For single piston calipers, a c-clamp is usually fine.
For multi-piston calipers, it is not always possible to get a c-clamp in there. Sometime you can use 2 or more c-clamps to good effect on the ends instead.
That is why the expanding 'scissors-jack' type pad spreader is such a nice tool. It simply goes in between the old pads (where the rotor was), and retracts all pistons at once.
Otherwise, you would certainly need to observe the precautions Larry mentions.
There are a million other ways to skin this cat without special tools, however. Prying, pushing, prodding, twisting, vise-grips, channel-locks etc...
I have certainly had to make do over the years, but now I have the perfect tool that works %100 for all (well, almost all;not the spin-in type) configurations.
There are a number of popular brake pad spreaders marketed that resemble c-clamps in principle. Those seem rather silly if one has the right c-clamp already.
Best of luck.
1986 300E 5-Speed 240k mi.
Last edited by csnow; 04-07-2003 at 11:05 AM.