I did this ride in August 2020 on my old 1995 Kona Explosif MTB (no shocks) on 2.25 tires. Started in the town of Fiesch, took the road to Binntal, and turned off onto the Helligkreuz road just before Binn. We road up the Helligkreuz side and down the Grengoils side; the road is stepper in the opposite direction. An alternative would be to take the post bus to Binn and ride from there. The road starts paved and in the woods near the Helligkreuz Gasthaus. This is the last chance to get something to drink or eat. It then crosses a small bridge and after a couple of kms turns into a dirt/gravel/logging road with no traffic. The pass is at 2300+ meters and so the road is above the treeline with good views most of the way. You wouldn't want to be caught up high in a lightning storm. There are many sections with 8% to 12% slopes, but no sections that will make you want to whimper and get off the bike. The actual pass is a narrow gap, with no sign but a great view of the villages of Riederalp, Betten and Kuhboden on the opposite slopes of the Wallis Valley. It's amazing how high above the main valley you are at this point. It's a long descent to village Grengiols on a logging road. I had to stop to rest my hands several times on the way down. In our case near the bottom, we took the bike trail back toward Binntal road. It's a pretty trail, with several short steep climbs, but my legs would have rather taken the train in Grengoils.