question about airing down

I'm thinking of putting some 275/70 18 bfg ko2 tires on my stock trd 4x4, giving it another inch. my question how much clearance do you lose when you air down to 25-30psi for off roading, did the wider profile after defrosting result in any rubbining? is this an acceptable off road psi for these tires. any personal results or experiences would be appreciated. been riding the stock size 275/65 18 at regular pressure, makes for a very bumpy uncomfortable ride, also read that airing down is better on the truck Thoughts?

 

The sidewalls of the tire, at least tires that are going to be off road capable, are generally going to be stiff enough that you won't deform the tire anywhere except on the ground when you air down. You should get no more rub at 20 PSI that you do at 40 PSI. I ran over Imogene at about 20 PSI in my 275/70R18 Wildpeaks, and I had no issues or additional rubbing.

On the note of PSI, you said the tires at "regular pressure" are bumpy and uncomfortable. What do you mean by "regular pressure", because 25-30 PSI is a little low, but it's not really airing down. I only ask because I have known some people that thought you needed to run a tire at it's max cold PSI and that is not the case. At max PSI you will get a stiffer ride, but you can run lower than that. I run my tires at about 40 PSI, and lots of people run 35 in theirs.

 

BTW those tires only give you a half inch more clearance. You go by the radius for clearance not diameter

 

With a 275 width, you’ll lose a bead from low pressure before you rub anything other than the stock splash guard. You may need to trim that… mine rubbed that with 275/70 18 at regular pressure. Nothing a jigsaw couldn’t handle.

I wouldn’t really consider 30psi “aired down” and wouldn’t expect much benefit. If I’m doing higher speed relatively smooth stuff I’ll run mid to low 20’s. Sharp rocks, extremely rough terrain, or sand gets 16-18.

The E rated tires don’t really start to lay out until sub 25 IME.

 

the psi from the door 30 33

 

that's fine i don't wanna put a lift in it cuz my bad knee, just thought that would help offset any drop from airing down

 

i was going off the 20% rule i read, so 25-20 would be more realistic and helpful, got a washboard road for 4 miles, then a mile of deep holes and rocks

 

Ya definitely would help.