Dodge RAM 1500 wheel/tire size/weight debate
 

I've had this truck for 6 years now (it's paid for--woo-hoo!), and the OEM tires are about due to be changed. Factory size is 275/60R20, on 20x9 OEM alloy wheels. Tires weigh 43# each and are 33 inches tall. Wheels, I'm told, weigh 42# each.
I'm considering, when I buy new tires, to get some lighter forged wheels. I realize the FE gain would take me forever to pay back (esp at $300 a piece :eek:), so I'm not expecting massive gains if I pull the trigger. 20x8 Centerlines for my truck (5x5.5 bolt pattern) weigh 28# each. 18x8 Centerlines weigh 22# each, and despite the fact Dodge doesn't put 18s on 1500s, Centerline told me no problem making a set. Replacement tires are the same weight for the 20"; I was thinking I'd get the new Firestone LE2s, which are low rolling resistance. For the 18" wheels, I'd get some 265/70R18s, which are 32.6" tall and weigh maybe 1 pound less.

(Squirrel--see the movie Up!) At $3/gal and $1200 for 4 wheels, I need to save 400 gallons of fuel. A 1 mpg gain would take a long time to pay back... So I did the math anyway. Using a 20mpg baseline, 21mpg as the new mpg, with fuel cost of $3/gallon, it'd take me 168,000 miles to pay for the wheels just in fuel savings. Actually, not totally out of the question as the truck only has 52K right now.:D (but that's YEARs of driving for me; we'll probably have flying Deloreans by then)

So with 20s, the truck would lose 14# a wheel, or 64# total. With the 18s, the truck would lose 20# a wheel, or 80# total. The 18 inch tires are also about $30 cheaper each, and the wheels are $20 cheaper each.

I've considered getting taller tires, but it seems the current OEMs are the top of the range, as 275/65R20s weigh no less than 53-61# each, 10# or more than the OEMs. I researched this when I was considering a manual tranny swap, as 6th gear in the (scarcely) available 6-sp manual is .78, and that is nearly 4th gear (.75) in my 545RFE auto (5th is .67). Rear end is 3.55!

I've gone back and forth more times than I care to count, so I'm curious as to your opinions and inputs...

I did look at this thread, but it didn't seem to fully apply to what I'm asking: http://ecomodder.com/forum/showthrea...ero-15914.html

Thanks in advance...

If you can obtain lightweight wheels, all the more power to you. However, as you've noted, it's going to take a while to recoup your investment.

If I was you, I'd also look at finding a way of making the wheel more aerodynamic in nature. If these Centerlines had a provision for installing half-moon wheel covers, for instance, that'd also help with your FE.

Do this one for fun. You'll be replacing those tires at the 5-6 year mark anyway (climate, tire aging facts) despite high or low miles. So have a look at the "spats" being put on the '14 Chevy's, etc. Make it an all-around effort.

Found these threads elsewhere on the Internet pertaining to wheel weight vs mpg:
Wheel Tech - Road Wheel Weights Can Affect Your Vehicle's Show...and Go
Light Wheels Vs Heavy Wheels - Wheel Tech - Comparison - Car Craft

Some interesting comparisons...

Like slowmover said, it sounds like you'll be replacing the tires soon anyway. You don't need to worry about the expected fuel savings paying for the whole set of tires. For the LRR or low-weight or what-have-you tires to be considered a good investment, the fuel savings should recoup the difference between those fancy wheels and the stock replacement wheels. And of course, it should recoup that difference within about five years, ten max, because by that time you'll probably have to replace them again.

You'll notice appearance and ride quality differences before mpg changes.

Great plan aside from using firestone tires.

See how much you can sell your 20 inch wheels for and grab a set of junk yard 16 to 18 inch wheels.

The OEM tires on the F150 were Firestones and by golly if I could get an exact replacement set of those I'd be on it before you could blink. They were far better than any of the aftermarket replacements it's had. :/

Have you been able to price a used set of the kind of wheels you want?

When I do a MPG mod cost and time to get it done is a big consern. I usually try to stick with $250 for 1MPG unless there are other benifets to be had.

Thank you all for the responses and feedback. Agreed, I am not sure I'd see much on the mpg gains, but as Frank indicated, the ride should improve.
@oilpan, I found a set on Craigslist, with tires for $400, but they disappeared the day after I emailed the seller. :( I'll be searching regularly though. Several guys on DodgeTalk that drag race their trucks (yes they do) go to 17" steel wheels, 'cuz they are lighter than the OEM alloy 20s.
@pryan, good point about the payback vs tire replacement.
@slowmover, I'll be looking at the 2014 Chebbies. I'm curious now...