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Discussion Starter #1
I have a set of goodyear duratrec on my 08 commander . How much air should i put in these tires for everyday street use. The sidewall says max 80 psi i've got mine at 55 psi any help would be great thanks
 

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Waaay too much!!

Always go by the psi listed on your door jamb. I forget off hand, but it should be 32-36psi. The psi goes up as your tires get hotter. You should probably make sure it never goes over 40psi hot. Always fill to the recommended psi when tires are cold and you might do a little extra to save a bit of gas.

If you off road, you can put them as low as 20psi and still be safe.

Good luck and welcome.
 

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The door jam is a good place to start getting your PSI set. When using tires and sizes Jeep never intended you to put on makes it a little harder then what the sticker states. Also 20PSI on my tires would hardly do me any good I have to air down to 15PSI to get some decent flex. I started at 20PSI and tested it and kept walking them down to see what works for me. The same with airing up you're going to have to check measure and pay attention to what the tire is doing wearing and sitting. My Bighorn MT's are wearing perfectly at 40PSI even wear side to side no issues.
 

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For almost ANY tire that will fit a Commander, 35-40 will work. Anything over 40 is usually overkill unless you're fully loaded. 55 is too much.

Here's a thread I created with a bit more detail on how to figure out tire pressures: http://www.xk-forum.com/showthread.php/664-How-To-Figure-out-LT-tire-pressure

Cliff Notes: You find out the load capacity of your vehicle by using the OEM tire capacities OR the GAWR (Gross Axle Weight Ratings), either works, then use the Load Vs. Inflation charts published by the North American Tire & Rim Association to find out what PSI you need to run your new tires to match the OEM capacity.
 

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I thought you always put 3 less than the manufacturers suggested PSI? It doesnt matter what it says on the door if the door is for the stock tires. Are you sure it is 80psi? 80 is a lot. It all depends on ride comfort, wear, handling, and gas mileage. I would not run a tire at half what it is supposed to be at but I do not think they are supposed to be ran at 80 PSI either. check again.
 

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The tire manufacturers don't suggest a PSI, they only give a MAX PSI.

The auto manufacturers suggest a PSI based on vehicle weight and load capacities. So you want to match the auto manufacturers tire capacity with the new tires.
 

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I had my tires and rims shipped mounted and balanced. they were inflated to 80psi. This is MAx Psi as stated on sidewall. No way would you want to run them at 80.
 

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I would not run a tire at half what it is supposed to be at but I do not think they are supposed to be ran at 80 PSI either. check again.
There is absolutely nothing wrong with running a C, D or E rated tire at 35 PSI (EDIT: when used in the proper application.). Remember, 80psi is not "what its supposed to be run at", That is just the absolute maximum pressure.

The TRA (Tire and Rim Association) has published data stating what pressures LT tires are actually "supposed" to be run at for given loads. And yes, they all have acceptable ratings down to 35 psi; most of which have a load capacity more than adequate for our vehicles at those pressures.

This isn't conjecture. .... its actually the proper method for determining tire pressure.

It should also be noted that there are also manufacturer warnings against LT tires in some applications where the required pressure (per the TRA) is actually too high for the vehicle and thereby decreases contact patch. This is normally reported as a crappy ride by users, but what most don't realize is that also translates into reduced traction, reduced handling and longer stopping distances. Being over inflated is a big problem, and people running 50, 60 or even 70 psi in vehicles that should only have 40-45 max when fully loaded is not good. Also, any "MPG" benefits of running over inflated tires are quickly counter acted by increased tire wear, wear&tear on vehicle suspensions and reduced safety. If you want better MPG, get LRR tires and run the proper tire pressures.... not E rated tires at 70 PSI. (Edit2: Not that anyone here has recommended this.... just a blanket statement )
 

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Discussion Starter #10
Thanks for the replys and after reading all of this info i will be lowering my air pressure. When i bought the tires they were at 80 psi and then at last oil change they were set at 32psi and the goodyear store that i bought them at had no clue. thanks again were all the help
 
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