The A83 main road from Glasgow through Argyll is not the best road for cycling and more and more is becoming used by forestry lorries and large vehicles transporting freight by land. This doesnt cause a significant problem for motorists although if you are a keen cyclist it is recommened that you perhaps bring a vehicle and use cycles on the less busy roads in and round the villages.
There are many single track roads (with no lorries) and off road routes throughout Argyll. You could cycle from Ardmarnoch to Portavadie and take your bicycle across the ferry to Tarbert where you can explore, possibly even have a day visit to Skipness before returning.
On another day why not drive your vehicle including bicycles down through Tarbert to Tayinloan and leave your car in the car park, take your bicycles across to Gigha and cycle around the island visiting the wonderful gardens. Alternatively there is bicycle hire over on the island if you do not have your own.
Some forestry roads and local walks also allow bicycles to be used, but it is worth double checking which ones do before you arrive so you can plan your holiday and get the most out of it. The local tourist information centres across Scotland should be able to give you up to date information.