Around 15 years ago, German tire brand Schwalbe introduced their Fat Albert line. At the time, the 2.4-inch width was a bit of a novelty, as tires of that dimension weren't commonly seen on bikes intended to be pedaled uphill. The new Alberts are front- and rear-specific, and basically toss aside conventional tread design and spacing. The front tire's knobs have rounded backsides for increased braking surface area, along with siping to provide additional biting edges. The rear Albert uses rows of knobs, similar in concept to a rear tire on a dirt bike, which are surrounded by pronounced side and shoulder knobs.
The Alberts, which come in both 650b and 29-inch flavors at 2.35 inches wide, utilize Schwalbe's Snakeskin cut-resistant sidewall protection. The TrailStar triple-compound rubber uses a firmer base layer to help the knobs retain their shape, while softer compounds make up the middle and outer layers which conform to terrain for traction at a variety of angles.
It didn't take anything more than a floor pump to mount the Alberts to a set of 30-mil-wide Roval Traverse SL wheels. Although the sidewalls are noticeably more firm to the touch than comparable tires of the same intended use, the front tire weighs a competitive 1 pound and 14 ounces (850g), while the rear Fat Albert was slightly lighter at 1 pound 13 ounces (822g).
I mostly ride in Santa Cruz, where the trails frequently swap between hardpack and sand with roots and rocks sprinkled in between. For this type of terrain, Specialized's Butcher Control and Maxxis' DHF Exo have become my go-to front tires, while the Specialized Purgatory and Maxxis High Roller 2 work well out back–they both have reliable braking bite and roll reasonably well.
How do the Alberts compare? The unusually shaped and widely spaced front knobs were at their best on loose surfaces. When the trails are sandy or gravely, the knobs dig deep and yield reliable traction. The center lugs are tall in relation to the side knobs, which gives the tire a round profile–even when mounted to a wide rim. At times, this makes cornering on dry, hardpacked trail less predictable, because there's a noticeable transition between the center tread and the side knobs when leaning the bike over. I'd be curious to see how the front Fat Albert would perform if the center knobs were just a millimeter or so shorter, which could make that transition quicker and more predictable.
Like the front Albert, the rear performs best when the terrain is soft and unruly. The rows of center tread roll with noticeable drag on smooth climbs, but dig in and allow acceleration when the uphills are steep and loose. Both the massive knobs of the front tire and the variety of biting edges on the rear Albert provide reliable grip under braking.
There are better front tire options for riders who mostly ride hardpacked surfaces, but if your trails are really loose, unpredictable, and you're constantly searching for traction, the new Fat Alberts won't wind up as spare tires.