-04-2014 09:22 AM

18" wheels, towing and MPG
 
I will have a 2014 Ram 1500 4x4, QC, Pentastar with the 3.55 rear end delivered here in a few months. Unfortunately my truck comes with ugly 17" steelies. So I am in the market at look at upgrading. Was looking at some 18" wheels and wanted to still come close the OEM size of tires for gearing, towing, and MPG reasons. what I was looking at was…

18x9" wheels weigh approximately 25-28 pounds per wheel
275/65/18 all-terrain E rated tires weight 55-58 pounds
total height is 32" for most tires (just slightly taller than the 31.7" OEM 265/70/17s)


Would my towing be greatly affected over the OEM 17s? MPG difference 1-2 maybe? From what I hear the 20's affect it greatly, however they are ridiculously heavy and 33" tall. thoughts? Should I not even worry about it and go for it even though I am on the Pentastar which has much less power than the hemi? Or should I go for a 17" wheel (2-3 pounds lighter), and go for slightly lighter all terrain 265/70/17 tires (2-3 pounds)? Also the 9" wide wheels I am looking at are 0 offset (18MM's different from the 9" wide OEM ones). So would these 275s stick out or rub on a 0 offset? I just want to make sure they tuck correctly and don't rub on the fenders as well. thanks.

TJC.geotech 01-04-2014 10:26 AM

I would look very carefully at the load rating of any 18" rim that weighs less than 30 lbs.

The biggest hit to mileage will be from the E-rated tires.

mean4g 01-04-2014 11:21 AM

Quote:

Originally Posted by TJC.geotech (Post 1285466)
I would look very carefully at the load rating of any 18" rim that weighs less than 30 lbs.

The biggest hit to mileage will be from the E-rated tires.

well tirerack sell a ton of truck wheels under 30 pounds in the 18x8.5-9" range. Ranging from Dick Cepeks to Ultras etc. Honestly they seem pretty heavy to me overall. Thoughts?

TJC.geotech 01-04-2014 11:48 AM

Unless it's a forged wheel, less than 30 lbs is more of a 'designer' product. You can see the full specs on Cepeks site.

E-rated tires are generally rated in the neighborhood of 3300~3500 lbs. The five lug Cepeks are 1000 lbs less than that.

mean4g 01-05-2014 03:13 AM

Quote:

Originally Posted by TJC.geotech (Post 1285522)
Unless it's a forged wheel, less than 30 lbs is more of a 'designer' product. You can see the full specs on Cepeks site.

E-rated tires are generally rated in the neighborhood of 3300~3500 lbs. The five lug Cepeks are 1000 lbs less than that.


So the designer wheels (Cepek, Ultra, and XD's)are probably suited for a C or a D rated tire I am assuming considering their weight?

Also how noticeable is the stability of an E rated tire at say 40 psi vs a C or D rated tire at 40 psi? Also any idea on changing my towing abilities for the rough idea of 18's and 265/65/18 "E" rated tires? thanks in advance.

TJC.geotech 01-05-2014 11:18 AM

You should not run an e-rated tire at 40 psi. They are designed to be inflated to 60~80 psi. Low inflation pressure is the number one reason for tire failure. This is how Ford and Firestone got into so much trouble with the Explorer.

An 18" E-rated tire at 60psi would probably feel very similar to the factory P rated 20" setup. Firm but not harsh.

Going to an LT tire will take some of the sway out of the truck, but you will still be limited to the axle rating of the truck. The axle becomes the weak link and believe me, you do not want to break an axle towing a trailer. Some prudence and common sense is required here.

Dragonmaster13 01-05-2014 04:15 PM

as long as the wheels a rated to carry more than your gawr they are fine. check the max pressure rating of the wheels to ensure they can take the lt tire max pressure, some cant

you will not notice any difference towing other than less sway/squirm.

mean4g 01-06-2014 12:16 PM

Quote:

Originally Posted by TJC.geotech (Post 1286457)
You should not run an e-rated tire at 40 psi. They are designed to be inflated to 60~80 psi. Low inflation pressure is the number one reason for tire failure. This is how Ford and Firestone got into so much trouble with the Explorer.

An 18" E-rated tire at 60psi would probably feel very similar to the factory P rated 20" setup. Firm but not harsh.

Going to an LT tire will take some of the sway out of the truck, but you will still be limited to the axle rating of the truck. The axle becomes the weak link and believe me, you do not want to break an axle towing a trailer. Some prudence and common sense is required here.

thanks for the advice. I am assuming that the weight of the tire and wheel combo doesn't have much affect on the towing ability as overall diameter. The weight just hurts my MPG. So would it be safe to assume my plan with the 18" wheel combo (similar overall diameter to OEM) would only hurt a little bit of fuel mileage and most likely no decrease of towing ability (as long as the wheels have the capacity to handle the load of course)?

TJC.geotech 01-06-2014 01:49 PM

Quite honestly if you're just towing to the capacity of the V6, then the P-rated tires are more than adequate. Even if you exceed the GCWR by a thousand pounds or so.... I wouldn't sweat it. Technically the E-rated tires will lower the rated towing capacity, however they are considered unsprung weight, so really only the braking performance will be affected, by an imperceptible amount.

smurfs 01-09-2014 01:32 AM

The LT E rated tires are more than your wheels are rated to carry, and unless you are riding with 60PSI in tow, you aren't gaining a thing- in fact, they will likely wear funny and quicker possibly leading to a failure. I run 50-55 daily in my E rated on the 20" rims I have, and boost the rear to 60 when I am loading heavy or plan on towing. This is the same as I did on my previous truck. I have NO idea what they are rated to carry (OEM Lariat 20's) and I can't find it online, but I have heard from the tire shops that they don't see issues with them until you start inflating to the 75-80PSI mark. 55-60 gives me the equivalent load capacity of the P rated tires at 44PSI, but they are a bit firmer- so I don't get that squishy feel.

As for a difference in mileage- you'll notice it unhitched and hitched. It's that little extra width, the more aggressive tread, and the added weight. You'll feel it too.

Like mentioned, be mindful of your axle rating- don't load to the capacity of your tire. Even the P rated are capable of more than your axle is. The only benefit for an E rated tire on a 1500 is for towing and taking out some of that sway in the backend of the truck.


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