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We had a big product-news week recently with the new Beargrease and Levitas rim releases. This week is a little more scattered, but there are still a few things we can check out.
One inexpensive winter tire caught my eye, the Fat Bike Birkie and Sun Peaks apparently don't agree with us on where the fat-bike tire-width line belongs, and Michigan continues to provide evidence that fat-bike racing does not require snow.
Let’s get into it.
The Big Stuff
A $119 Studded 26 x 4-Inch Tire? Well, kinda.
Surface 604 has put a new PolarForce 26 x 4-inch studded winter tire up for preorder at $119, with availability expected later this month.
That's cheap enough for a factory-studded fat-bike tire to garner some attention.
The tire uses carbide-tipped steel studs, an open-block winter tread and reflective sidewalls. It is wire bead and designed for tubes rather than tubeless use, and Surface 604 is primarily selling it for its full-size fat-tire e-bikes.
That doesn't automatically make it irrelevant to a conventional fat-bike, but I want a few more details before calling this a bargain. Actual casing width, weight, stud count, recommended rim width and how that casing behaves at proper low fat-bike pressures would all be useful to know.
We will know more when it gets out in the real world.
How Wide Does a Tire Have to Be Before It’s a Fat-Bike Tire?
This shouldn't be a particularly difficult question.
Apparently it is.
The 2027 Fat Bike Birkie requires tires at least 3.5 inches wide.
Fat-bike.com has traditionally used 3.8 inches as our working definition of a fat-bike.
Meanwhile, Sun Peaks in British Columbia requires at least 3.75 inches on its groomed winter fat-bike trails.
None of these numbers is wildly different, but the lack of agreement is interesting. Why 3.75 and not 3.8?
The Birkie isn't some random local ride making up rules at registration. It's one of the best-known fat-bike events in the country. Sun Peaks is operating a real groomed winter trail network. And manufacturers have spent years applying the fat-bike label to bikes and tires across a pretty wide range.
I don't think we need to rewrite the Fat-bike.com dictionary tomorrow morning, but this might be worth digging into.
What actually makes a fat-bike a fat-bike in 2026?
Fat-Bike Racing in Michigan
This Saturday, Custer's Last Stand at Fort Custer Recreation Area has separate men's and women's open fat-bike classes on a course that's roughly 95 percent singletrack.
The same day, the Maple River Gravel Chiller in Maple Rapids includes fat-bike categories across its 10-, 25- and 47-mile gravel events.
We've seen enough fall fat-bike categories over the past few weeks that this may turn into a larger story later this season.
Who is still racing fat-bikes when there isn't any snow, and why are they choosing to race fat-bikes?
If that's you, I'd like to hear about it.
Gear & Bikes
Winter Trail Rules With Actual Numbers
Sun Peaks recently published its winter fat-bike trail rules, and I like that they're unusually specific.
Riders are asked to stay off the trails following more than 5 cm of fresh snow. Tires need to be at least 3.75 inches wide. Maximum tire pressure is 8 psi. And if you're leaving ruts deeper than 2 cm, you're supposed to stop riding.
There will always be differences between trail systems, snow conditions and grooming equipment, so I wouldn't treat those numbers as universal law.
But they're a lot more useful than simply telling riders to "use good judgment."
Anyone who has spent time around groomed winter trails knows that "good judgment" occasionally turns out to be in short supply.
This might be another subject worth revisiting once the snow starts falling around here.
Around Fat-bike.com
The Bearclaw TŌWMAK Gen 2 Story Is Coming
I've been talking with Jason at Bearclaw about the second-generation TŌWMAK, and there's enough changing with the bike that I don't want to simply rewrite the product page and call it a story.
The titanium drop-bar fat-bike keeps its ability to run 27.5 x 4 to 4.5 tires, while Gen 2 adds changes including UDH, more mounting options and the ability to run 32-inch wheels.
Normally, 32-inch mountain-bike wheels wouldn't get much attention around here. They're not fat-bike wheels.
The TŌWMAK makes the subject more interesting because we're talking about an actual fat-bike frame designed to use both. That raises questions about how the swap works, what components carry over and whether the growing 32-inch niche could eventually help with availability of some fat-bike parts.
Jason has already answered one round of questions, and I've got another correspondence out to him now.
We'll have the full story once I have the rest of the details nailed down.
The Events Calendar Keeps Growing
The Fat-bike.com Events Calendar continues to fill in as 2027 dates are confirmed.
Rather than dump every event into every Weekly Dose, we'll keep the complete calendar there and use this newsletter to call out the things that are timely or particularly interesting.
If you're putting on a race, festival, group ride or other fat-bike event and we don't have it listed, send it over.
On the Calendar
Custer's Last Stand - October 10
Augusta, Michigan
Men's and women's open fat-bike classes on the Fort Custer singletrack.
Maple River Gravel Chiller - October 10
Maple Rapids, Michigan
10-, 25- and 47-mile gravel routes with fat-bike categories.
Fat Pursuit - January 8-10
Island Park, Idaho
30K, 60K and 200K winter events in the Greater Yellowstone area.
Norpine Fat Bike Classic - January 8-10
Lutsen, Minnesota
11.5- and 27-mile races surrounded by enough other activities to make a weekend of it.
St. Croix 40 Winter Ultra - January 9-10
Hinckley, Minnesota
Roughly 40 winter miles by fat-bike, ski or foot, with required survival gear and two checkpoints where participants have to demonstrate that they know how to use some of it.
Fat Bike Birkie - March 13
Cable, Wisconsin
47K, 21K and 10K on the Birkie Trail.
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Partner Store
Studded-tire season is close enough that the new Surface 604 tire is a good reminder to take a look at what you've already got hanging in the garage.
If your winter tires have missing studs, dried-out sealant or a casing that looks considerably older than you remember, now is a much better time to figure that out than the morning after the first freeze.
The Fat-bike.com Partner Store has links to companies and retailers carrying fat-bike gear. Purchases through those links help support Fat-bike.com without changing what you pay.
One More Thing
The Richard Tom Foundation Winter Fat Bike Rally in Vermont caught my attention this week.
It's February 7 at Catamount and includes free trail access, group rides, chili, hot cocoa and even loaner fat-bikes while supplies last.
No race license. No expensive entry fee. You don't even necessarily need to own a fat-bike.
There is a lot of discussion in cycling about how to bring new people into the sport. Handing somebody a bike, giving them a place to ride it and feeding them afterward seems like a good place to start.
That’s the Dose
I'm also hoping to have the full Bearclaw TŌWMAK Gen 2 story ready once I hear back from Jason. There are a few details I want to get right before we publish it.
If you've got an opinion on tire widths, fall fat-bike racing, winter trail etiquette or anything else in this week's Dose, bring it over to the Fat-bike Lab.
Join the Fat-bike Lab - free, no algorithm, just riders helping riders.
See you next week.
Greg
Fat Dash Bike Dot Com
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