I bought a beautiful carbon fibre gravel bike frame from Boardman. The frame was a steal and I bought it in the Christmas sale. I then added Shimano Ultegra components (Di-2 you understand), a wheelset and some other pieces, and hey presto! the bike was built. Super lightweight, 9kg gravel bike.
Except that I forgot to check whether the frame had any mounting points. It did not occur to me that I might change my riding style and consider touring with it. The fact is, gravel bikes are super flexible: with their increased tyre clearances you can mount skinny 25mm racing tyres or go up to 40mm mountain bike tyres. This is perfect if you have trails that have a combo of forest tracks, single trails and tarmac. It opens up new avenues and new interest. And touring is one of those new interests.
I spent a lot of time researching for the right pannier carrier rack. The fact is, there are loads and loads of reviews out there of racks and it is really confusing to find which is best for your needs. Relatively few reviews discuss the best rack to keep the weight down and that is compatible with Ortlieb backroller carrier bags. And even fewer reviews worry about how to mount it.
The Tubus Cargo Classic (Amazon UK) or Tubus Cargo Classic (Amazon DE) is what I found. It is incredibly light aluminium and weighs about 700 grams. The equipment comes with all the required mounting bolts, washers and spacers assuming you have mounting points (more on that in a moment). It fits a regular racing bike or gravel bike fitted with 622mm clincher rims. More importantly, it can take a load up to 40kg. Now if you have two side panniers (like the Ortlieb backrollers Amazon UK, Ortlieb backrollers Amazon DE) AND also another bag on top, you can see how that might come to 40kg.
The mounting assumes you have mounts to locate the screws near the drop outs (where the axle is) and at the top of the frame near the seat post. My frame had mounting holes near the drop outs probably destined for mudguards, but they seem to work well using the required spacers and bolts. For the top of the frame I purchased a Bontrager Eyeleted Seatpost Clamp. This is a collar that attached to the seat post and has mounting eyelets for the carrier.
In my experience, this was trickier to mount than I had anticipated. Firstly, I forgot that my seat post had the DI-2 battery in it, and when I pulled the seat post out the wiring detached. It took some fiddling around to re-connect the battery. Then I noticed that the clamp had a slight rim to it which made mounting it on my 32mm seat post rather hard work. It felt like it was meant for a seat post slightly narrower in diameter. Therefore, check rather carefully the diameter of your seat post. Nevertheless, eventually I got it installed and with the mounting arms of the Tubus carrier, it all worked well.
If you do not have mounts near the drop outs, you can purchase either a kit that fixes to the quick release or you can buy P-Clips.