Tires: Sequoia load rating, etc., assorted garbage, psi pressure

Question
Mr. Smith,

I've read through several of the posts that somewhat answered my questions. My issue is this: My 2003 Sequoia Limited 4WD came with 265/65SR17 tires. The placard recommends 32 psi. From the onset, with the recommended inflation, there is noticeable drag unless the pressure is bumped up to about 40 psi and the tires always look low below that. At 32 psi, it actually feels like you're slightly braking when you let off the throttle and coast, even in neutral. Even worse, when turning this beast, it feels like the sidewalls are collapsing out from underneath you. This sensation is extreme with the recommended 32 psi pressure. I've driven others that felt the same. The extra inflation greatly reduces this unsettling feeling.

I'm contemplating jumping up to a D or E rating and running at/above 50 psi. The ride is already very smooth. I would welcome a slightly stiffer ride for a slight bump in mileage. My thoughts are that running on a higher psi will lessen the frictional drag from the sidewall flex, and the extra plys will stiffen the sidewalls resulting in less fallout when turning. My vehicle is usually driven with at least 2 kids and 2 adults, and the assorted garbage that accompanies each. The other "tightwad" side of me also sees the extra roughly 3/32 tread depth on the higher ply tires and believes that would translate into longer life.

Summarized questions:
1) Would the higher PSI lessen the frictional drag from sidewall flex; hence increase mileage?
2) Would the higher PSI increase the treadlife?
3) Would the greater number of plys give me a stiffer sidewall?
4) The D or E rated tires I've looked at do not have traction/treadware ratings. With the extra tread depth, would the traction/treadware rating remain the same for the given tire?
5) Lastly, would you recommend this at all?

Thanks for your time in reading this,
Dave C.


Answer
Dave,

Let me do the last one first:

5)  No, I would not recommend this.  Your vehicle came with P metric tires and using tires with Load Ranges means they will be LT's.  The advantage you are seeking will be offset by the problems you'll create.

1)  Yes, higher psi will reduce the drag, but further increases beyond 40 psi suffer from the "Law of Diminishing Returns".  The improvement won't be nearly as much as the improvement from 32 to 40 (which is beyond the 3 to 5 psi I normally recommend.

2)  Yes, but again the big improvement is from 32 to 40 and much less after that.

3)  Most of the stiffness comes from the pressure not the plies.

4)  LT metric tires - and any tire rated as a snow or traction tire - is not required to have UTQG ratings.  The additional tread depth isn't that much of an improvement - Law of Diminishing Returns.

There are a couple of other items I should mention.

The rim may not be rated to take 50 psi.  This is a 50% increase in pressure and that's a substantial increase in stress for the rim flanges.

The pressure increase is going to have a harsher ride, and ultimately that is going to translate into rattles and noises - much earlier than normal.

But the one issue that I think is the most important is wet traction.  Using a pressure that is substantially higher is going to cause the tire to run in the center and while this may be good for hydroplaning, wet traction of the non-hydroplaning variety suffers because of the lower contact surface.

Overall, I think the benefits are not out-weighed by the disadvantages.