Hi team. I'm doing a 70 mile ride in a few weeks where approx half of it will be along the thames bike path (gravel and bumpy) and the other half on road. I do have a full suspension mountain bike but it's not very light and hard work on the road. So was thinking of converting one of my old road bikes. So is there a massive difference between a cross and a road bike, I won't have any mud to contend with but do they have a different geometry or stronger components or can i just stick some nobbly tires on it?