Just a little thing about tire pressures. Low tire pressures tend to build more heat than higher tire pressures in general. That is one reason why the "Ford Exploder"/"Firestone Tire" debacle happened. Tires at pressure "too low for conditions" (that is the key) can build up excessive heat and cause failure. That is plain and simple...not an opinion. It is the circumstances that dictate the "correct pressure". For instance, a Road Race car will usually have less starting air pressure than an Auto-X car. The Road Race car will build up pressure from the starting point due to heat caused by friction of high speed driving. The Auto-X car will start with a much higher tire pressure because they do not run long enough to build tire temps. The thing is BOTH of them are trying to get to the pressure that the tire works best at...handles better...where steering input and tire reacts together. You are trying to get an even tire temp across the tread from outside/center/inside. Since normally driven street vehicles don't use pyrometers ect to measure tire temps outside/center/inside, we are safer to go by tire and vehicle maker reccomendations. From there you can adjust a bit to suit your style, road conditions, climate, ect. Usually if your vehicle is aligned properly, you can use tire wear patterns to adjust you tire pressure.

This mean very low tire pressures offroad are ok because of conditions...LOW SPEED. Once you start driving higher speeds you need to be at the correct pressures for that speed. A low tire pressure also makes your steering input and tire reaction sloppy...just the way it is. Just because you CAN drive at low air pressures doesn't mean you SHOULD drive at improper tire pressures. To go to the extreme: You CAN drive on a flat but it doesn't do the tire any good.

_________________
Founder of L.O.S.T.
2006 CRD Sport
Mods: GDE Hot Tune w/ 364#@2000rpm/Air Box /3" Str8 Exhaust/ASFIR Alum Skids/245-75R-16 Cooper STT PRO/OME LIFT w/Clevis & 4 Spring Isos/AirTabs/Rigid 10" S2 LED/4xGuard Ctr Matrix Bumper
Drag Strip:Reac=.1078_60ft=2.224_1/8=10.39@64.8mph_1/4+16.46@80.8mph

what I do know is you should not go far at speed unless you have at least 80% of the recommended pressure in a tire, and that's the recommended pressure for the actual weight on that tire. and you have to go find load tables from the tire maker to knw what is the minimum pressure for your size tire and your actual weight.

reason I know, is that this is common stuff for motorhome owners to deal with.

I just returned from the annual 'Supersport Sand Show' and talked to the guys who build serious pre-runner cars for the rce teams. most of these cars all had load rance 'C' tires, either A/T, M/T or Krawler type treads. I looked at maybe 50 tires, all load range 'C'. 3/4 ton and up trucks seemed to run load range 'D' tires.

The over $100k cars all had Goodrich Baja T/A 'Project' tires, the $500 types and they are 3 ply sidewalls minimum.

I think we'll go with load range 'C' tires, they are somewhat stiff, but weight is less than a D or E and I think it's enough for a KJ.

3 ply sidewalls minimum? you ARE aware that a standard load tire is FOUR ply, right?

As far as LRD and E tires on the KJ...why on EARTH would you want to exacerbate the already problematic balljoints with an overly heavy tire? I carry a spare tire off road...I don't carry a front diff or balljoints or upper control arms on the trail.

and yes, the above statement makes me a bit of a hypocrite...I have 4 10 ply MTR's waiting for me at work, lol.

And to the guy tha's running 44 psi in his stock SR-A's or ST's or whatever his has...uh...44 psi is TOO MUCH. that's MAX pressure, and you should only increase pressure if your KJ is loaded way up, and even then, in most cases, not to max pressure.

Ply ratings and actual Ply numbers are different than they used to be...A tire can be constructed with less "ply" than the "ply rating". Heavier tires is a concern when it comes to braking and parts (ball joints on KJs) , but so are lifts. You just have to pay more attention to parts after adding a lift or bigger tires and not go too far. Of course a blown 2 ply tire is more dangerous than a properly inflated 10 ply...

_________________
Founder of L.O.S.T.
2006 CRD Sport
Mods: GDE Hot Tune w/ 364#@2000rpm/Air Box /3" Str8 Exhaust/ASFIR Alum Skids/245-75R-16 Cooper STT PRO/OME LIFT w/Clevis & 4 Spring Isos/AirTabs/Rigid 10" S2 LED/4xGuard Ctr Matrix Bumper
Drag Strip:Reac=.1078_60ft=2.224_1/8=10.39@64.8mph_1/4+16.46@80.8mph

Let me throw my .02 in this one
tires are "unsprung' weight so they have ALMOST no bearing on the suspension
you SHOULD run your tires at the correct PSI for your rig based on the weight rating of that tire
if you run a tire rated at 1250# @ 30 psi max in a KJ you will be fine as long as you run 30psi
on the other hand you could if you wanted to run a tire rated at 3000# @ 65 psi max but why?
it will wear like dung and ride like a psc. of farm equipment

Ther tire you run should be based on what you do in your rig
I know that the MTR's we run on my wifes KJ are a waste but the price was VERY VERY good so I have them
I have played with the pressure and some chalk from the kids down the street and found 30-32 psi gave a good wear pattern
on the KJ ,and at that psi the ride is bearable
on the other hand I run superswamper LTB's
even at 26 psi they are still stiff I have drove them on the highway at varing psi from 18-30 and found 26 to be good
I would NEVER run these on a DD but they are GREAT off road wich is what the TJ does
you can run them at 10 psi and not blow a bead but again why take a chance keep them around 15 and you get great flex from them
and they hold the rim great
OK I am done now

The complete opposite is true...unsprung weight (weight not supported by the suspension itself) has everything to do with the suspension and how it dampens irregularities in the road surface. It affects how much the shocks and springs have to work to keep contact with the surface. High unsprung weight directly correlates to "vertical acceleration". This means the tires/wheels/driveshafts/control arms/1/2 of the shocks weight/outboard mounted brake components/ect. move faster or slower depending on the ratio of sprung-to-unsprung weight ratio.

_________________
Founder of L.O.S.T.
2006 CRD Sport
Mods: GDE Hot Tune w/ 364#@2000rpm/Air Box /3" Str8 Exhaust/ASFIR Alum Skids/245-75R-16 Cooper STT PRO/OME LIFT w/Clevis & 4 Spring Isos/AirTabs/Rigid 10" S2 LED/4xGuard Ctr Matrix Bumper
Drag Strip:Reac=.1078_60ft=2.224_1/8=10.39@64.8mph_1/4+16.46@80.8mph

I know people are going to say "oh boy, why is he bringing up toy cars..." but..laws of physics are the laws of physics.

this truck always did great...never broke any suspension parts during hard use, didn't blow up drivetrain parts with this particular engine....
http://s23.photobucket.com/albums/b391/ThunderbirdJunkie/Savage%20X/?action=view&current=Savagedirty.jpg

Until I put these tires on it...

http://i23.photobucket.com/albums/b391/ThunderbirdJunkie/Savage%20X/S5030072-1.jpg
bigger and/or heavier tires will ALWAYS put more strain on all parts of your drivetrain and suspension...especially bushings, balljoints, and such. Now I'm curious as to what percentage of people that have blown up their front diffs were running E's...

*edit* huge pics, so i made links instead

You are correct Darby.Also bigger and heavier tires also take there toll on steering systems.But more unsprung wieght can also help lower the CG of a vehicle which can help in those off-camber situations offroad with a Jeep.

STD load range="P" tires,P=passenger car.Do you have a car or a Jeep?Jeeps should have "LT"(light truck) tires,"C" range would be ideal but 95% of the tires for 16" rims are at least "D"-"E" range,I have run both,both rides good with the correct psi(varies on vehicle wieght).

bad wording on my part
it should read tire load range and psi in them have almost nothing to do ....
because in theory the psi is pounds per square inch simply that
so 30 psi in a E tire will hold an equivilent load as a 30 psi in a C tire
or look at it like this
"X" tire is rated to hold 4000LBS @ 80psi
"Z" tire is rated to hold 2000LBS @ 40psi
put 1/2 the psi in tire X then the load should be no more than 1/2 or 2000# @ 40 psi
this has almost no bearing on the suspension


then there is the missconception that E and D range tires are heavier than C range tires this is both true and false
it is the combined weight of the rim and tire that will decide wich is heavier
a 31X10.5 R15 BFG MT ,LR C, weighs 43# add to that the common steel wheel ,wich is heavier than a 16" OE alum. wheel
or the 245/75 R16 BFG MT ,LR E, that weighs 37# and you use the lighter OE wheel

Look at the savings it is at best 10# per wheel
on the ground that is 1/110 of the total weight of your KJ
that has NO bearing on JACK POOP
say what you will but fact is you can run any tire that will fit on a KJ and have little to no issues as far as suspension
and weight go
the problems with tires and weight of them come come in when you look at a 30" tire compared to a 35" tire then you see issues
with weight and the whole leavrage thing

the only thing the manufacturer is concerned about then the KJ leaves the lot is how it rides. Its very smooth on all-season passenger tires.


I threw on some D rated tires and the shop (against my request) inflated them to 44PSI. It was stiff as a.... well, you know. The ride was horrid. Dropped the pressure to 35PSI and they look handle and ride like the old passenger tires, just a little more bumpy as they dont asborb the road shock as much. 30PSI and the tires look underflated. In the parking lot you can hear the tires work the pavement under full lock steering. At 32 to 35, its just right. I run 35 cuz I haul alot of car stuff around in the back.

_________________
In an epic quest for the perfect Diesel Liberty.
2002 Land Rover Discovery 2 SE

why on earth would the have inflated them to the max pressure of a std load tire?? That just sounds...stupid. I suppose they put high pressure valve stems in there too

You are mixing apples and oranges...comparing a random tire on a random wheel to another random tire on another randow wheel. That says nothing about tires from any same brand and type and the weight of C vs E. Within a specific tires , say Goodyear MTR, a "C" rated tire would weight less than an "E" rated tire of the same size. It might only be a couple of pounds, but their is a weight difference. The thing is it is not only the weight added but the OD increase that puts more strain on stock parts...tie rods, steering racks, ball joints ect. The advantages of taller tires beside adding lift is they roll easier, less tire deflection, over uneven surfaces...especially at slower offroad speeds. If you put 265/75/16 on steel rims on a KJ it will put more stress on these parts than the same tire on a lighter aluminum wheel. Even less backspacing will put added stress on these parts. All this means is you need to check those parts more often and replace them more often...including brake parts. It is just the cost of "building" an offroad vehicle. Going from a 29.2" (stock) to a 31.9"(265/75/16) will put added stress because of size and weight...maybe not a HUGE amount but it will affect them. The advantages are the added clearance, better grip offroad, smoother transition in ruff stuff and more puncture resistant. You just have to WEIGHT(pun intended) the benefits against the downsides.

_________________
Founder of L.O.S.T.
2006 CRD Sport
Mods: GDE Hot Tune w/ 364#@2000rpm/Air Box /3" Str8 Exhaust/ASFIR Alum Skids/245-75R-16 Cooper STT PRO/OME LIFT w/Clevis & 4 Spring Isos/AirTabs/Rigid 10" S2 LED/4xGuard Ctr Matrix Bumper
Drag Strip:Reac=.1078_60ft=2.224_1/8=10.39@64.8mph_1/4+16.46@80.8mph

Um BFG MT to bfg MT is apples to oranges?
Ok if you say so
I guess my view is that you are not doing what guys in TJ's do
lift the thing 4-6" add 35" tires and only regear to get power back
you can only go up at best 3" in tire OD so that is not huge
yeah stuff will wear faster but I just thought if you lift your rig you understood that?

why not compare an LRC Destination MT in 245/75-16 and an LRE Destination MT in 245/75-16 and call it a day? I'd look it up on Firestone's site, but my browswer's popup blocker is only allowing popups that I DON'T want