Fit and Geometry
At a time when different companies’ sizing is all over the map, the SB4.5 sits pretty comfortably in the middle ground. I’m 5’9” and rode a size Medium, and I didn’t feel like I was close to needing to size up or down. Indeed, Yeti’s sizing chart puts me smack in the middle of the range for a Medium, and I’d agree with that.
With a reach of 421 mm on the Medium, the SB4.5 is fairly average. The 605 mm top tube length on the Medium is maybe a smidge longer than average, but again, not so stretched out that it’s particularly noteworthy.
Like some of the other Yetis, the SB4.5 doesn’t go with the “make the chainstays as short as humanly possible” trend — at 437 mm, the stays are a smidge on the long side by current standards for trail bikes. But those slightly longer stays help out on climbs, and they make the bike a bit more stable at speed.
A 67.4° head tube angle is average-ish for a bike like this. There are a few descending-oriented, short-travel 29ers that are slacker, but the head angle on the SB4.5 certainly shouldn’t be considered steep.
Right out of the gate, the SB4.5 felt pretty snappy — throw some weight on the pedals, and the bike leaps forward. I don’t think I’ve ever ridden a short-travel 29er that feels like a couch, but some are certainly mushier (to use a technical term) than others, particularly the more descent-oriented options. The SB4.5 is low on the mush quotient, so it thrives on powering out of corners and sprinting up little climbs.
The flip side of that is that the bike doesn’t level out the trail as well as some other bikes in this class. Now, to be clear, it’s a relatively short travel bike — nothing in this class is steamrolling trail detritus. But bikes like the Transition Smuggler or Evil Following tend more toward an active suspension that’s a bit more cushy, at the cost of those snappy pedaling characteristics that the SB4.5 does so well.
Somewhat similar to the SB5.5, the SB4.5 relies on the bigger 29” wheels to sort out smaller obstacles, rather than having a cushy suspension tackling that task. And while that makes for a bike that feels a bit more taught, I also find it makes for a pretty efficient bike, and perhaps more importantly, a fast bike.
What’s a bit different about the SB4.5 is that it’s set up with a 140 mm travel fork, whereas most other bikes in this travel class are coming with a 130 mm travel fork. That means a couple things: first, the bike favors a slightly forward weight bias. There’s considerably more travel in the front than the rear, so the bike seems to work best when you rely on the fork to smash through obstacles and let the rear bounce around a little bit.
The taller fork also makes the front end feel a bit high. In some situations (like steeper descents), this is a good thing. In other situations (e.g., steep climbs) it means that the front end can start to wander.
But add all of that together and it makes for an interesting bike. On flatter, faster terrain and short, sprint-y climbs, the bike shows that there’s more than a little cross country blood in its veins. But open it up a bit, and the SB4.5 reveals that it’s more stable than it initially lets on, and when ridden aggressively, it can still hang.
The Yeti SB4.5 has the pep of an XC rig that works well when its pilot wants to lay down some power. But that’s wrapped into a bike that can still keep up on descents when asked to. It relies more heavily on its longer-travel fork, and less on an ultra-supple rear suspension. But it’s surprisingly comfortable at speed. I think swapping to some meatier tires and a wider bar would actually turn the SB4.5 into a decent contender on mellower enduro races, particularly ones where the SB4.5’s pedaling prowess would provide an advantage.
I’d recommend the SB4.5 to anyone looking for a shorter-travel trail bike who doesn’t want to give up too much ground in the efficiency department. The SB4.5 isn’t a marshmallow — it does what it needs to do to keep you moving quickly. Nothing more, nothing less. And when you’re moving quickly and the trail gets a bit more technical, the SB4.5’s geometry and longer-travel fork are there for you. It makes for a blend of efficiency and stability that’s a bit unlike a lot of other bikes in this class, and it took me a little while to figure out how to ride it. But once I got there, the SB4.5 performed impressively well.