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Mcrews,
The OP (orange) is talking about TRAILER tires, not "taller" tires. Tires that go on a vehicle you pull behind a tow vehicle.
Orange,
First, let me clear up a couple of mis-conceptions:
Rolling resistance is much, much more about tread compound than anything else. Sidewall stiffness is such a minor player you can pretty much ignore it.
Trailer tires are done differently than car tires. Since trailer tires don't have to steer or drive the vehicle, the affects of side forces and torsional forces allow the tires to be rated at higher load carrying capacities than car tires. Put another way, if you compare the load rating of trailer tires with any tire designed for a powered vehicle, you'll notice the trailer tire is rated for a higher load carrying capacity.
Notice that trailer tires are designated differently than car tires. They either have a different size nomenclature (like 4.80-12, or 20.5X8.0-10) or they have letters in front of or behind the size to indicate the type of service the tire was designed for (like ST205/75R15).
Because of the service, trailer tires aren't concerned much about traction or treadwear. Many trailers don't have brakes. Also, trailer tires tend to get old before the tread is worn off. As a result, the tread compound in these tires isn't designed with those properties in mind.
What is the major design factor? Cost!! That means that the tread compound - the thing that is going to have the largest affect on rolling resistance - is going to be a low cost, low tech rubber. Rolling resistance is not even in the consideration.
So assuming you could properly navigate through tire size and load rating, you'd find that a trailer tire will have a major deficiency in either traction, treadwear or rolling resistance (or more than one.)
That's why trailer tires aren't used on cars and trucks.
- and since the demand for these types of tires is small compared to cars and trucks, trailer tires are made by what I would call 3rd tier tire manufacturers - not the major tire manufacturers (with one exception, which is an interesting study in itself). Needless to say, there are issues with these tires.
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