TahoeRunner Posted March 28, 2012 Share Posted March 28, 2012 So last night I was in the garage digging around in my toolbox for something and found one of our tire pressure guages and thought, oh man I haven't checked the tire pressure on Sarge yet since I bought him almost a month ago. I had thought the other day to check the tire pressure just to be sure since the previous owner had the tires rotated and balanced at Costco (where he bought them) a few days before I bought it and it would let me know if any of the tires were leaking. Got out the trusty guage and almost leaped in the air! All 4 were inflated to 48 psi!!! the max listed on the sidewall! I can't tell you how many times I've had to correct people that if you are running stock tire size you should be inflating to what's on the inside of the door, but I was shocked that he just had it in for a rotation and they adjusted the pressure that high. The sad thing is, this isn't the first time I've seen this happen from a tire place that's going off the sidewall label on the tire and not the placard in the door. They must have had some new guy in there doing rotations or something. So I checked the door and saw that it only requires 26 psi! I don't think i've ever had a car that recommends less than 30 psi before. So that leads me to my question. I know most of you run oversize tires but for any still stock or back when you were stock, what psi did you run your tires at? This might explain why its been getting such good gas mileage because the tires were running on their tippy toes. Last night I let them down to 30 psi for now. Do any of you run higher psi, lower? notice differences? On my drive to work this morning it definitely took the edge off the ride! I thought it was awfully rough riding, even for a mid 90's SUV but now its not quite as jumpy and definitely less squirelly. Link to comment Share on other sites More sharing options...
5523Pathfinder Posted March 28, 2012 Share Posted March 28, 2012 (edited) I run 28psi in my BFG 33's. I have messed with the pressure up and down and that is where they seem happiest. Yeah, most kids working in a tire shop(really any shop) usually get that wrong. Usually because they are taught wrong(plus the average joe gets it wrong too). You only want to run the max pressure when at full load or towing. Edited March 28, 2012 by 5523Pathfinder Link to comment Share on other sites More sharing options...
Leo94 Posted March 28, 2012 Share Posted March 28, 2012 This seems like a mistake i would do. Why shouldn't you go use the pressure rating on the side wall to pump up the tire? Doesn't the pressure change for different types of tires or at least use the same pressure all round which is close to the sidewall rating Link to comment Share on other sites More sharing options...
5523Pathfinder Posted March 28, 2012 Share Posted March 28, 2012 The sidewall rating is for the max load the tire can handle. Inflating a tire to its max pressure blows it up like a ballon, and the weight of the vehicle onply compresses the tire a small amount, meaning that the treadpatch is not in proper contact with the road. The recommended tire pressure that is posted on usually the door jamb, is meant to give the tire the best contact patch possible, with the vehicle normally loaded(think you, a passanger, and groceries), so the vehicles handling is still predictable. You change that pressure and different things can occure, such has handling different, tire wear, lower fuel mileage, ect. The same is true if you underinflate a tire. That tire will pull up in the middle and you will be riding on the outer edges or "shoulders" of the tire. This would also create excess drag, heating and wearing the tire prematurely. Does that make sense? Link to comment Share on other sites More sharing options...
TahoeRunner Posted March 28, 2012 Author Share Posted March 28, 2012 The sidewall rating is for the max load the tire can handle. Inflating a tire to its max pressure blows it up like a ballon, and the weight of the vehicle onply compresses the tire a small amount, meaning that the treadpatch is not in proper contact with the road. The recommended tire pressure that is posted on usually the door jamb, is meant to give the tire the best contact patch possible, with the vehicle normally loaded(think you, a passanger, and groceries), so the vehicles handling is still predictable. You change that pressure and different things can occure, such has handling different, tire wear, lower fuel mileage, ect. The same is true if you underinflate a tire. That tire will pull up in the middle and you will be riding on the outer edges or "shoulders" of the tire. This would also create excess drag, heating and wearing the tire prematurely. Does that make sense? ^^yeah, what he said.^^ Link to comment Share on other sites More sharing options...
kdj Posted March 28, 2012 Share Posted March 28, 2012 Agree with 5523 Pathfinder. I keep mine at 30 lbs. even the door jamb tells me 26 lbs. I have even tire wear a good ride. Link to comment Share on other sites More sharing options...
Mr.510 Posted March 28, 2012 Share Posted March 28, 2012 With 31x10.5 all terrains I ran the factory recommended 26psi and always got flat, even wear. With 33x10.5 KOs I dropped to 25psi and get the same. Generally speaking the bigger and more 'balloon like' a tire is the less pressure it takes to form a proper contact patch. This is due to the larger internal surface area of a bigger tire. That said, with really aggressive mud tires it's often necessary to run much higher pressure to keep them from scalloping and/or rounding off the outer tread lugs on the street. This is a compromise that reduces traction on the street and wears the center of the tire more than the edges. The upside is the outer tread blocks (which have the most effect on off-road performance) last longer and remain sharper to better do their job on the trail. Link to comment Share on other sites More sharing options...
Precise1 Posted March 29, 2012 Share Posted March 29, 2012 I run 28-30psi, seems the best balance between even contact patch, ride comfort, cornering, wear and mileage. B Link to comment Share on other sites More sharing options...
Tungsten Posted March 29, 2012 Share Posted March 29, 2012 The factory recommended 26 psi is just fine but since I run highway tires and want to keep the extra overhead to prevent them from losing pressure below the recommended amount in the cold I always bump them up to about 30 psi. Link to comment Share on other sites More sharing options...
TahoeRunner Posted March 29, 2012 Author Share Posted March 29, 2012 Thanks for the tips. I have them set for 30 and the handling feels floatier and sloppier (go figure) than before. The truck has LT tires on it which is so overkill so I might bump up the psi 2-3. We'll see how it goes. One thing I noticed is that lowering the PSI seemed to help my speedometer be more accurate, which the day I bought it and brought it home I noticed on the freeway it was 5mph too slow. So either my speedo is more accurate because the tires are inflated so much to be riding on the center ridge, or traffic yesterday was flowing a lot faster than usual everywhere. Might have to get my wife to follow me somewhere this weekend to verify. Link to comment Share on other sites More sharing options...
5523Pathfinder Posted March 29, 2012 Share Posted March 29, 2012 Just use any GPS that displays mph. I do this with my 33's to know that im about 3-5mph off. Yeah, the tires you run now are probably way different than what came on our vehicle stock(obviously many different tires and sizes). The load rating of the tire can determine how much flex the sidewall will have. Some M/T tires have a D or E load rating which can stand up to low pressures better(guys with beadlocks will runless than 5 psi and you can hardly tell the tire is low). Raising the tire pressre higher can mask other suspension issues(shocks, bushings, correct ride height). Think, in the racing world(well use NASCAR as a example) they raise and lower tire pressure by sometimes a 1/2 a psi to help the car corner or "hook up" better. Link to comment Share on other sites More sharing options...
nismothunder Posted March 29, 2012 Share Posted March 29, 2012 Depends on the tire. Link to comment Share on other sites More sharing options...
kdj Posted March 30, 2012 Share Posted March 30, 2012 If I tried to run 25 LbS. I'd feel like I had four flats . Stock 265/70/15 BFG AT. I do most of my driving on dirt roads but highway at under 30 LBS?...no way. I don't have GPS but under 30 lbs...nope. Link to comment Share on other sites More sharing options...
ahardb0dy Posted March 30, 2012 Share Posted March 30, 2012 back when I used to mount tires we generally filled them to 32, I run between 30-32. The rating on the sidewall if you look will say something like 3000 lbs at 35PSI, so you times the max load by 4 to get 12,000 lbs, the truck doesn't weigh 12K lbs so you don't need to run the max pressure. Link to comment Share on other sites More sharing options...
Slartibartfast Posted March 31, 2012 Share Posted March 31, 2012 I keep mine 26-30 psi. I did have them at 50 for a while (after reading the sidewall, herp derp), and while I didn't drive enough to cause cupping, I could've slid a credit card under the outer tread. I'm gonna go ahead and guess that driving like this wasn't terribly safe. Link to comment Share on other sites More sharing options...
Precise1 Posted March 31, 2012 Share Posted March 31, 2012 You are still safe if you are at or under the max tire pressure, it just doesn't mean you are at a correct pressure. Handling, ride and tire wear would all be negatively affected. When in doubt, do the chaulk test. Mark a line across the tire, drive straight 100 feet and look at the line. If it is worn off in the middle only, you are over inflated, if it's the outsides only, you are underinflated. There will be a pressure range where the chaulk will wear off evenly across the tire and it is up to you to determine what feels right, handles fine, etc. Remember, tires will heat up some from driving and increase prerssure slightly... B Link to comment Share on other sites More sharing options...
Kingman Posted March 31, 2012 Share Posted March 31, 2012 32PSI... 26 is too squishy. Link to comment Share on other sites More sharing options...
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