Why carbon saddle rails are oval, or the ovalitude of railness.

[Serge_K]

I just asked my brain why carbon saddle rails are oval, and it came up with that:
carbon rails are lighter than metal rails, even if you make the cross section bigger (oval rather than round).
The oval is vertical, which means extra strength resisting the vertical force of fat asses crashing on the saddle

So, it makes sense.

Because other than that, having to accommodate / anticipate 2 types of saddle rails instead of 1 when building bikes is headache nobody needs. When you order a bike, make sure to ask about that. Otherwise it's very easy to find yourself unable to mount the saddle you bought. Don't assume the seat post is compatible with both types of rails. Don't assume the box will include both rail systems. Basically, don't do what i just did with 3 frames :/

[SillyMochi]

I had that grim awakening with my first ever road bike as well. To my surprise (once I discovered that different rails exist) the shop said there are no accessories matching that seatpost to allow for 7x9 rails (local retailer). Well, I looked around a bit and discovered the appropriate clamps myself (one bolt system).

I learned two things with that purchase:
1) Never trust a retailer that just wants to make a quick sell
2) ALWAYS ask for the additional clamps before making an order if the seatpost doesn't allow for different shapes/sizes by itself