I've planned out a route on the road between these two places, are there any 'bike routes' I can take to come off the main roads?
Sadly no. You have several options but assuming you want to go overland, there'll be significant amount of main road riding no matter which way you go.
Any reasonably direct route would involve going from Crianlarich to Killin - which means riding the busy A85 trunk road between Crianlarich and the Auchlyne turnoff and also having to ride a busy trunk road to get there:
- If you go via Dalmally you'd also need to ride the A85 from Dalmally to Tyndrum and the A82 to Crianlarich.
- If you rode the A83 around the top of Loch Fyne, cut off at Cairndow, took the back route up the B839/B828 over the Rest and Be Thankful, down via Arrochar, you'd still need to ride the A82 from Tarbet to Crianlarich
I can't really recommend riding the A85 or A82, both of which are far worse than the A83 IMO.
From Killin onwards it's easy - you can follow quiet roads the entire way into Dundee, along the south of Loch Tay, over the A826 moor road from Aberfeldy to Dunkeld, then follow the A984 southeast.
There are a few alternative routes that are generally much longer route that would avoid main roads: go via Dumbarton using one of two options:
- A83 north/RABT to Arrochar, then south along Loch Long to Helensburgh then Dumbarton (
https://ridewithgps.com/routes/29365629 )
- A83 south to Tarbert, get the ferry to Portavadie, ride to Dunoon, get the ferry to Gourock, and get the ferry to Rosneath then down through Helensburgh. (
https://ridewithgps.com/routes/29365516 )
An option that just occurred to me would be to go via A83/RABT to Arrochar (as in my first route link), but instead of going down Loch Long, you'd cross over to Tarbet on Loch Lomond - apparently there's a seasonal ferry to Inversnaid - from there you would go past Loch Katrine and have loads of very quiet eastward options.