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...

There are plenty of instances where steel wheels can be lighter than alloy show off wheels.
Also if you get the light forged wheels and happen to slide into something immoveable the wheels tend to break, saving you from bending or breaking an axle.

Smaller wheels will usually save fuel I've found on bigger trucks. My buddy went from 20" wheels to 17's on his diesel pickup and gained like 2mpg. Same size overall just the smaller and lighter wheels. Rotating mass is much more important than overall weight.

In order to provide some small amount of data for this debate, I have purchased a set of stock steel wheels for my Magnum. Today, I swapped out my stock alloy wheels with the steel wheels, and tomorrow I will top off the tire pressure and verify lug nut torque and do my daily commute thingy.

The steel rim weighs 23 lb 7 oz, and the alloy wheel weighs 22 lb 2 oz.

Stock alloy (10.035 kg):
http://www.originalwheels.com/dodge-...ls-2246b-b.jpg

Stock steel (10.660 kg):
http://www.originalwheels.com/dodge-...els-2240-b.jpg

On a side note, I got a really good deal. Normally, steel wheels go for about $60 per wheel in my neck of the woods. However, I found somebody who was willing to sell his wheels for $50 for the entire set.

Don't forget that tires have a HUGE variation in rolling resistance. If you are going to do A-B-A testing, the tires have to be indentical for both sets - and that includes the amount of wear.

Well, the tires themselves are identical. They're the same tires. Only the wheels have changed. ("the wheels have been changed to protect the innocent...")

Now, I'm not quite sure the tires remained in their same positions when I had the wheels changed. That might affect the results, but very likely not in a statistically significant way.

Were you considering doing warm air intake or more EGR or cooled EGR on your diesel?

There are loads of dodge trucks with 5x5.5 alloys in junkyards up here. Fords too.

I have considered that. I almost bought a set from the Classifieds on the DodgeTalk forum, but shipping was too expensive. They were OEM 17s and he weighed them at 28# each. Not as light as Centerlines, but certainly lighter than my 20s.

[edit] I've held off from pursuing 17" wheels because I am still looking to do a manual tranny swap. The factory 6-speed has a .78 top gear, and NV3500s (prior to the 6-sp) have a .73 top gear. The auto's top is .67, 4th is .75...and the truck doesn't do so great with the .75 on the highway. I've tried it a few times. I figure with 17" wheels the tires would be so short I'd regret it after the tranny swap. Typical size for my truck is 265/70R17, which is 31.6 inch diameter. My factory tires are 33 inch. With some math ratio MS Excel work, it looks like the 17s would make the engine turn another 100 rpms at 70 mph, with no other changes. But the .73 NV3500 5th adds another 170 rpm. Yuck.

All that said, I think she who must be obeyed is going to force my hand and make me buy new tires, and that means OEM size...

Hmmmm
I can see how 20 X 4 = 80# total
but I do believe 14 X 4 = 56# total
Not 64# total?
Right? :thumbup:

I mean it seems like basic math. :confused:

Steve, you are right. Now I'm even more disappointed. 16x4=64. Bummer. What's even better (or worse, depending on how you look at it) is the fact I discovered the OEM 20" wheels weigh 36# each if painted (like mine), 37# each if chrome plated. So, even less weight change per wheel. I still may go with some 17s like tvago if I can find a set for less than $110/wheel that don't look like ragged crash survivors...

The only 20s I found lighter than stock were Centerlines. There are some factory 17s that are the hot ticket: 0ZR75TRMAA and 0ZR76TRMAA. 17x8 wheels, 23 pounds each. There are a couple on Ebay... I could always get a set, and install a higher gear in the rear end.

Anything new?

Nothing new. I've been trying to sell a house for the past five months, move from San Antonio to OKC, and keep myself out of hot water.

Haven't been able to pursue the manual tranny swap yet either (sigh).

I did end up getting some Firestone Destination LE2s to replace the Factory Goodyear Wrangler HPs. Looking back, I should have stayed with another set of Goodyears. The LE2s are 45# each, where the Wrangler HPs were 43# each. Better yet, I just discovered Michelin Premiere LTXs are 37# each. Should have bought a set of those it seems... All are the 275/60R20 size.

I have been musing on this the past few days. It dawned on me that HEMI powered pickups and 4.7L powered pickups share the same 545RFE automatic. And since HEMIs were sold in much greater numbers, I'm guessing the 545RFE is geared for it, not for my 4.7. HEMIs had another 110hp from the factory; I think that may have some impact...but is it enough to notice? Hard to say.
So, I began to muse about getting a little shorter tire next time around, say 275/55R20s--32 inches tall, to potentially put this engine in a better operational rpm range.
All that said, the Firestone LE2s have been good tires. They wear well (53k miles so far), and have good traction, even in rain. I won't get another set because I want something lighter.
Admittedly, 275/55s only change gearing from 3.55 to 3.67, and will raise engine rpm from 1900 to 1964 at 70mph in top gear.
Or, I could take the plunge and get those lighter factory wheels...

Wheels, not tires if it comes at expense of tire quality. At 215k on my one ton my second replacement set is still new.