Towing a trailer means dealing with wear and tear before the spring season really gets going. An upgraded axle and brake system keeps you safe on the highway, but buying the parts and paying for installation usually hits all at once. Early spring is often the best time to line up parts before the summer rush drives up shop rates and part prices.
You should always negotiate the price of the parts and labor with the shop before you talk about how you are paying. A card window is just a tool for the bill, not a discount on the hardware. Let's look at how to spread out that $900 cost safely.
Remember that the intro window is a firm deadline, not free money. If you still have a balance left on the Discover it® Cash Back when those 15 months are up, standard interest will kick in on the remaining amount.