Tires: Inflation pressure table for Goodyear MT/R 35X12.5R17, jeep wrangler rubicon, proper inflation pressure

Question
QUESTION: I can not find Goodyear's inflation tables for the subject tire, load range C.  Kevlar sidewall.  Can you help me?

ANSWER: Chuck,

First, there some procedural things that go into determining the proper inflation pressure when changing tire size that isn't obvious from the load table.  The short version is that you should match the load carrying capacity of the original tires at the inflation pressure specified by the vehicle tire placard.  So this requires a bit more than just the load table for the particular tire size you are interested in.

I spent a bit of time trying to find the load table on the internet but was unable to.  However, I do have a copy of it.  Perhaps it would be best if you tell me what the original tire and inflation pressure was on your truck. That way I can walk you through the process.

You can find that on the vehicle tire placard, which is usually located on a doorpost or in the glove box.



---------- FOLLOW-UP ----------

QUESTION: The subject tires are replacing Goodyear 245/70 R16 load range E tires which are stock on a Jeep Wrangler Rubicon.  I am adding almost 900 lbs to the stock vehicle weight, and will need to get axle weights when the mods are done.  I need the table of tire pressures for different axle wts to determine proper tire pressure for street use.

Answer
Chuck,

Since you are modifying the vehicle, anything concerning the original tires is kind of a moot point.  So I'll outline my understanding of how vehicle manufacturers use the load table.

First weigh the vehicle.  If you can weigh each corner, good!  Use the max value, but at the very least weigh each axle and divide by 2.

Multiple that value by 15% and add that to the corner weigh.  Use that to determine the street operating pressure.

Plus since the tire in question is a Q speed rated, you'll want to keep the speed down to limit the amount of heat buildup.  Normal tires are S speed rated and the amount of heat they generate can be quite large at high speeds.  

And here's a copy of the load table out of the Tire and Rim Association Yearbook:

http://www.barrystiretech.com/traflot.jpg