View Single Post
Old 05-27-2011, 05:35 PM   #28 (permalink)
SentraSE-R
Pishtaco
 
SentraSE-R's Avatar
 
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,485

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
Thanked 284 Times in 181 Posts
Time to resurrect this thread. I just bought two used 195/65-15s for $20 each. When I get them mounted next week, I'll be able to test my stock 35 lb. 185/60-15s, my current 47 lb. 205/50-17s, and a lighter 37 lb. 195/65-15 combination. The latter two tire/wheel combos are 5.31% and 4.97% taller than stock, respectively, and have -5.605% and -5.224% rolling circumference differences from stock.

While my mpg has not suffered with the 17" tires, I think that's because my first three tanks with them were on a long road trip. The taller & heavier tires do best under highway conditions where their greater inertia isn't detrimental, and their taller height/taller gearing is beneficial. Also, my AB testing was done under constant speed conditions where the heavier tires' inertia ramp-up isn't measurable.

Using the new tires today under a competition low speed P&G regimen, I was unable to approach the 94.5 mpg I got with the stock tires. In fact, I could only get 70 mpg. I suspect that's because the big, heavy tires need more fuel to come up to speed.

Next week, I plan to do ABCA testing under cruise control and different P&G conditions. I think that testing will be very interesting and educational for me, and probably for all of us.
__________________
Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
  Reply With Quote