The voluntary bike ban on riding Snowdon's bridleways runs between 1st May to 30th September.
This means that, during the summer season, you shouldn't be on the designated bridleways after 10am or before 5pm.
The red dotted BWs are the ones affected by the ban, so basically the Llanberis and Snowdon Ranger Path which form the classic up and down route. The black dotted Bwlch Maesgwm (Telegraph) bridleway is unaffected by the ban and usually forms the return leg of the loop if you start in Llanberis.
Anyway, this of course restricts when you can and can't ride there. Either outside the ban periods where the weather can be unpredictable, or inside the restriction period, necessitating a dawn start or evening ride. Both options make timing critical. The weather can still of course be just as unpredictable.
To be completely honest, based on the sensitive nature of the voluntary ban I wouldn't recommend taking a big group up Snowdon.
The impact of such a large group could, in my opinion, be negatively received by other trail users, land managers and National Park Rangers.
It's logistically and politically much easier/better to tackle Snowdon in a small and low key group. I wouldn't like to go there in a group of more than six riders.
Good article here btw: -->
http://www.planetfear.com/articles/MTB_ ... _1110.html