WTB's original 27. 5in Riddler may be the ideal trail tire: cornering grip, straightaway speed, and a generous girth that provides comfort and grip without getting top floppy. The Riddler TCS Light Fast Clincher Tire imports those same characteristics to the gravel bike world. Its 45mm belly eats up gravel and washboard abuse while the molars on the shoulders bite into sloughy stuff and the low-profile, tightly packed center knobs maintain grippy speed across graded gravel. The compound follows suit, with WTB's dual-compound situating soft, grabby matter at the shoulders and harder, faster rubber over the center strip. The Riddler is set up to run tubeless on any UST rim with the application of a sealant. While 23 and 25mm tires can actually gain weight when run tubeless, these burly donuts definitely benefit from ditching those huge tubes. Going tubeless also lets you lower the PSI, adding additional plushness when cushion and grip are at a premium. At this point in a description, we'd typically lay out a tire's limitations; with the Riddler 45, we're finding ourselves unable to do so. Bikepacking, gravel racing, all-terrain adventure cycling--the Riddler approaches any multi-surface scenario with gusto.