Tire Pressure

[TJ_Jeep]

Whats the best psi to run on my 35's on a ratio between good ride and good mpg. I tried 20 and it just sucked gas but it was very smooth, but now i'm running 40 its a little rough but my numbers are going back up. (it holds 50)

Whenever i change my gears out i know i'll be better.

 

[Rubiconrich]

I run about 28 on the road. 20's to low and 50's to high.

 

[TJ_Jeep]

Forgot to say there 8 ply if that means anything

 

[xt master]

Well you tried 20 and 40..why not try in the middle and go with 30.

Best way is to find an empty lot and get some chalk.Make a line across your tire and drive.Check the pavement after wards to see if the line is continuous across the whole pattern.Air up or down till you have a solid line.This will help with tire wear also.I would do all four tires.Different weight from back to front and passenger and driver side.

 

[TJ_Jeep]

Well you tried 20 and 40..why not try in the middle and go with 30.

Best way is to find an empty lot and get some chalk.Make a line across your tire and drive.Check the pavement after wards to see if the line is continuous across the whole pattern.Air up or down till you have a solid line.This will help with tire wear also.I would do all four tires.Different weight from back to front and passenger and driver side.

Well i've been told that the higher you go, better mpg you get and i've tried the chalk thing. (i really need to get a portable air compressor lol)

 

[jfrabat]

The higher you go, the less roll resistance you will get (which can translate into better mpg). But it also means that the tires will wear out in the middle first, and that the ride will be rough.

 

[Bounty__Hunter]

Rim width and vehicle weight are also factors.

 

[phall92139]

Go back to your chalk "thing" and try it with different loads in the Jeep. I've found that no one tire pressure is the answer. After experimenting quite a bit I now know how much pressure to run depending on how much crap I'm hauling around. Also, I usually increase tire pressures slightly if I going on a fairly long road trip on the higjhway or freeway where higher speeds will build excessive heat in underinflated tires.

 

[SteelHeadz]

My tires has a 30 psi max. inflation. i run it all the time on 28psi. anything lower makes it wobbly, anything higher makes it too stiff and feels like there's no suspension.

 

[phall92139]

My tires has a 30 psi max. inflation. i run it all the time on 28psi. anything lower makes it wobbly, anything higher makes it too stiff and feels like there's no suspension.

I understand what you're saying about "wobbly." Another factor we haven't addressed yet is rim diameter. Your 35X14.50/15's with their wider section width than my 35X12.50/15's even exasperate the problem more. These tires actually fall into the "high flotation" catagory, are built with higher reserve capacity and are the little brothers of tires designed for 18-wheelers. Due to the large sidewall surface they tend to flex or wobble more than the same diameter and section width tire on, say a 17" rim.

That's why, IMHO, I think 35's are about it for a 15" rim for a rig driven substaintially on the street. 37-40's on a 17" rim aren't that bad, although one of the the trade offs for wheeling with low tire pressures is less sidewall flex.

 

[jfrabat]

One thing noone has mentioned yet is that the ideal pressure will result in lower pressure for the rear wheels than the front wheels, as th front wheels of the Jeep ussually carry more load (the engine weight and, in some cases, the winch).

 

[Bigcountry10]

i've got o saythat i never really give much thougt to the psi in my ride. i air down for sand and rocks, back up for mud and hwy. am i missing out on something good here

 

[jfrabat]

i've got o saythat i never really give much thougt to the psi in my ride. i air down for sand and rocks, back up for mud and hwy. am i missing out on something good here

I think you are; tire pressure will dictate how your Jeep handles and how much gas it consumes. Lower pressure will make for a softer ride, but handling will be reduced as will mpg. Higher pressures will have better mpg and handling, but the ride will be stiff. It is all a tradeoff of what you want from your ride...

 

[Turbogus]

In another incarnation I used to be a bus driver. The owner of the company always liked to run the tires at 60-50% cold pressure on account of wanting a greater 'contact patch' with the road. Whenever the bus came out of his shop I'd take the bus to the local truck stop and bring them closer to optimal pressure on account that we were constantly picking up fod in the sidewalls thus destroying the tires. :razz:

 

[Crazy4diesels]

Too high can also make things slippery in wet weather... A good "all the way across" contact footprint is usually what I look for. Just enough squish to get the full width of the tread working for you. And try to check your pressures often - just a few pounds low can affect MPG. I ran a set of LT tires last winter and they rode quite a bit rougher than the "flimsy" passenger tires that came on the Jeep. The sidewall construction makes a big difference in ride characteristics. Yes, fronts are usually higher than rears because of loading. Best of luck - John

 

[jps4jeep]

Depends on the type of tire. bias Swampers seam to work best at 17-20 psi a Bfg or MTR seam to work best closer to 25-30 psi. I would put your nitto's some where inbetween there. honestly, with a lifted jeep and 35" tall tires, you milage is not going to be that great, even with gearing to put your final drive ratio near stock, there are a lot of other factors, rolling mass and wind resistance for example.

 

[xt master]

Depends on the type of tire. bias Swampers seam to work best at 17-20 psi a Bfg or MTR seam to work best closer to 25-30 psi. I would put your nitto's some where inbetween there. honestly, with a lifted jeep and 35" tall tires, you milage is not going to be that great, even with gearing to put your final drive ratio near stock, there are a lot of other factors, rolling mass and wind resistance for example.

Another factor you left out is the weight of the tire itself..35" are not the lightest tire on the market.

 

[SteelHeadz]

Another factor you left out is the weight of the tire itself..35" are not the lightest tire on the market.

Very true that they are not light, however, just because they are bigger doesn't mean that they are heavier than the other. My BFG Baja champion 35X12.5 15's are heavier by 8 pounds than my 35X14.5 15's. The BFG's i have is a 6 ply steel and 2 ply polyester but the pitbull krawlers has 3 ply steel and 4 ply polyester. The carcass of these tires makes a significant variable on it's weight and the way they will handle on the road and on the trails. I wish i could find the same specs. on these newer BFG's.

 

[TJ_Jeep]

Depends on the type of tire. bias Swampers seam to work best at 17-20 psi a Bfg or MTR seam to work best closer to 25-30 psi. I would put your nitto's some where inbetween there. honestly, with a lifted jeep and 35" tall tires, you milage is not going to be that great, even with gearing to put your final drive ratio near stock, there are a lot of other factors, rolling mass and wind resistance for example.

Oh yeah i know that, but when it had 20 psi i got 8 miles to the gallon but now with 40 psi i get around 13 mpg i did the chalk thing and 35 was the best for the rear and 39 for the front. And i guess thats the best its gonna get til i regear