A car is already a heavy lift on your monthly budget between gas, insurance, and maintenance. Adding gear like universal roof crossbars and locking towers means you want to time your purchase right so you are not bleeding cash. Springtime outdoor equipment promotions are the sweet spot for these accessories because retailers are pushing inventory for the upcoming camping and road trip season.
When you are looking at the price tag, keep negotiations for the hardware separate from how you plan to pay for it. A financing window is just a tool to smooth out the cash flow, not a discount on the retail price itself.
That intro window is a deadline, not free money. If you still have a balance left on the card when the 18 months are up, regular interest kicks in on the remaining amount.