Gravel may not be great for the Frances, but need a rugged gravel for a May departure.
Saw a Nahamura Century (new) for €750 in Anglet's Intersport....
Sooo....Ivar's Intelligensia, any ideas??
Gravel? I'm not sure what you mean.
But your choice of bicycle depends on which route you're taking. There are two routes. One of them is the shared walking/bike path, designated by the Spanish authorities as such. And then there's a route that's completely on pavement. Either way, you don't need anything special. It's not technical, and almost any bike will serve.
In May, the Camino will be very busy and especially towards the end you'll find it extremely difficult to ride on the walking trail because you'll have to keep on stopping and dismounting because so many people will be on the trail.
The "Mapy. CZ" app does a really good job of showing both routes if you toggle on the outdoor overlay.
Due to an injury while walking a couple years ago I bought a used bike mountain bike in Pamplona. Cost €70. Another €75 at the Decathlon bike shop to fix it up and I was on my way. I just gave it away in Santiago. The thrift store I bought it that was called something like "Trabajos."
You can buy a new bike at Decathlon starting at €300 and there are lots of good bike shops in Spain.
If I was bringing a bike along, I would bring a hybrid road/dirt bike. That would be most useful.
And I would say, you don't get the Camino experience when you take a bike. It has almost no relation to the experience that you get walking.