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Old 10-12-2011, 07:44 PM   #2 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,007

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 53.47 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 73.57 mpg (US)
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Moral of the story: obviously... tire choice can have an enormous impact on vehicle efficiency!

Stuff I learned:
  • I was surprised how much better the RE92's were - not only did they have the best result overall, but they also had the biggest improvement when looking at the difference between each set of tires.
  • The spare tire/donut performance surprised me. Part of me hoped they would have magical properties. Instead they were awful.
  • PSI over 50 seemed to make little to no difference with the RE92s:
The next day I did a test of tire pressure vs. rolling resistance using the RE92's in the same parking lot. I went from 20 to 70 PSI in 10 PSI increments, 3 runs per increment. From 20-50 PSI, there was a measurable improvement each time. At 50, 60 & 70 PSI, there was no significant change in finishing position - the ending 9 chalk marks (3 PSI x 3 runs each) were mixed & clustered together along a 4.5 foot line.

I've done a test like that before: www.metrompg.com/posts/tire-pressure-rolling-resistance.htm
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