CAUTION ThunderSlot rear wheel on one side of my roadster had the correct coarse thread grub screw and the other wheel had the fine thread front suspension adjustment grub screw. After I trued the tires the wheel grub screws both came out. I did not get the fine screw back in its original wheel and stripped the wheel threads. Then I stripped the other hole in that wheel. Nice. I have looked at both screws and the screws on the wheels I just received in the mail and I never would have guessed they would use 2 different grub screws. The Professor lists two different spare grub screws, but I have not figured out which is the wheel and which is the suspension.