downsizing wheels

[ZoMojave]

I just hit 15.0 mpg yesterday after months of mid 14's. I am thrilled!

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[bleda2002]

I have a max tow, with factory tires and wheels (same wheels different tires, as Rubicon on my Freedom) I got 22ish the day I picked it up.

When I went to 285/75/r17's (34") it dropped to 17.5 or so, super charger dropped it to 15.5 or so.

So yes you will get better mileage. Yes it should be noticeable on the freeway.

Towing I get 9. You probably will not notice it there.

I would probably look at tire swaps vs wheel and tire swaps. Just buy a new set of tires and sell your old ones on CL or fakebook. I sold my factory tires with 500 miles on them for 75 ea set of 5.

There is literally no way that driving under the same conditions in the same manner you lost 3.5 mpg going up 1.25 inches. It's physically impossible. More likely you drove a good stretch at a lower speed or downhill or with the wind home, and then picked a more accurate average on 34s as 17.5 is pretty accurate with real world experiences at highway speeds of 70-80 on stockish tires.

The trucks aero sucks and wind as well as speed highly vary mpgs. You really need to average it over a few hundred miles in varying conditions with consistent speeds on round trips to get an accurate picture. 600 miles on 39s at 78-80 netted me an average of 15 with jaunts at 12-13 depending on wind and 16-18 also depending on wind (Florida so elevation is very minor). For comparison my first trip to and from Miami with the fully stock Rubicon got me 17.8 mpg over the exact same 600 miles. If I look down at 55 I can be anywhere from 30 to 20 as well, so momentary looks just aren't accurate.

 

[Josh00333]

Sorry Bled, the 400 mile trip home at freeway speed says otherwise vs the follow on freeway trips on the new tires.

It’s not all about rotation diameter but also tire weight. The 34” are something like 30 pounds each more than the stock tires were. With wider contact more aggressive trends etc.

Most mileage conversions show stock sport rigs getting 20-24 and aftermarket upgraded tire guys w 35” getting in that 16-17.5 range.

 

[bleda2002]

Sorry Bled, the 400 mile trip home at freeway speed says otherwise vs the follow on freeway trips on the new tires.

It’s not all about rotation diameter but also tire weight. The 34” are something like 30 pounds each more than the stock tires were. With wider contact more aggressive trends etc.

Most mileage conversions show stock sport rigs getting 20-24 and aftermarket upgraded tire guys w 35” getting in that 16-17.5 range.

Same trip, same speeds, same conditions round trip to cancel out elevation changes or was this a one off trip? Again 5 mph is worth a ton of mpgs on these things at highway speeds as well as elevation etc.

We've got a JT and a jl with nearly 50k miles between the 2, tires have varied from 31.5s to 39s and a few sizes in between (33s, 35s, 37s), for us in the city the difference between extremes has been 2 mpg city and 3-4 highway hand calculated.

 

[Idlethunder]

Did you recalibrate the speedometer for your testing?

Yes, and the calculations were done by hand and were withing .2 of the dash reading but what I listed were numbers by hand. Living in small town Oklahoma I get most of my gas at the same station, parking within a few inches of the same spot every time and I stop when the pump shuts off. I know it isn’t scientific proof but I was as consistent as I could be for both tanks. The only variable I had no control of was the wind. Today it has been fairly constant out of the north around 12 mph and yesterday it was from the west between 16 and 20 most of the day. And no, I’m not that anal about it but I need to do a controlled burn so I’ve been watching it fairly close.

 

[Dim]

my guess would be to go fo less agressives tires . same soze but more road oriented maybe it could help

 

[Barnaby’sdad]

My fuel economy is running within 1 MPG of stock and I’ve currently got bigger tires, heavier wheels, and a camper shell/Alu-Cab.

The fuel economy for these is terrible in all but the best of conditions. I.e. Proper tire inflation, no hills, tail wind, running 65 MPH steady on cruise control, empty/no payload, etc.

The most effective “mod” is going to be a trade-in for a more economical commuting vehicle.

 

[MOJAVEC22]

I just hit 15.0 mpg yesterday after months of mid 14's. I am thrilled!

Trying to get back to 14 myself after getting 11.5 towing and slight off-roading with my camper last weekend! Lol 15-16 again would be nice but haven’t seen that in a while. And just ordered 37s

 

[Beat Army]

My stock max tow gets 21-22 mpg highway on average according to the computer. Has been consistent for 15k miles. Goes down to 16ish in a headwind, as high as 24 with a tailwind…but averages 21 and change. This is relatively flat driving in Texas. I want bigger tires but a 3-4 mpg hit cuts my highway range by 60-80 miles per tank…I have not seen any claims of 20 mpg plus on 33”or larger tires.

 

[Pioneer7]

Nobody who has done their research before buying, comes to this platform with realistic expectations of hypermiling or extending the range beyond EPA estimates without compromises to the point you should probably have bought something else.

You are better off finding savings elsewhere in your life like eating out less or other discretionary spending than knee capping your own vehicle for what it was made for.

This 100%

 

[dcmdon]

This is a solution in search of a problem. The tires are going to make maybe .25 mpg difference if you are lucky but there is a high portability you will be too close to the stock shock under articulation and would damage it.

Exactly. It's a pointless exercise.

First, let's clarify, the OP wants to downsize the TIRES, Not the wheels.

Let's do some math.

We'll assume you drive 12,000 miles per year and currently get 16 mpg.

And that you get 1 mpg better with the smaller wheels and that gas costs $3/gallon

Standard tires
12,000 miles / 16 mpg = 750 Gal
750 Gal x $3/gal= $2250

Small tires
12,000 miles / 17 mpg = 705 Gal
705 Gal x $3/gal = $ 2115

So gaining 1 mpg will save you around $135 per year.
Gaining 2 mpg will save you about $270 per year.

Stupid idea.

 

[Vtur]

I think a solution to the OP is a diesel.

 

[ZoMojave]

Trying to get back to 14 myself after getting 11.5 towing and slight off-roading with my camper last weekend! Lol 15-16 again would be nice but haven’t seen that in a while. And just ordered 37s

The mileage is not in question with scenery like that!

 

[Hootbro]

I think a solution to the OP is a diesel.

The math has been done in other threads but the break even point on the extra up front and running costs of having a diesel in relation to MPG cost savings is a pretty long game. Most people never keep a vehicle long enough to realize that savings.

 

[Vtur]

The math has been done in other threads but the break even point on the extra up front and running costs of having a diesel in relation to MPG cost savings is a pretty long game. Most people never keep a vehicle long enough to realize that savings.

That's correct. But i think hurt once up front is easier to forget than getting hurt at every fill up. Plus extra torque

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