A question I can't find an answer to..

I'm not sure how to even word this question..

Tonight's game rams -3.5 at SF.

Almost always both sides of a spread is juiced at -110.. But every once in a while one side will be heavier. SF was -115. Rams were -105.

I've noticed the heavier side tends to cover more often than not. And it's usually the side the public isn't on.. Is there a way to find that out? Is there a way/site/database to look back at stuff like that? 

Thanks for any help. 

I guess I'm asking does the heavier side of a spread have a higher win % historically? 

@Dport

 No...All books are different, the vig is based soley on balance...has no comparison to a historical winning % light or heavy side is irrelevant...

@Dport

 The public is actually on the "heavier" side.  That is why the vig went from -110 to -115.  If the public continued to back SF, the vig would raise to -120, -125, and eventually-4 (-110)

i have noticed when live betting in my casino a 5 point dog in nfl was juiced at -130 the fav was -108 and the DOG always covered or won s/u