i just bought nitto 325 65r 18 tires and i put them on my stock ford 18x8 rims and they reccomend a 9 inch wheel size at least for the tires. i just left the ford dealer for a service and they inflated my tires to 65 in the front and 75 in the rear and i yelled at them b/c the max is 50, but the ride was a little better. Can i run my tires at a higher psi to make up for the rims being to small or will they blow up on me

 

ive got some TOYO AT i think there are 365 75R 16E and recommended psi is 80 pounds i think it all depends on the load rating of your tires and be sure to look on your tire to find the max psi dont inflate over that because if you have a tire falure and they discover that they were over inflated then your SOL also look at your gas tank cover it shows, or should, the recommended psi for front and rear tires

 

my max pressure says 50 psi for my new tires my gas tank for the factory tires says 65 front and 75 for the back and thats what the dealer aired them up to. Although they seemed to ride a little better with more air in them. They appear to be low at 50 b/c they are on a more narrow rim than they should be, but im really trying to avoid buying new rims b/c i like the ford factory rims

 

By running those tires on a narrow rim, you may move the center of the tireout, away from the wheel, making the center of the tread taller than the outside. This may cause pre-mature tire wear. The added tire pressures will add to this problem Most overinflated tires wear the center out of the tread. Now you have two reasons for the tire to wear out in the middle of the tread.
If you tow with this truck, you may also cause your own blowout by the increased preassures associated with the extra heat generated under load. The manufacturer has pressure and size recommendations for a reason. Breaking some of the recomendations, you might get away with, but breaking most of them has to have an impact somewhere down the road.

 

thank you much i keep them at 50 then

 

I would always use the correct rim for the tire you have because of safety...Never go over the max psi listed on the tire, again for safety..


Dick

 

well i guess i ll have to check out some rims then

 

fordtough03...

I replied to your other tire PSI tread here...

https://www.ford-trucks.com/forums/600014-tire-psi.html

 

Looks like your threads were combined...

325/65R18's should be run at 45 PSI front and 50 PSI in the rear. If you are not towing/hauling and just daily driving the rears would be better set at 40 PSI. Do not inflate your tires above the max PSI listed on the sidewall. You have to be especially careful not to have more air in your tires than needed. As you know running 325's on stock 8" rims will natrually cause the tire to crown as the tires are too wide for the rim and too much air will just make it worse causing the centers of the tread to wear out even faster.

Here is the load/inflation table for 325/65R18...

65 PSI - 3860#
60 PSI - 3600#
55 PSI - 3390#
50 PSI - 3195#
45 PSI - 2945#
40 PSI - 2715#
35 PSI - 2535#


For those of you who are running 35X12.50R18 they should be run at 50 PSI front and 60 PSI rear (unless max PSI is lower than 60 PSI). If your not towing/hauling and just daily driving the rears are better set at 45 PSI. I have been running my 35X12.50R18's at 50 PSI front and 45 PSI rear for over 7K now and they are wearing completely evenly across the tread and the ride is perfect.

Here is the load/inflation table for 35X12.50R18...

65 PSI - 3415#
60 PSI - 3220#
55 PSI - 3030#
50 PSI - 2910#
45 PSI - 2735#
40 PSI - 2530#
35 PSI - 2335#
30 PSI - 2075#
25 PSI - 1820#

All load/inflation information is accurate only for that particular size and only up to the max PSI listed on the sidewall.

 

hey thanks alot guys i appreciate the help i ll have to look into getting a wider rim somewhere down the road

 

The 05-07 SD came from the factory with 18x8 rims with either
LT275/65Rx18E 125S (2WD) Max Load = 3640lb at 80Psi max inflation
or
LT275/70Rx18E 125S (4WD) Max Load = 3640lb at 80Psi max inflation

You just replaced your tires with Nitto
LT325/65Rx18 D 121R Max Load = 3195lb at 50 Psi max inflation.

Not only are your new tires to wide for the factory rims (which will cause increased tire wear) but your new tires are also the incorrect load and speed rating for your truck. With your new tires you have just decreased the max per wheel load on your truck by 445lb which decreases the Max GAWR by 890lbs. It also decreases your GVWR by 1780lbs. So if you tow or carry much weight you are now going to have to pay closer attention to your weights.

Replacing your stock rims with wider rims will make these new tires wear better but it will not replace the lost Load Capacity or Speed Rating.

Also never inflate a tire above the max side pressure on the side wall, doing so can cause the tires to explode. Obviously whoever installed these tires for you knows very little about tires. The tire shop created a very hazardous situation by installing a tire on a rim that is to narrow for it per manufactures specifications and then compounded the problem by inflating the tires beyond the max recommended pressure.
At the very least you need rims the correct size for the tires, or better yet you need different tires that have the proper Load and Speed ratings for your truck.


Hope this helps

 

thank you much ill keep it in mind for next time and im def gonna pick up some rims when the funds are there for it

 

He actually only lost the 890# on the rear axle. He is still within the 6000# GAWR on the front axle. So he only reduced the GVWR by 890#.

When it comes to the speed rating, he is still within a safe range. Unless he is driving his truck faster than 106 Mph.

 

great well that makes me feel a little bit better

 

Since we are talking about tires and such...

Does anyone have the torque spec for the lugs?