It is not really possible to have too much tire clearance on a mountain bike. Clearance adds versatility, with tires being the fastest and most drastic way to alter the performance of your bike, and especially in the mud, excessive clearance has little downside. The one significant downside, the demand clearance places on chainstay length and drivetrain compatibility, has been decently addressed by machined chainstay yokes, 1x drivetrains, and wider rear hub spacing. Sadly, the bike industry is governed by fashion rather than product longevity, with most bikes being designed for the minimum current trends deem acceptable.
Fortunately, there are exceptions.
Plus (read ~3″ wide) tires are a fashion that peaked and rapidly waned. Tires this fat are a bit much for the manicured trails which have become the industries ideal. As the San Quentin frame demonstrates, it is very possible to make a bike with plenty of tire clearance, short chainstays (425mm), that also works with the largest chainring you’d ever want to run (I bet you could squeak a 36t in there). I wouldn’t have purchased the frame without plenty of rumors to this effect, but wanted to put up photos confirming it. So here they are.
This is a Teraveil Coronado on the stock i29mm rims, set up tubeless and with a good ~week to stretch. The Coronado is both truly 3″wide, and quite tall, especially on these narrower rims. As you can see, seatstay and downtube clearance are good, and chainstay clearance is adequate. It is possible that with such a voluminous tire one might run into trouble with wider rims.
The San Quentin has truly come alive with these tires. The stock Flow Snaps grip well, but have a very floppy sidewall, and the lack of both sturdiness and volume made them a big skittish and lacking in support. I always wanted more, especially on the front, while creeping down steep stuff. The Coronados, even in the supple casing, are nicely stout, and the tread pattern suits the volume well, gripping well enough and being quite fast. I did flip the front for better braking traction.
It is also worth following up on my previous difficulties getting the Flow Snaps to go tubeless. I never fund a sustainable setup, and went back to tubes out of annoyance. After chasing a few issues with getting the Coronados set up, I can say that both the stock rim strips and tires were the source of my original problems. The rim strips valve hole was too large to seal well with a Stans valve stem, and the Flow Snap sidewalls never stopped leaking a bit of sealant. An unfortunate spec shortcut that could be frustrating for someone buying the base model San Quentin as their first mountain bike.