I finally got around to comparing the rolling resistance of the 3 different tire options I have on hand for the Miata.
Available tires are:
- 185/60R14 GT Radial Maxtour - this is what came on the car. I'd never heard of them before, but they're described as a long treadlife touring tire with low rolling resistance.
...
- 165/65R14 Dunlop Ensave - these the stock LRR tire from a 2014 Mirage. They're nearly new (owner swapped tires shortly after buying). Really only suitable for using on the front wheels, since the diameter is slightly smaller than the OEM tire size, so using them on the rear wheels would send gearing in the wrong direction for fuel saving on the highway (where I mostly drive).
...
- 185/65R15 Motomaster Touring AW/H - these are tires from a major manufacturer (not sure which one), re-labelled and sold at Canadian Tire stores. They came on the 15 inch Honda alloys my neighbour gave me that I put on the back of the car for higher gearing/lower RPM.
Goal of my little test: find out the best combination for lowest rolling resistance and highest gearing.
Test method: all tires @ 50 PSI; low speed coastdown test, from a dead stop held/released by parking brake only; down a slight grade onto a level roll-out.
Tire combinations tested:
(average of 3 runs per combination)
1) 14 inch GT Radials on the rear, 14 inch Enasaves on the front.
Results: 76 feet
2) 15 inch Motomasters on the rear, original 14 inch GT Radials on the front.
Results: 110 feet
3) 15 inch Motomasters on the rear, 14 inch Enasaves on the front.
Results: 154 feet
So through sheer dumb luck, it looks like the hoped-for combination of the Enasaves on the front + 15 inch Honda wheels on the back is the way to go. Despite the so called "LRR" properties of the GT Radial Maxtours, they dragged down the rolling distance when tested.
