70 series tires on the rear of a 2002 (1st Gen) 'Wing ?

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  • #21
    What's your RPM at 70 mph with those?

    Compared to the 60 series, the 70 series should drop RPM by 1 or 2 hundred at highway speeds... wondering if that translates into better fuel economy...?
    George - 2013 F6B Standard - Largo, FL

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    • #22
      Originally posted by srt8-in-largo View Post
      What's your RPM at 70 mph with those?

      Compared to the 60 series, the 70 series should drop RPM by 1 or 2 hundred at highway speeds... wondering if that translates into better fuel economy...?
      I will have to pay attention to that . You would think that I would KNOW that number after 6500 miles , but we rarely went 70 MPH as the speed limits are typically higher than that in the West...although I couldn't tell you what the RPMs are at 80 MPH either...

      I DO know that my bike will hit 120 easy....

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      • #23
        Haha... no prob, I actually had to go remind myself too. I'm pretty darn close to being spot on 3000 RPM at 70. I use the OEM 60 series tires.
        George - 2013 F6B Standard - Largo, FL

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        • #24
          Originally posted by srt8-in-largo View Post
          What's your RPM at 70 mph with those?

          Compared to the 60 series, the 70 series should drop RPM by 1 or 2 hundred at highway speeds... wondering if that translates into better fuel economy...?
          I finally got back out on the highway and noticed my RPMs at 70 MPH -- Really it was the other way around...
          AT 3000 RPMs I am doing about 72 MPH with the 70 series tire on the rear ..it has some wear on it as it is now 6500 miles worn in . but it should be close enough.

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          • #25
            Awesome; thanks Wing!
            George - 2013 F6B Standard - Largo, FL

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            • #26
              Yes you get better mileage because when you switched to a taller tire you changed the gear ratio.

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              • #27
                Originally posted by wild turkey View Post
                Yes you get better mileage because when you switched to a taller tire you changed the gear ratio.

                The change affects the odometer as well - the reading you are getting is now accurate as before it was off by approx 6%.
                Unless you are calculating MPG via GPS miles - the calculations may be wrong.
                Now my ODO agrees with my GPS -- or v e r y close

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                • #28
                  Originally posted by srt8-in-largo View Post
                  What's your RPM at 70 mph with those?

                  Compared to the 60 series, the 70 series should drop RPM by 1 or 2 hundred at highway speeds... wondering if that translates into better fuel economy...?
                  Having run both and closely tracking mpg calculated from corrected miles (not based on OEM odometer), I have seen zero improvement of fuel economy.
                  The taller tire does change the final drive ratio, lowering RPMs, but it also increase slightly the load on the engine.
                  RPM's are only one of many factors that effect engine efficiency.

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                  • #29
                    Originally posted by wild turkey View Post
                    Yes you get better mileage because when you switched to a taller tire you changed the gear ratio.
                    Not so fast WT.. as JM is pointing out, RPM is not the sole arbiter of fuel economy. The only way you could make a statement like yours and be somewhat definitive is if you had access to the GL1800 BSFC table... and I haven't seen that posted much less discussed ANYWHERE.

                    RPM's may drop but engine loading doesn't; it still requires x amount of power to move the bike at highway speeds. The altered parameter will shift the operating point on the BSFC chart... which *may* move it into a *less* fuel efficient region.
                    George - 2013 F6B Standard - Largo, FL

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