I have searched the forums but it appears i have a rare tire. I am running Dick Cepek Crushers in 285/70/17 E. I can't find the recommended city PSI. I am looking for best psi for mileage. The max on the sidewall says 80 i have them at 40 right now but i am wondering if that's a bit high. I will be due for an oil change in 2000 miles so i will inspect the wear pattern at that time but am looking for some input. Thanks.

 

When in doubt refer to your door plate for reccomended tire pressures for your truck. I have Continental Extreme Winter Contacts in that size load range D and if I'm not running loaded I run 35 psi with good results. FWIW.

 

Forget about door plate pressure when you are running tires that are not the stock type of tire. Chalk the tires and check the contact pattern. I'd start somewhere around 50psi, move up/down from there.

 

With E rated tires I would run at least 50 empty. My truck has E rated tires and the recommended pressure is 60 front and 45 back unloaded, and 60 front 75 back when loaded.

 

Maintaining proper inflation is probably the single most important part of tire maintenance. But what is the right pressure?

While there are a lot of variables, and sometimes it'll take some trial and error, there are some general rules that can help get you off to a good start. Here are some general guidelines, along with a few myths or fallacies to avoid:

1. The pressure printed on the tire is the MAXIMUM, not a recommendation. Some vehicles, often heavier trucks, will run maximum tire pressure when heavily loaded. But for most cars running the maximum is too much.

2. The right pressure depends on the tire size and the vehicle. There is no such thing as a specific recommended pressure for a certain brand and model of tire.

3. The manufacturer's recommended pressure on the door jamb is a great place to start. It will list a recommended pressure or pressures, and also usually tell you the load index of the original tire. If the load index of your new tire is lower, you may need to add some additional pressure; if the load index of the new tire is higher, you can still run the recommended pressure.

4. Keep an eye on treadwear. If the center is wearing faster than the edges, drop the pressure. If the edges are wearing faster than the center, raise the pressure.


FWIW I copied this from a blog on the Tire Rack website. I have always run the same or lower PSI when going to a higher load rated tire on my cars or half ton trucks with good results. I do increase PSI to match tire recommended PSI if running loaded though.