Well new to me anyway – Carn Liath, the Munro at the southern end of Beinn A'Ghlo.
Upsides – 640m vertical descent over 9.5km, of which 6km is perfect singletrack and light heather bashing. Fantastic views. Short climb. Descent about an hour. It's a Munro
Downside – 1.25 hours with the bike on your back. Not rideable in the wet as the bottom part is peat track so would erode badly with heavy use.
Any hill walkers and anyone who has done the Beinn a'Ghlo loop will know it. Park car at Loch Moraig NN906672. Up the track and take the path from the bothy straight up the hill. From the cairn down to the bealach at 938715. Very obvious path heads round the corner and down. About half way down the path disappears but keep high through the burnt heather and pick it up again 100m later. One wee burn crossing has a 1m drop into it, unlike the others which are all rollable – you don't see it until too late, but it was a soft landing!. The path stops about 200m short of the LR track, but just head down across the heather to the right of the old grouse butts to pick it up.
Took us about 4 hours including a couple of stops. Kind of similar to Carn Ban Mor and just as good but in a different way. Shorter but more difficult climb as its a carry, and the descent takes much longer because it's slower, and it's physically much longer.
Enjoy, but don't do it if the ground is very wet as it won't be nearly as enjoyable and will cause erosion on the peaty bottom half