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Discussion Starter #1
Gotta replace the tires on my Ram. Anyone gone to 34" tires? How significant is the mpg hit? I know it would be bad going to 35s, but I'm hoping it wouldn't be terrible going to 34"s?

Considering the Michelin LTX AT2, Michelin Defender MS, Michelin LTX MS2, or the BF Goodrich Advantage TA Sport LT. The stock size is 275/60R20. I'd be goinig to 275/65R20. The 34" tires are all LT tires, while the majority of the 33" tires are just "normal" non-LT tires. Not sure what the difference is, except the bigger tires have lower mileage ratings, generally speaking.

Would appreciate any help/insight you guys could provide.
 

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Taller tires that are heavier well result in lower fuel economy but more so in stop and go driving. With highway it wont hurt as much. Expect a 2-5 mpg drop with the switch. You well also need to recalibrate the computers for the new tire size otherwise your odometer and speedometer well be off and you well have no idea how it actually effects the fuel economy.
 

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My how things have changed, or maybe it is just me. Growing up as a kid 35's were huge. Now trucks come with 33's and 34-35 isn't much of a change at all.

Personally if you care about fuel mileage I think going up in tire size is not the way to go.

You having issues with the stock tires already?
 

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Nah - the truck I bought had old-style Lone Star rims and tires with barely any tread. So I switched over my tires and rims to the new truck since I had upgraded Laramie wheels on the old one. But I was completely out of tread, so I need some new tires. I'm adding a leveling kit to this one, and I'm just afraid the stock tires will look small with the front end raised up. Maybe not.

The 34" would be purely for cosmetic reasons - I have never had any issue with the stock tires size-wise. I know going to 35" would be a hit on mpg, but with the Hemi I'm kind of imagining that maybe the 34" wouldn't make that big of a difference. Maybe it would. I also think the sidewall looks kind of small with the 20" rims and 33" tires, and they offer nothing with OWL due to the sidewall size. Normally I wouldn't care about that either, but I've always like the look of OWL tires on a black truck. But not only would the 34" be some amount of mpg hit, but they're also silly expensive - about $100 a tire higher.
 

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Right off your mileage will be off because your speedometer will be off. The EVIC will not report anything accurate until you re-calibrate the speedometer.

I have a 2017 Eco and the 3.55 diffs. Last spring I went from the stock P265/70R/17 to Cooper H3 LT275/70R/17 tires. They are heavier, and about 5/8ths inches taller. A slight effect to the mileage, about 1%, and I have to consider this in the big picture. But overall my hand calculated mileage freeway miles is still over 31 mpg when in no load/tow mode. Towing I really didn't see a hit, and I liked the stiffer ride.

These LT Coopers can be inflated to 80 psi, but I find 65 psi is a good ride, and the tires are wearing ok.

I can see that if you have the 3.92 diffs, you could use tire size to override the differentials output to equal the 3.55.

But with a 3.55, not much room to run there.
 

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I have a set of AMP All Terrain Pro tires in 275/60R20 which are 33" tires, same as the stock GY's. Difference is these are LT and E-rated. Being that I tow a TT and also wanted a snow rated tire I went with these. They are the same tread pattern as the BFG KO2 but have a warranty to 60k miles whereas the BFG's have 0 warranty. They are also a lot less pricy.
 

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Discussion Starter #7
I have a set of AMP All Terrain Pro tires in 275/60R20 which are 33" tires, same as the stock GY's. Difference is these are LT and E-rated. Being that I tow a TT and also wanted a snow rated tire I went with these. They are the same tread pattern as the BFG KO2 but have a warranty to 60k miles whereas the BFG's have 0 warranty. They are also a lot less pricy.
Any impact to mpg?
 

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Maybe a small drop as they are a bit heavier. I was after a reliable economical tire with which to tow and be a major upgrade for the snow. After the first two years with the GY tires I had no trust in them any more in the snow and did not want the added expense of snow tires and rims.
 

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I have some experience with this

4x4 with 3.55s

if you have any amount of stop and go it’ll affect you more than the guy who is a freeway flier

I put 4K miles on the stock sra then swapped out the 275/65/20 and I saw minimal difference.

next set of tires I got a good buy on some 17” vision wheels so I went for 285/75/17. Yes 75

these cost me a good 2-3 mpg on my commute. My theory is that they are much heavier than the previous set and I have enough stop and go to suffer. I’m going to look into going back to 20s next go
 

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Here's mine. 1.5" rear 2.5" front. 275 65 20s. Milestar AT-R. Like 58lbs a piece. Still average mid 20s on highway. Width and weight really kill driveability. That being said, I wish for more aggressive, but practicality wise this is great. I had 315 70 17 prior and they appeared more stuffed, but are just about the same height.
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Discussion Starter #11
Here's mine. 1.5" rear 2.5" front. 275 65 20s. Milestar AT-R. Like 58lbs a piece. Still average mid 20s on highway. Width and weight really kill driveability. That being said, I wish for more aggressive, but practicality wise this is great. I had 315 70 17 prior and they appeared more stuffed, but are just about the same height.
When you say you average mid-20s on the hwy, what speed is that typically?
 

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Discussion Starter #12
Nvm - I decided to just stick with factory size. I realized I'd also have to swap my spare, and the price on the bigger tires was too much and the reduced mpg just isn't worth the extra looks.

Found some BF Goodrich Advantage TA Sport LT at Costco for $190 each. They get good reviews for ice/snow and mild offroading, have a 65k mile warranty, and are made by Michelin.

Thanks to everyone for the help. Seeing the last post with 34" tires saying he lost 2-3 mpg is not a good feeling. I'd be upset if I lost 10% mpg going to 34" tires. Not close to being worth that to me.
 

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I went in the opposite direction. Dropped from 60 to 55 on the height and went from 25 to 30 mpg. I used GPS to verify my odometer readings and went from 1 mph over to 2 mph under. I really like the mileage towing performance. I towed a 4200 lb toyhauler 3450 miles across the Rocky mountains and my avg was 15.5 . I now have a replacement toyhauler @ 4600 lbs empty weight. With my HD Ultra Limited Low (900lbs), I'm in the 5500 lb range and my mileage is down to 13-15 depending on terrain. A taller tire would result in lower mileage and a lot of down shifting to stay in the power range.
 

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Discussion Starter #14
I went in the opposite direction. Dropped from 60 to 55 on the height and went from 25 to 30 mpg. I used GPS to verify my odometer readings and went from 1 mph over to 2 mph under. I really like the mileage towing performance. I towed a 4200 lb toyhauler 3450 miles across the Rocky mountains and my avg was 15.5 . I now have a replacement toyhauler @ 4600 lbs empty weight. With my HD Ultra Limited Low (900lbs), I'm in the 5500 lb range and my mileage is down to 13-15 depending on terrain. A taller tire would result in lower mileage and a lot of down shifting to stay in the power range.
Yeah I have the Hemi with the 3.21 gears - going taller really wasn't a great idea
 

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I run LT Coopers 275/65r20 with a Zone Offroad 2" level. It was an easy and cheap way to add to the looks of the truck. Although the tires are a bit more expensive and MPG loss was around 1-2.
 
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