We took the ascent via the outer Nazlike and extended the tour to Spitzhörli - which was definitely worth it. This at least gives you a first short descent before it's time to start climbing from Bistinepass at the latest. From there, however, it's all about carrying, pushing and only riding a little - the terrain is steep and very rocky. It's certainly at least a 5/6 in terms of difficulty and isn't very fun if you've already done one or two meters in altitude.

The return trip on the opposite side of the valley, on the other hand, is very beautiful and pleasant to ride, mostly along the Suone. From the Giw mountain restaurant, the route is varied and exciting all the way to Visp (we adapted the route slightly there).

We definitely recommend the tour with the extension to Spitzhörli, but with the knowledge that a longer section follows from the Bistine Pass.
In our rating scale from bronze to platinum, we would give this tour "silver".

The path over the Stockgräbe in the Nanztal is closed from 02.10. - approx. 02.12.2023 due to the replacement of the bridge.

At the Gibidum Pass in the direction of Nanztal (the trail along the Suone) there has been a no biking sign since summer/autumn 2022 :( .

The descent is very downhill-oriented, it has very long technically difficult sections and where it would be flowy, it goes down the rock face vertically for several hundred meters on the left. The path was broken from time to time. I really liked the scenery on the way up, but I didn't like this descent because I had to carry too much.

A worthwhile alternative for the uphill is to start directly in Visp.
Visp -> Visperterminen -> Giw -> Gibidumsee
Mainly asphalted road with very little traffic after Visperterminen.
From Visperterminen to Giw there is a chairlift that transports bikes.

We opted for this option as we could no longer reserve a bike space on the Postbus.

As I own a wigwam with a fireplace in Simplon-Dorf, I'll allow myself a few comments as a semi-local. I've been riding the Fulmoos for years, usually several times a year and usually starting and finishing in Simplon Dorf.
About the tour: I don't think the climb over the Bistinen Pass is a good idea. I normally use this route for downhill and that alone is hard enough. Would like to see who rides up there. I would recommend the ascent via Hopsche and Üsseri Nanzlicke. If you are really fit, you can ride everything except 2x 10min push (directly after Hopschusee and at point 2284). However, even this is hard enough and demands everything from you. You can leave the rest of the tour as it is, even if you have other options after Brig or Visp.
Personally, I always ride the Fulmoos counter-clockwise if at all possible, even if you then have to pedal uphill along the Suone. Advantage: the pushing/carrying sections are usually uphill and not downhill, and in my opinion there are more rideable sections in this direction.
I usually ride the following route: Simplon-Dorf - Simplon-Pass - Üsseri Nanzlicke - Nanztal (50% trail/50% gravel) - Gibidumpass (steep climb on gravel) - Obers Fulmoos - Bistinenpass - Bielti - Simplon-Dorf.
Consequently, you could also ride the ride tour analogous to this description, but then you would have to climb the Gibidumpass twice. Or you could ride down the Nanztal valley the second time until you reach the track again. Or you could ride from the Bistinenpass back to the Simplonpass and take the Stockalperweg from there. Or....

One of my most beautiful bike tours ever! Fantastic scenery, challenging and long, practically all single trails. You do have to descend and push from time to time, but it's limited.
The variant over the Üsseri Nanzlicke as described at https://blog.spoony.ch/2014/10/03/die-nanzlicke-gibidum-tour/ is very worthwhile, you are rewarded with two additional kilometers of trail flow. The variant up the Gibidum is worth it for the view, less for the riding fun.
Riding technique = 4/6 may be true, but riding safety is just as important on this tour, as some sections are very exposed and challenging ;)
Time requirement Simplonpass to Brig today = 7h (an info I wish I had in the description and comments).

We did the tour on 01.08.2019.
It's definitely not my favorite tour! It's not just a few sections of pushing and exposed sections, but mostly pushing and bumping until you reach the back of the Nantztal valley after just under 4.5 hours. A great tour in terms of scenery, but next time we'll do the route without a bike and enjoy it too.

We rode the lower part of the tour today, August 4th. In the tour description you should add that the whole "flowy" part before crossing the Gamsabach is often exposed and requires a careful riding style. The steep terrain before the Gamsabach is also very technical. After the Gamsabach, you have to carry your bike up most of the way. Basically, the part from Gibidum is an option for good/experienced riders, if you want to go straight to Brig, because of the exposed terrain, I only experienced flow in between and at the fast end.

We rode the route today (July 2, 2019). In the Bistinepass - Fumoos - Schafalp - Gibidumpass area, countless snowfields have to be crossed on the shady side, sometimes in very steep terrain. The melting snow brings a lot of water, which finds its way across the hiking trail in several places. In addition, paths have not yet been restored after the winter, there is a lot of rubble on the route and some of the paths slide down into the valley.

According to information from the Brig tourist office on September 7, the bridge has been repaired.

I rode the tour today ( 18.07.2018 ). Well, at the beginning you push and carry the bike up for about 1 1/2 hours. Then it continues with pushing and carrying until the end of the valley. After that it's really fun! The path on the opposite side of the valley is wonderfully flowy and easy to ride. The view and the panorama quickly make you forget the exertions of the ascent. The trail down from the Gibidumpass is first-class enduro territory and, with the right amount of suspension travel and riding skills, everything is rideable except for a few places - sensational!!! A small but decisive drop of bitterness at the end was that a mudslide tore away a crucial bridge at Aentschi. At the moment it is no longer possible to cross the valley or the stream to get to the hiking trail which then leads into the Nanztal and back to Brig. Unless you balance with your bike on your shoulders first 10m over a 30cm water pipe to the middle of the stream. There you then cross loose branches and tree trunks. Now through the avalanche of scree, mostly crawling or crawling, always somehow pulling or pushing the bike through the rubble. After this exertion, you then have to carry the bike up the forest over fallen trees and large boulders to the hiking trail to get to Brig via Nanztal. There is a warning about this in the forest just before Brig. "Hiking trail Nanztal - Aentschi closed until further notice! Liability for the use of the path is rejected!" Coming from the other side, i.e. from the pass, there are no signs or signals anywhere... Crossing the stream is really very, very dangerous and not recommended! There is a great danger of falling!!! If anyone wants to ride the tour again this year, it is better to first ask the municipality of Brig whether anything has been done about the bridge and connection to the hiking trail or whether there is any way around the disaster. Then ride the rest of the way down to Brig on flowing single trails following the signs for the Gondomarathon.