Bikes and Tech
A slack head tube angle makes for some fast,...

First Ride: Yeti SB4.5c mountain bike

The 29er cousin to perhaps the best trail bike on the market, Yeti's new machine could be a do-it-all bike — if climbing isn't your focus.

In 2014, Velo magazine picked the Yeti SB5c as the mountain bike of the year, and for good reason: Few bikes on the market today stack up in a category the SB5c simply dominates. The 27.5-inch wheel platform was nearly perfected with Yeti’s trail bike, and the Switch Infinity suspension system redefined how good suspension can feel throughout its stroke both up and down the mountain.

This year, Yeti has taken many of the features that make the SB5c great and has applied it to the 29-inch wheel platform. Yeti says its new SB4.5c is a 29er built for trail riding, enduro, and even cross-country.

As the name indicates, the SB4.5c rolls on 4.5 inches of travel in the rear courtesy of Fox suspension. Yeti’s usual long, low frame geometry is there, too, a versatile design that has worked well for trail and enduro riding in the past. Yeti says the SB4.5c is ready to tackle cross-country riding with equal ease, a claim that seemed immediately dubious when I first threw a leg over it. The carbon frame weighs in right around five pounds, and while the bike itself is by no means a tank, it’s no XC-featherweight either.

Yeti was slow to embrace 29-inch wheels, perhaps for good reason: With its tried and true geometry based on 26-inch wheels, 29ers felt clunky, slow, and to boil it down, just goofy. Now that 29ers are here to stay, Yeti has found a way to make big wheels work for its geometry and it has even embraced the wheel size to open up trail riding to a new segment of riders who have become accustomed to 29ers over the last decade or so. In keeping with that theme, Yeti has introduced a Boost 148 rear hub to stiffen up the rear end for better control and less overall flex. 17.2-inch chainstays are short enough to make climbing a bearable endeavor while maintaining stability for confident descending.

First ride impressions

What better way to try out Yeti’s new rig than to head to the company’s own backyard? Apex Park in Golden, Colorado winds up from the parking lot on steep, dry, tight switchbacks. It’s a good 20- to 25-minute climb, so it’s a great place to test out the real uphill abilities of a bike that’s advertised as a little bit of cross-country and a lot of rock n’ roll. On the back side of the park, the Enchanted Forest winds down through sometimes-tacky black dirt and tree roots spaced just perfectly for a bit of boosting.

Like its 27.5-inch cousin, the SB4.5c has perhaps the best rear suspension design on the market. The Switch Infinity worked flawlessly as expected; the system soaks up small bumps but doesn’t become sloppy at the top of the stroke, and pedal bob was minimal to non-existent. The mid-stroke feels smooth and responsive, too: At high speeds the suspension seems to be continually moving, yet it never bucks, bottoms out, or ramps up in stiffness. Combining that kind of compliance all the way through the stroke is an amazing feat, and the Switch Infinity works wonders. Switch the shock from trail to full-open — either way, the stroke feels well-defined from top to bottom.

This translated into confident pedaling up the mountain, but that confidence was frequently negated by the slack head tube angle coupled with a tall 29-inch front wheel. With a 27.5-inch wheel, a slack head tube angle (66.5 degrees on the SB5c) isn’t too much of an obstacle on uphill rocks and roots, but powering up and over obstacles on the 29er SB4.5c was difficult because the front end wanted to come off the ground; sections I’ve never struggled to clear became hike-a-bikes due to the unwieldy front end.

This big bike felt bigger than it should have on the steep climbs, so while it seems like it fits firmly in the trail category, the cross-country label is a bit of a stretch. A cross-country bike needs to be nimble and quick on climbs, and while the SB4.5c wasn’t necessarily a poor climber, it didn’t inspire confidence, especially in tight, techy stuff where quick steering is vital. The dreaded 29er wheel flop reared its head a few times, right when I needed a boost of power through a tech section or pinpoint steering around a switchback. While the head tube angle on the SB4.5c is steeper (67.5 degrees) than that of the SB5c, it still feels quite slack, perhaps a bit too much.

Of course, the descent is what a trail bike is really made for, right? Pointing the SB4.5c downhill was immediately exciting. The slack head angle that was irksome on the way up the trail was quite the opposite on the way down — who needs to steer when you’ve got 5 inches of travel up front, big wheels, and slack geometry to soak up Colorado’s chattery trails?

According to Strava, I set PRs going down Enchanted Forest, and I wasn’t even pushing the pace. That speaks to the capabilities of Yeti’s suspension and geometry platforms more than anything else, but ultimately, the 29er wheels didn’t add a whole lot to the experience. In terms of control, the SB4.5c felt stable enough to rip through rock gardens; picking a line, should it have been necessary, would have been an easy undertaking as well. As it was, the suspension took care of most of the bumps down the trail, and whatever chatter was left was swallowed by the big wheels. But the question is, did the SB4.5c do anything better than the SB5c would have done?

Not really.

Did it do anything worse? Yep. It doesn’t climb as nimbly as its smaller cousin.

To really get the most out of the SB4.5c and enjoy it for what it is, perhaps treating it as a trail/enduro bike is best. While it’s got some cross-country chops, this 29er feels out of its element on most tough climbs. With the Switch Infinity suspension and Yeti’s trademark geometry, the SB4.5c could own the 29er trail/enduro category. Just don’t sign up for any cross-country races.

MSRP as tested: $6,899 (SRAM X0, DT Swiss wheels, Shimano XT brakes, Fox suspension)
Availability: Mid September to early October