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First of all thanks for adding me as a member.

I’ve searched for awhile trying to get an answer to a question I have about recommended tire pressure for over size tires. If someone here can help me I would much appreciate it.

I recently purchased a 2014 Rubicon Unlimited. The Jeep came accessorized with a aftermarket front winch bumper, a 12000 lb winch, it looks to be lifted, and has 35 x 12.5 x 17 tires on it.

I know that in the door panel it has a sticker that shows the recommended tire size and recommended tire pressure for the stock tires which is 37 psi.

My question is, what tire pressure should I run in the over sized tires?

When I purchased it, from a dealer, the tires were inflated to 40 psi. I have deflated then to 34 psi but the tires still seem to me to be over inflated.

Should the larger tires be inflated to the recommended 37lb psi or can they be run with less air pressure and if they can be run with less air pressure what would be recommended or is there a calculation to figure the correct tire pressure?

Thanks
 

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The number on the door is for the original tires. The over sized tires will have a max PSI on the sidewall near where it says the size. My aftermarket tires have a max psi lower than the number on the door, so you can just forget about that. A lot of people will run with lower pressures for a more comfortable ride, higher pressure gets you better fuel economy.

I recommend doing that chalk test. Use chalk to draw a line a couple inches wide across the width of the tread. Drive around for a little bit and then look at the chalk line. If the chalk is present on the outside of the tire but gone in the middle lower your pressure, if it's the opposite raise it. If it looks like the chalk has been rubbed off evenly then you are good. This will ensure that your tires wear down evenly and they will last longer.
 

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Discussion Starter #3
The number on the door is for the original tires. The over sized tires will have a max PSI on the sidewall near where it says the size. My aftermarket tires have a max psi lower than the number on the door, so you can just forget about that. A lot of people will run with lower pressures for a more comfortable ride, higher pressure gets you better fuel economy.

I recommend doing that chalk test. Use chalk to draw a line a couple inches wide across the width of the tread. Drive around for a little bit and then look at the chalk line. If the chalk is present on the outside of the tire but gone in the middle lower your pressure, if it's the opposite raise it. If it looks like the chalk has been rubbed off evenly then you are good. This will ensure that your tires wear down evenly and they will last longer.
Thank you!
 

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Welcome aboard.
I run 32 in my JKU with 35's. Lowest pressure while still not squirmy on the roads around me.
Rotate your tires every oil change. Use some kind of cross rotation so the tires move around to all positions.
 

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...I recommend doing that chalk test. Use chalk to draw a line a couple inches wide across the width of the tread. Drive around for a little bit and then look at the chalk line. If the chalk is present on the outside of the tire but gone in the middle lower your pressure, if it's the opposite raise it. If it looks like the chalk has been rubbed off evenly then you are good. This will ensure that your tires wear down evenly and they will last longer.
Yea, what he said. I've found that I only need to drive just enough to rotate the wheels/tires a couple of revolutions to rub off the chalk from the tread. If it comes off only on the middle of the tread then they're over inflated. If the chalk is rubbed off only on the outer edges of the tread, then they're underinflated. Tire size/type, wheel size, vehicle weight all contribute to determining the correct pressure. Good Luck!
 

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I have found that Iuse 2 different pressures, a bit lower for normal driving (28 lbs for 315/70R16), and 30 PSI when heading on a wheeling trip due to the extra weight of all the offroading gear. Adding 400+ lbs of gear makes a difference (tools, parts, camping...)
 

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^^ That's sort of what we do, when it's a long trip and we're conserving fuel, I'll air up to 35 ^^
 
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