I am so tired of being gouged in Canada on everything. . .

Have a quesiton about buying rear tires for my car in USA :

Say I buy 2 tires at $300 / each ($400 each in canada).

Stay in US for 48 hours.

My gf and I come home. We declare one tire each (i.e., under our $400 limit).

a) I know my tires are duty free as they are covered under nafta.

Quesiton:

Do I have to pay Cdn HST on the tires at the border? I know my cost to get the tires, just not sure when I come back through customs

If so, why? I have declared lots of goods after trips to US on flights and never had to pay HST on the purchases in US assuming they did not exceed my limit.

Please post a link if you are sure of the answer so I can take it with me . . . 13% on $600 makes this far less attractive.

Thank you.