Quote:
Originally Posted by rmay635703
It is my belief that long term proper testing is the only way to really know how a tire will affect FE on any given car.
I think the tires load rating (and loading), PSI and aero drag likely play more of a role than their size in terms of FE. (although they are also related)
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Here's my take (and experience), In the day to day reality world of a slight upsize on a car (trucks are another discussion),
1. the load rating is higher so it's not a factor.
2. the width is actually SLIGHTLY narrower, but even it slightly wide, aero gain or lose is non-mearsurable and not an issue.
3. PSI - you should run the desired PSI (40+) regaurdless of size. Since you would run the same psi, then psi is not an issue
4. Size - need atleast a 5% increase in diameter for it to statisticly matter.
5. If you go from a high performance tire to a LRR tire you will see an increase even w/ same size. That is why it's important for all posters to state the full size and type of tire.
6. Downsizing to gain areo is UNSAFE. Period. running narrower (defined as 90% or less) tires is just too risky
Let me give you an example. driver A is got his car all stripped down, scangauge in the ashtray and running donut tires. He is in an accident w/ driver B in a normal car. If I am driver B's attorney......I'm going to own driver A. I wont settle for the insurance claim. I'm going after criminal malice, neglect, ........ I'm sure you see where this can head. When you step out and 'mod' a vehicle uotside the standards, you are setting yourself up for truoble, ESPECIALLY if you didn't notify your ins company of the mods.....