yes, I realize that tire inflation has been discussed to death here, but I was hoping I could get some help with my particular situation and vent my frustrations.

I recently purchased a set of 31x10.50R15LT load C rated Bridgestone Dueler A/T Revos for my Tacoma Xcab PreRunner to replace the same size and load rated Goodyear GS-As that came with the truck.

I'm currently running 34 psi cold in front and 32 psi cold in the rear UNLOADED for normal on-road driving at highway speed. The front tires seem to have a good contact patch at this pressure. However, I noticed that the rear wheels don't seem to making full contact with the ground across it's width at both the inside and outside shoulders of both rear tires. Maybe half or over half of the inside and outside lugs aren't contacting. That leaves me to believe that they are overinflated. I haven't done the chalk test yet, but pulling into my garage after driving on a wet road for about 1 mile, the rear tires definately did not leave the full width's tread marks on the garage floor. Even getting down on the floor and eyeballing it, they don't seem flush.

So, I guess I'm a bit concerned about the tires wearing down in the center and not achieving full traction potential. I've checked the door jamb placard and it lists 26 psi cold in front and 29 psi cold for the rear on the standard 225/75R15 tire. Fortunately, the owner's manual lists the psi for 31x10.5R15 tires, which is exactly the same at 26/29. So, then I checked http://www.thedieselstop.com/content...re%20Inflation ,which I read about in another forum here and it states that the door jamb placard lists "the RECOMMENDED pressure - based on normal load of a passenger car and MAXIMUM load capacity of a pick-up truck." So then I'm thinking should I be running even lower than that while UNLOADED? I definately don't want to run too low and cause over heating and damage the tire, but even at 29psi, that seems low.

So let say I do go down to 29psi cold and unloaded and that (just for example) it does even out the contact patch; at highway speeds, I'll be back to 32 or more psi and the contact patch will be overinflated again.

Also, to make matters more confusing, I also ran across http://www.toyo.com.au/TechInfoPDFs/...20Part%204.pdf while doing more research. It mentions that LT type tires should be inflated more than passenger tire for the same load. Though the article isn't clear about LT "Floatation" type tires. Another article from Toyo tires, http://www.toyojapan.com/tires/pdf/TTT_08.pdf has a diagram of a contact patch that's less than the tire's actual width, but I'm not sure if that appiles to all tires or just passenger or performance tires.

So that said, has anyone else experienced anything like this? Maybe the Tacoma's rear end is just too light for this particular tire? Oh, and when I got rid of the the original Goodyears they also seemed to have more tread left on the shoulders, but the centers didn't seem excessivly worn or anything. But then again, I never paid as close attention to that as I am now. Well if all else fails, I've still got about 15 days left on the Bridgestone trial period, so I'm thinking of maybe switching to the P265/70R15 "standard" load Revo.

Thanks,

Austin

 

the longer you wait to do the chalk test, the more inaccurate it becomes.....

i run all my tires on my pickup at 25 psi

the stock spec for my truck is actually 29 in the front and 26 in the rear.....

 

Thanks,

The rain finally let up this afternoon, so I tried the chalk test. I aired them down to 29 psi cold on the rear and tested them pretty much cold (drove a few hundred feet to a dry spot on the road) and the center chalk definitely disappeared more than the edges. I aired down to 26 psi and it was a bit better. Drove back and forth on that 5 or 6 times to make sure as much chalk wore off as possible and the edges still had significant chalk across most of the lug/blocks.

Also, with the fronts still at 34 psi, I was still getting more chalk left on the edges. Not nearly as much as the rear though. Man, I thought for sure that the heavier front end would have made for an even chalk line.

Oh, also, I've got 456 miles on these tires.

 

it may be too late to have accurately done the chalk test..... especially if you have any alignment issues....

 

I run mine at 22psi on the front and rear. But they are bias ply. My radials run at 30 psi. Wide floatation LT's are pretty much going to wear in the center. You just gotta keep them rotated and balanced. By the way, LT=light truck and P=passenger or P metric.

 

Yeah, thanks for your replies...I guess I'm just paranoid.


if anyone's interested, I found some load and inflation tables:

http://www.goodyear.com/truck/pdf/da...dInflation.pdf
http://www.trucktires.com/zip/Light_Truck_Tables.ZIP

Unfortunately, the bridgestone document doesn't list LT "Floatation" sizes.
The goodyear one does.