Originally Posted by gladding24
with new D218 on the rear, and a 16T on the front, 12,800 rpm in 6th should be 188mph actual, not indicated. 189 indicated-12.4%(correction)=is only 166 mph. 166MPH actual with a 16T should be about 11,300rpm.
Not sure what you were turning for revs though.
Actually, with a 190/50 tire (77.25" circumfrence) 16/39 geraring at 12800rpm would be 182.676mph under ideal conditions without areo drag and tire slip.
At 12800 engine rpm in 6th gear, the front sprocket is turning 6093 rpm.
12800 / 1.611(primary reduction ratio) / 1.304(6th gear ratio) = 6093.0794(front sprocket rpm)
6093.0794 / 2.44 (final drive ratio of 16/39) = 2497.1636(rear wheel rpm)
2497.1636 * 77.25"(tire circumfrence) = 192905.8881(inches)
192905.8881" / 12(1 foot)= 16075.490675(feet per minute)
16075.490675' * 60(minutes) = 964529.4405'(feet per hour)
964529.4405' / 5280(feet per mile ) = 182.676 mph
I have measured my rear tire with a stagger tape to get the size of 77.25"
I have tried different gearing and have radar'd my zx10r each time, and 1 tooth in the rear equals about 1.5 mph difference. Going down 1 tooth in front is like going up 2 7/16ths in the rear. The best speed I could get out of mine in 3/4 mile was 178mph with the stock gearing(17/39). The best I could get out of it with a 16/39 was 174mph. I have 17/41 on it now and get 176mph. It seems the error from theoretical speed and real speed is about 6%. The same 6% as the speedo error with the stock gearing. my speedo healer seting with 17/41 is -13%, and its within 1 mph at top speed.
I have come to believe that the tach may also have error.
Sorry for getting technical, but I had to back up my answer with the figures so i don't get flamed or told to STFU. [smilie=B: