It was about 4 years ago a group of us mountain biked in the area, including Ben Nevis, but thinking back...
There are two routes up. The most travelled one is on the south side. On this side, near the base, there are campsites with washroom facilities, shops, and you could put the bike in here, asking nicely if they would watch them.
The other route is marked on the map with a Mountain Rescue Post, on the opposite face. It has a few steeper gradients. This is the route less travelled, but was good for the moutian biking because it was a rideable gradient, with a few sharp jumps up. There are some houses at the base, which are off the main road, but you're less likely to have the bike guarded.
I suppose it's a long way of saying to take the bike to the side with the campsites, but don't leave them overnight.
A good map site is www.multimap.co.uk
[This message has been edited by Scottydog (edited 15 March 2002).]