Cross-country riding calls for a whole different science from the traditional all-mountain machines we see dominating the marketplace these days. Instead of the long-low-slack trend that makes your ride feel akin to a Clydesdale, you need a speed machine built to operate with the thrust of a rocket ship fighting its way against gravity, beyond the atmosphere, and out into orbit. And so it takes a careful eye, keen attention to detail, and a different approach to build a beast like Pivot's all-new Mach 4 SL Carbon Team XTR Live Valve Complete Bike. This race-ready steed spins forward with progressive XC geometry that's roots combine the coveted Mach 4 and Mach 429 SL, and a sharp carbon layup that drops a whopping 300-grams off of the previous 429 SL's already feathery stature. But don't let this lightweight demeanor fool you -- with steep geometry, 29-inch wagon wheels, and a new vertical shock layout, this space ship is ready to take flight up climbs, and soar down slick roots and chunky rock gardens while you charge your way to the front of the pack. And you don't have to just take our word for it, the bike is already making an immediate splash. How immediate' Woodruff racked up a Short-Track within 24-hours of its launch, giving us sound proof that its built for speed. As we've seen throughout the bike industry, the Mach 4 SL takes on the popular trend of longer-slacker, but doesn't go overboard into Trail territory, pulling the head tube out to just 67. 5-degrees (paired with a 120mm fork). Compared to the previous 429 SL's 69. 3-degree head angle, the Mach 4 SL's head tube will lend the slacker angle to a bit more stability on descents, so you can take on steeper drops, and chunkier rock gardens without your bike feeling noodly under pressure. But this is a cross-country machine after all, and with pedaling being top priority, Pivot's engineers make things steeper in the hind-quarters, moving to a prime perch for power at 73-and-a-half degrees -- ideal for sp..