Down The Trail: ProFlex 4000

Fondly remembering MBA’s past

The ProFlex 4000

Any mountain biker who’s been into the sport for more than a couple decades remembers ProFlex full-suspension bikes. They were the iconic, bullet-proof, elastomer-sprung dual squishers and can occasionally still be seen on trails today. Back in 1998, the successful ski company K2 bought the up-and-coming bike brand and made its own version of the bike. The big bike brand buyout resulted in a bold new line of full-suspension machines that we had the duty to put through the test.

What MBA thought of the K2 4000: We thought it was a stellar trailbike for the time “in the ultimate sense of the term.” As a sport-level racer or a weekend expert, the 4000 could be competitive. The 4000 was lightweight and solid, and the suspension fork worked well. We gave this bike two thumbs up. My, how things have changed.

The Noleen fork: Noleen suspension was one of the first to bring electronics to the mountain bike world. The new F-Smart fork used what they called “piezoelectric-controlled” damping to give the widest range of impact control on the market. The valving allowed the fork to run with essentially no compression damping over small impacts, yet allowed the electronics to turn on the damping on the big hits. The system was controlled with a 9-volt battery that would last 24 hours of ride time.

“K2 Bike doesn’t mess with success”: That was the line we wrote about the new K2, which was essentially a re-branded ProFlex. The bike weighed a claimed 27 pounds with 4 inches of travel in the rear and 3 inches of travel in the front via a Noleen linkage fork. The new bike got rid of the elastomers the previous generation ProFlex relied on in favor of a coil-over shock. The Easton aluminum frame came with a 70.5-degree head angle, a 12-inch bottom bracket and a 72.5-degree seat angle. If those numbers seem out of whack, you never rode mountain bikes in the ’90s. Those were pretty aggressive back in the day.


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