The shoes are made of different materials and engage diffferently.
White, teflon is the hardest and will slip more. For low traction tracks where you want a soft engagement of the clutch.
Black, Carbon is medium and an all around good comprimise between wear and grip.
Red, roulon is the softest material and bites the hardest. This is the shoe that you want to run if you are on high traction (blue groove) type of tracks but wears the most.
Out of the carbon shoes you should get around 2 1/2 gallons of use. Also the clutch comes with 3 different springs, gold (soft, grey (medium), silver (hard). Go with the gold spring to start. Adjustment is easy, simply set the spring tension nut flush with the top of the clutch nut and you should be right in the ball park. This clutch is the greatest thing ever made for buggies!
Hope this helps.