tires at 40 psi ?

[cosine]

i know the tires are over inflated from the factory. mine was at 47 psi. so i aired them down to 40 psi when i came home with it and been running them since then. i will be hitting the road on a 1500 to 1900 mile round trip.

so my question is, will running the tires at 40 psi be ok even with the pressure fluctuating from the heat. or should i drop them down to 38-39 psi. tires are stock michalins.

what are you folks running at for a nice comfortable ride on the interstate.

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[Az-jewel]

That seems high to me...what is the recommendation on that tire? I’m running my 35” Nittos at 34.

 

[goingsolo2]

Mine were inflated to 45-47lbs. from factory when I took delivery Friday. I lowered them to 35psi when the tires were cold. The sticker on the door says 37. Once they heat up, they get to 37. The Jeep drives night-and-day better with them at 35. It was a bit squirmy with them over 40.

 

[liquids]

You'll feel every crack in the road at 38+. If you want a "nice comfortable ride" like you say, stay in the 32-35 range. Taking sharper highway bends at 80 mph like that will feel a bit squishy, though. Stay closer to the speed limit the lower you go.

 

[EZMFE]

i know the tires are over inflated from the factory. mine was at 47 psi. so i aired them down to 40 psi when i came home with it and been running them since then. i will be hitting the road on a 1500 to 1900 mile round trip.

so my question is, will running the tires at 40 psi be ok even with the pressure fluctuating from the heat. or should i drop them down to 38-39 psi. tires are stock michalins.

what are you folks running at for a nice comfortable ride on the interstate.

What does the sticker in the drivers side door jam say you should run them at?

Many run larger tires and reduce the air pressure but that doesn't mean you should since you are running stock. Tires have different load ratings and handle weight differently depending on that rating and weight of the vehicle. Some have a max psi of 80 (10 ply) but are made for tons of weight while others max psi is lower and have softer sidewalls (less plys). I'd start somewhere around the recommended tire pressure that is posted by the mfg and go from there. Try it a few lbs lower and see how she feels and increase if needed. It would be pretty rare that you would go over the recommended pressure though... unless you like a stiff ride.

As far as the long trip you will be taking... do a chalk test on the tires when fully loaded and make sure the tread is wearing evenly. Take some chalk and spread it across the tires and roll the vehicle over the chalk a couple times. You will see the current wear pattern and if you need to raise/lower the air pressure to make the tread wear as evenly as possible. That will give you the longest tread life but may not be ideal for how you like it to ride. It's would be a trade off at that point. Do you want a softer/stiffer ride or longer tread life...

If running a higher psi, the middle of the tire will wear faster than the outer and if running a lower psi, the outer will wear faster that the inner. You wouldn't see that will small increment changes but will when getting too far away from the recommended. That can all be confirmed with the chalk test.

 

[marjamr]

i know the tires are over inflated from the factory. mine was at 47 psi. so i aired them down to 40 psi when i came home with it and been running them since then. i will be hitting the road on a 1500 to 1900 mile round trip.

so my question is, will running the tires at 40 psi be ok even with the pressure fluctuating from the heat. or should i drop them down to 38-39 psi. tires are stock michalins.

what are you folks running at for a nice comfortable ride on the interstate.

40 psi is too high. Do a search for the chalk test to see the best pressure for your set up. Set my Falken Wildpeaks (OEM size) at 34psi. They ride great there.

 

[goingsolo2]

What does the sticker in the drivers side door jam say you should run them at?

Many run larger tires and reduce the air pressure but that doesn't mean you should since you are running stock. Tires have different load ratings and handle weight differently depending on that rating and weight of the vehicle. Some have a max psi of 80 (10 ply) but are made for tons of weight while others max psi is lower and have softer sidewalls (less plys). I'd start somewhere around the recommended tire pressure that is posted by the mfg and go from there. Try it a few lbs lower and see how she feels and increase if needed. It would be pretty rare that you would go over the recommended pressure though... unless you like a stiff ride.

As far as the long trip you will be taking... do a chalk test on the tires when fully loaded and make sure the tread is wearing evenly. Take some chalk and spread it across the tires and roll the vehicle over the chalk a couple times. You will see the current wear pattern and if you need to raise/lower the air pressure to make the tread wear as evenly as possible. That will give you the longest tread life but may not be ideal for how you like it to ride. It's would be a trade off at that point. Do you want a softer/stiffer ride or longer tread life...

If running a higher psi, the middle of the tire will wear faster than the outer and if running a lower psi, the outer will wear faster that the inner. You wouldn't see that will small increment changes but will when getting too far away from the recommended. That can all be confirmed with the chalk test.

Factory sticker on the Rubicon says to inflate front and rear to 37psi.

 

[tablerock]

Dealers are supposed to due a PDI [pre- delivery-inspection ] you would think that would include the proper tire pressure !!!!

 

[EZMFE]

Factory sticker on the Rubicon says to inflate front and rear to 37psi.

Yep, that is what the rubicon says but I'm not sure about the Sport as that is what the OP has. I'm running D rated 37's @ 28psi cold and it is perfect as far as tread wear. Obviously, the lower psi you go the more surface area/resistance you will have on the road and that could cost you in mpg and excessive wear.

 

[cosine]

the sticker said 36 psi cold. i remembered that i ran my other tires at 37 psi. so, i aired them down to 37. that should be fine. my guy at the shop sometime air them to 38-39 psi.

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