Tires: Profile, Pressure, & rolling resistance, inflation pressure, profile tires

Question
Dear Barry,
My 04 Camry (LE) 4 cylinder was originally equipped with P205/65R15 92H tires.  A more deluxe version (xle) was equipped with P215/60R16 94V.  Factory inflation spec is 29 pounds all around for both.  

The replacement tires that I have (in the original 15 inch size),  have much higher max pressure ratings (44 psi) then the original Continental Contacts..  On the advice of the dealer, I've run the replacements at 35 psi.  This has been satisfactory, with a slightly stiffer ride (fine by me), and better fuel economy (which I wanted).

Now it's tire to replace again, and the dealer suggests that a lower profile tire such as the 16 inch mentioned above would offer lower rolling resistance. He suggests that going to an even lower profile like a 215/55-17 or a 225/50-17 would offer even lower rolling resistance.

Of course I realize that rolling resistance is highly dependent on the individual tire, inflation pressure, and other factors.  But for the same tire brand and model, set up to give a similar ride (I specifically did not say same inflation pressure because I realize that high profile tires run at higher then normal pressures give a stiffer ride more similar to a low profile tire), do lower profile tires generally offer lower rolling resistance?

These different tire sizes would also change the shape of the contact patch, and the wider width tires would cause higher wind resistance.  

So the bottom line questions are: do lower profile tires generally offer better fuel economy?  In the sizes mentioned, how would the change in contact patch from a more elongated shape to a wider shape affect handling?

What would you recommend if I want to maximize fuel economy, minimize noise (concrete and asphalt road surfaces on Long Island).  I am a very conservative gentle driver, but do care about braking performance and other safety aspects of tire performance.

Thank you for considering my questions Barry!

Answer
Harry,

It's hard to do these comparison because if you change one factor another also gets changed.

Using your situation as an example:

If I were to change to a lower aspect ratio, but keep the same diameter, I also change the width of the tire.

I change to a larger diameter, in addition to the aspect ratio and width change - I also change the load carrying capacity.

But here's a clue - the dealer doesn't know what he is talking about in this area.  I have no idea what theory he is working against, but he hasn't researched this very well, as there is plenty of information out there that would contradict his assertion.

Here's a little thing I put together on RR:

http://www.geocities.com/barrystiretech/rrandfe.html

At the end I give me assessment of the situation.

Briefly, I think people should buy long wearing tires rather than low RR tires.  When you consider the amount of energy to make and distribute tires, the overall effect is that less energy is used with tires with high UTQG treadwear ratings.

Also, it takes more weight for a larger diameter rim, so small diameter rims and high aspect ratios would be better for fuel economy.

And as I pointed out, higher pressure are better for RR.