felixcat

Hi guys, I just picked up my new IS. It comes with the 18 inch wheel, and the factory Bridgestone tire. In the owner's manual it says the tire pressure should be 35 front and 38 rear. Since I am coming from the normal FWD family sedan with the traditional 15 inch wheel, so now I am a bit scary to put this high pressure in my new car's tire.

But I know this is performance and it need some special treat, so is it safe to put the 35 and 38psi into the front and rear tires respectively? (I am living in the hot Texas) Or your guys put lower pressure? Higher pressure?

Byprodrive

iTrader: (1)

Always start with the vehicle manufactuers spec & tweek slightly from there.
My 2007 IS350 says 37 psi in the rear. To get better tread wear/handling on front I run 37psi front & rear. IS is very prone to wearing the extreme inner edge of the front tire that is why I increase front psi.

slee18

iTrader: (1)

I usually put about 2 psi more then what is recommended. Just for better gas mileage and tire wear. Rides little stiffer if your ok with that. I wouldnt be too worried about the temps. We get as hot ast 112-114 in the summer time.

Stokdgs

Something that says, "Do not exceed xx psi in these tires. You want to stay at least 4-5 psi below that "do not exceed xx psi" rating when you check the tires cold, like in the morning before you take the car out. As you drive the car the tires heat up and add psi to the total amount so that's why its not as accurate to check them after you have driven them awhile and they are hot. The Lexus sticker says 35 front and 38 rear, start with that and see how it works for you.
If you add too much air, it will make the middle of the tire stick out and cause it to wear faster. A few more psi of air from what the sticker says is supposed to help a little in handling , and mileage, perhaps.
The worst thing is to have too little air in the tire, which will cause them to overheat and possibly blow out on you..
Look at the rating of the most air allowed on the tire sidewall and work backwards from there, allowing 5psi for expansion when driving, and always check them when they are dead cold, not warm, cold.. In the winter, they will also lose so much air per drop in temps, so it its outside you need to allow for that too.
Good luck, be careful, get a good accurate gauge of your own, the one at the station is crap and should not ever be trusted to be accurate. It will help in a pinch but you need another gauge of your own..
DanF

icantsee

If it was my car...I would run 40 psi

When I use to work at Wheel Works...a porsche came in.

Fronts: 245/40zr18
Rears: 265/35zr18

...I did 40 or 42 psi

Anything w/ lower profile...I may even go higher.

Some guy w/ a Corvette running on Run Flats, we put 40 psi & he wanted 30 psi.

I informed him that it isn't safe, but he still insist. Whatever you want buddy.

supaIS350

35 in the front, 37 in the rear for me..that's what it says on the sticker when you open the driver side door.

Gr8Dane

I work at a tire store and I take my wheels off and rotate them side to side every 2,500 miles. I check the tread depth as I do it, to make sure the tire is wearing evenly. I have 19,000 miles on my tires and will probably get another 5-10,000 miles out of my tires. I run 35 psi in the front and 30 psi in the rear.

If you run a higher psi in the rear you will wear out the center of the tire prematurely.

lobuxracer

iTrader: (2)

Ummm. No. The maximum pressure on the sidewall is the maximum COLD pressure. You don't need to subtract anything. In fact, the tire's load capacity is measured at that pressure, and there is nothing you will ever do that will stress a tire as much as full load testing at the rated pressure.

aQuarius26

iTrader: (2)

Just recieved my 06 IS350 on Sunday, noticed that the warning lights were on, so I went out and bought a "Slime" guage and checked each tire. Here are the results.

I have Dunlop Sport Maxx (51psi max)

F:225/40/18 were @ 29psi
R:255/40/18 were @ 30psi

So being that stock reccomends 35psi F & 38psi R, Im quite a bit off.

What kind of "play is there", meaning how many psi can a tire drop w/o the warnings going on?

THANKS!

Bichon

Roughly 5 psi; any more will trigger the light.

IS-SV

Note: tire pressure checks should be done when tires are cold (before driving).

Duke02

iTrader: (2)

I actually came across something interesting (to me at least) in the manua this morning. I was looking for the coolant type for the 2IS and came across the tire pressure section as I was flipping through.

For the 18in wheels, it says to add 7.2psi (I think that was the #, operating off memory now) if you plan to travel above 100mph, but of course not to exceed the max cold tire pressure when inflating.

I'm guessing this is because the 35/37psi may be a bit on the lower end of the acceptable range for performance to allow for comfort and that high speed operation would cause too much heat to build up at that pressure and damage the tire.

Let me fully disclaim that I am not an engineer or professional mechanic, so I may have gotten this completely wrong, but found it interesting

Byprodrive

iTrader: (1)

The increased pressure helps to maintain the round shape of the tire at highspeeds. This helps the tire stay cooler