I just got my new rims and tires and checked the air pressures and I think they were a little high so I just wanted to see what everyone else is running? I am running 205/40/17 and the tires say a max of 44lbs of air. A couple were actually over 44lbs so I dropped the front down to 35 and the rear to 30 and I seems to have made a world of difference in ride and performance.

so what is everyone else running?

It depends on size and profile. The stockers like 32 psi. Bigger wheels (16's - 19's) need to be a bit higher to guard against pothole damage. Like 35 psi or so IMO.

Toyota says 29 PSI (http://tijil.org/xB_tire_size.gif) in the owner's manual, service manuals, and the sticker on your "B" pillar.

That's what I run on mine (15s).

http://www.scionlife.com/forums/viewtopic.php?p=1422693#1422693

Tom

From everyone I have talked to it seems like 32-35 is a pretty good range with 17's

Toyota says 29 PSI (http://tijil.org/xB_tire_size.gif) in the owner's manual, service manuals, and the sticker on your "B" pillar.

That's what I run on mine.

http://www.scionlife.com/forums/viewtopic.php?p=1422693#1422693

TomThat 29 psi is like for a cushy soft ride. 32psi will give better MPG and still ride good. If I ran 29 in my 17's I think a rim would crack on potholes. I'll stick with 32 -35 psi.

38psi for me. But then again im running 225/35/18 on a 9.5 inch wide wheel so I gotta keep the air pressure up with the super stretch.

29-30 on stock tires.

I am running 33psi in my 215/35/18s. That is what my tire guy said to run. I wouldn't run the max pressure because that is for maximum load capacity, and I don't think the xB is anywhere near the max load of any tire.

I am running 35psi in my 215/35/18s. Since you are running a 40 profile I'd run 32-35psi. That should give you a decent ride and guard against pothole damage.

40lbs in my nankang NS-II's (215/35-18)

32 psi in the 15" stockers, all 4 tires.

Im running just abit high 38 lbs on 17's.

30 psi on three and 10psi on right rear. freaking leaks :@!!!

44psi all around rides a lil harsh but thats how i like it and the firmer the tire the less friction the more mpg's i check my tire pressure every 2 weeks

Front: hankook 15's 195 55 15 36psi
Rear : Toyo proxie W tread 18's 215 35 18 44psi

works wonders on my box with Df210s'

34

Tell me if this is right. To much air preasure will cause excessive tread wear in the middle of your tire. To little preasure and the outsides of your tire will wear faster.
If that statement is true, how do you know what psi to run when your tire says max psi 44, and then everyone and their mother tells you to run something different?
I have maintained 35 psi in my 205/40/17's. When I changed out my last set of tires, the tread wear on the outsides of the tire was rediculous. I am just looking to prevent uneven tread wear no matter how it rides.

....I have maintained 35 psi in my 205/40/17's. When I changed out my last set of tires, the tread wear on the outsides of the tire was rediculous. I am just looking to prevent uneven tread wear no matter how it rides.

Sounds like you answered your own question.

In my opinion, Scion offers up a pressure that is too low. Remember what happened with the Ford expeditions (or whatever model it was). Less pressure is more dangerous than higher pressure. I have already noticed an increase in milage from going up to 32psi from 29. Now im up to 34psi and lovin it!

When I had my wheels installed, they put the pressure @ 44 and the ride was too rough for my taste.

Treadwear patterns are also the result of driving style and tire position on the vehicle.

Aggressive driving puts a lot more wear on the outside edge of the tires, especially the front tires.

Front tires, because of the steering inputs tend to 'roll-under' more than rears and wear more on the outside edges than the rears do, even with gentle driving, which is why tires are rotated.

These effects are exaggerated if the pressures are too low for one's driving style.

So, the more aggressive one's driving style, the more pressure required for even tire wear, which also improves cut-in and ability to handle rapid and excessive control inputs (but worsens ride).

The pressure indicated on the "B" pillar tag is for "normal" driving, not spirited. The pressure indicated on the sidewall is the maximum safe cold pressure for the tires, beyond which one can damage the carcass. Somewhere between the two is the best pressure for your particular driving style, offset, tire size, vehicle load, and road conditions.

Oh! Harder tires do handle better, BUT are also much easier to damage with road debris, potholes, and such. With softer tires it is much easier to 'break the bead' and lose air when driving very aggressively.

Running a rim width that is out of the design range of the tire size also makes a tire more prone to damage - too narrow and the tire can 'roll under', to wide and the bead does not seat properly. Rims wider than those the tire is designed for will also increase edge wear. (I see a lot of folks running rims waaaay too wide for their chosen tire size...)

An aggessive or spirited driver will fare better increasing tire pressures (within reason) over the recommended pressures from the vehicle manufacturer for "normal" driving.

It's really a lot more than just being black, round, full of air, and fitting in the wheelwell... :P

http://tijil.org/xB_Data_Plate.jpg

Yep, I went to 29 PSI and it runs just fine. The dealer had set them at 32. It is a little softer feeling in the corners, but I got used to it. I like to get a lot out of my tires.
Matt

The pressure you should run depends on the Load Rating of the tire. Stock is 29 psi. If your aftermarket tire has a higher Load Raing then you can run lower pressure. If your aftermarket tire has lower Load Rating then you should run higher. Ulta low profile tires tend to have ultra low load ratings, so you will need to bump up the presuure.

The stock recommended 29 psi is the amount of pressure for the given car's weight for the given tire's load rating.

It seams that every time I check the tire presssures after the car has been to the dealer they are wrong. When we bought the car they where set to 35 all around and I corrected it to 29. Since then they usually come back from the dealer around 26-27 and are never the same all around. Right now they vary from just under 26 to 28 after getting the car back from them for bad wear on one tire and an alignment. You would think they would be correct since it was in for tire issues and correct tire pressue and weight in the car are mandatory for a propper alignment as far as I know. After reading many posts in the forum I plan to run 30 from now on.

Why would they ALWAYS lower the pressures in my tires?

Why would they ALWAYS lower the pressures in my tires?Even just driving a few miles heats up the air in the tires enough to change the pressure - which is why they should be read BEFORE the car is first driven for the day, NOT after it has been driven to the dealership for service.

I keep my tires accurately inflated to the pressure I want, and so far every time the dealer has had it in the shop, the tires come back to me with assorted too low pressures. Last time I checked pressures just before driving to the dealership - they were right on. When I got the box back, they were all 2-3 pounds low. :( (...and it was ONLY in for a simple oil change...)

I have instructed the service folks at that dealership several times to NOT touch the tire pressures - to no avail. That is reason number four why I'm looking for a new dealership. :tap:

Tomas is spot on, as usual.

One of the least appreciated and most underused automotive tools is the tread depth gauge, like this-

http://www.amazon.com/gp/product/B000FNRO92/002-5962974-7735206?SubscriptionId=0GKY5T9AP29X0E3X4XG2&n=228013

That's a cheapie, but they work just fine. There are dial iindicator and digital models available as well. Using one every few thousand miles will let you know if the inflation pressure really is correct, and will help diagnose alignment problems early on. Particularly valuable for people running very expensive ultra low profile tires on oversize rims...

Seriously under inflated tires will run hot out on the highway, particularly in the summer, and run a much greater risk of blowout... the problem is exaggerated with heavy loads and the accompanying increase in sidewall flex...

While you bring up a good point of tread depth, there is no reason to spend more than a penny for a depth gauge. In fact, just use the penny as a depth gauge.

Place the penny into a tire groove with Lincoln's head upside down. As long as the tread covers part of Lincoln's head you are ok. It means you have more than 2/32" of tread depth. If you do the same thing on the opposite side of the coin and at least part of the memorial is covered you have at least 6/32" of tread depth. If you get below 2/32" it is time to replace the tires.

Also, place the penny in each of the grooves and compare how much of the penny is covered by tread. This is a good indicator of uneven tread wear even before it is visible to the naked eye. Uneven tread wear is an indication of either improperly inflated tires, or a bad alignment.

Find a penny pick it up... all day long you can check the tread depth on your tires.

I also like to run my pressures on the higher side, mainly to prevent rim damage in the event of ??? My 215 x 35 x 18's have 38psi in front and 35psi in the rear.