So the stock Geo Tracker tire size is like 205/60'ish?/15, and the factroy plate says they should be aired up to 22psi.  But i have 235/75/r15's on there now and the sidewall says maximum psi is 44.   When I air these guys to just 22psi i feel like i'm driving on marshmellows.

Since I went to a bigger than stock tire size, should i still follow the suggested psi from the factory or should i maybe air up a bit more?  Is there a basic formula for if you go up so many sizes you should increse your psi base by x amount?

So the stock Geo Tracker tire size is like 205/60'ish?/15, and the factroy plate says they should be aired up to 22psi.  But i have 235/75/r15's on there now and the sidewall says maximum psi is 44.   When I air these guys to just 22psi i feel like i'm driving on marshmellows.

Since I went to a bigger than stock tire size, should i still follow the suggested psi from the factory or should i maybe air up a bit more?  Is there a basic formula for if you go up so many sizes you should increse your psi base by x amount?

Are you sure it's 22 and not 26 or so? I'd go for some poundage around that, 26lbs.... Ultimately and if your into tweaking, a good way to find an appropriate road pressure is to find a pressure that is firm but that allows all of the tread surface to be in contact with the road. So, start a bit high and verify how much of the tread you're using. Then let air out until your using the entire tread face. Stop there... This is only one idea. I'm sure there are more and better ones.

-Eric

yeah, 22psi it says.  i thought it was really low too.

It is "recommended" by the manufacturer to run your tires per the specifications....Of coarse since you up sized I think you know you really dont fall inside the specifications anymore. By going with the bigger tire, you raised the COG and changed the overall handling response, maybe not much, but you did change it.

Pressure will affect your vehicles handling by varying the contact patch and the "stiffness." More pressure would mean less contact patch and a "stiffer" tire characteristic, and vise versa. If you are familiar with any kind of auto-racing you know that the pressure can be tweaked and adjusted to suit the scenario or conditions. So apply this to your driving.

You should never over-inflate (maximum psi+) or run extremely low pressure in normal driving conditions, but as long as you are cautious and mindful of any tire wear conditions you can vary your pressure to your liking. I like to run my tires usually somewhere between 30-35psi.

<edit- 22psi does sound low...>

Like Eric said you just need to find a pressure that make you comfy, I run my 31-11.50 |removethispart|@ 20psi on the street and 30 if I'm going on the Highway

Your recommended tire pressure on your tire is for the weight range of the vehicle your tire was designed. For example, most MT/AT tires with more than a 4 ply design are made for full size trucks that weigh WAY more than our Zuk's. Therefore with the recommended tire pressure of 44 psi is probably for a 6-8000# truck or car, not a 3000# Zuk. I only run 18 rear-20 front psi on my MT's on the tracker while being used on road. Off road I drop the WAY down (but running Staun beadlocks).

Erics suggestion is about the best way (trial and error) to get it firm yet comfortable with good tire wear.

HTH,
Z

   A easy way to get a jump start with what Eric said is a chalk or a tire pencil if you have one.  Draw a thick line arcoss the width of the tire and drive them for a few blocks.  Stop and look, if the mark is worn in the middle then its too full.  If its mostly the sides then too little, once they are filled so that line wears off even straight across you should be pretty good. Also be sure that the tires are warmed up when you do this as that will effect it.

  Also the PSI is based off of the vehical weight and providing enough pressure that the side walls do not directly carry that load.  Unless you run off road tires made for it too low of air pressure will destroy the thread bond inside the side walls.  That leaves you prone to blow outs at higher speeds.

So the stock Geo Tracker tire size is like 205/60'ish?/15, and the factroy plate says they should be aired up to 22psi.  But i have 235/75/r15's on there now and the sidewall says maximum psi is 44.   When I air these guys to just 22psi i feel like i'm driving on marshmellows.

Since I went to a bigger than stock tire size, should i still follow the suggested psi from the factory or should i maybe air up a bit more?  Is there a basic formula for if you go up so many sizes you should increse your psi base by x amount?

You seem to be making the mistake that a lof of people make when reading a tires sidewall.  The max. psi listed on a tires sidewall is what the tire should be aired up to if the load on the tires equal the max load that is listed on the tires sidewall.  For example, your tire sidewall probably says something like "max load 3000lbs at 44 psi".  In that example, if each of your tires has 3000lbs of weight on them (that would be 12000 pounds total weight), then you should air up your tires to 44 psi.  If the weight on the tires is anything less than the max load, then you need to adjust the tire pressure accordingly to a pressure that is safe, gives a comfortable ride, provides good MPG (as a general rule, the lower the air pressure, the less MPG you will get....because of increased rolling resistance) and gives a good treadwear pattern.

That being said, I run my tires at 30 psi.  That pressure wears them slightly faster in the middle of the tread, but that pressure also meets all the other criteria, so I live with it.

when you do the choke test you just go to an empty parking lot and drive around 100' in a straight line. if you turn then it won't show true contact wear. Play with it until you find a complete wear down.

I run 15psi in my 413K but don't drive it too much. I know it's low but when I go to 20psi then it's like driving on 100psi...way to stiff. I've been driving with low pressure for 10 years and never had a tire blow. The fuel takes a hit but it's not a daily driver.

I run the LTB Swampers at 5 or less, even on the street, which isn't much at all
these days, but when it was a DD on the same tires I ran 10

Wild

30X9.50X15 on little sammy I run at 18-20P.S.I. on the street. 8-10P.S.I on the trail. 35P.S.I. if doing a lot of freeway driving.

I don't figure I'm more knowledgeable than the Suzuki engineers. So I use (close to) their nameplate tire pressures on asphalt.  Your OEM tires are loaded to about one-third to one-quarter (!) of their maximum load rating, so the full 44 psi is NOT NEEDED, and only makes the tire wear in the center and ride very stiff.  When you increase tire size, you also increase load rating, so LESS pressure is needed to keep the contact patch flat on asphalt. Rolling resistance does increase, but you cannot have it both ways.
   
With your new, larger tires you might try reducing the tire pressure by a couple of pounds from Suzuki-specified for driving on asphalt.  When off-road, 10-12 PSI might work well if you're rims are within the recommended width for YOUR new tires (guessing 6-7").  Just keep your speeds DOWN, and air-up or drive slowly when back on asphalt.  Airing down when off-road can greatly improve traction and ride comfort, but can be stressful on sidewalls, so use good judgement. 

Chalk is the best way to find the best contract pattern on tires, tire manufactures cannot give proper pressures
for every car/tire combos. and Suzuki only rec. OEM tire sizes    i can only run 25psi in my Sammi
30/9.50-15 or it feels like a superball on the freeway.