A Teeny, Tiny 29ie: Surly Karate Monkey Build

The goal for this build was to put together a fairly capable, yet kid-proof bike with neutral geometry and reasonably-priced parts.

How do you know when it’s time to say goodbye to a perfectly functional bike? Clearly, there are many things to consider, including whether the bike might be holding the rider back from progressing their skills, confidence, or fitness. That was the case for our daughter who was riding her Mom’s Trek 8000 hardtail, purchased in 2003. Seventeen years is a pretty good run for a mountain bike, but following two seasons of Little Bellas and a recent growth spurt, it was time to move on.

The goal for this build was to put together a fairly capable yet kid-proof bike, with neutral geometry and reasonably-priced parts. Sure, I’m the editor for a major mountain bike publication, but I’m also a Dad, so I wanted a bike that I wouldn’t be wrenching on all the time and one that could eventually be passed down to the little brother. Even Mom should be able to ride the bike once all the kids have outgrown it.

The frame

Several of my riding buddies swear by their Surly Karate Monkeys, some of which have been rolling for many years, and my favorite local bike shop is a dealer so I decided to order one up. I’m told that at the time we bought it, this was the last extra-small frame available anywhere in a proud color called Porta Potty Blue. The Karate Money features a 4130 Chromoly Steel frame with Boost spacing in the rear, and the option to run a 142mm rear hub with Surly’s “Gnot Boost” design. Sliding dropouts also make it possible to run the bike single speed should anyone in our crew have the desire.

With a 69° head tube angle, the bike is easy to pedal and could even pull duty as a reasonable NICA steed should it be called into service. The frame ships with a rigid steel fork that’s bristling with bolts for mounting racks or cages, though we opted to add a 120mm suspension fork instead (more on that later). One of the big draws of this frame is its versatility, which will be key to getting a long life out of it as the pilots grow, and eventually pass the bike along.

The build

Starting with the cockpit, I went with an alloy bar, stem, and grips from Pro. Since this bike will no doubt see some crashes, and likely some tosses of frustration too, the Pro Tharsis 3Five alloy bars are a safe choice. The 35mm clamp diameter bar and stem might be overkill in terms of stiffness, but with more and more bikes moving to 35mm cockpits it could be a bit of insurance against future obsolescence. The single-side, lock-on Pro grips are easy to slide on and off for brake or shifter changes, though the flanged version might not be the best choice for small hands. We’ll see.

Speaking of fit, it’s clear these 800mm bars will need to be cut down to size to match the extra-small frame. Fortunately, the bars are clearly marked for cutting as narrow as 720mm. With 20mm of rise and 9° of backsweep, these give the rider a pretty neutral hand position and offer some flexibility in terms of fit depending on how they are rotated.

This kinky seat tube doesn’t leave much room for a dropper post, though the frame does have routing for one.

I managed to use an old Titec seat post I had in my parts pin. I think it’s the Hellbent Duke Prolite, circa 2009, but it’s hard to say for sure since most of the paint has been worn off. The seat tube on the extra small Karate Monkey doesn’t leave enough room for any of the dropper posts I tried, and I even had to trim a good three or four inches off the Titec to make it fit.

The SDG Radar saddle seen here is one I’ve run on my own bike, and honestly I chose it because it looks cool. After swinging her leg over the freshly-assembled bike, my daughter immediately announced she didn’t like the saddle. In her defense it’s a pretty racy saddle, so I plan to swap for a wider, padded SQLite saddle to see if that works better for her.

The Teenie, Tiny 29ie is running a 12-speed Shimano SLX drivetrain. The old Trek 8000 was still running a triple chainring up front, which was confusing and difficult even for me back in the day, and I know it caused great frustration for my daughter too. Thanks to the threaded bottom bracket and quality parts, the drivetrain installation was a joy. We chose a set of XT flat pedals from the parts bin, mainly because the pins on this pair are less sharp than any of the others I found. Sharp pins are never a good match for delicate shins.

Four-piston Shimano Deore brakes in the rear provide more than enough power for skids (only on durable surfaces, of course) and the adjustable reach lever can be set to fit multiple hand sizes. The brakes come with a quick hose connection option, though I decided to cut the rear hose to size since the frame is so short. The front hose on the two-piston stoppers could probably use a trim as well, but I’ll save that for another day.

The Karate Monkey frame came with a rigid fork, and while I was waiting for the SR Suntour Axon Elite34 fork, I mounted it up just for fun. I’m definitely saving this one for the future in case anyone in the family gets an itch to turn the bike into a commuter or an off-road bikepacker.

SR Suntour bills the Axon Elite34 as a cross-country fork which is likely how this bike will be used at first. With 120mm of travel, it’s actually a bit under-forked compared to stock Karate Monkey builds from Surly that feature forks with 140mm of travel. Despite being fairly lightweight, it seems to be well-constructed and should hold up to hard riding without a lot of maintenance hassles. The Axon Elite34 comes with a racy remote lockout which I don’t expect will see a lot of use.

Perhaps the one piece of this build puzzle that is admittedly out of place is the wheelset. Shimano XT wheels on a kid’s bike borders on spoiled brat territory, unless your kid is a podium racer or a paper route mogul I guess. However, the light weight is certainly appreciated on a bike this size, and for riders who haven’t quite developed their fitness. I suspect the XT wheels will rotate onto Dad’s bike eventually.

Finally, where the rubber meets the dirt, the Karate Monkey is wearing Teravail Ehline tires in 2.4″ and 2.6″ diameters. These tires are lightweight and feature a pretty fast-rolling, XC-oriented tread pattern. They should roll fast on everything from pavement to family-friendly singletrack.

Stay tuned for more in-depth looks at the individual components used for this build.