The group is asking trail users to meet at 5 p.m. Thursday, Oct. 1, at the lower Apex Park parking lot at the Heritage Square amusement center.
The group then will ride to the Jefferson County Open Space board meeting, 700 Jefferson County Parkway, Suite 100, in the county government complex.
The Open Space Advisory Commission is scheduled to consider voting on the plan at the Thursday meeting, which begins at 7 p.m.
COMBA objects to the current proposal on grounds that it is unfriendly to bicycle riders. The plan designates the enchanted Forest Trail and a section of Apex Trail as one-way for biking and eliminates downhill biking or shuttling. A new trail is proposed at the park access point.
Traveling downhill on Apex Trail by bicycle under the new plan will entail negotiating a steep ridge with about 10 switchbacks to the top of a ridge.