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Unread 10-26-2005, 01:35 AM   #1
Sweet Liberty
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Correct Tire Pressure Help!!!

hello all,

i have a 2002 jeep liberty limited and i have 235/65/17 tires on there. the stock tires were 16" but i upgraded to 17" (took them from a 2003 jeep liberty). But in my jeep it says only tire pressure for the 16" stock tires, not the 17" one's i have. Can anyone help out. The tire itself says max psi of 44, so i don't think i should go that high...let me know.

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Unread 10-26-2005, 02:33 AM   #2
roderunner
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44 is the maximum safe pressure, set by the tire manufacturer. You should never set your initial tire pressure that high. Keep in mind that tire pressure fluxuates while driving about 3 - 4 psi.

I would start out at about 35 (cold) all around. For better mileage or heavier loads, you could go up to about 40 (cold) max. For more comfort, you could drop down to about 33 (min).

The performance on your 65 series tires is a little more dependent on correct tire pressure than the higher profile 70 and 75 series tires.

To double check, go to a level, empty parking lot. draw a heavy chalk line across each of your tires. Roll the vehicle forward or back about 20 - 30 feet and examine the chalk line. If it is more faded in the middle of your tread, your pressure is too high (overinflation). If it is more worn off near the edges, the pressure is too low (underinflation). If the chalk wears evenly across the tread, you're about where you should be.

As the weather gets cooler, pressures will tend to drop, so be sure to check your pressure regularly with a reliable gauge.
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Unread 10-26-2005, 08:38 AM   #3
TRO
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I figured a good balance, for overall, is 37 psi. The heat up balance seems acceptable and the loss only seems to be .5 typically.
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Unread 10-26-2005, 10:12 AM   #4
jeepjeepster
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I keep my 235/65/17's right at 35psi and it seems to work out great. They suck in the rain though, great for dry traction. Idk if the high pressure causes them to slide or if the tires just suck for wet handling, but i about died the other day and am not happy. I dont see how some people drive without checking there tire pressure. I know people do not check there tires like i check mine, but one day i put 35 in them and the next them cooled down to 33, and then the sun came out and they were 38. So i would say some people are driving around with 20psi in there tires and do not know it! No wonder so many people have blow outs!
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Unread 10-26-2005, 10:38 AM   #5
TerpFan
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I can tell you that having too little pressure in the tires is a LOT worse than having too much. Low pressure causes the tires to heat up, which leads to blow outs. And in a vehicle with a hight CG like the Liberty, that could be a real problem at highway speed.

I think 35 psi is just about right. I usually add 3-5 psi to whatever the vehicle manufacturer recommends.
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Unread 10-26-2005, 01:59 PM   #6
Sweet Liberty
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Quote:
Originally Posted by jeepjeepster
I keep my 235/65/17's right at 35psi and it seems to work out great. They suck in the rain though, great for dry traction. Idk if the high pressure causes them to slide or if the tires just suck for wet handling, but i about died the other day and am not happy. I dont see how some people drive without checking there tire pressure. I know people do not check there tires like i check mine, but one day i put 35 in them and the next them cooled down to 33, and then the sun came out and they were 38. So i would say some people are driving around with 20psi in there tires and do not know it! No wonder so many people have blow outs!
Well so far some have said 35 as yourself and another said 37, so maybe a safe bet would be 36 (makes everybody happy). But you are right, the Goodyear Wrangler Tires i have on, are very poor in wet conditions, i made a left turn not going very fast and my rear tires fish tailed on me (i was scared silly). But i am going to buy a new set of rears next month for the Winter cause i think it's time to replace them anyways. I had adjusted the tire pressure to 33 a few days ago, but i'm going now to adjust to 36 and i always check my tire pressure, especially with the random weather patterns we get from cold to warm and vice versa.
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Unread 10-26-2005, 02:30 PM   #7
roderunner
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It's best not to mix tires. Several studies have confirmed this. Replace all 4 if you can. Sometimes you can get a better deal that way also ("buy 3 get one free", etc.).
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Unread 10-26-2005, 02:41 PM   #8
Sweet Liberty
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Quote:
Originally Posted by roderunner
It's best not to mix tires. Several studies have confirmed this. Replace all 4 if you can. Sometimes you can get a better deal that way also ("buy 3 get one free", etc.).
i totally agree with you and i really want to get 4 new tires, but it'll cost me $800 instead of $400 and i won't be back to work for another 4 weeks (bad back), but i may do it if the front one's are really bad...do u recommend i get the same Goodyear Wranglers or is there a better tire out there for all season?
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Unread 10-26-2005, 02:58 PM   #9
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I have the 16" wheels and as for my tire pressure, I shoot for 35 cold, 37 hot (it's been my experience that 35 cold will expand to exactly 37psi once it gets hot)
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Unread 10-26-2005, 03:09 PM   #10
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If you have to get just 2 for now, put your new ones on the front, and your best remaining pair on the back. Front tire traction is most critical.

The right tire for you depends a lot on where you live and your type of driving. I've had no problems with the Goodyear SR-A's but a lot of people here hate them. Revo's are very popular as an all around tire including off-road, but I think there are better choices for road applications.

Your most critical traction issues regarding safety are rain and snow conditions. Spend some time on the Tire Rack website. http://www.tirerack.com/index.jsp They have extensive reviews and ratings on just about every thing made -- an outstanding source for information! They rate regarding wet traction, dry, snow, noise, longevity, etc. If you find one you like, check out their price, and either buy from them or shop it around locally. If your local shop doesn't have what you want, they can usually get it within a couple of days.
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Unread 10-26-2005, 04:20 PM   #11
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Quote:
Originally Posted by roderunner
44 is the maximum safe pressure, set by the tire manufacturer. You should never set your initial tire pressure that high. Keep in mind that tire pressure fluxuates while driving about 3 - 4 psi.

I would start out at about 35 (cold) all around. For better mileage or heavier loads, you could go up to about 40 (cold) max. For more comfort, you could drop down to about 33 (min).

The performance on your 65 series tires is a little more dependent on correct tire pressure than the higher profile 70 and 75 series tires.

To double check, go to a level, empty parking lot. draw a heavy chalk line across each of your tires. Roll the vehicle forward or back about 20 - 30 feet and examine the chalk line. If it is more faded in the middle of your tread, your pressure is too high (overinflation). If it is more worn off near the edges, the pressure is too low (underinflation). If the chalk wears evenly across the tread, you're about where you should be.

As the weather gets cooler, pressures will tend to drop, so be sure to check your pressure regularly with a reliable gauge.
Roderunner- That is the best darn explanation i ever read on how to go about determining your tire pressure with a lightweight vehicle. Darn good advice like that deserves note.

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Unread 10-26-2005, 05:47 PM   #12
roderunner
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Thanks, that made my day! I've also benefitted from some great tips and suggestions from other members of the forum -- couldn't have accomplished half of my projects without the talent that lurks around here!!
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Unread 10-26-2005, 10:27 PM   #13
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I use the truckers rule of thumb of 10%. For example start with 36psi cold. Go for a drive of at least 10 miles to get the tires up to operating temperture then pull over to a safe area and take pressure readings on all the tires. If you started with the correct cold pressure the hot pressure should be no more than 10% above the cold reading ex. 10% of 36 would be 3.6 add this to 36 and your hot reading should not be more than 39.6 psi. If the hot reading is more than this(10%) your cold pressure was too low and your tires got too hot. If they don't reach the 10% amount the tires had too much air them to start with. Do not adjust tire pressures when they are hot. To be accurate do it when they are cold.
If your planning a trip load up the Jeep as best as you can ahead of time and go for a ride to check the pressures. One can do the same for boat or camper pulling. Jot your numbers down for future trips. This is a way of tuning your tires to your vehicle and your loads.
It's very important to have correct tire pressures for safety, traction, longevity and mpg etc.

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Unread 10-27-2005, 05:16 AM   #14
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Hmmm, that sounds like a pretty good way of checking it. I've never heard that before. Maybe I'll give it a shot. I usually just fill them to 3-5 psi over what the vehicle manufacturer recommends. Then I adjust based on ride quality. The 10% rule is an interesting idea though.
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Unread 10-27-2005, 07:55 AM   #15
Diesel Inferno
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Its always WORSE to be 2lbs under than 2 lbs over. I always keep mine at 35 psi all around. Check your pressures often and NEVER EVER let them drop below what it says on the door sticker. I always look at the printed on the tire max inflation rating. If it says 44 psi than dont inflate them with more than 40 psi cold max. I find on the Liberty 35-36 is best. Assume the "HOT" driving pressure will be about 3 psi HIGHER than what the cold pressure setting is. Also dont cheap out buy a GOOD tire pressure gauge.

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