RESULTS IN
Testing description
Testing was performed 6/19/11. Weather was 70-77 F, sunny, with crosswinds of 0-15 mph initially, increasing to 15-25 mph by the end of the testing. I performed the testing by driving out to the testing area on my 195/65-15 mules (C tires), calibrating them on the test loop, and switching to the A (205/50-17) and B (185/60-15) tires for testing before testing the (by now cooled off) C tires, then retesting the As. All tires were well-used. The As still have 7/32" (70%) tread depth remaining. The Bs have greatly-accelerated center wear, with 2/32" center tread depth, but about 6/32" (60%) edge tread depth. The Cs have 6/32" (60%) tread depth. The A tires are mounted on non-aerodynamic alloy wheels. Bs and Cs are mounted on stock steel wheels. Following photo shows A tires/wheel on car ready to be dismounted, B tire/wheel on ground ready for mounting.
Testing and setup took a total of 10 hours! I used an IR thermometer to check ambient and tire temperatures. Before mounting, the tires were ~75 F. After the low speed testing, they reached 92 F. After freeway driving, they reached 114 F.
I weighed the mules (C tires), and got a 0-3 lb difference from the stockers (B tires). The mules weighed between 35.5 and 38.2 lbs. Some back-to-back testing had both B and C combos weighing 35.5 lbs - on three consecutive weighings. Since I don't think that's possible, I'll call my scale flaky, and the mule Cs 1.5 lbs heavier than the stocker Bs. The heavier A set at 47 lbs each, are 12 lbs heavier than the Bs, and 11 lbs heavier than the Cs.
I inflated all tires to 51 psi cold for consistency. I drove the Cs over the test course (a 10.6 mile loop on a frontage road, mostly untrafficked on Sunday) to calibrate them for distance accuracy before starting the testing. I was only passed by three cars while driving during my 10 hour test routine. Of course, a lot of the time, I was parked changing tires, recording data, etc. The UltraGauge calibration was 1.033 for the Bs, 1.09 for the Cs, and 1.099 for the As.
Cruise control testing
All testing was front tires only, dragging the same A (205/50-17) rears. Testing with each pair of front tires was one lap with cruise control at 34-35 mph (calibrated by GPS and verified by calibrated Ultragauge).
Pulse and glide testing
The results were recorded, the UG and GPS trips were reset, and I proceeded to the second test, a Pulse and Glide on the 10.6 mile frontage road loop between 1500 and 2500 rpm (roughly 20-30 mph in third gear, keeping the engine load between 78% and 83%. My earlier testing of A and B tire sets found no significant difference during cruise control testing at low 30 mph speeds. My real world driving with the A tires indicates they may slightly improve mpg, or at least not hurt it. At the time of testing, I'd driven 2900 mostly highway miles on the As, and achieved a 51.3 mpg average with them v. a 48.8 mpg average over 20,000 miles with the B set. My theory, and the reason for this test, was to see whether the 4.97% taller than stock but essentially same weight C mules performed better in P&G, where the greater inertia problems of the 5.31% taller than stock but 12 lb. heavier As should be a handicap.
Highway testing
The results were recorded, the UG and GPS trips were reset, and I proceeded to the third test, a 9.6 mile highway drive on the highway paralleling the frontage road. This necessitated entering the highway, driving at 54-56 mph for two exits, exiting the highway, turning around, re-entering the highway, rexiting it, and returning to my starting position to swap tires. There was a lot of variability in acceleration rates entering the highway. I tried to decelerate at the same spots before exiting the highway, but results of this third test are inherently the most variable. The double acceleration to highway speeds should favor the lighter B and C tires.
Anomalies
The plan was to start testing each test tire set cool, to be consistent, but I made two errors. Switching from A tires to B, I reset the UG's trip too soon, and was unable to calibrate the UG for the B tire size. I had to drive the B tires four miles to get trip values to set the UG distance calibration, inadvertently warming them up, prior to testing them. At the beginning of testing tire set C, I got a couple of miles down the road and realized I'd left my IR thermometer where I'd been parked. I sped back at high speed to recover the thermometer, heating the tires to 114 F before starting the C tire testing.
Test results
A = Goodyear NCT-5 (V), 205/50-17, 47 lbs, 5.31% taller
B = Trazano H550-A, 185/60-15, 35 lbs, OEM
C = Continental ContiproContact, 195/65-15, 36 lbs, 4.97% taller
A1(cc) 49.3 mpg
A1(P&G) 69.9 mpg
A1(hwy) 39.4 mpg
B(cc) 50.6 mpg
B(P&G) 71.1 mpg
B(hwy) 41.5 mpg
C(cc) 53.0 mpg
C(P&G) 71.8 mpg
C(hwy) 41.8 mpg
A2(cc) 50.3
A2(P&G) 68.6 mpg
A2(hwy) 40.0
By test, green=best, red=worst
tire set A1....B.....C......A2
cc.....
49.3-50.6-
53.0-50.3
P&G..69.9-71.1-
71.8-
68.6
hwy..
39.4-41.5-
41.8-40.0
Conclusions
The light and tall C mules clean the other tires' clocks. The heaviest A tire/wheel combo came in last in each test. The reason I went to taller tires was to free up my poor car's engine. In stock form, it buzzed at 3200 rpm @ 60 mph. With the A and C tires, it still buzzes at a very rapid 3000 rpm @ 60 mph, but at least the taller tires provide a little relief from uber high rpm operation. Taller and lighter (C) conclusively wins. Taller and heavier (A) conclusively loses.
It's possible the warm tires caused the significant performance improvement of the mules, but higher inflation pressures typically don't produce much improvement above 40-45 psi. It's more likely their taller height and light weight are bigger contributors.
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