Cairn Toul & Beinn Bhrotain, maps 43, 403S
13th July 2003 & 21st June 2008

Route: Walking Part: 1715m = 5625' ascent; 17.9 miles; 9¼ hrs
Cycling: 132m(out) + 35m(return) = 167m = 550' ascent; 10.0 miles; 2hrs

Route: This is a longish day with several possible variations. Really fit walkers could add in the whole of Braeriach by walking up the Lairig Ghru almost to its highest point. Less fit walkers could omit Cairn Toul whilst those not doing Munro tops could save 50m of ascent and 1¼ miles by cutting out Tom Dubh.
There is a natural pairing of Braeriach with Cairn Toul when approaching them from the south. For such a walk, the start would be Derry Lodge from which there are excellent paths all the way up the Lairig Ghru, as here.
However, Beinn Bhrotain and Monadh Mor demand an approach from White Bridge, and the paths from there to Corrour Bothy are poorer than from Derry Lodge, no matter which side of the Dee you are. By 2016 both paths had had some maintenance. On the west side, the path is easily cyclable for 2 miles north from White Bridge but then deteriorates more and more as one goes further north before turning westwards along the Geusachan Burn. Path construction had not gone beyond the Allt Garbh in April 2016. Geusachan Burn can be crossed without too much difficulty if it has not rained for a day or two but the path does not continue northwards to the Bothy. I recommend not trying to cycle beyond the small cairn at NN996899 marking a path up to the Munro top Carn Cloich-mhuilinn, and instead continuing from there on foot.
As long as Cairn Toul is to be included in the walk, a more sensible alternative is to leave any bike at White Bridge and walk up to Corrour Bothy using the path on the east side of the Dee. In my opinion it is not cyclable beyond the first few hundred yards and there's virtually no indication in the peat of mountain bikers ever passing this way. Nevertheless, the path does go as far as Corrour Bothy and is of better quality on the non-cyclable sections, which form the majority of the distance. This choice would exchange about four miles on the bike (on the west bank) with four on foot (on the east bank) and avoid potential difficulties crossing the Geusachan Burn. Note that the River Dee cannot usually be forded safely before the bridge at Corrour Bothy.
Tackling only Beinn Bhrotain and Monadh Mor without Cairn Toul can be done from Glen Feshie. However, from the south one choice is to ascend Glen Geusachan. It is easy to reach Loch nan Stuirteag at which point the route given here can be joined. If Tom Dubh is not an object of desire, then it would be easier to take a route over Beinn Bhrotain to Monadh Mor, returning via the bealach between them and contouring round the SW flank of Beinn Bhrotain's summit if necessary to avoid a re-ascent. This return route would be much easier and shorter than going via Glen Geusachan.
The flattish area to the north and north-west of Tom Dubh is fairly boggy due to its height and rainfall, and the burns are not that simple to cross as there are few significant stones to aid a dry crossing. It may help to keep north of the Allt Luineag on the approach to Tom Dubh and, on leaving, to cross the burn just where the gully starts.
There is also an optional minor detour to the top Carn na Criche of Braeriach which adds 245m ascent and 1.1 miles to the version which includes Cairn Toul.
Lastly, this route includes a trivial detour to the east top of Beinn Bhrotain for the view. A more obvious and direct line of descent would omit this.

Weather 21/6/08: Neither warm nor cool; dry, some light cloud, sunny intervals, light breeze. 4°C at car at 0630 after overnight frost.