That's a nice setup, BlueDevil. What ISO do you usually shoot? I'm assuming something low since you mentioned long exposures.

If the wrinkles in your cloth backdrop are giving you fits, it's fairly easy to remove them in Photoshop. There's more than one way to do it, but one method that might be worth a try is this: create a curves adjustment layer, brighten the RGB curve until the wrinkle details blow out from the backdrop (creating the curves as adjustment layer lets you go back and adjust as much as you like), create a mask on the curves layer and use a black brush to block out the bike. This way the bike stays untouched, the backdrop gets blown out and you should still have nice little things like shadows near the wheels that keep it from looking like you just dropped out the background all together.