When the surface turns to sloppy mud, sand, and loose rock, tread spacing matters more than tread depth. The Protocol RCG-4 from Silca answers those conditions with an aggressive, widely spaced knob profile, using fewer but significantly larger lugs than the mixed-terrain RCG-3 in the same range. That intentional spacing keeps sticky loam from packing between the knobs, so instead of clogging and turning slick, the tire flings mud away and keeps biting when the ground shifts under you. This is the loose-conditions tire in Silca's Protocol gravel lineup, sitting past the hardpack RCG-1 and the mixed-terrain RCG-3, and it's the one to reach for when the course goes properly off-grid.

The whole Protocol range starts from a different premise than most gravel rubber. Rather than bolting a heavier casing onto a road carcass, Silca took an XC mountain bike design and distilled it to essentials, building a high-volume 120 TPI casing tuned around modern low-pressure dynamics. The idea is inverse-proportional: pair bigger air volume with a thinner, high-density casing so that at lower inflation pressures the reduced thread tension lets the tire deflect impacts rather than fight them. That gives you a supple ride and lower rolling resistance without giving up structure, which is a real shift from the old approach of adding weight and calling it durability.

Because the RCG-4 is built for terrain that punishes casings, it carries SealSkin bead-to-bead puncture protection rather than the lighter GhostShield layer used on the faster RCG-1. That full-coverage protection is the point here. It guards against sidewall tears when you're picking through off-camber loose rock, OHV roads, and singletrack, so you can commit to a line without babying the tire. If your rides regularly leave the groomed stuff behind, this is where the added protection earns its keep.... Read More