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Old 02-22-2013, 11:43 PM
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Correct PSI for aftermarket tires?

Hi everyone,
My GC has Dunlop Radial Rover A/T's, LT225 17r16. The listed recommended PSI for my Jeep is 33 PSI, but that was for the stock tires...max PSI for the Dunlop's is 80 PSI. I'm a little confused on where to go...can't imagine running for than ~38 PSI, I've been running around 35 and its worked well. Seems I'm missing something.
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Old 02-23-2013, 05:26 AM
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Re: Correct PSI for aftermarket tires?

Use the 4 psi rule.
Tyre psi
Has worked so well for me for over last 15 years.
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Old 02-23-2013, 09:03 AM
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Got it. So basically, take the psi from one front tire and one back tire(making sure l and r tires are the same pressure), and then drive for 20 minutes on a freeway, take psi again, and if the change is more than 4 psi, original psi is too low, and if the change is less than 4, original psi is too high. Seems kind of tedious, but I guess I'll try it anyway.
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Old 02-24-2013, 02:56 AM
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Re: Correct PSI for aftermarket tires?

That is it.
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Old 02-24-2013, 04:20 AM
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Re: Correct PSI for aftermarket tires?

The 4psi rule is about as accurate as kicking the tyres with your boot. The correct way is to use load/inflation tables. You can get them from you national rim and tyre association. Your sticker pressure of 33psi is for the OEM passenger type tyres. Find the table that covers your OEM tyre size and read off the load at 33psi. Because you are talking about and SUV/truck the passenger tyre load has to be discounted by 10%. This is done by dividing the load you got off the table by 1.1. Find the table that covers your LT tyres and read off the pressure corresponding to that discounted load. I would expect that pressure to be of the order of 10-15psi higher than the sticker pressure.

The max psi printed on the tyre is the pressure you require if you intend to load each tyre to its max allowable load. Your LTs, I think have a load index of 115. That is 1,237kg/wheel or 4,948kg total. The GC has GVM of about 3,000kg. So to warrant using 80psi, you would have to have the GC loaded with the equivalent of 97 20L jerry cans of water. I don't that would even fit. Nevertheless, It's amasing how many people think the max tyre pressure printed on the tyre is the one to use for normal operations. I recon they would be bouncing around like on pogo sticks.
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Old 02-24-2013, 08:38 AM
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Re: Correct PSI for aftermarket tires?

It find the correct tire pressure , you will need a piece of chalk and a flat section of asphalt.

You color a strip of the tread ( about 8-10") then roll forward . Look at the imprint on the asphalt and see if the entire tread pattern is showing .

If you are only getting the center then let some air out of the tire and do the test again .

If you see the entire tread minus the center add a little bit of air until you see the entire Tread cross section

Tire Pressure Checker: Righting the Pressure in Your New Tires-RH2
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Old 02-24-2013, 02:17 PM
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Quote:
Originally Posted by BobT View Post
The 4psi rule is about as accurate as kicking the tyres with your boot. The correct way is to use load/inflation tables. You can get them from you national rim and tyre association. Your sticker pressure of 33psi is for the OEM passenger type tyres. Find the table that covers your OEM tyre size and read off the load at 33psi. Because you are talking about and SUV/truck the passenger tyre load has to be discounted by 10%. This is done by dividing the load you got off the table by 1.1. Find the table that covers your LT tyres and read off the pressure corresponding to that discounted load. I would expect that pressure to be of the order of 10-15psi higher than the sticker pressure.

The max psi printed on the tyre is the pressure you require if you intend to load each tyre to its max allowable load. Your LTs, I think have a load index of 115. That is 1,237kg/wheel or 4,948kg total. The GC has GVM of about 3,000kg. So to warrant using 80psi, you would have to have the GC loaded with the equivalent of 97 20L jerry cans of water. I don't that would even fit. Nevertheless, It's amasing how many people think the max tyre pressure printed on the tyre is the one to use for normal operations. I recon they would be bouncing around like on pogo sticks.
I found all of the specs for the oem tires, but I cannot find any(any!) specs for the Radial Rover LT225s! Unbelievably frustrating.
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Old 02-24-2013, 02:23 PM
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Re: Correct PSI for aftermarket tires?

Contact the tire manufacturer and tell them what tires and what vehicle you have.



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Old 02-24-2013, 02:35 PM
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Re: Correct PSI for aftermarket tires?

Ok , I sent a message to Dunlop Tire with this message

about what is the correct tire pressure for a set of Dunlop Radial Rover A/T's LT225 17r16.
is there anyway you could tell us what the recommended pressure should be ?

here is the thread to the discussion

Correct PSI for aftermarket tires?
Thanks

Lets see what they say
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Old 02-24-2013, 02:53 PM
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Awesome, thanks a ton for that.
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Old 02-24-2013, 03:01 PM
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Re: Correct PSI for aftermarket tires?

No Problem , Lets see if they respond. as soon as they do I will post it
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Old 02-25-2013, 01:30 AM
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Re: Correct PSI for aftermarket tires?

Quote:
Originally Posted by fin1211 View Post
I found all of the specs for the oem tires, but I cannot find any(any!) specs for the Radial Rover LT225s! Unbelievably frustrating.
All you need is the size, which is LT 225/75R16. Look up that size tyre in the LT load/inflation table. Most manufacturers use the same tables. I'm guessing you are in the US so you would get your tables from The Tire and Rim Association, Inc. http://www.us-tra.org/index.html .
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