gistfile1.txt

if(scrollView.contentOffset.y <= self.maxScrollDistance) {
        NSLog(@"REGULAR");
        float newY = self.startScrollViewY - scrollView.contentOffset.y / 3;
        float newScrollViewHeight = self.view.frame.size.height - newY;
        
        scrollView.frame = CGRectMake(0, newY, self.scrollView.frame.size.width, newScrollViewHeight);
    } else if(scrollView.contentOffset.y < 0) {
        NSLog(@"NEGATIVE");
        float newY = self.startScrollViewY - scrollView.contentOffset.y / 3;
        float newScrollViewHeight = self.view.frame.size.height - newY;
        
        scrollView.frame = CGRectMake(0, newY, self.scrollView.frame.size.width, newScrollViewHeight);
    }

http://stackoverflow.com/a/28097548/2833978