I often use Specialized’s bikes as a benchmark for sizing; I’ve never wanted to ride anything other than a Medium bike from them. A few years ago, they were on the long side relative to other bikes, but then everyone started growing top tubes. Now their sizing is right in the middle of the field. Throughout all of this, my feelings on their sizing have never changed, and a Medium Stumpjumper continues to work well for my 5’8” frame.
By the Numbers
A 67 degree head angle keeps the steering snappy, but is just slack enough for most steep and / or high-speed riding. Many new bikes are starting to come with slacker head angles, but I find that it’s at about 66 degrees where steering can start feeling floppy on flat ground.
17.2” (437 mm) chainstays are pretty short for a 29er full suspension bike, and I use that as a reference point because 27.5+ tires come in at 28.5” in diameter, and so 29er geo is a closer reference than 27.5 geometry.
I really liked this chainstay length. They are longer than on many Specialized bikes (I’ve often thought Specialized uses chainstays that are too short), which placed me more centered between the wheels and makes weighting the front wheel oh-so-easy. Yet they are still short enough to feel nimble and make lifting the front easy, too.
The bottom bracket is pretty low at 13.03” (331 mm). Especially with the stock 175 mm cranks, it was common to hit the pedals on rocks (or anything else). However, the low bottom bracket makes the bike carve very well, and I’ll personally take this trade-off every time. But I would probably swap out the cranks for 170 mm cranks—the 5mm difference ends up mattering more than you might think.
Seat Tube Angle
The seat tube angle is on the steep side at 74 degrees, but when paired with the offset Specialized dropper post, it feels very average. This combo doesn’t push you toward the front like on many new bikes. But at the same time, the Stumpjumper isn’t super slack like many new bikes, so a really forward saddle position isn’t needed.
Wheelbase, Reach, Top Tube
Wheelbase, reach, and top tube length are all very average: 45.24” / 1149 mm; 16.26” / 413 mm; and 23.23” / 590 mm respectively. I like that they spec a 60 mm stem; it’s a nice balance between quick reactions to handlebar input, and letting you stretch out on the bike without requiring a cumbersomely-long wheelbase. And I say that I’m coming with a bias toward shorter stems.
NEXT: Frame Details