TC...don't forget to calculate in the effect of tire circumference change
due to heat expansion and centrifical force ; )
cheers, Terry
-----Original Message-----
From: TC <[EMAIL PROTECTED]>
To: V-MAX TECH LIST <[EMAIL PROTECTED]>
Date: Thursday, June 15, 2000 11:17 PM
Subject: Re: Rpm at 70
>Hal,
>If you want a really true calculation then the measurement should
>include the entire loaded vehicle. The 12.47 figure that I use for a
>stocker is from a Cycle World test indicating 809 revolutions per mile
>with the K525 on the bike. This is a typical value to use for a
>stocker since this is supposed to reflect the results of a stock tire.
>
>If I used a 591 or something similar .... which is advertised as
>having a 25.6 diameter then I doubt that it would lose 1/2 inch
>sitting on the ground .. but what do I know. That is why you will get
>different results ... if this tire only compressed 1/4 inch then the
>rolling diameter would be 25.6 / 2 = 12.8 - .25 = 12.55 .... this .08
>difference would yield a 5th gear RPM of 4404 at 70 mph as opposed to
>4433 for the dunlop, (a more exact RPM calculation than the 4450 I
>stated earlier).
>
>Assuming you have no clutch slip .... the gearing on the stocker is a
>known value .. so an easy way would be to simply see what RPM you are
>turning at that speed and calculate the "rolling radius" from that.
>Unfortunately, this is no easy task with the mini-tach .. and is why I
>really rounded the RPM off to 4450 as I doubt anybody can tell the
>difference between 4433 and 4450 or our stock tach. Also .. the
>chances of 70 mph actually being exactly 70 mph is questionable.
>
>Soooooooo .... sitting the bike on the ground ... having someone sit
>on it or simply hold it up ... and measuring from the center of the
>rear axle to the ground will get you pretty darn close for most
>purposes. An even easier way is to put a mark on the sidewall of the
>tire with your favorite dragstrip white shoe polish and the ground ...
>roll the bike forward until the mark rotates around again to touch the
>ground ... measure the distance between the two marks and you have a
>pretty accurate "rolling circumference" like Eric was talking about
>... and that work just as well, (if not better). The "rolling"
>circumference is infact 2 x (rolling radius) x (pi) so to derive the
>"rolling" radius from that would simply be .... (rolling
>circumference) / 2 x (pi) ... Back to our stock tire .. if we did the
>"mark on the ground" routine .. we should have recorded a distance of
>6.53 feet or 78.36 inches ..... plugging that into our formula we have
>78.36 / (2 x 3.14) = 12.47 .........
>
>Hope that helps ...
>campbell
>
>
>----- Original Message -----
>From: "Hal" <[EMAIL PROTECTED]>
>Subject: RE: Rpm at 70
>
>
>> TC,
>> Is that 12.47 a static measurement? Does it include the
>> rider? Is tire rise at high speed ever significant enough to
>> be a factor?
>
>> -----Original Message-----
>> From: TC [mailto:[EMAIL PROTECTED]]
>> Subject: Re: Rpm at 70
>>
>> Eric,
>> The rolling radius is the distance from the center of the axle
>> to the ground with the bike sitting on the ground. 12.47 is
>> the advertised rolling radius of a Dunlop Qualifier K525 ...
>> If you want to talk distance per wheel revolution I'll take that
>> too .. for the 12.47 rolling radius stock tire that would be 6.53
>> feet.
>
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