Specialized pump track concept bikes

By now many you have seen the Specialized StumpPumper concept bike elsewhere on the interweb. Some hate it, some love it. I like it.

I think I’m gonna make a real-life concept bike: the P.PUMP

The StumpPumper concept

Build the ultimate pump-track-specific weapon. Jason Chamberlain at Specialized is credited with this beautiful disaster. Highlights:

• P.3 frame
• Light parts throughout
• White Brothers rigid carbon fork for maximum pump (pump tracks are smooth, right?)
• S-Works carbon cranks installed with an offset to lower the pedals below the bottom bracket.
• The effective bottom bracket height is only 10.9 inches.
• Total bike weight is only 17.9 lbs!

Photo by Ryan Cleek from Pinkbike

Photo by Ryan Cleek from Pinkbike

More photos and the original post here:


Also see:


What I think

• Pump tracking is rad, and it’s extra rad to see Specialized push the envelope and try crazy stuff. This is where good, usable ideas are made.

• The Renegade tires shown in the photos work really well on pump track. They are light and fast, and they grip well in moderately loose dirt.

• For a pure pump bike, a rigid fork makes a ton of sense. As Chamberlain said, small bumps can be handled with tire pressure. My BMX bikes with 40 psi (considered low for BMX) feel really good on pump tracks — even non-smooth ones.

• I will soon be building a fresh p.bike. While I’m mostly a pump guy, this bike will be jumped, and it will hopefully be dual-slalomed (on smooth tracks). A Fox 831 is definitely worth 3.75 pounds of confidence. That isn’t exactly heavy, and the lockout can be set to any threshold.

• As for the offset cranks, I don’t know; I’ll have to try. The lowness makes sense, but I sure like to pedal from time to time. I also like to switch feet.

• As Chamberlain said, most riders will be fastest on whatever they’re most comfortable on. The StumpPumper is probably too extreme for most riders — that’s the whole idea, to push the concept as far as it will go — but there’s a lot of merit in a light, low and stiff pump track bike.

• If you really want a light and incredibly fast pump track machine, try a 20″ BMX race bike. The 2012 Intense Podium XLT has an 11-inch BB height with standard cranks. Of course, most mountain bikers can’t ride tiny wheels and 74-degree head angles.


Hmm, maybe I should turn my new P.3 into a real-life concept bike: The P.PUMP

• Light, stiff P.3 frame.
• Fox 831 fork set hella stiff.
• SRAM Rise 60 carbon wheels (I’ve been testing them on the Stumpy 26, and they are ridiculous).
• Reasonably light parts throughout. If I take a big hit, my shoulders are gonna fail before any bike part.
• Level cranks. Probably.
• Specialized Renegade tires. I like the 2.3s, but dare I lower the bike with a set of 2.1s? Wait, why not 1.9s?



Know more. Have more fun!

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