37's or downsize to 35's?

Currently on Toyo RT's 37x12.50R18 tires that I put on the truck in early 2020. Tires are about worn and in need of replacement. I am contemplating downsizing to 35's, looking for thoughts.
I installed 5.29 gears prior to 37s, but when towing our 26' camper, I average 6-6.5mpg in 4th gear. Daily driving I average 12, mostly all highway

• I could move the full size spare from the bed to under the truck
• would get a little more power and MPG when towing
• should gain a little MPG for daily driving. was getting 13.5-14 when on 295s w/gears

 

Well im on 37's and currently love them. I have also though about down sizing to 35s once I need new tires, but probably will stick to 37's. I cant image that the mpgs would increase enough for me to be willing to give up the offroad performance and looks of 37's. I guess you have to just ask yourself the question of do you need 37's? How often do you offroad? How much is gas in your area? How much would 35's save you in gas a year? I would say if you dont offroad then 35s are better for your case. I dont tow at all so 37s dont hurt mpgs and performance for me as much as they do for you. I will say that since you mainly drive on the freeway the biggest hit to your mpgs is the front bumper. These offroad orientated bumpers create an immense amount of parasitic drag which really hurts highway mpgs. The bigger tires mainly hurt mps in the city where you constantly have to stop and accelerate. On the freeway drag is the biggest factor.

 

1) can you post pics
2) can do any bfg in 37 which is actually a 36 and splits the difference between the two!

 

I don't off-road, just driving on the beach 2-3 times a year and occasional cutting thru the grassy medium. In addition to the bumper, I have rock sliders, 46 gallon steel tank, and other gear that adds weight.
Gas was 2.48 today when I filled up, so if I gain about 1mpg, I would save 97 gallons a year at 15k milesxa year, or $240 a year.

 

yeah I think at MOST you would save 1mpg. But you are already regeared so I think it would be just under 1mpg difference

 

Damn if gas was that price here I would have a supercharger and 40s lol

 

I'd look at a different tire first. Those RT's are pretty good looking, but I went on a small road trip with a friend in his 6.4 Hemi Jeep (before it was a factory option) with 37" Toyo RT's; it was not pleasant. Driving it, they felt heavy, sluggish, and not well suited cruising down the road. It's not just the weight but the tread compound and pattern.

Kai got pretty decent mileage with his 37's; I wouldn't expect to get the same mileage with your truck, but he points out the load rating, weight, and tread pattern contributing to his better-than-average mileage.



My vote would be a less aggressive tread, no matter the tire size. They are starting to make much more aggressive sidewalls on more mild mannered tires so you don't have to necessarily give up the looks. Plus, IME, a good all terrain does great in the sand vs an MT or RT tire.

I'm interested to see what you go with. Who doesn't like a good tire thread

 

here is how my truck sits currently

 

Thanks for the feedback, I am looking at getting Nitto Recon Grappler A/T

 

Ridge Grapplers and an ~8K 296 TT, so 35' frame length. I get anywhere from 6.5-8MPG with OEM 4.30s. The biggest factors seem to be my travel speed and wind (obvious, I know). How fast are you going?

Two things I'm going to eventually try, aside from regearing this winter, are a less aggressive tread since I don't have time to offroad anymore and the possibly snake oil intake manifold spacer. Hopeful that shifting the torque band 1K down will help efficiency while towing.

 

The weight of the wheel/ tire plays a significant role. My 17s and 37s weigh less than my 35s and 18s. The weight on rotational mass is what matters also significantly

 

This right here. When I made the jump to 37's I purposely went with a lighter M/T, so I only lost about half an MPG over what I had with BFG 35's (really 34's). What's more, that's with my Speedo and ODO still set to factory calibration, so I suspect I'll gain that back when I recalibrate.

 

I have a 6k 264 Jayco, which is a 32' frame. normally a camping trip involves at least 2 hours at highway speed. I am normally going 68-70 mph.

 

Just got back from Discount tires, went with the Recon Grappler A/T's in 35x12.50R18.
The ride is much quieter and smoother.

 

I tend to hang around 62-66.

Keep this post updated since you've now swapped to 35s. Would like to hear the difference.

 

Looks nice with new tires. I had the Toyo RT on my other Tundra also. I'm looking at Nitto recon grappler or the new terra grappler G3.

 

What is the "lighter MT" you went with our of curiosity?

 

Kanati Mud Hog in 37x12.5R17. I think they come in at 75 lbs per tire coupled with Icon six speed wheels at 31lbs per wheel, yields a total weight of 106 lbs. I will say, the Mud Hogs are not a very good tire. They don't balance very well and have tons of road noise. If I had to do it again I would have taken the weigh penalty and gone with a higher quality tire. I'll lean towards BFG KM3's next time, which are lighter for an MT but have a much higher quality construction, but the price tag definitely reflects it.

 

word. thanks for the explanation. good intel. crazy that the BFG ko2 37s are only 64 lbs... c load. and d load at 68

 

Since it’s a highway truck, 42” sticky MTR’s so that you can command respect

 

The 37" BFG AT's in Load C measure a a true 35" on my JK

 

wild…. What the hell bfg!

 

To be fair, tires are shorter when on the vehicle and loaded. That’s how you get a contact patch. If the tire was off the vehicle it would be closer to 36”.

 

Sounds like if that is all you do I would go back to stock tires and save the money but you already changed the gears. Your decision

 

I like!

You will have to let us know how they ride.

 

valid point. I have 35x12.50x17 KO2 and they measure 33” while mounted…

 

That would make him a member of the ‘I Run Stock Tire Size on Purpose’ Club, along with me and like seven other members. Yes, a very exclusive club to be a part of, but you’ve gotta have some chops if you wanna be a part of that club.

 

This will be unpopular but it looks dramatically better on 35’s. The 37s didnt look proportional to the lift height