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tire pressure, per tire rating or vehicle sticker?? #1229727 05/08/12 08:16 PM 05/08/12 08:16 PM
Joined: Aug 2004 Posts: 466 U.S.A. C Captain Flapjack OP mopar
Captain Flapjack OP mopar C Joined: Aug 2004 Posts: 466 U.S.A.	recently replaced tires on a suv i got in a discussion with another as to should the pressure be set to the tire max pressure rating or the vehicle manufactorers sticker on the door jamb? im pretty confident i know the answer, but dont want to sway anyones input also, let me know what you are basing your answers upon?

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Captain Flapjack] #1229728 05/08/12 08:21 PM 05/08/12 08:21 PM
Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O 70Cuda383 Too Many Posts
70Cuda383 Too Many Posts Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O	depends. I monitor tread wear and adjust air pressure accordingly. the max pressure on the sidewall is for when the vehicle is fully loaded. I typically run 35psi on all vehicles. if I'm going to pull a heavy load in the truck, I air them up to 45, the max on the sidewall. on performance tires with a much wider footprint, and more surface area to spread the weight out on, I air them down a little to prevent from ballooning out the tread and wearing them out in the middle. so...not sure there IS a correct answer short of "it will vary with current use" Photobucket sucks

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Captain Flapjack] #1229729 05/08/12 08:55 PM 05/08/12 08:55 PM
Joined: Mar 2007 Posts: 3,277 West Coast, USA jbc426 master
jbc426 master Joined: Mar 2007 Posts: 3,277 West Coast, USA	Most people run the max rated air pressure, but aren't at the maximum load capacity. They don't have enough weight to force the tire into the proper shape, so it wears in the middle of the tire. They end up burning off the tread around the center of the tread pattern. Assuming the proper size tire and rim, tire air pressure is all about adjusting the shape of the tire where it flexes against the ground given a certain load. I use kid's chalk to rub a line across the tread. Then drive the car straight forward until it wears off enough to see how much of the tread is contacting the road. If the outside tread is lifted off the ground, I lower the air pressure until it scuffs off evenly and visa versa. 1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's 1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Captain Flapjack] #1229730 05/08/12 10:49 PM 05/08/12 10:49 PM
Joined: Aug 2003 Posts: 43,157 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,157 Bend,OR USA	The car builder is going to reccommend a pressure that rides good, the tire maker is telling you how much maximum weight the tire will hold safely at the pressure they have on the sidewall. The pressure you run is up to you My thinking on my Ram 3500 is to run the pressures off of the tire makers recommendations, it is a truck I do run it empty 95 % of the times, maybe even 98 % of the time Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Cab_Burge] #1229731 05/08/12 11:24 PM 05/08/12 11:24 PM
Joined: Mar 2005 Posts: 3,141 Central NC gch master
gch master Joined: Mar 2005 Posts: 3,141 Central NC	I start by setting them by the sticker in the door jamb.You can usually adjust that 2-4 lbs higher of you like a firmer ride but do have to watch for uneven tire wear. In some instances the auto maker may call for 26,28,or some other number less than 30 and I generally disagree and run 30 as a minimum. The average passenger vehicle will run fine with 32-35 psi. Low profile tires(like on my vette)call for 30 and I never run over that. Some cars like BMW and Mercedes will spec 4-6 psi more in the rear tires. Go with the sticker in the door jamb and adjust it 2-4 psi up if you want a firmer ride. Air up accordingly when carrying weight and air down after weight is removed. Remember to set air pressure when the tires are cold.

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Cab_Burge] #1229732 05/08/12 11:31 PM 05/08/12 11:31 PM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	On a car or SUV I never run less than recommended. I consider that minimum. I usually run a bit more but not max on the sidewall. Most cars or SUV's like 35 psi cold. As several have posted, vary to get the most even treadwear. For a long loaded high speed run in hot conditions, I might run max pressure but not much need for that in the US. On a trailer or fully loaded truck, different situation. I run maximum pressure. Keep them as cool as possible so they don't blow.

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Captain Flapjack] #1229733 05/08/12 11:45 PM 05/08/12 11:45 PM
Joined: Sep 2003 Posts: 1,688 Marlboro, NY, USA R Rick_Ehrenberg top fuel
Rick_Ehrenberg top fuel R Joined: Sep 2003 Posts: 1,688 Marlboro, NY, USA	Within safe parameters, you'd be amazed at the profound affect some moderate F/R TP bias changes can make in a vehicle's handling characteristics. This can be a crutch to mask problems, of course (EG: look up TP specs for a Corvair), but it can also equal G-machine FUN! Rick

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Rick_Ehrenberg] #1229734 05/09/12 12:02 AM 05/09/12 12:02 AM
Joined: Oct 2005 Posts: 4,945 WI Dcuda69 master
Dcuda69 master Joined: Oct 2005 Posts: 4,945 WI	If the vehicle has TPMS the game changes

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Dcuda69] #1229735 05/09/12 12:03 AM 05/09/12 12:03 AM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	OK... I'll bite. How does it change?

Re: tire pressure, per tire rating or vehicle sticker?? [Re: ahy] #1229736 05/09/12 12:11 AM 05/09/12 12:11 AM
Joined: Dec 2006 Posts: 602 N.E.Ohio P pacifica mopar
pacifica mopar P Joined: Dec 2006 Posts: 602 N.E.Ohio	Quote: OK... I'll bite. How does it change? Depends on whether you care to stare at the low tire message/warning or not

Re: tire pressure, per tire rating or vehicle sticker?? [Re: pacifica] #1229737 05/09/12 12:48 AM 05/09/12 12:48 AM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	OK... on my wife's '08 Caliber RT the OE tire size was 215/xx/18. An oddball size with little selection. I replaced with 225's to get more selection and reduced pressure from 35 to 32. TPMS is still happy and so are the tires. We also put snow tires/wheels on it. Didn't want to spend $225 on new TPMS sensors and went without. The TPMS warning comes on at start-up. Press the little button on the dash and the major fault warning goes off. The little tire symbol remains, just a reminder we are dealing with winter driving. No problem. She/we adjusted. Eyeball the tires each day and check pressure monthly still works. If we ran the Caliber (or Durango) at a track event - which we don't - and set the tire pressures real low for handling we would press the button and move on. Not arguing... at the end of the day the computer is there to help, not limit.

Re: tire pressure, per tire rating or vehicle sticker?? [Re: 70Cuda383] #1229738 05/09/12 11:15 AM 05/09/12 11:15 AM
Joined: Apr 2005 Posts: 15,134 Kelowna, B.C. Canada D DPelletier I Live Here
DPelletier I Live Here D Joined: Apr 2005 Posts: 15,134 Kelowna, B.C. Canada	Quote: depends. I monitor tread wear and adjust air pressure accordingly. the max pressure on the sidewall is for when the vehicle is fully loaded. I typically run 35psi on all vehicles. if I'm going to pull a heavy load in the truck, I air them up to 45, the max on the sidewall. on performance tires with a much wider footprint, and more surface area to spread the weight out on, I air them down a little to prevent from ballooning out the tread and wearing them out in the middle. so...not sure there IS a correct answer short of "it will vary with current use" Best post with honorable mention to jbc426. I'm a bit of a stickler on the whole tire pressure issue because I have a fleet of trucks and trailers where tire pressure is even more important than it is on a car. My dually has load range E tires with a max pressure of 80 psi; empty, I keep the fronts at 70 (that Cummins is HEAVY) and the rears at 55, loaded up to max GVW I put the fronts at 80 and the rears at 65 which is all they need to support the weight 'cause there is four of them. Only thing I'd add is that I'd always error on the side of overinflation; far better to wear out the middle of the tire prematurely than to suffer a catastrophic failure due to excess heat caused by underinflation. Handling and mileage suffer with underinflation as well. ...the chalk test is a good one IMO. Dave 1970 Super Bee 440 Six Pack 1974 'Cuda 2008 Ram 3500 Diesel 2006 Ram 3500 Diesel 2004.5 Ram 2500 Diesel 2003 Ram 3500 Diesel 2006 Durango Limited [url] http://1970superbee.piczo.com [/url]

Re: tire pressure, per tire rating or vehicle sticker?? [Re: Captain Flapjack] #1229739 05/10/12 10:54 PM 05/10/12 10:54 PM
Joined: Jan 2006 Posts: 957 Heart of Ohio 4boxers4 super stock
4boxers4 super stock Joined: Jan 2006 Posts: 957 Heart of Ohio	Always go off of the vehicles certification label in the door jam. The car goes through alot of vehicle dynamic testing to develop the appropriate characteristics that allow for the optimized condition. There are a few times when I would slightly adjust that thought process...in winter with ice, I drop a pound or two. For long highway trips I add a pound or two and for towing, I add about 5 extra PSI to the rears. As for TPMS...the system you describe sounds like an indirect which uses rolling radius and possible the tire harmonics to judge tire pressure. These systems are run through the ABS/Stability modulator, using the input from the wheels speed sensors and an algorithm to judge the pressure. Regulation has an allowance of 25% below the cert label pressure to set a light. When you push the button, it begins a calibration sequence that can take a long time to complete.Hence the inconsistancy of the light. Persistance is omnipotent Durability Engineer, Chair and Couch division...

Re: tire pressure, per tire rating or vehicle sticker?? [Re: 4boxers4] #1229740 05/14/12 08:22 AM 05/14/12 08:22 AM
Joined: Aug 2004 Posts: 466 U.S.A. C Captain Flapjack OP mopar
Captain Flapjack OP mopar C Joined: Aug 2004 Posts: 466 U.S.A.	hanks alot for the input boxers, thank you especially, i was able to make the most sense and agree with your post the most

Re: tire pressure, per tire rating or vehicle sticker?? [Re: 4boxers4] #1229741 05/14/12 12:33 PM 05/14/12 12:33 PM
Joined: Jan 2003 Posts: 16,123 Grand Haven, MI patrick I Live Here
patrick I Live Here Joined: Jan 2003 Posts: 16,123 Grand Haven, MI	Quote: Always go off of the vehicles certification label in the door jam. The car goes through alot of vehicle dynamic testing to develop the appropriate characteristics that allow for the optimized condition. There are a few times when I would slightly adjust that thought process...in winter with ice, I drop a pound or two. For long highway trips I add a pound or two and for towing, I add about 5 extra PSI to the rears. As for TPMS...the system you describe sounds like an indirect which uses rolling radius and possible the tire harmonics to judge tire pressure. These systems are run through the ABS/Stability modulator, using the input from the wheels speed sensors and an algorithm to judge the pressure. Regulation has an allowance of 25% below the cert label pressure to set a light. When you push the button, it begins a calibration sequence that can take a long time to complete.Hence the inconsistancy of the light. the manufacturers recommendations are a compromise rather than an optimization--for example, the firestone rollover era explorers were found on their production validation testing to ride somewhat harshly, so instead of redesigning the suspension with changes to spring rates, shock damping rates, bushing durometer, etc, they lowered the tire pressure...IIRC it's somewhat ludicrously low, like 26PSI. that caused excessive heat, and in hot climates and high speed, enough to cause the tires to tear themselves apart. I consider the door sticker the minimum for that specific tire/size. otherwise I prefer the chalk or drive through a puddle of water to check contact patch method.... my old 5th ave, which I put 255/50R17 BFG KDWS's (IIRC max pressure on the sidewall was 44-45PSI) it liked ~42 in the front and 40 in the rear. my wife's grand caravan had P series bridgestones from the factory (36PSI max inflation. 35PSI on the sticker)), and I replaced them with Nokian WGR2 SUV tires (45 or 50 PSI max), and run those at about 43 PSI. Last edited by patrick; 05/14/12 12:35 PM. 1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod SOLD!* 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)

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