Yeti Cycles

SB4.5 Turq X01 Eagle Complete Mountain Bike - 2018

If you're looking for a whip-fast bike that can handle some bigger terrain on occasion, look no further than Yeti Cycles' SB4.5 Turq X01 Eagle Complete Mountain Bike. It blends XC speed with geometry to handle the bigger stuff, so it's effectively the missing link between enduro and trail—something we'd feel comfortable with literally calling all-mountain.

This SB4.5 also carries Yeti's new Turq designation, which means the frame is even lighter and stiffer than the brand's standard carbon construction. It features a more precise carbon layup that's carefully molded to reinforce key stress points without adding bulk, resulting in strength where you need it and fewer grams where you don't. In the end, Yeti claims a reduction of 300g compared to the regular SB4.5 Carbon—a stat that lends the SB4.5 Turq more climbing pedigree and complements the ultimate bailout gear on the X01 Eagle drivetrain.

Yeti also says that the SB4.5 has a stiffer pedaling platform than most of its other bikes. While we don't have numbers to verify this claim, it's definitely a responsive go-getter when the going gets mashy, and we think the inclusion of a Boost 148mm rear axle is at least partially responsible for the bike's eagerness on climbs. Coupled with the innate aggression of 29in wheels and the stiff, collet-style hardware, the boosted rear triangle certainly feels every bit as stiff as—if not stiffer than—any of Yeti's other models.

The frame's aggressive speed is not to be outdone by its slack front end and surprisingly capable Switch Infinity suspension, though. Its 67.4-degree head tube is one of the slackest we've seen on an XC-leaning 29er, and it makes for a boost of confidence while picking lines across terrain that would make a more typical 70-degree head tube stumble. The Switch Infinity suspension is equally confidence-inspiring, and its linear travel hits the sweet spot of anti-squat to keep pedaling sharp across rocky climbs. It also erases the momentary harshness that its predecessor, the Switch Link design, would display when pushed to the absolute limit.

Of course, most riders didn't experience that dead spot on the Switch Link, but the SB4.5 isn't for most riders. It's for the all-mountain racer who demands that their machine flattens big hits with the same tenacity that it cleans long climbs. In our experience, the SB4.5's Switch Infinity suspension isn't quite as soft off the top as the 5.5 and it finds the bottom when we overshoot a landing. That said, the steeper head tube produces sharper handling and rewards technique while picking lines, making the SB4.5 more fun if you value finesse over just bombing terrain.

While Yeti's Shimano builds tend to feature Race Face cranks, this build takes full advantage of SRAM's Eagle gearing. The 30t chainring and comically huge 10-50t spread out back ensure you'll almost never find yourself without a gear whether you're burning up hardpack or laboring up a punishing grade. Either way, the finishing touch of Race Face's ever-popular Turbine dropper post ensures that you'll never be more than a switch throw away from keeping your saddle at the right height.