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  #13  
Old 02-25-2013, 06:32 PM
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Quote:
Originally Posted by BobT View Post
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 .
Can't find any charts...sounds pathetic.

My lt tires DO have a load index of 115, and I believe the oem tires had a load index of 104...
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Old 02-25-2013, 09:20 PM
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Re: Correct PSI for aftermarket tires?

Not sure I did this right at all...but divided the max load of one of my lt tires by the max load of the oem tires. Got 1.35. Multiplied 33 PSI by 1.35, got 44.55. So by that math, I should be running at 44-45 PSI...
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Old 02-26-2013, 01:15 AM
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Re: Correct PSI for aftermarket tires?

Quote:
Originally Posted by fin1211 View Post
Not sure I did this right at all...but divided the max load of one of my lt tires by the max load of the oem tires. Got 1.35. Multiplied 33 PSI by 1.35, got 44.55. So by that math, I should be running at 44-45 PSI...
There is some logic in what you have done and the answer seems about right but it's definitely not the right way. If you are looking on the net for the tables, you are unlikely to find them. The Tire and Rim Association, Inc. would be more than happy to sell them to you. Maybe your tyre bloke will let you look at his.
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Old 02-26-2013, 02:54 PM
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OK , here is what Dunlop sent back.




Operating air pressure is determined by the vehicle manufacturer.

If you're using the same size tire that came as original equipment on your
vehicle, the proper air pressure is indicated on the door placard or owners
manual of your vehicle.

The air pressure indicated on the sidewall of each tire is the inflation
pressure required to carry the maximum allowable load for that tire.

Vehicle manufacturers have invested considerable time and testing to
establish an air pressure that will provide a smooth comfortable ride in
addition to an even treadwear pattern.

Our recommendation would be to stick with the air pressure established by
your vehicle manufacturer.

All Tire Guide Publications had Load&Inflation Tables in them. You listed
the size as LT225 17R16? I assume you mean LT225/70R16?

35psi - 1,435lbs * 40psi = 1,575lbs * 45psi 1,710lbs * 50psi MAX 1,875 (C)

Thank you for your inquiry through our web site.

Jennifer - Consumer Relations

02/24/2013 02:34 PM




From: * * * * *


To: * * goodyear_cr@goodyear.com
cc:
Subject: * * * *Contact Us request from www.dunloptires.com




Hi , There is a discussion going on at Jeepgarage.org 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
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Old 02-26-2013, 04:00 PM
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Re: Correct PSI for aftermarket tires?

here is a chart I found
Attached Images
File Type: jpg load_range.jpg (85.6 KB, 14 views)
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Old 02-26-2013, 06:43 PM
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My tires are the same size as stock, BUT they are light truck rather than passenger tires. The OEM tires had a load index of 104, mine have a load index of 115. I think I'll set it at 42 psi and forget about it.
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Old 02-27-2013, 01:16 AM
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Re: Correct PSI for aftermarket tires?

Quote:
Originally Posted by spyder873 View Post
here is a chart I found
Not sure what that table is about. I'm talking about something that looks more this but for your country:
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File Type: pdf LT load v pressure table TRA.pdf (59.3 KB, 14 views)
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Old 02-27-2013, 08:38 AM
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Re: Correct PSI for aftermarket tires?

i have not been able to find a chart like yours for our country. Its hard to get a straight answer from tire Mfg.s due to ( IMHO) what happen with firestone a few years back . I really believe no one wants to take the responsibly to give you a air pressure.


I have even had Tire shops ask me what pressure I would like my Tires to be at . I usually keep mine at about 35 to 37 psi. If I am towing Heavy( car hauler , camper ,etc.) then I will take them to the Max amount shown on the tire ( usually around 50 psi) .
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Old 02-27-2013, 09:55 PM
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Re: Correct PSI for aftermarket tires?

Quote:
Originally Posted by spyder873 View Post
i have not been able to find a chart like yours for our country. Its hard to get a straight answer from tire Mfg.s due to ( IMHO) what happen with firestone a few years back . I really believe no one wants to take the responsibly to give you a air pressure.


I have even had Tire shops ask me what pressure I would like my Tires to be at . I usually keep mine at about 35 to 37 psi. If I am towing Heavy( car hauler , camper ,etc.) then I will take them to the Max amount shown on the tire ( usually around 50 psi) .
Mind me asking what happened with firestone? Relating to that...when my Dunlops go away, planning on some Destination LE2's unless someone guides me somewhere else, they seem like a steal.
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Old 02-28-2013, 08:16 AM
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during the early 90's ( if I remember right) they had some problems with quality . Part of this is when the ford explorer would flip over easily. ford and firestone went back and forth for a while arguing about air pressure . firestone would say the pressure was to low and Ford would say it was fine.

This is also about the same time as firestone employees went on strike and they replaced them with people who were not trained correctly . Therefore turning out tires that were not up to standard.

The ford / firestone argument is what brought about smaller sidewalls and the development of electronic stability controlin later models .

The problems have been corrected so , no worries on buying them now .

It just seem that no tire MFG. here ( in the states) want to take the liability to give a normal operating pressure. They will give you max and that about it . This is how I remember it . If I am wrong or someone else remembers more I hope they will post up.

It also depends on how you like the ride. at 50 psi the bumps are going to feel harder then they do at 35. so alot depends on ride comfort as well
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  #23  
Old 03-02-2013, 09:21 PM
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Re: Correct PSI for aftermarket tires?

Quote:
Originally Posted by fin1211 View Post
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.
You have said that the sticker pressure on your Jeep is 33psi but you haven't said the tyre size that this applies to. Lets assume you have a 08 Wrangler X with P225/75R16 OEM tyres. On page B8 of http://www.tiresafety.com/images/Tir...t%20Manual.pdf for 33psi on the this tyre, the load capacity is 1911lb. This is a 2006 document but probably still OK. Assuming the Wrangler is more of a truck than a passenger vehicle, this load has to be discounted by 10%. So the resulting load becomes 1911/1.1=1737lb. Plug this load into page 24 of the document and you get about 46psi. This is in the right ballpark and pretty close to the 44.55psi you calculated above by another method.
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  #24  
Old 03-03-2013, 12:33 AM
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This is for p225 75r16 tires. It should be considered that the GC used to be way lighter(I.e. wj is way lighter than wk). So it makes sense for p225 75r16 tires to be at 33 psi.

But when it's lt225, it's just sorta confusing figuring it out. Running at 38 psi right now for the hell of it.

But that's an awesome link!

Did my own valuations with it, hmm. According to that info, somewhere around 54 psi would be optimal. Seems excessive. Will try though.
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