Full size wheelbase

[rruff]

I lost 1.5 mpg going from 285-75-17 to 35-12.50-17's. More mass to get going and a wider track with more tread drag with the same tread pattern and manufacturer.

Is it the same tire, just a little bigger size? I'm getting a little better mpg overall with tires 3" bigger in diameter, 2.5" wider, and >2x heavier than stock.

I've grown weary of trying to educate people regarding the physics. Tread doesn't drag, it rolls. Tire weight is a negative factor, but a minor one. Greater width is a positive factor for rolling resistance, as well greater diameter, because they have less casing distortion. Tread thickness and tough sidewalls are negative factors because there will be higher hysteresis losses when they flex. And when you put bigger tires on a truck, your aero drag will also go up... and even more if you add a lift. But... the most important factors for rolling resistance are the tire compounds and construction. Bottom line is that we can't tell what the rolling resistance will be without measuring it (and does anyone?), and there is a lot of variation between manufacturers.

 

[Regcabguy]

There's wind resistance too. The tires are Toyo AT3's. Same tread,3-ply sidewall. The 285-75-17 are only 5# lighter. I checked both tires on the highway,straight ahead with my GPS. I wish my experience was the same. Diesel's killing us now.

 

[rruff]

Curious exactly how you compared them?

 

[skrypj]

I have a 157” F150 and will say that my stock running boards self-removed after some fairly mild trails. Well, actually, I removed them but they were pretty bent up.

I am not sure that having a 145” would have made the difference in those situations though.

 

[Todd n Natalie]

I have a 157” F150 and will say that my stock running boards self-removed after some fairly mild trails. Well, actually, I removed them but they were pretty bent up.

I am not sure that having a 145” would have made the difference in those situations though.

Is that truck stock height?

 

[skrypj]

Is that truck stock height?

Kinda. Its on Bilstein 5100’s on the 2nd from bottom ring, so like a .75” level i think. But it is on 315/70R15 raptor takeoffs and I’ve installed 1st gen Raptor running boards now which should have more clearance.

Testing my sway bar being disconnected.

 

[Grassland]

Kinda. Its on Bilstein 5100’s on the 2nd from bottom ring, so like a .75” level i think. But it is on 315/70R15 raptor takeoffs and I’ve installed 1st gen Raptor running boards now which should have more clearance.

Testing my sway bar being disconnected.

That's a long boi.

Sway bar make a big difference?

 

[skrypj]

That's a long boi.

Sway bar make a big difference?

Yes its substantial. These trucks ride really rough offroad with the swaybar connected. Especially if you have the max-tow package as it comes with a larger, solid sway bar that is quite stiff.

 

[rruff]

That's the downside of the fully boxed, torsionally stiff frame. The suspension needs to be able to articulate well offroad, and the swaybar prevents that.

Not a big deal though. I have Ironman FCP shocks on my Tundra and it doesn't need the swaybar to handle well. Most aftermarket off-road oriented shocks will have much higher compression damping than stock.

 

[Todd n Natalie]

Kinda. Its on Bilstein 5100’s on the 2nd from bottom ring, so like a .75” level i think. But it is on 315/70R15 raptor takeoffs and I’ve installed 1st gen Raptor running boards now which should have more clearance.

Testing my sway bar being disconnected.

I've actually been thinking about adding an anti sway bar to my 157" Max Tow truck, haha

I've read it makes a difference while towing.

 

[skrypj]

I've actually been thinking about adding an anti sway bar to my 157" Max Tow truck, haha

I've read it makes a difference while towing.

Ive got a hellwig in the front of mine and its very stiff, stiffer than the max tow bar. I do not have their rear bar but I think that is the one that makes the biggest towing.

TBH, the rear bar may actually help because it would help “fight” the front bar.

 

[Regcabguy]

That's the downside of the fully boxed, torsionally stiff frame. The suspension needs to be able to articulate well offroad, and the swaybar prevents that.

Not a big deal though. I have Ironman FCP shocks on my Tundra and it doesn't need the swaybar to handle well. Most aftermarket off-road oriented shocks will have much higher compression damping than stock.

I'll take a fully boxed frame with a compliant suspension any day over the opposite. It's nice to be able to open the doors and hood if you have to get out and survey an obstacle. The older Ford's come to mind.

 

[rruff]

I'll take a fully boxed frame with a compliant suspension any day over the opposite. It's nice to be able to open the doors and hood if you have to get out and survey an obstacle. The older Ford's come to mind.

I agree... an undamped spring (the frame) isn't a great way to get compliance or articulation. But I don't think the stock suspensions are very compliant, though they are tuned decently for street use. Offroad, it's good to get rid of the swaybars and get better shocks.

 

[Regcabguy]

Curious exactly how you compared them?

A friend re-installs a spare set of 265 Michelin's in place of his 35-12.50-17 AT3 Toyos whenever he tows. With that change alone he experiences more power,better mpg and superior braking. With the 285's and their coarser tread,wider width(more wind resistance) weight(more fuel to start) and more braking effort he can't tow the vehicle as efficiently. Regearing could negate the performance lag with the larger tires I'll concede. But braking and drag from a larger,heavier tire and courser tread. Nope. I wear a size 10.5 shoe. Throw some 13's on me and tie them real tight it's going to take more physical effort and sweat to run as fast. Regarding comparing my tire and fuel economy difference. I went the same freeway route GPS certified and prior to that I I adjusted the speedo and odometer to eliminate that factor. Your results may vary as the saying goes.