Review: Spot Rocker 29er Belt Drive Singlespeed
- by John Hawkins
- Published: 24 September 2010
“Steel? Singlespeed? and a 29er? Belt drive as well. This will be interesting – sign me up!”
29ers have been on the fringe of the mountain bike scene for a few years, now they are almost mainstream – all of the big MTB brands have 29ers in their 2011 range. These big wheeled bikes have been the subject of vigorous discussion recently on the BNA Cycling Forums. Between steel, aluminium, titanium and carbon fibre, the Frame Material Wars seem to have had a temporary ceasefire, though no armistice has yet been signed. And belt drive is still so new that most people look at me blankly and ask “What did you just say?”
So when the chance to review the Spot Rocker came, I was excited. It was going to answer a lot of questions. Would steel actually be real? Would the 29″ wheels just roll over anything in sight? Would the belt drive go the distance, or would my legs win? Would singlespeed rule over gears?
It’s immediately obvious the Spot Rocker is not your run of the mill mountain bike. Firstly, the bulky frame tubes we are all so accustomed to seeing are missing. In their place are relatively slender tubes reminiscent of the days of old when steel ruled the roost for frame construction.
Secondly, the wheels: they’re huge. The proportions made the Large frame size I rode look like a Small. Next to our 26″ dual-suspension bikes and my 700x23c commuter, and it was enormous. My teenage son dubbed it “The Horse”.
The usual crowd of chainrings on the front and the forest of sprocket teeth up the back are? missing. No derailleurs either. In fact there isn’t even a chain.
In the place of the usual whirligig of gears is a simple Gates Carbon Drive toothed belt. No sharp-toothed cogs, rather ‘sprockets’ that seemed to be half air, these gaps grab the ‘teeth’ in the belt itself. The belt drive was probably the most controversial component on the bike, a couple of fellow riders speculated about higher friction levels and a skipping drive train under load. Trail testing would soon tell the truth on those claims.
Belt drives pose special challenges to frame builders: it is not possible to break and rejoin belts like we are accustomed to do with a chain. The Polyuerathane and Nylon compounds of the belt cover carbon fibre bands that run the length of the belt. The Spot overcomes the difficulty of a non-breaking belt with a neat and strong bolt-together joint at the junction of seat and chain stays, on the drive side. Removing the rear wheel to change a tyre is also much simpler than on chain-driven single speeds with rear-facing dropouts. The Spot has vertical dropouts that integrated with the belt tensioning system and the disc brake calliper mounts.
A benefit of this arrangement is that regular external bearing cranks can be used. On the test bike Shimano LX were fitted.
On the Truvativ Noir Low-Rise carbon handlebars were a pair of Avid Elixir brakes and a lockout lever for the fork. A very nice Rockshox Reba 29er dual air fork performs the front suspension duties providing 100mm of plush travel. The handlebar fitted for the test was a light and stiff Truvativ Noir low-rise carbon unit, mated with Spot’s excellent infinitely height-adjustable stem. Grips are blue foam ESI Chunky Silicone and a FSA SLK carbon seatpost and white Selle Italia SL saddle looked after the back end.
On the first time out on this bike the immediate sensation was of being perched up high, instead of being “in” the bike and part of it. The combination of 3″ larger front wheel, riser stem and riser bar felt a little awkward. While this upright position was great for descending I found it unsettling when the track got twisty, and it affected my confidence negotiating fast direction changes and selecting the line through slow tricky technical trail sections.
The first attempt at the rocky roll-down near the Manly Dam Hydraulics Lab resulted in getting way off line and what must have been an amusing-looking over-the-bars clipstack.
Flipping the stem dropped the bar down and the bike immediately felt more balanced. A flat cross-country bar would have improved handling even more.
Despite the Crossmark tyres being a poor match for the wet and greasy conditions, the Spot Rocker performed well in the corners, the longer tyre contact patch that the larger wheel generates providing more grip than I expected.
This extra grip was particularly noticeable on the climbs. As the gradient steepens, you no longer have the option of sitting and spinning. With a singlespeeder you must stand up out of the saddle and grind. Normally this translates to instant wheelspin over loose rocks and dusty hardpack. Though with the Spot Rocker it just seemed to catch traction again, after spitting out the occasional rock, and keep going. Locking-out the fork with the handlebar lever became second nature whenever the track tilted upwards, and I found myself flying past guys on geared bikes as I sought to maintain momentum and a sustainable cadence. The big wheels just flowed over the bumps.
Of course this soon cames to an end about a third of the way up Manly Dam’s Heartbreak Hill. It doesn’t matter how strong you are, with a singlespeeder you will eventually have to walk some trail sections. The guys on geared bikes spun their way past, but were eventually beaten themselves by the last water bar. I caught them again a kilometre or so later at the start of the medium climb up to 19th Hole. By the time I reached the turnoff they were no longer in sight behind me, though the heart rate let me know maintaining cadence had its price.
It did feel odd at first that my thumbs had nothing to do, and I kept trying to push down on the brake levers to change gears more than a few times until I remembered that I had to spin a bit faster on the downhills and harden up going uphill.
Climbing out of the saddle with the fork locked just seemed really natural, and when necessary lofting the front wheel up onto the top of tree roots and rock step-ups happened without needing to think.
Even in very wet conditions, the belt drive worked really well. When tightened to the tension indicated on the supplied tension gauge, there were no problems whatsoever. One of the test rides was particularly wet and muddy (you will notice this on the photos). Anything caught by the belt was simply squeezed like vegemite through the holes between the cog teeth, and spat out. It spins up to speed really well, and the feather weight of the belt more than makes up for the extra rotating mass of the bigger wheels. As to extra rolling friction, I didn’t notice any.
The belt drive does require attention to tensioning. Neglecting it won’t send you over the bars or result in lost belt teeth, but the tendency of the belt to “ping” if not quite tight enough was a little disconcerting until I learned what it meant. With the supplied gauge and two Allen keys, setting tension is at most an easy two minute job before the start of the ride.
The 39/24T gear ratio was excellent for most of the trail, but it does work your legs hard on the climbs. The high demand it places on your cardio system takes some time to adapt to, and forces a change in your riding style. You soon learn to stay off the brakes and focus on maintaining momentum – which is what we should be doing anyway if we want to go fast.
The Spot hub and freewheel had a quick takeup which came in handy when ratcheting over technical trail sections.
The combination of steel frame, big wheels and carbon seat post I loved. It really took the sting out of the trail bumps, and it just ate up the rock garden section of the Wakehurst Parkway singletrack as I reeled in a couple of guys in dual-suspension 26ers.
The Rockshox Reba Dual Air fork was smooth with great small-bump compliance. The thumb-operated lockout was convenient, removing the need to take a hand off the bars and feel around for a lever on the fork crown. The fork however is somewhat flexy, the combination of big wheels, flexy stanchions and 9mm quick release axle had a noticeable impact on steering accuracy through the rough stuff. A 15mm or 20mm through-axle fork would go a long way to addressing this and making the most of the responsive geometry.
The Verdict: One Ring to Rule Them All?
I really enjoyed myself on this bike. Far from being a retro eighties throwback thing, I can see that steel frames have a firm place in the current market and I found the ride qualities very attractive. So attractive in fact that – fitted with a 27 or 30-speed transmission – I can see myself getting one for enduro racing.
The 29 inch wheels offered a noticeable improvement in the rolling resistance. This was most obvious when the trail got choppy. The Spot Rocker just seemed to flow over the bumps, and climbing and cornering traction was outstanding.
The belt drive does require a little attention to accurately set the tension. On the plus side is the much lower rotating mass (no gears), an excellent tolerance to mud, and a silent ride. Plus, you’ll never have to lube your drivetrain again, just hose it off. It makes for the perfect wet weather bike.
Does one gear rule them all? I’m not sure about that yet. With time I reckon I could get to enjoy it. The intensity would certainly push my fitness to a new level – although on my late forties legs that might take a little while. It’s a very different style of riding to what most are used to and I can see why it has such a strong following.
What I am sure of is that if singlespeed is your thing, the Spot Rocker is a great ride.
– Low rolling resistance in the rough
– Very comfortable ride
– Needs flat bars
– Stiffer fork needed
Spot Bikes are available in Australia from Black Mountain Sports www.blackmountainsports.com.au. The Spot Rocker frame alone retails for $1695 and the bike as tested retails for $3995. A Trail-build version is available for $2995.
They also carry Carver Bikes and together with the Spot Bikes, you will find a comprehensive range of 29ers, 650B (27,5″) and Belt Drive MTBs.