Max. RPM Discussion....
I often get remarks from GC users that I have entered the wrong Maximum RPM in the GC database for their bike and therefore the top speed is calculated wrong. They mostly want me to put in their redline RPM or the RPM the rev-limiter kicks in. But I use the M.P.RPM (Maximum Power RPM), the RPM at which the bike produces the maximum amount of horsepower in top gear. I will try to explain why:
When calculating motorcycle speeds, one of the key items is of
course the RPM the engine makes.
But, the more speed the more wind (and other) resistance will
occur. In fact, the air resistance force is approximately proportional to the square of the speed. So doubling the speed will increase the wind resistance 4 times.
That is why a motorcycle can easily reach the redline RPM on the
tachometer in the first 3 or 4 gears.
But when driving high speeds in higher gears (5 and 6), reaching the redline (or rev limiter) RPM depends on the available amount of horsepower. That is why some motorcycles (and cars) reach their top speed in 5th gear instead of in 6th.
To calculate the top speed of a bike, you need the RPM the bike
can make at that speed in highest gear.
Since most manufacturers specify the maximum amount of horsepower at a certain RPM, it is also save to use this RPM (at which the bike produces the most HP) to calculate the top speed of the bike !
An even more accurate M.P.RPM is the same RPM but now taken from
an actual dyna-run.
In this case the maximum horsepower (136) is delivered at 9750 RPM. Now this is the RPM that is entered in the Gearing Commander database as the Max Power RPM. So when sending in data for your bike, please try to find out this RPM at which the bike delivers the most horsepower, either specified by the manufacturer or mentioned in a published dyna-run. If available on the Internet, please send me the link to this data.
Using this M.P.RPM as the RPM in the GC database also means that
your actual top speed in lower gears will probably be higher than indicated
because in those gears you can actually reach the redline RPM which normally is
at a higher RPM as the Max Power RPM.