I remember some members saying they do run 5 or 10 lbs over max pressure.... as printed on sidewall.
Does anyone KNOW if the saftey margin built in will allow this?

My reason for asking..... had 285's with 65 psi max. Now have 315's with 50 psi max. There is a noticable increase in rolling resistance with the 315's. Can feel it when coasting down my street (cool down time) to my driveway; also when manually pushing truck back in garage, making room to work under the hood.
I'm afraid it will show up at the diesel pump also... as poorer mileage?

Love the look ... and the ride, but have I made a mistake going to 315's or can I experiment with the pressure?

RJ

 

I don't think there would be a problem if you aren't hauling a load but the tires may wear faster in the middle.
Easy way to find out is to paint or chalk a line across your treads and go for a short drive on dry pavement. If the line disappears you are ok, if the outside edges of the line are still there the tire is running on the center.

 

I have put 80 in the rears on my truck for towing with no problems. The tires are rated for 65. I have also seen many customers come in with way to much air in their tires. We had an older gentleman come in last week with a Neon with almost 110lbs in his tires. He said that they "looked" low so he kept adding air until they looked right. You might not get the most miles out of them with higher pressure, which could cost you more in the long run.

 

you must only be runnig a d rated tire. My 285's are 80 max and they are e rated. I have had my tires too 100 psi with no problems other than crappy tire wear and one heck of a rough ride!!! I keep them at the dodge recommended unloaded tire pressures, and throw mor air into them as i need it for towing/hauling. 50/40 is perfect ride, and i get .1 mpg less than max pressure!!

 

Bill, Good tip

 

RJ
I ran my last 2 sets of 285BFG ATs (rated at 65max) at 70front/55back empty with front to rear rotations every second oil change. Both sets went 100Km(60k miles) and they still had tread left at take-off time and all my driving is done in town. I should have known Bill would have known that trick LOL I use a yellow grease marker on all my new tires and go for a short drive to see what air pressure they like as its not a one size fits all. Then air them to where they seem to wear off evenest. Our trucks are very heavy in the front and would be suprized to see them run the same PSI front to back for even wear. I'll bet 80psi in a set of 245s and you could push that thing around your shop with one hand

 

One thing to remember, is that when you increase tire size, you can lower the pressure and keep the same weight capacity. but I think in this case, the 315s are probably only D rated. When I had a set of 265/75 D-rated tires on my truck I really noticed the increased rolling resistance and poor cornering. With the 235/85 E-rated, it rides and handles much better.

Jim

 

Thanks all! Great tip Bill!
Ratsun - Like the idea of more in the front... will play with it.
Yes my 285's and these 315's are both D rated.
So concensus is no saftey problems running higher pressures... just concerns over even tread wear?

Just to be sure I understand. I do lots of 1-3 hour highway trips at gross weight (no towing). Still no saftey concerns with pressure build up if over inflated??

RJ

 

RJ
I would run for 3/4 of your average trip (so the tires are up to temp) then shut down and run a marker accross them and see what you get. You may find that after they warm up theres to much in the fronts but .... you will just have to play with it. I personally belive that running with a full width contact patch rather than 2"down the middle or 1" on either side is safer than any recomended pressures however I am no expert. One other thing I that just clicked..are you are running those 315 on the stock 7" rim? That tire should be on a 8-8.5 " wide rim shouldnt it?

 

02 Rims are 8" stock..... at least they are with the Camper and/or Towing Package. This package also came with 265's.

RJ

 

My bad sorry
I thought the stock ones were only 7s
As I said I'm no expert but I look at it this way if only 50% of you tire is touching the road due to improper inflation then you would be better off with a 50% narrower tire. One thing I've noticed (it may be just in my head ) but the larger tires dont wear as long? You would think since the dang things make less rotations than the smaller ones that they would last longer, but this has not been the case for me?

 

I run 50psi at all 4 corners and my tires are wearing nice and evenly and I used to get 20mpg with them. Now I'm only getting 18. Dang injectors.

 

I'm curious, have you seen a drop in MPG since changing? Our 97 did not change going from BFG A/T in 285 to the Mudders in 315. There is a noticable change in coasting, but I fell it is a small enough HP # (like A/C) it has little affect on total. I run 45 in the front and wear is even accross the tread. Rear I need to drop.

Along with Bill's suggestion if you just drive onto some hard pack dirt you'll get the same effect.

Randy

 

First fill up on new tires cost me a little over 1 mpg! Yes, corrected 5.4% for the bigger tires.

Put front 315's at 60 psi and backs at 55 psi. Rides (and rolls) similar to previous 285's... feels like it anyway.
Still rides flat... at least from testing with a chalk line at the end of a short trip. Will test again on a longer drive but I think these pressures will work out OK, at least in the cooler weather. Probably need to test again when our 6 months of "every day over 85*" weather shows up.

Thanks to all for the advise.

RJ

 

What is your MPG? Was it ever corrected for the 285's? Our 97 was off by about 4% with the 285s. With the 315's it is just under 10%. I still need to get the speedo gear. I've just been occupied.

Randy