I rode and extended the tour today. The previous speakers criticized the few single trails. Start/finish point Elsau, but can also be Winterthur. 72km 2120Hm with the following details: The first 500Hm belong to Schauenberg, challenging but all rideable descent via Langegg to Seelmatten, 300Hm up to Chabishaupt, from point 823Hm all on the Kreten single trail (approx. 5km), over on the tarred road to Käfer and down on the road coming from Tablat. Follow the Steinenbach road for 7km. Don't fret about the tarred road, but enjoy the totally rustic Zurich Oberland. At the end of the valley, it's time for some real uphill training - up to 25% up to Gfell - all very rideable. In Gfell, I join the Ride-Sitzberg tour and follow it to Bichelsee. There up to Geretswil, down to the Guhwiler mill, back up to the Heidenbühl (725). Down on a cool single trail (about 3km) to Elgg (insider tip, not on any map), via the cycle route back to Elsau.
In total, about 1/4 to 1/3 of the tour consists of single trails - really recommended. However, you should allow 5-6 hours for this.
Here is the link to Strava: https://www.strava.com/routes/3015674955395662474

Ok, first the positive: the view from the crests is really great and there are a few nice trails.
But: the route between Sternenberg and Höllwald is completely paved and there are lots of cars and motorcycles on the weekend. In between, you can try small detours along the parallel hiking trail, some of which are rideable. At Höllwald (Allenwinden), the tour would branch off onto a hiking trail that is no longer signposted. According to maps from geo.admin.ch, there is no longer a hiking trail there and a sign indicates the forest reserve. The detour leads over a gravel path and then back up a road, which fortunately is then closed to motorized traffic. Perhaps the path via Hohlenstein and Groot to Höll would be nicer?
The lower path at Ottenegg is again not signposted, but then you miss out on part of the view.
The second part of the tour to Fischingen & Sitzberg then consists of individual single trails and tarred climbs. The part of the tour that overlaps with the Hörnli bike route is nicely playful and the trail is apparently also maintained there. However, steps have been built on the wood trail, which is not particularly exciting.
The first part of the descent at Rengerswil to Bichelsee is no longer so feasible in my opinion, especially where there are large sawn tree trunks in the way. Well-versed bikers (not me) have looked for a path along the hiking trail there, but this contains jumps with little space in the upper part (definitely more than a 2 in terms of riding technique). Further down, the hiking trail was also secured with steps, while experienced bikers then took the path to the right, which in turn included a nice drop/jump.
All in all, unfortunately, a pretty bad combination of elements: lots of paved road, few attractive single trails.

I can only agree with the two comments above: Lots of tarred roads, some gravel roads and very little singletrack. A nice bike tour but nothing more. I would recommend this tour to gravel bikers or e-bikers but not to mountain bikers. I would downgrade the technical level from two to one-minus. Quite ok as a leisurely bike tour ;)

Not worthy to be on ride tours!!! It is a bike tour on the road with gravel paths and the few trails about 5% of the route are very easy. I think the tour should be removed from Ride. There are enough beautiful trails in this region that are worth riding.

Scenically beautiful tour. It is often ridden on tarred and gravel roads and occasionally on single trails. You make fast progress but we expected a bit more single trail. The highlight for us was the last downhill to Bichelsee.