wmcvey

Will need to get a new set of tires very soon. I now have the stock Dueler A/T 255/70r18. Have wanted to upsize the tire a bit, looking to go with 275/70R18. But every brand tire in this size is a LT E/10 type . Is this type too hard/stiff of a tire for a mostly road DD Jeep. Should I go with a 265/70R18 or 275/65R18 as these are available in the "P" type tires. I know the height and width of each size, I am just not so sure about the sidewalls and stiffness of the two types.

spinlock

If you haven't done so already, check out this current thread:

https://www.jk-forum.com/forums/show...d+range&page=2

Particularly the last few posts including one with a link to tech bulleting by Toyo which discusses this topic.

nwjk

The 10pr tires should be fine as long as you choose a quality tire that is mounted and balanced properly. Make sure you use the correct air pressure and remember to rotate, so they dont get cupped and unvenly worn.

wmcvey

OK I looked at the link you sent me, thanks. Then followed the link to that "tech bulletin" http://home.comcast.net/~kingslea1/J...bstitution.pdf It's saying a under aired LT tire (at 30psi.) no less, is going to run HOT. I would think most of the folks on this forum running 33" and larger tires are the LT type. And I have also read many posts on the PSI question. And almost every post states they run (on the street) form 26 to 32 PSI, with these larger tires (33",35",37") So my question? Are these tires running in this PSI range running hot (which is not safe). Or is this tech bulletin just being over cautions.

horwitzs

From that same thread:

RedneckJeep

A 10 ply tire will beat you to death in a Jeep. Some say you can adjust air pressure to make up the difference, but the truth is they will never ride as good as a comparable 8 ply or especially a 6 ply. The 10 ply is really overkill for a Jeep unless you plan on some EXTREME rock crawling where severe sidewall damage might be a problem.

wmcvey

Yes this is what "Spinlock" posted on that thread. And it does make some sense to me, that the load (or lack of) has a large influence on the heat buildup of a tire. This bulletin doesn't state what the load (weight) used on their heat buildup test was. And I guess that's mainly your point.

So than their statment: "Moving from a passenger (“P” designation) to a light truck (“LT” designation) markedly changed the handling characteristics of the Tahoe. Not only was the ride stiffer, there tended to be instability created from a “hopping” effect when encountering bumps at road speed. This
most likely was due to the stiff tires absorbing less impact. The instability effect increased with road speed. I would think a lighter vehicle
such as a Jeep Wrangler would experience even more instability characteristic from LT tire application." AND "Any increase in the tire's running temp. will have an adverse effect on the long term durability and safe operation of the tire."

So again is it everyone's opinion that the above statment is wrong, when the vehicle is a JK , two or four door.

spinlock

For a given air pressure, increasing loading on a tire makes the tire contact patch larger which creates higher friction
(ignoring the heat generated in the sidewalls due to flexing) and therefore more heat. Increasing air pressure within allowable range reduces this trend.

Higher load range tires are designed to carry a higher max load at a higher inflation. This table from Goodyear is a good example:

http://www.goodyear.com/truck/pdf/ra...read_S14_V.pdf

The relationship between inflation and load capacity is quasi-linear for a range of psi.
I use this assumption in picking my air pressure. The max allowable load on my 35" KM2s is 2910lbs@50psi. I assume the max weight of my JK is ~5500 lbs(if I
exceed this weight, I better get out and walk to loose some weight ) and a 60/40 conservative weight distribution, therefore each front tire must carry 1650 lbs.
At 30 psi using the linear assumption of the inflation/load curve, because I could not find an inflation/load tatlbe, 30/50 x 2910= 1746 lbs.

So being conservative at 30 psi I still have a load capacity safety margin at highway speeds in my fully loaded JK.
I know the ride on my KM2s feels better at 26 psi, but for my personal taste going below 30 psi on my DD is bad Ju-Ju.

In this case the tradeoff, and there is always a tradeoff, is between ride and handling vs safety and tire longevity. Just find your happy medium.

BTW, here is another good resource from the Rubber Manufacturers Association with information on this topic.
It is a bit dated, but I believe it is only published so often and the updated version has not been released.

https://www.rma.org/getfile.cfm?ID=606&type=publication

It seems like a lot of this information is no longer public since the Firestone fiasco about 10 years ago.

Freedom of choice. Choose wisely.


.