The organisers of Cowalfest have asked me to pass on details of MTB rides that they are running; the full list is here.
Amonsgt them there are two Sunday rides that look interesting on 9 October and 16 October. Google reckons about 90mins drive from Glasgow via the ferry between McInroy’s Point and Hunter’s Quay (car £20.70, bodies £7.50, details here), or you could just take the bikes over (free) and ride the 6-7 miles to the start point. The rides are £4 each to join.
