P3 D-CJ
“DIRT-CHEAP JUMPER”
2005 Specialized P3
This build was sparked by a lucky find on Facebook marketplace. A P.3 dirt jumper for $175 sitting right at the top of the suggested postings page. Within five seconds of test riding it, which was within an hour of finding it online, it was acquired.
Unfortunately, while it rode well, it looked absolutely tragic, covered in peeling stickers and a horrible, rough paintjob reminiscent of an army surplus storefront.
A few days of diligent sanding later, the aluminum frame was revealed, extra cable stops were grinded away, and custom 3D-printed decals and a hand-drawn accent on the head tube was added - all sealed under multiple coats of KBS Diamond finish top coat. With the goal of keeping build costs to a bare minimum, 3D printed decals replaced typical outsourced custom vinyl ones.
A raw aluminum/tan/black motif required some tan-walled Billy Bonkers tires, while indecision about black rims versus matching raw aluminum ones lead to a rebuild of the wheels using a couple of old Stan's ZTR rims and leftover DT Swiss spokes after sanding half of each rim to get the best of both worlds.
A new, slightly higher-toothed rear sprocket to made chain length impossible to match, so a chain tensioner became the next addition. But not one off of Amazon.
After a few months of design, prototyping, testing, and some crashing, the 10SHNR composite chain tensioner was born. Designed to fit exactly to the derailleur hanger and paired with a rear hub-mounted chain retention disc, it uses the uniqe strenght and slight flexibility of carbon-filled nylon composite to apply tension to the chain, while retaining enough flex in the entire system to allow for the minor chain elongation that happens when tires compress during landings. What's more, the 10SHNR can be tuned to either let the cranks spin freely or 'lock' (the same thing as riders achieve by wrapping tire tubes around the crankset or tightening a bolt against the bottom bracket), simply by adding or removing spacers around the tensioner's jockey wheel.
During development of the 10SHNR, the idea of barspin capability for the D-CJ begain to take hold. Not wanting to forgo the front brake, and unhappy with the available options online, SpinCap was designed - a top cap system that routes the front brake hose through the steerer, keeping the front brake in place. It also features a unique, sealed design that hides the stem bolt under a tiny trapdoor for a super-clean cockpit.
A BOQS (bolt-on, quick swap) mudguard design dapted for the Marzocchi Bomber DJ3 lets the fender pop in and out without any tools (perfect for footjam tailwhips), and “Crankies” crank arm guards help keep the Descendant 7k crank arms from getting damaged.
With a final tally of well under $500, the D-CJ lives up to it’s monicker quite well, while being plenty capable for someone looking to get into dirt-jumping and MTB trickery.
The tensioner continues to undergo testing and refinement at skate parks, local dirt jumps, and around town.
