Like others I've travelled a few thousand miles with a bike & a 5x4, I always carried my Wista, wrapped well in a pannier, with a bracket to hold the tripod. Although I only use racing bikes I was often off road on rough tracks/terrain. In hindsight a Graphic would be better if you you can cope with the very limited movements.

I'll be biking with a 5x4 again in a few days (when I'm in the UK) and will have to use a Speed Graphic (no shutter) so will see how practical it is.