The Straight Dope wrote:
It's a lot easier to get a chimp in roller skates than it is to get him to pump iron — hence, most of the data on chimp strength is anecdotal and decidedly unscientific. In tests at the Bronx Zoo in 1924, a dynamometer — a scale that measures the mechanical force of a pull on a spring — was erected in the monkey house. A 165-pound male chimpanzee named "Boma" registered a pull of 847 pounds, using only his right hand (although he did have his feet braced against the wall, being somewhat hip, in his simian way, to the principles of leverage). A 165-pound man, by comparison, could manage a one-handed pull of about 210 pounds. Even more frightening, a female chimp, weighing a mere 135 pounds and going by the name of Suzette, checked in with a one-handed pull of 1,260 pounds. (She was in a fit of passion at the time; one shudders to think what her boyfriend must have looked like next morning.) In dead lifts, chimps have been known to manage weights of 600 pounds without even breaking into a sweat. A male gorilla could probably heft an 1,800-pound weight and not think twice about it.
That was in the 1970's so there's probably some more extensive data by now. Chimps may not be 6x stronger than humans but they are definitely much stronger. Of course, spider monkeys ain't chimpanzees.
