Not really. The wheel diameter is irrelevant because that's what gearing is
all about.
The engine has a max rpm and in an ideal world it makes it's max power at
that rpm. If you know the drag for the motorcycle you number crunch to
calculate the top speed for the power it produces. Lastly you gear the
motorcycle
to produce that speed at that rpm. On a motorbike you can increase the drive
sprocket size or you can reduce the wheel sprocket size to change the overall
gearing. You can change the wheel size but you don't need to because it's
simpler to swap sprockets.
To say the wheel diameter effects top speed on a motorcycle and makes it go
faster is like saying fitting 15inch wheels to a Spridget will make it go
faster. The fact is on a Spridget you fit a taller diff rather than increase
the wheel diameter. Also on the Spridget neither fitting a 5 speed box or a
taller diff increases the top speed unless it was undergeared in the first
place. In fact a lot of power tuned Spridgets might have a higher top speed
in
4th than 5th because using 4th at 110mph+ drops the rpm better on the peak
power than using 5th does.
W e s l a k e 1330
In a message dated 21/10/2008 19:58:57 GMT Daylight Time,
oldsaabguy@comcast.net writes:
Maybe this is a matter of semantics...
True, the motorcycle absolute top speed is limited by drag and HP.
However, for a motorcycle with an top speed limited by gearing or
engine revs then a larger diameter tire will allow for a higher top
speed ALTHOUGH this tip speed may not be the absolute top speed
limited by drag.
For example a 20 hp bike motor that will turn 6000 revs (and
pretending that the tranny is direct drive) will turn the tires 6000
revs. If those are 10 inch circumference tires then the bike will go
speed x,(no, I'm not going to calculate it out.) but if you have 20
inch circumference tires then the bike will go twice as fast *** IF
*** it is not limited by drag and that the engine can turn the 20
inch circumference tires at 6000 revs.
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