I've done my share of posting about tires here (woo, hoo, another voice on the internet!). My only qualifications are having an interest in the subject and a decent ability to find information (and a lot of reading). While I'm reasonably confident in the accuracy of the info, alas, display of confidence in Homo Sapiens is not highly correlated with being able to distinguish anatomy from topography.

Fortunately, there are people with real qualifications on the internet like tire engineer Barry Smith who cuts a wide presence, but primarily at the two links below.

The first link is to allexperts dot com where he fields tire questions.

The second link is his Barry's Tire Tech page which is loaded with info. One caveat, though. The site deals mainly with passenger tires (P) and could be confusing if someone tried to apply some of the info to Light Truck tires (LT) without being aware of the significant difference between the types.

It's not impossible, of course, that someone could claim to be something they're not, but I've been able to corroborate most of his info with separate, reliable sources. Validation has often worked in the other direction, as well.

Tires - Auto Parts - Autos - AllExperts.com
Barry's Tire Tech

Will have to spend some time over there, thanks for the links.

Good links!

Great links. Just read for an hour. Quite interesting since I'm looking for tires. Thanks for posting.

Interesting quote!

"Further - the easiest and most effective way to get good rolling resistance is to use higher inflation pressures - along with frequent inflation checks to assure that the pressure doesn't drop much over time. I recommend 3 to 5 psi above the placard specification. Anything more than that starts to compromise traction - with decreasing effects on fuel economy - and in my opinion this compromises safety too much.

A later addition: Apparently, the above paragraph has been interpreted to mean that I am advocating high pressures in tires.

Let me be clear - I AM NOT!!

I prefer a car that is crisp in steering. I am also willing to put up with the increase in ride harshness. and it does help fuel economy.

But under no circumstances am I advocating the use of inflation pressures higher than what is written on the sidewall (with the exception of tires with 35 psi max. on the sidewall - and there's a long story there!)"

Koz

My favorite nugget is the fact that the difference between 35psi and 44psi as max pressure on the sidewall of a P-metric tire is due simply to a difference in the interpretation of a regulation.

Interesting... first post I read though he acted as though a minor increase in tire sire (LT to slightly bigger LT) was a big mistake, citing all the testing a manufacturer does to get the suspension tuned right with the tire. Obviously I disagree with the first entirely and couldn't care less about the second - seems like a "Consumer Reports" type guy, conservative to the point of being useless... read a few other posts but didn't see much meaningful either. He probably has the knowledge, just not an off roaders viewpoint and probably gets pissed if his kids don't have a front license plate on their cars. :P

You would be surprised by how much a bigger heavier tire will effect a vehicle.

More rotating mass and its location – The worst type of increased rotating mass is when the mass is added to the outer perimeter and/or increasing the overall diameter (weight's distance outwards from the center of wheel). Every time you double the speed of the tire (RPM) you double the amount of energy (energy = HP and braking power) needed to accelerate/stop the wheel/tire. If you double the weight of the wheel (same diameter) you double the energy needed. If you double the diameter (same weight) you need 4 times the energy (and that multiplies every time you double the RPM). Now add weight and diameter! This is why it is VERY important (when replacing wheels) to know where the mass of the wheel is located (did you ever wonder why carbon fiber is used for the rim of very expensive wheels). The better wheels have most of its mass close to the center point. That said, when you increase the overall diameter of the tire and also use a heavier tire, all the extra weight is added in the worst possible place (the perimeter) and the energy needed to accelerate/stop is quadrupled every time the RPM is doubled. This is why depending on how far you deviate from the designed OEM overall diameter and weight the negative effects multiply proportionally.

The suspension on a vehicle is designed and tuned for specific unsprung weight and can not be adjusted easily. If you change it, one way or the other and can not adjust the compression, rebound and dampening, you MAY affect the handling in a negative way. It's sort of like adding an intake and exhaust and not re-mapping the fuel delivery. Also the overall diameter of the tire effects the final gear ratio and could effect the OEM's max tow rating.

Koz

Actually it sounds like someone who has been designing something for 30 years and knows what he is talking about instead of some weekend warrior who THINKS he knows more than the engineers who design this stuff.