Top Speed varies even when using the same bike

Question

I own a Hero Honda CBZXtreme bike. The top speed that I have reached is 122Km/Hr. But I am not able to reach this speed always. Sometimes the speed does not even cross 105 Km/Hr while travelling on the same road. Whats the catch here? On what does the top speed depend?
I don't seem to understand this. Because I am using the same bike and the same road every day. But the top speed differs daily.Does it depend upon how and when I shift the gears or something like that?

Answer 1

You'll find the following will all affect your speed and acceleration:

• wind speed - a head wind will slow you down more than you would think
• your clothing - this directly impacts drag
• bike configuration - you'll go slower with panniers on than with them off
• weight - a full tank will mean you accelerate more slowly
• temperature - cooler air can give you a better top speed
• what type of fuel - if tuned for it, an engine can get a higher speed on better petrol
• how warm the engine is - many engines will not produce full power until warmed up, and engines that are too hot will also underperform (see temperature) so cooling is essential at high rpm
• type of tyre - some have higher rolling resistance than others
• air pressure/oxygen content - engines are more efficient at sea level than up a mountain
• exit from previous corner - if you come out of the previous corner faster, you can get up to speed faster
• gear choice - a lower gear has more torque, but a lower top speed, so changing up early will lead to a slower acceleration (known as short-shifting)

So see which of these have changed between your different attempts.