Rear shocks today generally fall into two categories. Those with deep travel/slower rebound perform best on large obstacles (like three-foot drops), while those with shallow travel/quicker rebound excel on smaller, washboard bumps. The problem: Drop a cliff with your quick-rebound shock and you might get bucked—or, conversely, ride fast bumps with your slow-rebound shock and you'll get bogged down. The solution: RockShox's Vivid 5.1, due out in 2008, whose Dual Flow Adjust system promises to dole out the right kind of cushion regardless of terrain.

1) How It Works
Unlike most rear shocks, which have a single tube, the Vivid uses a twin-tube circuit. The addition of the second tube gives the shock's oil an alternate pathway, so it doesn't have to flow through the piston on rebound. The upshot: The compression and rebound adjustments are no longer linked, so you can fiddle with them individually.

2) Small Bumps
With the Beginning Stroke Rebound Adjuster (red knob), you regulate how quickly the shock returns from small bumps. This adjustment is isolated from the rest of the shock, allowing the rear suspension to hug the ground in quick, teeth-rattling sections. Essentially, it turns the beefy Vivid into a shorter-travel shock that won't slow you down.

3) Big Drops
You'll stay in the saddle after landing a big drop, thanks to the Ending Stroke Rebound Adjuster (manipulated with a 2.5mm hex). It tweaks the rebound speed to keep the shock from quickly popping back—and bucking you off the bike. Using both adjust-ments, you can create a system suited to your riding style, your weight, and the terrain.

4) Compression
RockShox plans to install factory-set, nonadjustable high-speed compression on the Vivid, but riders can fine-tune how it behaves on smaller, quicker drops with the Low Speed Compression Adjuster (the blue knob)—without affecting rebound. With this last customization, compression can be adjusted for big, gnarly drops.