First look: LightBicycle RM29C06 ‘flyweight’ wheels

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It doesn’t seem all that long ago that mountain bike magazines and blogs were abuzz with the question “who really needs carbon mountain bike wheels?”. In the heady days of 2010, we had just about accepted that carbon bars were not going to explode and kill you if you accidentally scratched them with a sharp fingernail, but perhaps memories of Tioga disc drives made us all a little more cautious when it came to wheels.

Debate raged – would they stand up to the rigours of rocks, roots and “exuberant” riding, or were they purely for racing snakes with single-figure resting heart rates? Nobody knew.

You know they’re good when they’re approved by Bunn-Rita!

Seven years on, and it’s fair to say the debate seems to have been all but settled. Carbon fibre, that magical nanotube-reinforced plastic composite, has made it everywhere, even into tensile components like spokes. Whilst many of us would (probably rightly) shy away from using carbon spokes in mountain bike wheels, carbon rims are here to stay. The main concern today seems to be not the generalities of carbon, but rather on the specifics of which layup, which tensile strength and which price bracket. It’s in the last category in particular that Chinese carbon fibre manufacturers, many of them with years of experience gleaned from working with household name brands, have been able to effectively disrupt the industry status quo (see Stu’s report here). Whereas a set of Enve’s, with all of the brand name recognition and customer support that that entails, will set you back the best part of three thousand US dollars, there are brands that will offer you products of a similar appearance at almost a fifth of the price.

The LightBicycle RM29C06 wheel build

DT240 hubs keep everything light, dependable and serviceable.

After being approached to review the new offerings from LightBicycle, all I had to do was exchange a few emails with Kartrin (one of their very helpful employees) to discuss hub spec, spoke count and delivery, and then settle up through Paypal. A couple of weeks later, I got a note through the door from Swisspost telling me I had something waiting for me at the central office. And so it is that I found myself wandering down to the local post office at 8am on a rainy morning a couple of weeks ago to pay my customs charges and collect what at first sight seemed like an empty box. In the spirit of full disclosure, I should point out that, whilst I did get a bit of a discount on the cost of the wheelset I am writing about, I did still pay the lion’s share of the cost, rendering me free to make with my opinions. Hell, if you’ve read my articles before, you’ll know I already do that.

Don’t miss our review on the LightBicycle XC923 wheels.

Inside my “empty” box were a pair of LightBicycle’s latest XC offerings, the catchily-named RM29C06 ‘flyweight’ rims, nicely parcelled up. The outer box itself looked as though it might have been in the wars, but the wheels inside were well protected from the less-than-sensitive embrace of the Swiss posties. The rims themselves weigh in at a scant 280g each, and I had them laced to ultra-reliable DT240 straightpull hubs with 28 Sapim CX-ray spokes front and rear.

Light Bicycle Wheels RM29C06 MarathonMTB mountain bike

Despite a 27mm external width to ensure tyre stability, the estimated weights turned out to be remarkably close to the truth, with yellow tape and valves installed, the whole setup weighing 1238g. The build quality is excellent, with good, even spoke tension, and excellent trueness and roundness.

Getting tyres up on the wide profile rims proved that tubeless systems have come a long way. Scary bottle-based inflators are a thing of the past!

Setting up the LightBicycle RM29C06 wheels

A long wait for a Shimano 15mm bolt through centrelock doodah later, and it was time to fit tyres. I love the geometry and ride of my Open 1.1, but the tight ‘wire’ seatstays do pose a bit of a conundrum when it comes to tyre choice. If there’s even the sniff of a chance of mud, anything bigger than a 2.1 is not advisable, and with the modern range of most rubber suppliers starting bigger than that, it can prove a bit limiting. I think I broadly agree with Mike’s take here that narrower can be faster, but not necessarily more confidence inspiring when things are loose or dusty. In the end, I chucked on a 2.1 Schwalbe Thunderburt paired with a 2.25 Rocket Ron up front for a bit more front wheel grip. The front required only a valve and a single wrap of Tesa tape to go up first time with a track pump, the rear requiring a layer of gorrilla tape (duct tape to those not in the know) to seal up nicely. Minimal sweat, only a couple of mild, short, anglo-saxon words uttered – definite bonus points for that! The inner width of the rim (22mm) is great to give the tyre a bit more stability, and a nice wide contact patch for a pretty skinny rear tyre.

Let’s ride

As you probably already know from our previous five years of output, we take testing pretty seriously here at MarathonMTB, and not to be outdone, I wanted my first ride on these wheels to be, ahem, suitable. Luckily, a good friend was flying out from the UK for a race in Ornans, and wanted to ride in La Clusaz on the Friday before – rocks, roots, steep climbs and testing descents; perfect for my needs. We were doubly lucky to pick what is now looking like the last day of summer in the mountains to ride, meaning buff, fast, dusty trails.

Here at we like to suffer so you don’t have to. Don’t thank us, really!

So, how did they perform? Well, pretty much flawlessly. Whilst I am not the heaviest of riders, I’m also a bit old school, sticking doggedly with a hardtail where most have gone full-suss, so the whole package got a reasonable workout over 50km in the French alps. Despite a few months of dereliction in terms of training, rotating weight was clearly not the thing holding me back, and similarly rusty skills were nicely compensated by wheels that just go where you point them. Running 23/25psi in front/rear, the tyres stayed perfectly seated on the hookless beads, and at no point did I feel the dreaded squirm that sometimes comes from such low pressures on narrower hookless rims. After two years of riding alloy Stans NoTubes rims, the stiffness of the LightBicycle hoops was a bit of a revelation, giving barely any flex even when cornering hard over hoof-marked alpine meadows. The DT240 straight pull hubs speak for themselves in terms of quality and light weight, and CXray spokes keep the build light but not at the expense of performance. Dodgy skills from too much road riding made for one notable oopsie into a big root which would have definitely left a war wound on my previous wheels, but not a mark on these. Who says carbon is fragile?

La Clusaz. The perfect place to test wheels.

Obviously durability remains to be seen, but with good quality components and a good even build, I am optimistic that I’ll be just as happy when I check in after a few months on these wheels. Summary so far: understated, superlight yet sure-footed, making me a very happy reviewer.

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