Hola Padraig. I did the
Camino Frances via cycle in Sept 2015 starting from Pamplona. Unfortunately, IMHO, there really is not a cycle guide that really explains where you can follow the walkers camino and where you have to get onto the sealed roads. I did manage to get to the top of the Alto del Perdon - following the walkers. Now I road my mountain bike/hybrid - which has suspension on the front forks and this was really of assistance. As this was my first day it was a real tough intro. From the Alto I took the road (N1111) all the way to Puente La Reina - it would have been possible to rejoin the camino at Uterga. Day 2 I again tried to follow - made it to the Old Roman Bridge a few KM west of Cirauqui, from there it was follow the road to Los Arcos. (The lack of real data on the walking surface overroad my desire to follow). Day 3 I stayed on the road until Viana and from there until Burgos I followed the pilgrims. But it was really, really tough going from Atapuerca to Orbaneja. From Burgos to Rabanal you can follow the walkers without to much trouble. I will write about the last 260 km later if you need it.
Have a look back at some of the post from "newfydog" (he has ridden the whole way and is a really experienced cyclist). I am happy for you to PM me if you want more info. Cheers for now!