Discount Tire Direct via eBay cuts $100 off orders of $400 or more via coupon code "CMOTORS0314". Plus, all tires qualify for free shipping. That's the best dollar-off coupon we've seen from Discount Tire Direct. (For further comparison, we saw up to $75 off orders of $500 or more in October.) Some exclusions may apply. Coupon expires March 17 at 3 am ET.