With help from Santa Cruz, White Brothers, Pacenti and a few other companies, we’ve got an interesting creation here at Dirt Rag HQ—a longer-travel 650B bike.
By Eric McKeegan
In issue #131 Andy reviewed the Pacenti 650B hardtail and concluded, “The bottom line is that I’m curious to see what else is possible with 650B’s. As far as hardtails go, the prototype I rode was a fun all-around bike. But if the real benefit of 650B’s is on bikes with greater than 4 inches of rear travel, you’ve got my attention. I’d like to see more.” I wanted to see more, too, as did other Dirt Rag staffers, and so this project was hatched.
In reality the 650B movement is the result of the 29er movement. As riders started clamoring for longer travel 29ers, the inherent problems with trying to fit both big wheels and big travel into a frame with relatively “normal” geometry became apparent. Already high handlebars become even higher and chainstays need to grow to keep the rear wheel from hitting the seat tube and to let it clear the front derailleur. With the increase in speed that usually accompanies an increase in travel, components need to be stiffer and stronger, particularly wheels and forks. This can lead to a pretty hefty package full of oversize parts: short 1.5″ diameter head tubes to deal with the longer lever of the fork while keeping the handlebar height reasonable, a 150mm rear hub with matching 83mm bottom bracket shell to add some strength to the rear wheel, and room for pivots and front derailleur up front. Front hubs may need to go oversize, too, as the current 100/110mm standard offers little in the way of spoke triangulation for 700c wheels. The list could go on, but each part falling outside the “normal” standard adds cost and often weight to the equation.
In theory 650B wheels should allow designs to take advantage of proven 26″ geometry and more standard parts while keeping some of the 29er’s positive traits, mainly increased traction and ability to roll over trail features rather than hanging up on them.
I was interested enough in this theory to start the ball rolling on a longer-travel 650B bike, and with help from a few companies we’ve got an interesting creation here at Dirt Rag HQ. Santa Cruz was kind enough to send along a Heckler frame, and White Brothers sent their 130mm travel, 650B-specific, 20mm thru-axle fork. A pair of Neo-Moto tires came from Mr. 650B himself, Kirk Pacenti. Wheels came together with help from Velocity (Blunt rims) and Hope (Pro II hubs). The last piece of the puzzle came in the form of a Pearl 3.3 rear shock from RockShox. This was a key part: if the Heckler’s stock 150mm of travel was not reduced, the larger wheel could contact the seat tube or front derailleur under full compression. If my math is correct we are running about 120mm of travel and could probably get about 130mm by reducing the height of the internal travel-limiting spacer.
Spring showers have kept my rides short, but initial impressions are good, good enough to plan a day with long descents and lotsa rocks. Keep an eye on our blog for updates.