MPG question regarding new wheels with different dimensions.

2016 Tacoma TRD Sport. Stock suspension

Hi All. I just got a set of Method Roost in 17x8.5 +30mm. I mounted the stock tires on them.

The OEM wheels are 17x8 +0, so the new wheels stick out 30mm further on either side.

I took a 4hr road trip that I usually average 24-26mpg and with the new wheels I got 19mpg.

Does this sound right for adding .5" rim width and 60mm total offset?

I knew I'd take a small hit, but I didn't think it would be a 5-7MPG hit! That's 20%-26%!!!

 

What is the difference in weight between the wheels, that could be your issue, but still sounds high

 

I'd imagine if it was mostly highway without many hills heavier wheels shouldn't have much of an effect once they get rolling.

That's a pretty significant drop though, no other changes for the trip? I can't visualize how much more offset that is, but are the tires/wheels sticking past the fenders now? Even if it's just a little bit that's a lot of extra wind drag at highway speeds.

 

Rolling resistance of the tires should still be the same; even if the wheels were twice as heavy (unlikely) as the stock wheels it shouldn't have that sort of effect. I'd say check your tire pressures and make sure that the shop inflated them properly. Tires that are low on pressure can definitely have that sort of impact on fuel economy.

 

What about wind?

 

For sure a possibility, if not a combination of a bunch of factors.

My opinion, try to get an average over a month or so before blaming the new wheels.

 

I get about 13-14 mpg combined with my -12 18x10 motto metals wrapped with 285/65r/18 Cooper STT Pro M/T’s.

 

The stock and roost wheels weighted about the same. Just judging by my calibrated "hand" scale.

 

They stick a tiny bit past the fenders now. no flat face visible from the front of the truck. 30mm wider is around 1-1/4"

 

Yikes!

 

Weight is the best guess.

 

Yeah, I wonder if there wasn't something else going on. When I went from stock 16's to the 255/75/17's, I think I only took about a .5-1mpg decrease. Could have been poor fuel, a slight headwind, both?

Drive it for a bit and see if it stays the same.

 

Driven 1k miles in 2 weeks on 3 different brands of gas. no change unfortunately. I'll give it a couple more weeks to see if it changes. Might do a hard reset of the truck too...

Anyone in the market for new wheels...?

 

I'd hate to see you go back to the stock wheels and the mpg not come back at the same time.

 

is this calculated by hand or are you just looking at the MPG trip meter thing?

 

Umm, those would be used wheels.

Hope you get this resolved. I'm dealing with my own wheel issues right now, and it's really frustrating considering I have a 3000 mile road trip in 2 weeks.

 

Was by the truck for the first tank, second and third tanks were calc'd by hand.

 

Aerodynamics. I just went on a long road trip pulling a small utility trailer to pick up furniture and other junk from my parents estate. On the first leg down to SoCal with an empty trailer my normal hwy mpg dropped about 5 mpg. Once the trailer was loaded it went back to normal mpg??? All I can figure is that the trailer when empty was sort of a wind scoop.

 

Did anything happen with this, this is the exact topic ive been researching. Same tire, similar weight wheel, but change in aerodynamics from offset change.
Ive been going down a rabbithole realizing that offset could be one of the primary factors of MPG. People only think to MPG of offset when we talk extreme negative offset.

First to OP if youre still there. I assume you meant -30mm because +30 would be less poke than +0 but nobody commented on that so I assume he meant -30?

I dont think a +30 8.5" wheel would even fit on your rig, but maybe with the stock tires.

Secondly, 17x8 and 17x8.5 makes a difference, you're adding another 15 or so mm so its actually a -45mm difference. not a -30mm difference, thats 1.7 inches, is that correct?