The original Jack Flash was the first MTB from Yorkshire, UK direct-sell brand Planet-X and it became a cult classic for its blend of ride-all-day weight and responsiveness but case-jumps-all-day toughness. This brand-new version has been updated with 29er wheels and more contemporary geometry to make it a proper performer with a retro vibe.
Design and components
If you’re wondering what we’re on about with retro vibe, the big cheek gusset plates as well as plates on the top and down tube plus a drilled block yoke at the head of the chainstays are classic mid 90s construction/cosmetic features. The internal cable routing - including dropper post - bolt through Boost axles and 65-degree seat angle and 75-degree seat angle are all thoroughly modern though. There’s room for 2.4in tires, too.
The wire-bead Panaracer tires are an old design in hard-wearing rubber that’s best replaced promptly if you start pushing your limits. When you do upgrade the tires, the broad Alex rims are ready to be turned tubeless. Brakes are SRAM’s Level hydraulics and SRAM SX Eagle gearing which gives you a super-wide 12-speed range from a single shift trigger. That leaves space under the left-hand side for a dropper remote lever if you pay the £200 upcharge for a RockShox Reverb Stealth dropper post. RockShox also provides the Judy fork which you steer via a 50mm stem and 780mm wide bar from Planet-X partner brand On-One.
Ride, handling and performance
That combination immediately gives the rider a firm command of a front end that’s already slacker and more stable than most budget MTBs. The result is a naturally confident character that won’t get knocked offline by rocks and roots easily and holds a steady line at speed too. The tires definitely lack sticky connection - particularly in the wet - but the stem is short enough to react fast and grab traction back if it starts to slip away. The slightly steeper-than-average seat angle helps keep weight on the front tire so it doesn’t wander about too much on climbs and while the reach isn’t super long (460mm on a large) it’s not cramped either. Relatively long 445mm chainstays also help with climbing traction and the chunky, reinforced alloy frame means direct power transfer through the stiff oversized axle crank. Add the wide range SRAM gears and even at over 14kg it can still make short work of climbs and hustle singletrack at speed. While the Panaracer tires are plasticky, the Level brakes have a lot more feel than Tektro, Clarks and other budget options which definitely boosts bravery on descents.
You need to stay loose when things get rough though as that back end stiffness means it’s a bumpy ride in the saddle. The Judy fork can soon get spikey if you start pushing hard down prolonged steppy/rocky/rooty sections too, especially if you’re braking or turning at the same time. From experience, smoothness doesn’t degrade nearly as fast as the Suntour XCM and XCR forks you’ll still find on a lot of bikes at this price. Being able to adjust air-spring pressure and rebound is a ride-tuning bonus, too.
Like all bikes at this price, the Planet X Jack Flash isn’t perfect and the reinforced frame is definitely unforgiving when things get rough. It deserves better tires as soon as funds allow but it’s a good shape for confident trail riding, the fork and brakes are as good as you can expect for the money and the SRAM Eagle gearing is a definite win for flattening terrain. Remember it’ll arrive in a box after being built to order, and you won’t automatically get support and set up help from your local shop. So it's worth factoring that into the equation as that might actually be more valuable than comparing components.
Tech Specs: Planet-X Jack Flash 29er
- Price: £799.99
- Discipline: XC/Trail
- Head angle: 65-degrees
- Seat angle: 75-degrees
- Sizes: Large
- Weight: 14.1kg
- Wheel size: 29 inch
- Frame material: 6061-T6 alloy
- Suspension: RockShox Judy Silver TK 130mm travel
- Drivetrain: SRAM SX Eagle 11-50T 12-speed gearing
- Cranks: SX Eagle DUB 32T chainset
- Brakes: SRAM Level brakes with 180/16mm rotors
- Cockpit: On-One 780mm Enduro 6 bar and On-One Hot Box 50mm stem
- Wheelset: Alex EXR30 29er rims with Formula Boost 6 bolt hubs
- Tires: Panaracer FireSport Wire Bead 29 x 2.35in tires
- Seatpost: 31.6 x 400mm seat post
- Saddle: San Marco Monza Start saddle