Fox RP23 XV BV air shock review£339.00

More control and performance

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Fox’s Boost Valve (BV) and Internal Floating Piston (IFP) technologies have controlled bottom-out in their downhill shocks for some time, but for 2010 BV gets a two-fold tweak.

Increasing the preset air pressure behind the damping piston (choose from 175-250psi) increases the force needed to push the shock through its last phase of travel, ideal for linear or falling rate suspension setups or big, aggressive riders.

Higher pressure settings also increase the effective preload of the shock, making it less likely to move under light pedalling loads but it feels fractionally stiffer over small bumps – barely noticeable on lower BV pressure tunes, though.

The real gains from the position-sensitive damping are in the mid-stroke and transition from ProPedal to open. The IFP-based damping meters oil flow more accurately for better control and stability when all hell breaks loose under your wheel.

It also collects big hits better, and every bike we’ve tried it on has gone noticeably faster and felt tighter as a result. Velocity (ie compression) and rebound tune ranges can be preselected for different bikes, giving you an accurate ‘factory’ feel.

Guy Kesteven

Freelance Writer, UK
Guy started filling his brain with cycle stats and steaming up bike shop windows back in 1980. He worked the other side of those windows from '89 while getting a degree in “describing broken things covered in mud" (archaeology). Dug historical holes in the ground through the early '90s, then became a pro bike tester in '97. Guy has ridden thousands of bikes and even more components the world over since then and can remember them all in vivid, haunting detail. Can't remember where the car keys are, though.
  • Age: 44
  • Height: 180cm / 5' 11"
  • Weight: 68kg / 150lb
  • Waist: 76cm / 30in
  • Chest: 91cm / 36in
  • Discipline: Strict sadomasochist
  • Preferred Terrain: Technical off-piste singletrack and twisted back roads. Up, down, along — so long as it's faster tfhan the last time he did it he's happy.
  • Current Bikes: An ever changing herd of test machines from Tri bikes to fat bikes and everything in between.
  • Dream Bike: His Nicolai Helius AM custom tandem
  • Beer of Choice: Theakston's Old Peculier (not Peculiar)
  • Location: Yorkshire, UK

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