The Speed rating is, of course, the top speed of each vehicle. Note that the top speed averages only vary 1 to 2 mph per star, but over 3 laps, it all adds up. The Kart's weight factor will not only determine how much you slow down if you go off course, but also how much speed you will lose by making a turn without power sliding. For example, Bowser's Kart may have a ***** rating on speed, but the ***** rating on weight tends to make him lose more speed unless you power slide into your turns. The rule is, the heavier you are, the more power sliding will be necessary to keep that nice top speed bonus. Remember, the difference is fractional, but after three laps it all adds up. Other factors in-race that will alter your top speed is turning without power sliding (it will knock you down 1-2 mph), incline of the road (down-slope faster, up-slope slower), and turning while power sliding (which will actually raise your top speed 1 mph if you sustain it) will not lower your speed at all. The class speed breakdown is as follows. Note: This is an average. One star of weight more or less will alter the speed 1 mph or so respectively:
 
50cc 100cc 150cc/mirror
* 42 mph 47 mph 54 mph
** 43 mph 48 mph 55 mph
*** 44 mph 49 mph 56 mph
**** 45 mph 50 mph 57 mph
***** 46 mph 51 mph 58 mph
Note: It does not matter who you have driving; speeds remain the same no matter what character you choose to drive.