DT Swiss has in recent years been going through their wheel lineup and introducing top of the tree wheelsets for each riding style. The XRC wheels cover XC duties. Their XMC wheels cover more all-mountain demands, and the final piece of the puzzle was the EXC wheels, which are pointed directly at the more aggressive end of little bike riding.

This missing jigsaw piece of the lineup didn’t force DT into a rush to have it filled. Instead, they took their time to engineer something that they see fit for the job.

As is always the case with something new from the Swiss brand, it’s engineered to within an inch of its life and always deserves a minute or two to sit down and just appreciate the quality. Maybe this is just what engineers do and could be construed as a bit odd, but the EXC 1200 Spline is a lovely bit of kit when you get it out of the box.

As is the same with a whole bike, a wheel is a system of multiple parts that work together to do the job. It’s necessary to break the system down to its constituent parts for easy digesting of information, but it should be remembered that DT engineered this as a system and looked at how each part played its role in the grander scheme.

Hub

The EXC wheels use their new 180 hubs. We took a closer look at these a couple of months ago and, as pointed out by Mike Kazimer, the hub is often something taken for granted. DT's previous design had been a mainstay for quite some time but, they didn’t rest on their laurels and they set to work fine tuning it to extract even more performance. The old Lotus philosophy of simplify and add lightness rings true here.

The hub is primarily constructed from aluminium and the attention to detail is fascinating. Intricate machine work is rife and removes any and all unnecessary material. Even the end caps got the treatment and are slimmed down to the bare minimum. Hub spacing is 15x110mm front and 12x148mm rear only.

There's a brilliant interactive view of what's going on inside the new hubs on the DT Swiss website.

The hubs run on SINC ceramic bearings and thanks to the new freehub design the bearing are also spaced a little further apart and offer a better support to the forces coming through the hub.

The SINC bearings were developed by DT Swiss and further show their engineering focus on the details. The balls are made from silicon nitride, which is tough as old boots both in consideration to wear and corrosion. The bearing races are made from a specific steel alloy which was used to match the properties of the ceramic balls to reduce the rolling resistance to next to nothing while giving a greater durability than conventional bearings and removing any issues with corrosion. Given the high toughness of the ceramic balls, they are constantly smoothing out the steel races to keep the bearings running smooth.

DT have a very tight control on the tolerances, inspecting and testing each and every SINC bearing. Balls, races and seals all fit together like a dream.

 Straight pull spoke holes, center lock rotor mounts and everything machined to within an inch of its life.

There are 28 straight pull spoke holes, rather than slots, which should remove any issue of spokes popping out of the hub shell in high load situations. Something which has been seen on other straight pull hub designs.

The rotors are attached via a center lock mount, but, if you have 6 bolt rotors then there are adaptors to fit between the two different mount systems. Max rotor size is 230mm.

 Freehub maintenance is a doddle and tool free. There's also options for every drivetrain.

One of the biggest changes to the previous hub design is the new freehub body, called Ratchet EXP. The new system reduces the number of parts and simplifies one of the best functioning freehub systems that was available on the market. In the same way that many an Intense M1 was re-branded back on the day, the previous Star Ratchet system was hiding away in many other brands hubs, a testament to how good it was.

The simplification comes from physically screwing one of the Star Ratchet pieces into the hub shell. Therefore, they could ditch one spring and make it a constant diameter, compared to the previous tapering spring design. Overall there’s two less parts but the same Star Ratchet sound is still present. It’s an absolute piece of cake to take apart and service and requires no tools to do so.

 Ratchet EXP layout on top, older Star Ratchet layout on the bottom.

The wheelset comes standard with a 36T ratchet system but has the option to upgrade to 54T. The only downside of the new system lies in this upgrading. If you want to do it, you’ll now need either the tool or have a well-equipped local shop who can unscrew the ratchet piece threaded into the hub shell.

The wheels come with either an XD driver body or the new Microspline body needed for Shimano’s new 12 speed cassettes. There’s a standard Shimano freehub body available too.

Rim 

The rims are constructed from carbon fiber and for the EXC versions DT focussed more on impact resistance given the riding intentions of the wheelset. Internally DT set its standards incredibly high for their required impact resistance and used clever engineering to align the fibers as best they saw while having a composite structure with a good ratio of fiber to resin content to handle the energy from impacts. They also focussed on the production process quality to ensure that this intended fiber alignment and resin content was repeatably attained in manufacturing.

 The rim has more of a focus on impact resistance and DT took their time to make sure it exceeded their high standards.

Some of the stigmas for carbon fibers are carried over from the industries other metallic materials. Aluminum is homogenous. If you were to cut it, you’d find the same aluminum all the way through the structure. On the other hand, carbon fiber composites are anything but the same if you were to cut through them. The multitude of individual fibres and resins on offer, each having their own stiffness and strength properties, can be blended together in so many ways that no two carbon structures, or rims, are the same. Often lots of the engineering that goes into a carbon composite is hidden away inside the interior and it’s come from the collective minds of some very intelligent people, so it’s also often closely guarded secrets. 

Tarring every “carbon” rim with the same brush isn’t going to help to separate the wheat from the chaff. Because one manufacturer's carbon rim doesn’t stand up to the job doesn’t mean that another’s will suffer the same fate. We’ll be putting in the miles on the EXC wheelset at our Champéry-based testing area and throwing everything we can at the wheels. Look out for a comprehensive long-term test on these wheels in the future to find out if they hold up.

The rim's profile is a hookless design and uses an internal width of 30mm for the 29” wheels and 35mm for the 27.5”. The rims came taped out of the box and even a set of Magic Mary wired DH tires seated with the gentlest pushes from a track pump.

DT don’t advise using inserts such as ProCore. The added air pressure from the inner chamber drastically reduces the spoke tension in the wheel. Their mantra regarding spoke tension is to build the wheel as close as possible to the maximum given spoke tension while keeping the deviation in tension between individual spokes to a minimum.

Spokes & Nipples

The hubs and rims are laced together with DT’s own Aerolite and Aero Comp bladed spokes and Pro Lock Squorx aluminum nipples. The front wheel uses the slimmer and lighter Aerolite on both sides while the rear wheel uses a mix of Aerolite on the brake side and the slightly more meaty Aero Comp on the drive side to handle the added input forces present at the rear wheel.

For their carbon wheels they managed to do away with the small PHR washers between the spoke and rim.

As mentioned above, DT focus on building a reliable wheel with the use of maximum allowable spoke tension and minimum variance from spoke to spoke. They then use the geometry of the spoke to adjust the stiffness to reach what they require.

 28 straight pull spokes in a 3 cross pattern and Squorx nipples attach them to the rim, but without the PHR washers used on the aluminum rims.

Spoke lengths for the 29” wheel are 300mm on both sides, front and rear. Meaning you only need one spare spoke length and you’re covered.

DT also carefully control the additives that are used in their resin to stop any galvanic corrosion between the rim and aluminum nipples and keep everything running as it should for a long time.

Valve

The attention to detail didn’t stop there as they even threw their attention to the valves. There’s a lighter aluminum valve that is claimed to be 40% less weight than the brass version used elsewhere in their wheel line. 40% of a valve may be the same grams as a gnat’s whisker, but spinning that valve up to 60kph results in the equivalent valve weight increasing. Most of the World Cup race bikes now employ additional weights stuck to the rim or clamped on the spokes to balance out the wheels when they are spun up to race winning rpms. Reducing the valve weight really may seem insignificant, statically. But dynamically its gains are multiplied.

 The new aluminum valve has a built in core remover on the valve cap.

The new valve includes a valve core remover in the cap and the internal rubber shape of the valve base is circular and conical, meaning there’s no worry in valve orientation to ensure a good quality seal.

System 

After examining each individual part, we now zoom out to the system.

The carbon rim used on the EXC wheels is inherently stiffer than its aluminum counterpart and as a result DT used the spoke count and the different spoke geometry of aero spokes to generate the wheel stiffness they were after. They set their target to be at least as stiff as their aluminum wheels, while not crossing over the threshold into the realms of too stiff.

DT tested a lot of their own wheels and also many competitor wheels internally in their own testing facility and also out in the real world with a variety of rider skills and styles to determine how they wanted their wheels to behave and also where this limit of useful compliance and too harsh was.

There’s a maximum system weight of 130kg (287 lb) on the wheels. System referring to the rider, dressed up all ready to go, plus the bike.

Facts & Figures 

DT generally aren’t a company to throw around cliché claims when marketing a product. Their engineering DNA shows through in the use of facts and figures to explain the performance. Their biggest fact comes about impact resistance.

Using their "Puncture Test” (dropping a fixed weight from certain heights vertically onto the wheel, same as the UCI Impact Test) to examine the local fracture behaviour of the rim, they’ve recorded an 18% energy increase with their EXC wheel without critical failure. This was compared to two of their most relevant carbon rim competitors, although no exact names were mentioned. It seems it took perseverance and over 20 different layups to get to something that stood up to their high standards.

 DT's Puncture Test to examine impact resistance and their rotor testing to verify their max rotor size of 230mm.

DT also talk about the moment of inertia of a wheel. One way of describing this is how the mass of the wheel is going to determine the force needed to reach a desired acceleration. It’s not a linear change either, with the square of the distance that the mass sits from the axis of rotation coming into play too.

Seeing as we’re talking about 29” wheels that distance is fixed, so the remaining factor to work on to lower the moment of inertia is the mass. Frankly, I’ve not helped matters with mounting a set of DH tires, but at least DT has gone the extra mile to lower the weight of the components furthest away from the wheel axle thus lowering the amount of force needed to accelerate and decelerate the wheel. According to their testing, they’ve measured a 6% increase in average speed with the EXC wheels when compared to the aluminum 1501 Spline wheels due to the weight reduction they achieved at the rim.

Claimed weight for the wheels is 1670g for the 29” version and 1659g for the 27.5” version. That’s without valves or tubeless tape and with XD freehub body.

Putting all the parts of the 29” wheelset on the scales we have:

Rear wheel with XD freehub: 896g
Rear wheel with Microspline freehub: 905g
Front wheel: 794g
Two valves: 7g

So that makes 1697g for the pair with an XD freehub and valves fitted. A touch heavier than the claimed weight of 1670g but, the difference is due to the tubless tape.

As mentioned, we have a set of these wheels currently being ragged in Champéry and will report back with a long-term review in the coming months. DTs claims seem to be more factual based rather than cliché, but only more ride time will tell how the wheels perform. But for now, they're as impressive a piece of kit as any top tier DT Swiss component should be.