Fouriers MageSK CR-DX004 Cassette Add-On

With the growing popularity of 1x drive trains, Fouriers has refined the overdrive setup and developed a full conversion kit. Combining it with the CR-DX003-AH narrow wide chain ring up front makes for a weight shedding, granny gear climbing machine. The MageSK CR-DX004 cassette add-on includes a 16t chain ring for clean shifting and a longer b-tension screw for proper derailleur setup. While designed for Shimano cassettes and not SRAM their website states, "...but you can give it a shot." And we did just that.

MageSK CR-DX004 Cassette Add-OnHighlights

• Conversion kit for 10-speed Shimano cassettes
• Full 7075-T651 CNC in 40/42T sized sprockets
• 16t sprocket and b-tension screw included
• Weight 40T: 67-g / 42T: 71-g / 16T: 15-g
• Colors: Black, Blue, Gold, Pink, Purple, Red
• MSRP: $86.99 USD

CR-DX003-AH Narrow Wide Chainring Highlights

• CNC made narrow-wide chainring for 1x system
• Teeth: 30T, 32T, 34T, 36T, 38T, 40T
• Fouriers' snug fit wave design for improved chain retention
• CNC cut holes for mud clearance.
• Fits 104mm x 4 arms
• Weight: 49-g(34T)
• Colors:Black, Red, Blue sandblast anodize
• MSRP: $73.49 USD

Initial Impressions

Out of the box you immediately notice the amount of precision CNC work that went into shaping mud clearance holes and carving out the snug fit wave design of the narrow wide chainring. As for the MageSK 42t sprocket, it is quite large and feels sturdy, well built and with added bonus gold bling.

Installation is very easy and only requires a couple of minutes and the necessary tools to remove the cassette. Since the 42t will take up space on the freehub body, you need to remove a sprocket from the cassette cluster to make room for it. Removing only one sprocket would leave too big a gap between the remaining gears however, so Fouriers offers a 16t sprocket to take the place of both the 17t and 15t sprockets in the cluster. This bridges the shifting gap and creates the extra freehub body space needed for the 42t. The MageSK is compatible with most medium and long cage 10-speed derailleurs and tuning is straightforward. For fine tuning on Shimano derailleurs, replace your old b-tension screw with the longer b-tension screw that is included in the kit. If you are unsure if your derailleur will work, Fouriers suggest the following formula to determine compatibility: (biggest chainring - smallest chainring) + (biggest sprocket - smallest sprocket) = rear derailleur capacity.

On The Trail

The MageSK was designed for Shimano cassettes, there's a slight mis-alignment on SRAM cassettes. As you can see in the picture at the top of this page, one of the sprocket support arms makes contact with the cassette pins - pushing it out farther than normal. Although the sprocket wasn't perfectly straight it still functioned well on a number of rides and performance was better than expected given the misalignment.

Within an hour on the trail, I was sold on the 1x setup.  The 42t size provided an excellent granny gear to chug along in steep sections that would otherwise be a little too much effort with a smaller sprocket. After a number of trail rides across steep terrain, I found myself quite impressed with the 1x setup and didn't miss the ease of climbing that 2x systems provide.

One of the interesting features of the CR-DX003-AH is the CNCed hole near each tooth for mud clearance. After charging through muddy rivers trying to cause a problem I'll say it would have to be extremely muddy conditions to really notice a difference. For those new to the narrow wide design, it's quite a strange feeling to pedal through aggressive trail sections without a chain guide, but the CR-DX003AH was flawless and didn't drop a chain once. The drive train felt locked in and tight even after repeated river crossings and all the mud we could manage to throw at it. The snug fit wave design kept the chain locked in place, prevented any slippage and disengaged the teeth smoothly. With the 16t installed between the 13t and 19t sprockets, shifting remained smooth and consistent even with the larger 13t-16t and 16t-19t gaps.

While the MageSK was primarily used with a SRAM cassette which is not officially supported yet, we also tested the cog with a Shimano cassette. The MageSK fit snugly on the Shimano cassette without any issues with the protruding pin that the SRAM cassette suffered from. But aside from the Shimano fitting perfectly, the SRAM cassette performed virtually the same. While Fouriers claims they have vastly reduced the chances of a chain drop while back pedaling, both cassettes suffered from this issue. Smaller back pedals, like returning to level with the crank arms didn't cause chain drop but larger back strokes are definitely still a problem. The Shimano cassette seemed to drop slightly less often but it is still a factor to take into consideration when switching to a system like this. How big of a problem this is for you may come down to riding style and how often you require a large back pedal on a trail segment.

Things That Could Be Improved

Fouriers claims to have improved chain retention when pedaling backwards, a common problem with over drive sprockets.  However out on the trail it repeatedly dropped when giving a large backpedal. We double checked to make sure this wasn't a result of the bend in the sprocket and found that it was occurring at various points in the sprocket. The issue occurred both with Shimano and with (non-supported) SRAM cassettes. Not being able to back pedal in the shortest gear didn't impact my riding style but it is potentially something to keep in mind for other riders.

Other than that, Fouriers can improve on the CR-DX003-AH is one simple way, by not calling it the wordy: CR-DX003-AH. After installing the Fouriers setup I had a lot of questions while out on the trail and the response was always, "The what? Oh, you mean the Fouriers narrow wide chainring?"

Long Term Durability

The anodized coating wore off on the teeth after only a couple rides rides even with the chain line fairly dialed in. However, the wear wasn't significant enough to warrant serious durability concerns. An acceptable tradeoff for adding some bling beyond the standard silver look. For more aggressive riding over rocky terrain, you'll definitely want to run a bash guard of some sort up front, if you habitually plow into stuff with your chainring. Fouriers makes a CR-DX003-AH kit with bash rings and direct mount hardware.

What's The Bottom Line?

Anyone looking to lighten their Shimano setup and ditch some cable routing should consider the Fouriers 1x system. And while Fouriers didn't design the MageSK for SRAM, it works (note that Fouriers has listened to the market and is currently working on a SRAM compatible design). On the topic of SRAM, Fouriers has also released a CR-DX003-X1 narrow wide chainring version that is compatible with SRAM's XX1 crank (74-mm asymmetrical BCD).

Great build quality with conversion parts included make this kit worth checking out. With the additional Fouriers narrow wide chainring up front you've got a solid 1x system that doesn't just look good but also keeps the chain on at all times. And it should be noted, after years of running chainguides for all mountain riding, I've officially retired the guide to the spare parts bin in favor of the Fouriers narrow wide 1x setup.

For more information, head on over to www.fouriers-bike.com.

About The Reviewer

Andy Holloway has been riding bikes ever since seeing New World Disorder 3 back in 2003. Inspired, he immediately began sculpting dirt jumps and pump tracks that have a unique and technical style while keeping it flowy. Dirt sculpting highlights include the construction of Boulder's Valmont Bike Park and a host of private pump tracks. Recently, he has discovered the adventure and sense of accomplishment from trail riding and is one of those riders who will choose the jump-transfer over the faster line - after all, it's all about keeping it fun.