Here're the results of a little experiment I'm doing: comparing speed to road angle. Bike is a stock 2006 Blade, I weigh 187lbs, riding at sea level.
1) On a flat surface, the top speed I ever got was 166mph, and it takes a long time and road stretch to get there.
2) On a 1mile fairly steep uphill, I can hit 162mph!
3) On the same uphill with a 170lb passenger I got 147.
4) On the same hill going down, I max out at 159
So, going uphill I can almost do the same speed as flat road, and in a much shorter period. Going downhill, I can't reach neither the flat nor uphill speed.
I didn't realize wind drag made such a huge difference: the steeper the uphill, the less drag there is. Opposite goes for downhill.
Comments? If I'm right it means the double-bubble windshield I've ordered should make quite a huge difference?