Hey Guys.

I recently got Big O Bigfoot All Terrains which are obviously way more aggressive than the Wranglers. The size is a 225 rather than the 215 that the stock tires come with. I know I'm losing gas mileage by a few percent. The max PSI on the sidewall for my new tires says 44 PSI. I know the stock good years are supposed to be at like 32 f and 34 rear. What is a good PSI you think for mostly on road driving with these all terrains to get better mileage?

PLEASE help. I probably over inflate them, could you guys give me a good range for pressure? Thanks

In theory you can try anything between the 32/34 and 44. You could have done the same with the HPs. Below 32/34 you risk flexing the tires too much and damaging them (especially at sustained freeway speeds). Increasing the pressure will reduce the contact patch area, and potentially improve gas mileage. But it will also make the ride harder, and may make steering feel squirrelly as you feel every irregularity in the road. No guarantee that you will get your original mileage back (after adjusting for the 2% size difference).

I'd suggest starting at 32/34, and step the pressure up by 2psi front and back. Stop when you get handling that you like. I run 2-4 above the sticker pressure.

paulj

i run my wranglers at 36 front/38 back.

i'd try those biggies up like that too

how's that been for the wear on the tires?

excellent.

the wranglers have plenty of depth in the center, but little on the outside. raising the pressure biases the wear towards the center.

i'm at 38k on the wranglers, and they would be fine in SoCal for another 10k. but since i'm a skiier, i'm going to change them out this month for something better (nokians, i think)

i was talking to a physics teacher about this... but yeah I just figure going from 225 from 215 is a 4% increase...so I adjusted the air pressure from what it was...and to even it out I gotta run it at about 2 psi less than the original tire size. So...right now I am running it at 32/34, assuming that's already a little higher than the pressure should be. But I'll try 34/36 sometime I guess. i just wanna make sure I get the most out of these tires.

Does deflating psi only occur for soft sand? would that be a good idea for snow/ice (snowy mountain driving) or is it better to keep the original inflation?

225/70/16 tires are about 2% larger in diameter than stock. However my estimate of interior air volume is about 10% larger, as is the typical load rating (1874 lb v 1709 lb). For a fixed rim diameter (16") and profile (70%), air volume approximately varies with the square of the section width (225^2 v. 215/^2).

I haven't seen a good discussion of how tire pressures should vary with tire size. For example, should tire pressure vary with tire section width, tread width, diameter, or air volume? It is easy to identify the problems caused by going too far either direction, but in between there is a wide range where you just trade off one factor against another. Given the unknowns, I wouldn't drop below Honda's recommended pressures for any size tire, at least not for highway driving.

At low, off road speeds, over heating of the tire due to excessive deformation is less of a concern, so you can temporarily lower pressure to increase contact patch. This makes most sense in sand, where you want to stay on top as much as possible. In theory this true for deep snow as well, but in practice it only matters with large wide tires, the kind used for Icelandic glacier Cruisers. In most winter conditions, grip is more important than flotation, so a hard, narrow tire is better than a soft wide one. Also the water evacuation channels work better when a tire is fully inflated.

paulj

Swapped the GoodYear's for Toyo Transpath A-14's same size 215 that came on it and have 32 f and 34 r and handles and drives fine to me. Gas 20-22 mpg city 25 hwy so happy with that.

yeah..i would just stick with the stock air pressure...i don't think the size of the tire has anything to do with the air pressure you use...it's just bigger ...but the air pressure should be the same