Tire pressure

[KM2]

I don't know what tire pressure to run at. My car and SIL Tahoe have aftermarket wheels and tires. The tires say max pressure of 44psi and the drivers door says 32psi. Since we are not runing factory tire or size I think we should fill them near the tire rating max. The goodyear website says to run at the manufacturers recommended level. But doesn't say if that applies to tires that are different then OEM. What to you think?

 

[JB]

Re: Tire pressure

I would still go with the maker's recommendation, KM2.<br /><br />Though their recommendation assumes stock tires it is the weight and balance of the vehicle that makes the most difference.<br /><br />My son has aftermarket wheels and tires on his M5 Beemer. He decided to run them at 45psi to get better fuel mileage. The ride went to heck and he wore out the center of the tread on those $200/each tires. Mileage did not improve. Now he runs BMW recommended pressures. Rides and handles better and he will get 45-50K out of the tires this time.

 

[DJ]

Re: Tire pressure

THE DOOR STICKER, THE DOOR STICKER.<br /><br />Is that Clear and Loud enough????<br /><br />People mess around with PSI, to their own demise.<br /><br />Guess what, the people that designed/built/tested your vehicle just MIGHT have a clue. If you'll hear it.

 

[islandboat]

Re: Tire pressure

I'm sorry, but I will step out there and disagree with the rule of running what is printed on the door post. Over inflation and underinflation are both dangerous. First you should have the proper tire and wheel combo for your vehicle. Tire load rating, speed rating, wheel offset and size (if aftermarket) are all critical for proper safety and handling of a vehicle. Running a tire 25% underinflated would not seem to be recomended by the tire manufacturer, although I agree that it may not be necasary to inflate a tire to the max at all times. Example, running tires rated at 3500 lbs each on a vehicle that weighs only 5000 lbs does not mean the tire pressure would be proper at 50% of rated inflation pressure even though 50% of the load capacity of each tire would be sufficient. When a tire is manufactured, the recommended tire pressure is stamped on the sidewall of the tire. Providing the tire is correct for the vehicle and installed on the proper wheel, the tire manufacturors recommended pressure should be correct. <br />If a vehicle was built in 1995 and new tires were installed in 2005, could the vehicle manufacturor have known what tires would be installed 10 years later and would the original inflation sticker on the vehicle be valid? Although the vehicle weight may not have changed much, the tire engineering may have.

 

[JRJ]

Re: Tire pressure

When you change from stock tires and wheels, the door sticker no longer applies if you change tire size. Go with what the tire maker recomends for the weight rating your vehicle plus load should have.

 

[ZodFutMk2]

Re: Tire pressure

Open mouth, shove in foot.<br /><br />Very good points from everyone.<br /><br />Shouldn't we have more background on the situation? <br /><br />What type of aftermarket wheels and tires? We talking 20's and bling wheels or 36's and lifted suspension?<br /><br />Has the suspension been modified in any way to allow the new wheels and tires to fit on the vehicle? Shocks, struts or spring changes?<br /><br />Is the rig still at factory height?<br /><br />These factors should be considered when determining the best tire pressure for the application.<br /><br />The higher the tire pressure (above manufacturers suggested numbers), the more intense the forces on the suspension and higher tire pressures are known to cause a serious reduction in control performance (steering & braking)and traction in wet conditions.<br /><br />It's best to start with the pressure indicated by the manufacturer and then change the pressure according to tire performance and personal preference.<br /><br />When in doubt, go back to where you purchased the wheels and tires and talk to the the service tech. They usually do so many vehicles that they have a good idea what works and what doesn't.<br /><br />Just my 2 cents worth.

 

[SS MAYFLOAT]

Re: Tire pressure

KM2, I see your from a cold cold state. Tires will increase or decrease in pressure with change in outside temp. A mid range air pressure will allow for the expansion and contraction of differences in the tire temp.<br /><br />On vehicles that carry loads, sometimes it is necessay to increase the tire pressure for extra weight. Then in your case where you maybe driving in snow, a lower PSI can benifit. <br /><br />Back in my days of autocrossing, just a few pounds or air can make a big difference in handling.<br /><br />For a normal daily driver, air pressure will determine ride comfort. Higher air pressure will give you a rougher ride. Lower will give you a softer ride. Going to low will make your car work harder to roll the tire using more gas. That is why motor clubs insist that tire pressure should be checked often.

 

[dolluper]

Re: Tire pressure

If you drive on highways alot do not put the maxinum rated pressure in your tires,they can expand up to 6LBS [hot day over 50 miles at 60mph]<br />The tires you bought have 44 max,so try 38Lbs filled when "COLD" not after running around.You might not like the handling if so play with the pressure till your comfortable[decreaseing pressure]" NEVER PUT 44LBS IN"

 

[oddjob]

Re: Tire pressure

I didnt know they had the tire pressure on the door....Thats for the stock tire. In my experience, when you change to a different brand of the same recommended stock tire the pressure max is usually the same. But when you change to a different size you follow the tire recommendation. I always follow the tire rating. I'm no expert, my best friend spent some time managing a tire shop so usually get his advice about tires. All the specs for a tire are on the tire itself. IMO

 

[KM2]

Re: Tire pressure

I don't know what came stock, because both vehicles were not purchased new. <br /> <br />FYI<br /><br />The car has 15" firestones, I have no idea what was stock on a focus. <br />The tahoe has 20" goodyears. Yea the puff daddy looking things. It's kind of embarassing to drive. <br /><br />Thanks for your replies. I was hoping for more of a consensus.

 

[ZodFutMk2]

Re: Tire pressure

Excellent discussion here:<br /><br /> http://www.eng-tips.com/viewthread.cfm?qid=15003&page=1 <br /><br /> http://www.type2.com/library/tires/tirefaq.htm <br /><br />and finally from: http://www.maxxis.com/Services/automotive_tire_school.asp <br /><br /><br />Your vehicle manufacturer will specify the inflation pressure necessary for your OE tires. Check with your tire dealer if you no longer have OE tires installed.