Compatible seatpost for Brooks C13 saddle with 7x9 oval carbon rails? I just purchased a Brooks C13 saddle (7x9 oval carbon rails, the more recent version with no tape) and was hoping it would fit on my existing post (2016 Jamis Coda Sport - it's a top/bottom clamp with a single bolt) but found that the rails don't align well, so I think I need a different post.
Does anyone have any experience pairing this saddle with a Ritchey comp 2-bolt seatpost? It says it is &quot;compatible with multiple rail types&quot; and boasts good contact area with the saddle, which I believe is what I'm looking for. Or could anyone recommend a different seatpost option that they've paired with the Brooks C13? I'm ideally looking for a lower cost solution.
Also, this is my first time installing a carbon rail saddle and understand that this may need greater sensitivity - is it critical that I invest in a torque wrench to do this properly?
Saddle rails converged on a 7mm diameter round rail and stayed there for quite some time. You can make them out of solid steel, or tubular steel, or solid or tubular titanium. Then we came to the carbon fiber era. I don't have solid documentation of this, but I'd guess that 7mm round carbon rails can't be made durable enough.
So, we came to the 7x9mm standard. I don't have my hands on such a saddle. However, it seems like (as stated on forum threads like this one, this one, or this one) these rails are 9mm tall, but 7mm wide. The tops and bottoms of the rails are circular, and many seatpost clamps should fit them.
Now, why many and not all? Many seatpost clamps cover the rails on top and on the bottom. Some clamps enclose the rail entirely. For example, Enve's clamp is shown below:

Thus, they ship two separate clamps for 7mm round rails and 7x9mm rails with each post. Alternatively, Kent Eriksen's titanium seatpost doesn't fit oval rails at all, and they say so on the product page. Basically, any seatpost where the bolts clamp side to side are not likely to work unless specifically designed (e.g. Enve). Or, sometimes a saddle's bolts won't offer long enough threads to engage fully if you put a carbon-railed saddle in there. I'm not able to find specific documentation for this, but I believe Thomson seatposts may sometimes be in this situation. Thomson offer a 7x9 (or 7x10) clamp on their site, but I have heard people say their stock clamps work fine. In any case, I believe the Ritchey clamp should work, as it clamps from above and below the rails.
So, why does the OP's original seatpost not work? That's a mystery, as it seems like it should from the description. Some photographs might be helpful if the OP wants to diagnose the issue.