The northern part of a possible circular route, you may need to walk some sections
A compass, O.S. Landranger Map 43 and the ability to use them are necessary for this route. Sufficient warm waterproof clothing and food are essential at any time of year. Do not cycle alone.
The southern section here, marked in purple is a circuit via Gleann Fearnach, passing to the south of Beinn a' Ghlo; virtually all of this is bikeable. The route can be made into a circle using public roads via Pitlochry. There are other possibilities however in Glen Tilt.
If you are prepared to walk for maybe three miles you could do a northern circuit linking Fealar Lodge to the top of Glen Tilt. This would create a northern loop entirely off road. Do not bike in this area during the stalking season (Aug - Oct) without checking locally first.
If you are prepared to walk a bit you can go by way of Glen Tilt and Gleann Mor. Walking with a bike may seem tedious, but doing this for a mile or so often opens up distant areas. The hiking alternative would mean a camping expedition.
It's a surprise to see a remote sheep farm at Fealar Lodge, don't frighten the sheep, particularly at the spring lambing. The section west from Fealar Lodge is only partly bikeable, you will have a better chance of doing it in a westward direction as this is a descent.
Once you enter Glen Tilt and start to travel south from Bedford Bridge and the Falls of Tarf, some parts need care due to the steep slope. After just under two miles you meet the Land Rover track further south, then progress is much easier and very rapid.
The track stays on the north-west side of the river for five miles to Marble Lodge, then crosses over. A couple of miles after this it enters woodland near Gilbert's Bridge. Staying on the east bank here is the prettier option as this runs down by the river through mixed woodland. A mile after this you'll have to cross over anyway. Another mile or so after this you join the road at Old Bridge of Tilt. A few minutes after again and you'll be in Blair Atholl.