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Tire pressure: What pressure do you run?

45K views 27 replies 20 participants last post by  Jersey Devil 
#1 ·
Most people just take their tire pressure for granted. They don't realize it plays a big role on how their car handles as well as their gas mileage. Lowering your tire pressure increase grip but also decreases gas mileage. While increasing your tire pressure reduces grip but improves gas mileage. Just wondering what you guys use for tire pressure on your daily drivers? Personally I run 38 for my fronts and 42 for my rears on my rwd car. I found that I get pretty good gas mileage and also decent grip with that setup.
 
#5 ·
Run at the manufacturer selected pressure. The factory setting takes into account vehicle load and suspension set-up. The tire is designed to give a good footprint and operate under the loads given by the manufacturer. Deviating from this, will change the behavior of the vehicle in many ways. Most of them bad.

Underinflation:
Contrary to popular belief, under inflation does not improve handling. It reduces the footprint meaning less contact with the road. It causes more roll in the tire from lateral forces. It causes severe shoulder wear. It causes high heat build-up in the shoulder, apex and sidewall. It causes reduced gas mileage. Nothing good comes from lowering tire pressure on pavement.

Overinflation:
Overinflation will improve gas mileage. It will change the footprint reducing grip in dry, wet, and snow conditions. Overinflation will also increase wear in the center of the tire. What you make up for in gas, you will lose in tire milage while reducing handling. Over inflate if you are hypermiling with your buddies.
 
#7 ·
As odd as it may seem my, Subaru WRX requires 32 up front and 29 in the rear with stock 16" rims and 33 up front and 32 in the rear with 17" rims. Dealer told me it has to do with the AWD split and rear spoiler.

Here's some excellent information from Tire Rack.
Tire Tech Information/Air Pressure: Tire Rack
 
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#22 · (Edited)
I've had my Juke 6 weeks now, had Blizzaks put on a couple of weeks ago, and for the first time yesterday the Low Tire Pressure light came on. The temp had dropped to 9 F, and I assume that's why the light came on, but my question is, do I inflate them to 34 psi (AWD) now that it's so cold? Or do I let it warm up outside and the light will go off?

Thanks much.
 
#16 ·
I have the stock Goodyears
I just lower the air pressure for a softer ride yesterday.
28 in the front
26 in the rear
I immediately noticed the difference on the ride and the reduced road noise.
I'm not worried about gas milege

Had my Froginator for 2 months 600 miles.
Still breaking her in.
 
#17 ·
I would suggest trying something less drastic. 10 psi is alot of pressure drop. 36 is the recommended pressure for the vehicle load. You are running way under pressure, as a result, yes you are getting a softer ride because there is less air in the tire and you are getting more side wall flex.

You're goign to cause an increase in tire wear, especially side wall strenght reduction. Not to mention the decreased footprint you now have. THere is plenty of documentation available about running with too low a tire pressure. Go to the Tire Rack - Your performance experts for tires and wheels and read up. THere are tire manufacturer provided photos of how much grip you are loosing due to a severe under inflation. You are currently running @33% under inflated. Far too much. Try to keep your numbers with in 10% of the rated load.

THe stock eagle tires are just crap. They are hard and noise. IT's just a crap tire and a fact of life. If the tire bothers you that much replace it with a touring tire for increased ride comfort. Decreaseing the tire pressure to make a bad tire feel good is not the right direction to go.

For the rest of you peeps wondering what the best tire pressure is. Read the door jam on your drivers side. It has the correct pressure for you particular model.

Unless you change your tire/rim package there is no reason to alter from this number. This number is a calculated number based on the vehicles weight and distribution to provide optimum effeciency in both grip and economy.

Anythign more than 10% above or below this number and you have over or under inflated your tire and therefore caused a reduction in grip.

I dare say that TIRE GRIP is the SINGLE MOST IMPORTANT part of you car's operation. Everything your car does (cept maybe a/c perferformance and your wiper blades) depends on this factor. How well you car brakes, accelerates, handles an emergency manuver, all this relies on your tires.

Run your tires in the recommended tire pressure window and stay safe. IMO, gaining a 2mpg from over inflating your tire by 10 psi is not worth the risk to yourself or another due to reduced tire traction.

Also, there are very few tires/rim options that will actually change your air pressure needs. Most tires follow a standerized pressure rating. There are a few that don't. The front tires I have on my del sol (Fusion ZRi's) don't. So long as your tires follow the standarized pressure ratings you dont' change your tire pressure. That means if you go from a 215/45/18 to a 245/25/20 tire, the pressure stays the same. Lower profile tires don't need more air, the side walls are stiffer to account for their reduced height. If the load rating on the tire is the same, then the pressure is to follow the manufactures (car, not the tire) pressure numbers.

Don't look at that number on teh side wall either. It's meaningless to the average consumer. For example, our goodyear RS-A tires are rated 44psi@1433lbs. This means that inorder to run the tire at it's maxium load of 1433 lbs you need a tire inflation pressure of 44psi cold. If you inflate your tires to 44psi, then you are expecting a maxiumum load of 5732 lbs. Our Jukes are heavy, but ****.. they're not that heavy. You're a ton over in your expected weight, buy doing this. That much of a weight offset and you WILL see a reduction in tire traction. You're just too far off the mark. This is why our are set at @36 psi. At that pressure the expected vehicle weight is the Juke's wieght plus it's maxiumum payload capacity.

There are more factors involved, such as front/rear weight bias etc. but I hope you get the idea of what's going on.

Simply put. Inflate to the car's spec tag for maximum life expectancy. (of both the tire and yourself)
 
#19 ·
When I bought my Juke the dealer had the tires at a ridiculous 42+ psi. It rode terrible and made a lot of noise. I dropped them to 33 and the ride quality is much improved (no different in mpg either). Unless you are autocrossing or towing a load/fully loaded I would stay away from the max end of the range.
 
#25 ·
Just found out last week that I had been running at 42 from the dealer. Reduced to 35 per the door sticker. Ride is better, but tight corner handling is not as good. The Conti's seem to slide a bit at 35. Going to split the difference and try 38.5.
 
#27 ·
Always runnign 35 is the best way to go. It's not a blanket pressure to cover everything. It greatly depends on the vehicle weight and load ratings of the tires. If I ran 35 psi in my del sol front and rear it would be a total mess. It's only 2200 lbls and has a 65/35 distribution. I run 32/28. If you have stock tires, run the recommended pressure which is on the door jam. This is a calculated pressure based on the vehicle weight and tire load ratings. Most people make the mistake of inflating the tire to the pressure on the sidewall which is completely irrelevant. This only tells you what the maximum pressure the tire can handle at a given weight load. If you switch to aftermarket tires you can ratio out the max inflation pressure vs load to get the correct inflation pressure for the new tire. It'll at least get you close. One of the major tire brands had a great video on their website of the effects of tire pressure on tread contact patch and how it's just as bad to over-inflate as it is to under-inflate. I"ll see if i can find it again, it's been a few years.
 
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