I just bought a WTB saddle for my road bike. It's replaicing a Terry Liberator Ti Race saddle. I'm not sure if the WTB is designed for a mountain or road bike, but it won't fit on the seat post. The saddle rails are spaced too far apart, and it doesn't sit in the grooves like the Terry saddle did. I thought saddle rails were universal and should fit any seatpost. What's going on here? Does it matter if it's a mountain or road saddle?