Hi,
It is somewhat possible.
You can create a discount of the type "coupon" restricted to a category with these 2 products in it (it can be their second category for example), with the minimum number of item option set to 2, and the auto load option activated.
The coupon will then be displayed on the checkout automatically if the 2 products are in the cart.
The catch is that the coupon will also be displayed if the customer purchase 2 left suspensions.
Alternatively, you could create a third product "left and right suspension" which would be the price of both products with the discount already included.