Tech Breakdown – 2014 Crank Brothers Iodine, Cobalt Alloy Mountain Bike Wheels Roll Out

Last week, we treated you to an inside look at Crank Brothers, the company. This week, we’ve got the full story behind their 2014 wheels. Or, the alloy ones anyway, the carbon rimmed 11 series will get official next year (but, like most of these, we got a sneak peek at Eurobike).

At first glance, the wheels look the same. But like true beauty, the real story goes much deeper. And in this case, shallower and wider, too.

Before we get into the tech, some background: Crank Brothers’ wheels program started in 2005. Cofounder Frank Hermanson said prototyping the wheels was tougher than their other parts because they couldn’t just whip up rapid prototypes in house. And getting third party manufacturers to create such a radically different design before there was any guarantee it would work was tough. There weren’t many manufacturers that thought their paired spoke rim design would work.

They actually faced the same problem when they first introduced their pedals, which is why to this day their pedals aren’t made by a pedal manufacturer.

With the wheels, they wanted to do it differently in a lot of ways…

All of their rim designs start out with FEA stress analysis for lateral bending, vertical loading (buckling), radial stress and loading and static tire pressure. Once it’s worked out in the computer, they make prototypes and test it for real.

Side note: They said it’s hugely surprising how much of a difference seemingly small changes make. Like changing a curve’s radius by a fraction of a degree can sometimes make or break a rim in certain tests. So the challenge is making tweaks that improve one feature without ruining another.

During lab testing, which is done in their 18-person Taiwan facility, they went through several iterations even after opening tooling. They perform testing on the rims first, then built as complete wheels. Then they hand them off to their sponsored athletes.

2014 UPDATES & IMPROVEMENTS

The split spoke design was created because they couldn’t put the nipples at the rim because the paired design wouldn’t give you much room to put a spoke wrench on it for truing.

The first prototypes used a one-piece “wishbone” spoke that looped through the rim hole (image at left, click to enlarge). They were rideable, but they were very hard to balance and true because as you pulled one side, the curve would slip to one side or the other. Separate spokes pulled through pins were the solution.

For the hubs, they didn’t want to reinvent it. There were plenty of reliable, proven ratchet and pawl mechanisms, so they went with a vendor they knew. Unfortunately, that vendor’s product didn’t hold up well on the trail -it had about a 17% failure rate- which caused more than a few warranty issues.

With the 2nd generation of the wheels debuting in 2010, they wanted to get a more robust hub and improve their build process. The new hubs proved to be much more durable and reliable -less than 1% failure- and ended up with a better axle endcap system. They also introduced their numerical heirarchy system, offering tiered products at different price and performance levels.

Now, they’re debuting their 2014 wheels. It gets a streamlined heirarchy with just three lines: Cobalt (XC), Iodine (AM) and Opium (DH). Sage is gone. Within the lines, you have up to four tiers: 11 is the best, designed with everything they want in a premium wheel and cost as an afterthought. The 3 level is high performance for those where cost isn’t an after thought. 2 is a solid upgrade choice for enthusiasts, and 1 is really aimed at the OEM spec level for bike brands that want to use a branded product to enhance showroom value.

With the hubs and spokes dialed from the 2nd gen, the rims saw the bulk of the advancements for 2014. When they first started, tubeless was really coming into its own, so they wanted to make a rim that was tubeless ready right of the box, not needing tape to cover spoke holes. That part of the design hasn’t changed -the rims still have a solid rim bed- but the depth, bead seat and width have. Those changes helped them achieve all three redesign priorities:

• Improve the strength to weight ratio while keeping their design aesthetics
• Optimize durability and stiffness
• Improve vertical compliance

For alloy rims, the tire bead wall heights are lower, rim are wider and the extrusion has overall taller rim height. The rims are all 2mm wider, and total rim depths grew while interior bead hook walls all got shorter. Depths vary depending on the rim’s intended application:

The result is rims that are laterally stiffer while being lighter, improving the overall wheels’ stiffness to weight ratio anywhere from 9% to 14% (Cobalt 29er rear used for the example).

They also wanted to improve tubeless tire compatibility. With tire technology improving, they could improve the interface. The rim bed’s center groove has a smooth curve leading to sloping, ramped faces, all of which helps the tire slide into place easier during initial setup and helping it settle back into place quickly if you do burp air on the trail.

The 1.7mm reduction in bead hook height helps hold the tire in place. The 0.2mm hook thickness reduction and revised profile, along with the wider stance, all help make for a bigger, rounder tire footprint. Like the depths, the bead hook shape varies from Cobalt to Opium, catering to the type of riding and tires likely to be used.

Their original rims had a brushed finish. It looked good, but the 3rd gen rims get a new cold worked, shot peened finish that hardens the surface and reduces the likelihood of cracks. Overall strength is improved by 15%. Logos and graphics are laser etched on top.

Part of their real world testing is done by Hans Rey and Richie Schley, both of whom head out for multiday rides in remote areas. Obviously, the paired spokes aren’t standard items most shops are going to stock, so their vote of confidence by using them when they’re out of range of easy repairs speaks to the wheels’ durability.

EASE OF SERVICE

The other side of the durability story is their ease of repair, something their engineers say isn’t commonly known. In fact, they say some shops send back wheels to be trued simply because the design intimidates them or they looked complicated. In fact, that couldn’t be further from reality.

Tim Young, product developer and former service and warranty manager, demonstrated how to build a wheel in under 20 minutes and without any special tools. In fact, the only things needed are a standard spoke wrench, truing stand and spoke tension caliper. The wood base can be made by any shop that actually thinks they may build a Crank Brothers wheel from scratch – it’s a high tech chunk of 2x4s and duct tape with a cheap skewer drilled through the center.

Simply insert the lower part of the spoke through the hub holes. The spokes don’t weave between each other and the holes are spaced and oriented so that you can’t mess it up. And the upper part of the spokes will only reach far enough to connect to the correct bottom portion, so there’s literally no way to do it wrong. To install the upper spoke, simply slide the pin into the rim hole and insert the spokes about half way while angled flat with the rim bed. Once both are halfway in, pull and twist them toward the hub.

The spoke heads have two flattened edges that rest against the side of the rim flange so they won’t spin during truing. From there, simply hand tighten the threads evenly before putting in a truing stand for tensioning and balancing. It really couldn’t be easier. Oh, well, actually it could: Need to order parts? Front and rear, drive and non-drive side spokes are all exactly the same per model. Get a couple extra and throw in your pack and you’ll have what you need no matter where the damage occurs. And you can repair the wheels trail side without even having to remove them from your bike.

Most standard bicycle wheels are touched by human hands during assembly, but some are mostly built by machine and only see a quick inspection in a truing stand. Others get intermediate hands on attention. Crank Brothers wheels are all 100% handbuilt at all price points.

SPECS & MODELS

Quick notes: Cobalt 11/3 and Iodine 3 only come in 27.5 and 29er, lower level models will have 26″ options. Cobalt 3 gets an alloy freehub body and secondary machining on the rim’s spine. The Cobalt 2 has a steel freehub body and no machining, and it comes in 26″.

All endcaps are included in the box, and XD driver bodies are available aftermarket. For them and dealers/distributors, they went from 50 wheel SKUs to 13 by making all models use swappable end caps rather than dedicated axle systems.

Wheel size options? How ’bout this handy chart:

What about the carbon wheels? They’re coming, but they won’t be shipping until spring 2014, so they’ll announce all the tech info on those closer to release. The basic idea behind the alloy rim updates were applied to carbon, too, but the stiffness improvements on those were considerably higher. Should you wait? Only if you wanna spend more than twice as much or you’re super hard on your XC equipment. Our initial rides on the new wheels were impressive, doing their best to hold a line on some severely rutted out trails and loose, obstacle-laden descents. They’re on their way back to our office with an assortment of other fresh Crank Brothers parts for a proper long term test on local trails.

CrankBrothers.com