eclipse641

I am just curious as to how much air pressure everyone is running in their tires? The last tires I had were nittos and I ran them at around 42 psi. I have kumhos now and am running at 40 psi. The max pressure for both tires is 50 psi. I have ran the car as low as 36 psi which makes the ride feel stock smooth. Is this too low? Should I stick with 40 psi or go lower or higher? Any advise is greatly appreciated. Thanks

princelybug

iTrader: (16)

Just my humble opinion, but I think ANYWHERE in between 36-40 psi is safe. I think 42 is pushing it maybe a little bit. Remember, 50psi is the MAX under any conditions, and your tire, depending on how far/fast/long you've been driving will increase in pressure up to 7 or 8 psi possibly. You don't want to be anywhere near max psi, if possible. Fyi, I currently am running 235/35/19's, and I run 40psi up front, and 37 psi in the rear. The less pressure in the rear helps to alleviate the understeer a tad bit.

Hope that helps!

eclipse641

The customer service guy at tirerack said to run the tires at what is recommend on the door of the vehicle. Obviously he know nothing about tires and tire pressure. I have noticed that running the tires at 36 reduces gas mileage by a lot but the car has a great ride. Running at 40 is a bit thougher ride but gas mileage is better. I am not sure if this is all in my head or if it is really effecting gas by that much. I will definetely take your advise at running the rear a bit lower. Maybe 40 in the front and 38 in the rear. Thanks

darksky

I'd go with what the door says... 33/32 on my 2008 TL. Also know that as the tire heats up the air pressure will increase. I've seen about +5 in the front and +3 in the rear but it's cold now. I'll bet it'll increase a little more once ambient is 80-90 °F.

You might wanna spend some time reading the "tech" articles over at tirerack.com for additional info. There are a number of them that cover aspects of air pressure you should check out. Running over inflated tires is a bad idea for a number of reason (read the articles).

geekybiker

set your tire pressures cold according to what is on the door. It is what should give you a nice flat contact patch.

LudaChris

The door PSI info is for stock tires only. He is running on 20s. I attended TechTire tire repair class and remembered asking this question before. They said go by the tire and not the manufacturer info because tires vary from brand to brand. He also told me to run close to max psi to get the most gas mileage and longest life, but this is on regular passenger tires with like 60 series or more. I am currently running 245/30/20 on 04 TL @ 38psi all around 3 inch drop, no rub and looks tight. I used to get 22 mpg city @ 45psi but was too rough. 38psi gets me 19mpg now. Oh well, gotta give somethin' up.

darksky

The door jamb or your Owner's Manual is the best place to look. Now if you're using a plus size tire, I'm not sure, but I don't think LudaChris' advice to go with near the max pressure is a good idea regardless of tire size/aspect ratio. Remember that air pressure in a closed system [the tire] is a dynamic thing. As your tires heat up, the pressure will increase according to the ideal gas law. I've seen mine go from 33 psi (cold) to 38 psi after about 20 highway miles as an example.

Over inflating tires can be dangerous and can also cause excessive wear. I'd point interested parties to the tire tech articles on tirerack.com for more. Another resource is your local tire shop and/or dealership about recommended cold pressure on various brands/sizes of tires that aren't OEM size.

That said, if you are planning to drive at excessive speeds (over 100 MPH) it is recommended to use more than the door jamb recommended pressure. Right out of the 2008 Owner's Manual:

rodneyc77

iTrader: (1)

I ran that same size tire for 2 years at 38psi