I've always been curious how best to do this. Apparently most simply start with a hammer and chisel or use a scraper blade, such as a moderately narrow blade in a recip saw held at a shallow angle, then follow that with solvent, like on a scrubbie, to dissolve and remove the remaining reside, either paint solvent, kerosene and if that doesn't work then try acetone. Another tip I've heard about is freezing it with dry ice left to sit on top of it then hammering up under the floor pan to fracture and loosen it, followed by scraping a now much more brittle and less gooey substance. If there's surface rust then the pad should come away much more easily in those areas. Please post back with how you make out on those fairly thick Volvo pads.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now