If you're ever going to cycle a high mountain trail you'll remember, you should cycle this one. You start with a 15-minute climb up a dirt road and tractor road up to a ridge. There begins a narrow path consisting of hard-packed earth and a few stones, all above the tree line, with a view over the støl areas on Nystølsfjellet, towards Valdres, towards Hallingskarvet, towards Jotunheimen, and down towards Høgevarde, absolutely fantastic.
The first part after you have come up on the ridge is gentle climbing, up towards several intermediate peaks, before you top out on Rauddalsfjellet (1205m). From there, it's an absolutely fantastic downhill drive north-east until you reach a junction. Resist the temptation to continue all the way down to Vesle Grevsjøen (there is a lot of traffic) and instead turn to the right (southeast). Here follows a small section with slightly more tortuous cycling with some heather and driving, but it is quickly forced, and then a fine dirt path takes over between the heather again.
When you reach the outlet of the Dansartjernet you have cycled east of, you cross the stream. There you will find a well prepared, sometimes steep and technical, but fun path down to the dirt road. Turn left approx. 50 meters and then down to the right where the path continues down to a new dirt road. From there, just turn right and cycle back to the car.
I think this one is a bit difficult to grade. I would say that many of the parts up on the mountain are blue, while some parts are clearly red. I mean it's light pink or dark blue, like the whole, I mark it as blue so as not to scare anyone away from a nice experience. Expect one and a half to two hours on the trip.
Drive to Herad, east of Gol, and turn off at Liagardsvegen (signposted to Bagn) and follow this, remember your card or coin for the barrier (50 kroner). Drive on to Brennesætri/Søreli-Nystølen (it's a bit). Park where the road breaks down again.
Step up the gravel road 20 meters from the car park and turn right when you meet a tractor road. This tractor road takes you up to the ridge and path (about 15 minutes of pedaling up there).