Tax assessed value, how and when to contest?

[Josh Teunissen]

Originally I wasnt going to worry until we close in two weeks hopefully. 

First, the #'s on the duplex

Tax assessed value- $175000

Appraised value- $163400

Purchase~ $156000

The reason I'm asking now is if we close and the tax is in escrow, if I contest and lower the property tax, will I be required to continue to pay the $275 a month as part of the mortgage payment? I assume taxes fluctuate on their own so I wonder how that is dealt with.

- Also in your opinions are the #'s different enough to justify trying to lower? The current owners are doing some minor repairs. I plan to make some improvements as well. Nothing like a major rehab though. Will this have any bearing on the decision?

To put my question more clear, is it worth pursuing the lower property taxes? 

I understand theres bigger fish to fry in the real estate game but I want to be proactive. 

Thanks for the input, - Josh