While other brands fall over themselves to produce a high pivot bike, British brand ARBR goes in the opposite direction with its new RB2.
What’s the hottest trend in analog mountain bike design right now? Yup, you guessed it, it’s the high-pivot idler suspension design. From niche brands like Forbidden, Deviate and Antidote, to mainstream manufacturers like GT, Norco, Cannondale, Commencal and Trek, it seems like everyone is getting in on the high-pivot hype in the quest to make the best full-suspension mountain bike.
One brand, however, that’s swimming against the idler tide is a small UK manufacturer called ARBR. It’s first bike, the Saker, was a 165mm travel 27.5in enduro rig with a high single pivot suspension layout, and, you guessed it, an idler. Five years on since the launch of that bike and it should come as no surprise that the geometry on the Saker looks dated. But with the addition of 29in wheels and a few updates to the numbers, like a longer reach, slacker head angle and steeper seat angle, the Saker would be bang on trend in the current market place.
Need to know
- 29er enduro bike with a full carbon frame that’s designed and manufactured in the UK
- Rocker link suspension with pull link delivers 160mm travel
- Frame geometry is designed around a 170mm fork
- External cable routing for ease of assembly and maintenance
- One frame size only
So why did ARBR decide upon a different suspension layout for its second bike, the RB2? To answer that question I spoke to Robert Barr, the man behind ARBR bikes. Rob’s day job is at McLaren so ARBR bikes is something of a passion project. Being a small agile brand has benefits, namely it’s not constrained to a single design ethos. Based on rider feedback on the ARBR Saker, Rob wanted a bike that pedalled better and had a more traditional frame layout. Removing the idler also reduces drag and complexity, so the RB2 is more efficient and reliable. Two traits that are essential on any bike, but really important on an enduro bike. Also the RB2 isn’t a replacement for the Saker, it’s designed to run alongside it.
So the idler has gone and the pivot height has been reduced to bring it in line with a 32t chainring. But other aspects of the suspension, namely the ones that make the biggest difference to performance, remain. As such the RB2 employs the pull link suspension design, where a rocker link drives the shock and is connected to the underside of the swingarm by a second link. Not only does this layout provide the ability to manipulate the progression rate, it helps reduce side loading of the shock.
And while the shape of the frame has changed the design philosophy and carbon construction have not. The carbon lay-up is still painstakingly controlled from beginning to end, where the front triangle is a monocoque construction and the swingarm is a two-piece design that’s bonded together. There’s currently only one mould though. So the RB2 is size L only.
How it rides
At 5ft 11in tall, I’m lucky enough to fit the one frame size available from ARBR. And while I appreciate that it’s purely a numbers game, where it manufactures the single frame size at the centre of the bell curve to fit the highest possible number of riders, when you are paying £4,250 for a frame and shock, you could be forgiven for expecting a choice of frame size or a degree of customisation other than the frame colour. That said, you’d pay the same price for a mass produced Yeti SB150 or Specialized S-Works Enduro frame, so maybe the ARBR isn’t so expensive after all.
With that out of the way, let’s take a closer look at the actual numbers. I measured the RB2 as having a 472mm reach, 63.5º head angle and 448mm chain stay length. So it’s a little longer at the rear than most modern 29ers, bar the likes of Forbidden, where the size L Dreadnought also has a 448mm chain stay length. Scan the rest of the geometry chart and it’s obvious that the RB2 is pretty standard for a modern 29er enduro bike with 160mm travel. In fact, the riding position felt remarkably similar to the Nukeproof Giga that I tested in the May issue. How can I be so certain? Well, I rode the RB2 on the exact same trails at Bikepark Wales, in very similar conditions.
But I didn’t just return to BPW so I could see how the RB2 measured up to the Giga. I was there to ride the ARBR with Fox Factory suspension to see how it compared to the EXT build that I first rode several months ago. Specifically the rear shock, as ARBR lists the RB2 with a Fox Factory Float X2 shock as standard. And the plan was simple. Pick one trail and ride it a couple of times on the RB2 with a Fox Float X2 Factory shock to get up to speed then rotate it with the EXT Storia Loc V3 to see how they compare. And while that’s not really an apples to apples comparison as one is coil, the other air sprung, I wanted to know if the RB2 felt better with the standard Fox shock as I wasn’t that impressed with my initial experience on the EXT equipped bike.
Swapping between both shocks highlighted that there are indeed differences in performance. It also highlighted that the collet style shock bolt on the ARBR made swapping shocks harder than it really needed to be. It’s a great example of an engineering solution to a problem that doesn’t exist, as I can’t remember the last time a standard shock bolt worked loose.
In terms of ride quality the Fox Float X2 gave the bike a much more dynamic characteristic. Not only did the Fox shock make the bike more agile and easier to get off the ground, it was better at ironing out the constant onslaught from the armoured trails at BPW. With the EXT shock set to the exact same static sag, the bike rode lower, and this was most evident at the handlebar, as it felt like the bar had been rolled back in the stem. By adding some low-speed compression damping to the EXT shock the balance of the bike was instantly restored. I was still riding more defensively than on the Fox shock however, especially under braking, where I would instinctively clamp the saddle with my thighs to help dampen the ride.
What you lose in small bump sensitivity and pop with the EXT Storia you gain in chassis stability. So if you like riding around jumps rather than over them and have a wheels on the ground riding style there’ll be no unpleasant surprises with the Storia. Send it deep though, and the EXT shock doesn’t offer the same pillow-like landing as the Fox shock. I’m not sure if that’s due to the hydraulic bottom out, or maybe even the specific shock tune, but on some landings it felt like the rear suspension stoped abruptly, but without bottoming out. But this isn’t a head to head shock test, I’ll save that for another time.
After three solid days of riding on the RB2 frame I’m totally convinced of its potential. The sleek carbon chassis feels direct without feeling overly stiff on off camber roots and rocks, while the slightly longer stays help keep the front tyre loaded without having to consciously lean into the bar and weight the fork. The neutral riding position makes the RB2 a bike you can instantly ride fast, so it definitely has racing woven into every thread of its carbon construction. Now, if you were to put me on the spot and ask which suspension set-up I’d race next weekend, I’d go with the Fox shock on the RB2 every time.