Has it ever occurred to you that your bike’s wheels do two different jobs? Well Crankbrothers says that is the case, so they’ve tuned the front and rear wheels of their new Synthesis carbon wheelsets to perform their separate duties as well as possible.

The theory, in short, is this:  Your front wheel’s job is to find traction, so this wheel has more compliance than the rear and is slightly wider. The rear is stiffer and stronger as it will bear the brunt of most hits and lateral cornering forces.

This article covers the development and tech specs on the new enduro, DH and XC/trail Synthesis wheelsets, but I’ve actually been riding the E 11 wheels since late August; be sure to check out my review to see how they handled on the trails.

To develop the Synthesis wheelset, Crankbrothers brought together two wheel builders with opposite approaches. On one side is Jason Schiers, founder of ENVE, whose wheels were known among MTBers to be very stiff. On the other hand, Mello Bouwmeester was building compliant, single-wall carbon rims under his own brand in Australia. With expertise on both ends of the scale Crankbrothers started building test wheels to determine what level of stiffness, and in what combination, was best for mountain bikes.

The company put test riders on unmarked prototype wheelsets that offered different stiffness levels and combinations front to back, and eventually the test group’s preferences narrowed down to one set – the pair with a compliant front wheel and a stiff rear ticked the most boxes, and the Synthesis formula was found.

Crankbrothers Synthesis carbon wheelset- enduro rim cutaways

The concept certainly seems logical – the softer, compliant front wheel offers a slight degree of flex to keep you better connected to the trail as you thrash through rough terrain. The rim is also slightly wider than the rear, to spread the front tread wide and round. Pairing different rim widths isn’t a new idea, but it simply furthers the concept of running wider front tires with narrower rears, which many riders have done for years.

Since it takes the hard hits and deals with torque and cornering forces, the rear wheel was kept stiff and strong. The rear rim is a bit narrower than the front so the tire keeps a sharper profile and solidly bites into corners.

Crankbrothers Synthesis carbon wheelset, front wheel on Trek Remedy

One obvious way Crankbrothers kept the front wheel softer was using fewer spokes than the rear – the Synthesis wheelsets all come with 28 spokes up front and 32 out back. What the eye won’t see is that the front spokes are under less tension than the rears, and while the front rim is wider it actually weighs less than the rear rim. Out back, higher spoke tension, heavier gauge spokes and a stronger rim keep things tough enough for off-road abuse.

Crankbrothers Synthesis carbon wheelset, rear wheel on Trek Remedy

If you’re skeptical about carbon rims because you’ve seen them blown to pieces, you might want to hear this; while building the Synthesis wheels, Schiers honed in on how to make these rims fail without doing so catastrophically. The Synthesis rims are designed to crack like an alloy rim would, and not explode upon impact. And since they’re carbon, you can’t flat spot them like aluminum rims.

Crankbrothers wasn’t shooting to create the lightest wheelset available, but favoured durability and ride-tuning instead. There is no rider weight limit, and the Synthesis wheelsets all carry a lifetime warranty to the original buyer.

Crankbrothers Synthesis carbon wheelset, front Synthesis 11 hub, bladed spokes

There are three different Synthesis wheelsets with two specs for the trail/enduro models and one premium-level DH set. The lesser models offer the same ride qualities as the higher-end options, but the pricier wheels are lighter. The rims follow the same design across the board but the rim width, hubs and spokes vary between models.

Synthesis E and E 11:

Crankbrothers Synthesis carbon wheelset, E 11 pairAs you might guess, the E series wheels are intended for enduro riders.  The front rim has an inner width of 31.5mm, while the rear is 29.5mm. The E model runs a three-pawl Synthesis Standard hub with 17° engagement, and they’re laced with Sapim’s D-light front and Race rear spokes.

The premium E 11 wheels (pictured above) have a Project 321 built Synthesis 11 hub with 2.5° engagement, and bladed Sapim CX-Ray front and CX-Sprint rear spokes. The Synthesis 11 hub has six low-drag magnetic pawls (as they come stock) that make the hub run nearly silent. However, an optional ‘loud kit’ is available for those who like to hear their hub buzzing. The loud kit uses the same number of pawls and offers the same quick engagement, but the pawls are shaped differently to create more noise.

Both sets are available in 27.5” and 29” with Boost spacing for Shimano/Sram. See the below graphic for pricing and weights.

Crankbrothers Synthesis carbon wheelset, E and E 11 pricing/weights

Synthesis XCT and XCT 11:

Crankbrothers Synthesis carbon wheelset, XCT 11 pairThe XCT wheels are the lightest option for XC/Trail riders, and come in 29” only. This set’s front rim is 26.5mm wide, and the rear is 24.5mm. The basic XCT set uses the Synthesis Standard hub and Sapim D-Light spokes front and rear. The XCT 11 steps up to the Synthesis 11 hub and Sapim’s CX-Ray spokes. The XCT wheels come in Boost spacing only, and are Sram/Shimano compatible.

Crankbrothers Synthesis carbon wheelset, XCT and XCT11 prices/weights

Synthesis DH 11:

Crankbrothers Synthesis carbon wheelset, DH 11 pairThe DH 11 wheels are intended for downhill riding. Since DH riders typically run 2.5” treads front and rear this is the only Synthesis wheelset where both rims are optimized to the same 31.5mm width. This set runs the Synthesis 11 hub, and Sapim’s CX-Ray front and CX-Sprint rear spokes. The DH 11’s are available in 27.5” Boost and Standard DH spacings (157x12mm rear/20×110 iso front – a separate axle kit is available for 150x12mm rear hubs too). 29” models come in Boost only, and all are Shimano or Sram compatible.

Crankbrothers Synthesis carbon wheelset, DH 11 prices/weights

The Synthesis enduro wheelsets are available online as of today (Oct. 1st), and in stores for November. The DH and XCT sets will be coming later this year. The E, DH and XCT rims are all also available separately for $699 USD per pair, with 27.5” and 29” options for the DH and enduro sets and 29” only for the XCT.

Eventually, ‘super boost’ 157mm rear hubs will become an option on the Synthesis wheels. For those interested in buying rims alone, Crankbrothers will provide wheel building specs to bike shops.

crankbrothers.com

9 COMMENTS

  1. Was originally cautiously optimistic that CB was helping bring the Bouwmeester rims to a larger audience, as I thought they had a really cool design. Now, not so much. The original single wall ones were supposed to be compliant, due to the single wall design, and also durable, due to the doubled up wall thickness. These CB versions just look like a standard wide double wall carbon rim from any of dozens of suppliers.

    Also, not sure if the CB marketing machine is still out of control despite their supposed shift from “design focus” to “engineering focus”, or if the author just misinterpreted some of their claims, but all of the following raises an eyebrow:

    “The (front) rim is also slightly wider than the rear, to spread the front tread wide and round. Pairing different rim widths isn’t a new idea, but it simply furthers the concept of running wider front tires with narrower rears, which many riders have done for years.” A lot of people complain about wide rims squaring off a tire too much, how does this wider one make it more round?

    “Since it takes the hard hits and deals with torque and cornering forces, the rear wheel was kept stiff and strong. The rear rim is a bit narrower than the front so the tire keeps a sharper profile and solidly bites into corners.” I thought the front tire is the one that has cornering maximized, due to the wider profile rim. How is the “sharper profile” that a narrower rim brings supposed to do the exact same thing?

    “One obvious way Crankbrothers kept the front wheel softer was using fewer spokes than the rear – the Synthesis wheelsets all come with 28 spokes up front and 32 out back. What the eye won’t see is that the front spokes are under less tension than the rears, and while the front rim is wider it actually weighs less than the rear rim. Out back, higher spoke tension, heavier gauge spokes and a stronger rim keep things tough enough for off-road abuse.” It is well established that, short of a wheel completely detensioning under load, spoke tension does not affect stiffness of the wheel system. World Cup riders might loosen their spokes to accomplish a controlled detensioning, but their mechanics have to re-tighten them daily and it will compromise the long term durabiliy of the rim, spokes, nips, and hub flanges. Pro racers don’t care, because they swap them out several times per season, but for everyone else you never want your wheel to completely detension under riding loads. So basically, either CB either runs slightly lower tension in the front and doesn’t understand that it accomplishes nothing, or they run significantly lower tension and have compromised long term durability.

    Also, if they are touting the compliance of these rims they should provide figures for radial and torsional compliance vs. some industry benchmarks.

    That is all.

    • Also with the spoke counts and tensions, how is this any different than pretty much any high end wheel out there? Lowered spoke count on the front wheel is typical because high count isn’t always necessary and it drops weight. Rear wheels will naturally have significantly higher tension on the drive side compared to any front wheel, and that is only due to flange diameter and distance from center due to the cassette location. This whole article sounds just like marketing fluff for a normal carbon wheelset.

      • That said, I’m sure these could be excellent wheels, but give us quantitative data. Compare them to previous wheels or heaven forbit competitor’s wheels. Compare lateral stiffeness, radial stiffness, impact resistence, weights, etc…

    • There are lots of elements that make up a wheel and you raise some good topics of conversions.

      What Synthesis wheels are, is a lot of subtle things put into a tuned wheel package for the customer. For the most of it, the lab and field testing dictated the R&D pathway rather than marketing dreaming up a product they wanted. We feel we have done enough testing that the product is real and people that ride it feel the benefits.

      The rim is an evolution of a lot of the key principle that made the Bouwmeester rim special. Synthesis made important gains in lateral stiffness while still balancing out radial characteristics and reducing weight. It is a super shallow hollow profile with considerable overlapping supporting fibers in the rim wall area. It’s unique in its profile and layup, it has a front and rear rim, it’s incredibly quiet and the ride characteristics reward the interface with the trail.

      We trialed lots of different inner rim widths and we feel we have found a sweet spot for the 2.3-2.5” range of tires customers will use on the Synthesis E (Enduro) wheels. We agree that if you go too wide in the front you square off the edges of the tire. Our front is 31.5mm inner width and a good size to balance the tires contact patch through a nicely rounded profile. To your point on the rear, maybe something has been lost in translation but we are talking about another subtle change to 29.5mm inner width. This is re-positioning the bead in relation to the tires edge and changing the tires profile and radius. In effect sharpening up the tires profile.

      In saying all this, it’s not just about a rim, it’s not about a specific lab test we did, nor is it about a spoke tension, it is about a wheel system; It’s all these elements put together that make up the ride quality. Choosing key elements that improve how the front wheel handles as a system, then looking at the rear wheel differently and optimizing certain characteristics in it. Rim profile, layup, materials, spoke elongation properties, tensions, spoking patterns, spoke count, hub to rim bracing angles and optimizing the tire interface.

      If you get the opportunity through a Crankbrothers dealer we would welcome you to test ride it. The proof is in the ride and the Synthesis wheelset rewards the rider out on the trials. If you still don’t like it that’s OK, riding is down to personal preference. We’d be happy to meet you we’re next in your area and Crankbrothers staff can go for a ride and thrash out different ideas on wheels.

  2. No idea whatsoever whether or not they achieved it with these wheels, but engineering flex in the right amounts and directions, while keeping stiffness where it is needed, is a worthy endeavor.

  3. The concept is interesting and time will tell if this the direction things go as riders gain experience and other manufacturers evaluate the benefits. However at this price point I’m definitely not going to jump in as an early adopter, been burnt before doing that. Rather I’ll stick with the tried and true, in this case Enve. I recently swapped out a set of Niner carbon wheels for a set of M525’s and the impact was immediate and likely most related to the weight reduction. Enve bills the M525’s as more compliant but they still feel plenty stiff. My preference is for the wheel to be stiff and then dial things with a combination of the suspension and tire choice/pressure.

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