Keep an extra tool set in your car or truck. Think of it as an insurance policy against road emergencies. You'll be glad they're there when you need them.
Ratchets have a square shaft that holds the socket. The size of this shaft determines the drive size. Heavy-duty automotive work generally requires the strength of a 1/2-in. drive tool which has a longer, thicker handle to provide maximum leverage. A 3/8-in. ratchet is a good all-round size. 1/4-in. ratchets are smaller and ideal for lighter tasks in tighter work areas. Drive adaptors are available that convert sockets from one drive size to another. You should avoid using a small socket on a 1/2-in. drive ratchet, because the excess torque can damage the smaller tool.