First of all, thank you for the accept.
You are absolutely right, I guess it 's that there are too many variables. As of now theoretically the Rottweiler appears to have the strongest bite,(see Wikipedia reference below) also training should be considered as well, I own two Rotties and they would never bite more than a lick!
Bite inhibition is another factor, puppies learn to not bite too hard their litter mates and develop a "soft mouth". If the puppy is taken away too early, he/she may not have learned this important life lesson and therefore will bite harder.
Reference from Wikipedia stating Rottweilers have strongest bite.
I guess it's like saying which man in the world is the strongest? The Asian, the American, the Italian? If let's say the Italian would win this would not suggest that all Italians are strong. He might have had good bloodlines, good conformation good training and motivation as well.
Also notice how in the you tube video each dog breed scored differently with each bite each time.
The below article is very good in explaining all the variables involved:
"Dr. I. Lerh Brisbin of the University of Georgia states, To the best of our knowledge, there are no published scientific studies that would allow any meaningful comparison to be made of the biting power of various breeds of dogs. There are, moreover, compelling technical reasons why such data describing biting power in terms of ‘pounds per square inch' can never be collected in a meaningful way. All figures describing biting power in such terms can be traced to either unfounded rumor or, in some cases, to newspaper articles with no foundation in factual data. (From the ADBA booklet, "Discover the American Pit Bull Terrier.) "
I don't think in the near future a serious study will be done. Even if it would I don't think the results would be accurate enough to be sufficiently reliable. If you want to discuss further, please feel free to press the reply button-no need to press accept again-