I'm not sure I'd judge a bike by a single ride where you clocked 37 seconds faster. I would cycle that same route five times and average to see how you do.
On my 7 mile loop my times vary quite a bit but bounce around within about a 50 second spread. Some days I feel strong, other days not so much so.
A single 37 second ride improvement wouldn't be a good indicator for me; however, if my last five rides are 37 seconds faster than the previous average, then yes, something is different.