The all-new Kona Explosif 27.5 is the company’s first 650b bike and in many ways it’s a mid-wheel size version of the Honzo 29er  — its cro-mo frame even shares the same raw steel finish and accent orange graphics.

Frame

It’s not just the frame material and finish that crosses over. The Kona Explosif 27.5 also gets the same oversized XX44 head tube, traditional BB shell with ISCG tabs and adjustable rear dropouts that offer 20mm of chainstay length (rear centre) adjustment. The Honzo and Explosif’s front centre and chainstay measurements are within millimetres of each other too, but the frames aren’t identical: the seat tube on the Kona Explosif is straight, as it doesn’t need to accommodate the massive 29in rear wheel, but for some reason you still can’t lower the seatpost all the way down. More importantly, the Explosif comes with a front mech and 20 gears, making it considerably more versatile than the single-ring Honzo.

Suspension

Again, the 120mm-travel Revelation looks very similar to the fork on the Honzo, but it too is subtly different. To start with it’s a dedicated 650b design. It also has 15mm Maxle lowers, saving a little weight over the stiffer 20mm set-up found on the Honzo. External differences aside, the Revelation gave the same excellent small bump sensitivity and grip, with good mid-stroke support and no harsh bottom out, making it one of the best trail forks we’ve tried.

Wheels

The tubeless-ready Maxxis tyre combo offers the perfect balance of grip, low rolling resistance and pinch puncture protection for smashing out laps at your local trail centre. You will, however, need a rear tyre with bigger knobs if you intend to venture down the path less followed. Both hubs were super smooth and the wide WTB rims make for a bomber-solid 650b wheelset.

Groupset

After a couple of particularly wet, muddy rides, the action of the SRAM X7 rear shifter became really stiff and sluggish. The cause was water making its way into the gear cable outer casing and causing it to partially seize. For extra weatherproofing, we’d like to see Kona switch to full-length gear outer for a quick and easy fix — just as rival Norco has done from the outset.

Components

We really liked the short 60mm stem and wide 760mm bar on the Honzo and were a little disappointed that they weren’t carried over to the Kona Explosif 27.5, too. WTB’s Volt saddle is comfortable, even if we couldn’t drop it far enough without first having to chop down the 350mm post. Not getting a seatpost quick release was a pain, but at least Kona has had the foresight to include line guides for upgrading to a dropper post.

Performance

In full stock guise we found the riding position on the 19in Explosif a little stretched, where the 80mm stem was pulling us too far over the front end on the descents. Fitting a shorter stem improved matters, without making the cockpit feel cramped, but it wasn’t until we slammed the rear dropouts into the shortest setting that we started to feel more confident on the bike. This arrangement didn’t seem to eat into the Kona Explosif’s climbing prowess, but it definitely put us in a better riding position for railing corners and attacking fast, technical descents. Overall the handling of this 650b bike is very similar to a well-proportioned 26in hardtail, but we never fully gelled with the Explosif — all too often it made us feel more passenger than pilot.

Verdict

For anyone currently riding 26in, the 650b Kona Explosif would be an easy transition to slightly bigger wheels, as you won’t need to adjust your riding style. It probably helps that your eye doesn’t need to adjust either. That said, the whole time we were testing the Explosif we couldn’t shake the feeling that it would have been better with even bigger wheels. More grip, better rollover and riding on top of the bumps are all major advantages on a bike with only front suspension, and while 650b may offer a slight improvement over 26, we definitely preferred the ride of Kona’s Honzo 29er.

MBR rating: 7

Specification
Frame Kona butted cro-mo
Shock n/a
Fork RockShox Revelation RL 650b
Wheels Kona King/ Formula, WTB Speed Disc i23 rims, Maxxis Ardent 2.25in Crossmark 2.1in
Brakes Avid Elixir 5 180/160mm
Drivetrain SRAM X7 chainset, X9 rear mech, X7 shifters/front mech
Components Kona XC/BC
Sizes 15, 17, 19, 21in
Weight 12.94kg (28.5lb)
Contact konaworld.com

Angle finder
Size tested 19in
Head angle 68°
Seat angle 72.5°
BB height 304mm
Chainstay 435mm (long)
Front centre 705mm
Wheelbase 1,140mm
Down tube 700mm

This test appeared in the April 2013 issue of MBR, alongside the Jamis Nemesis,Scott Genius 740 and the Norco Range Killer B-2.