The combination of derailleurs with clutches and narrow-wide chain rings has allowed many riders to move away from using a chain guide, especially those people who aren't racing on a regular basis and don't need the extra insurance, but MRP's new SXg guide is designed specifically for that type of drivetrain. The Colorado-based company says that the SXg provides as much protection as what we're used to seeing on a downhill bike, but with none of the perceived drag and complication that usually comes with that.
The SXg is available in options to fit 30 to 34 tooth rings or 34 to 38 tooth rings, as well as with either an aluminum backplate like the $169.95 model that's reviewed below or a $224.95 USD version with a carbon fiber backplate.
• Intended use: single ring drivetrains
• ISCG-05 mounting only
• Full-size, enclosed upper slider
• No-contact 'Whippersnapper' lower slider
• TPU co-moulding in upper and lower slider
• Integrated skid guard
• Sizes: 30-34t, 34-38t
• Alloy (tested) and carbon backplate options
• Weight: 158g (30-34t, alloy, w/ hardware)
• MSRP: $169.95 USD (alloy), $224.95 USD (carbon)
The SXg employs an enclosed upper slider, much like what you're probably used to seeing on those aforementioned DH guides, but MRP has paired that with a no-contact (and, therefore, no drag) lower slider that they say makes the SXg suitable for everything from DH to trail bike use. ''That feature, as well as the lateral containment of the chain provided by the inside and outside wall structure, makes for a guide as secure as any we've ever produced,'' MRP's Noah Sears explained, ''but at a class-leading weight and with none of the perceived drag or suspension interference of a traditional, full-size guide.''
What sets the SXg apart from other full-sized guides is its lower slider, otherwise referred to as the 'Whippersnapper' by MRP. It looks a lot like the lower slider that's used on any big chain guide, but two things make it very different: its position relative to the chain ring, and the fact that there's no pulley wheel tucked inside of it. A more common lower slider sits much farther back and higher up in order to add tension to the chain in all gears, but the Whippersnapper's location (lower and ahead of the six o'clock position of the chain ring) means that it makes no contact with the chain.
Because the chain isn't making contact with this slider during pedaling loads, MRP was able to use a softer, co-molded TPU material on the inner walls of the Whippersnapper to help keep chain slap noise to a minimum.
The Whippersnapper and skid guard, often called the taco, are moulded together as a single piece, and the whole unit is attached to the backplate with two bolts, one of which can be removed to allow the whole thing to swing out of the way to make installation easier. MRP has also built in an adjustment that allows the Whippersnapper (and, therefore, the skid) to be set in a high or low position to work with the chain ring size that you're running; my test guide is for 30 - 34 tooth rings, and the larger size works with 34 to 38 tooth rings. This two-position system takes the place of an adjustable lower slider that can be tweaked by just a whisker before being tightened down into place, which is what you'll find on most full-sized chain guides.
Installation and Setup
The main installation points of the SXg are very much the same as with any guide: you bolt it onto the bike's tabs, center and clock it correctly, and then adjust the positions of the upper and lower sliders to wherever they need to be. This entails removing your drive-side crank, of course, but the upper slider is split and half of it can be rotated up so you don't have to break your finicky eleven-speed chain. The lower slider also rotates down and out of the way in order to clear the chain ring, and both it and the upper slider go back together with a single bolt once the crank and chain are back on.
Setting the height of the upper slider is pretty straightforward thanks to laser-etched height markings that correspond to whatever chain ring size you're using, although I did end up having to raise the slider a touch higher in order for it to clear the tall drive-side chain stay of the 6Fattie that I used for testing. MRP says that these markings serve as more of a starting point than anything, and, as I discovered, that some fine-tuning may be required. I could have rotated the backplate clockwise by a few degrees instead, but that would affect the position of the lower slider (which is important), so raising the upper slider by a few millimeters made more sense.
I used the SXg with a 32 tooth chain ring, which is smack in the middle of the two 30 and 34 tooth height settings for the lower slider. MRP said to go with the upper setting, although the chain did brush on the slider ever so slightly when it was in the 42 tooth cog and the bike wasn't sagged into its travel. Rotating the backplate counterclockwise a touch would have created more clearance, but this would have moved the upper slider back towards the 6Fattie's chain stay while moving the lower slider down to the 34 tooth setting, creating about 10mm of clearance, far more than the 2mm that MRP recommends.
In the end, the chain did make slight contact with the lower slider when the bike was in the stand, but not at all when I was in the saddle.Performance
There's always a lot of banter about whether riders should be using a chain guide with their single ring setup, with a lot of non-racers choosing to forgo mounting up even a minimalist guide, presumably because they don't feel that the added security is worth the complication or perceived drivetrain drag that can occur in some gears, especially when it's really muddy. That pretty much describes me, and I only need a single hand to count the number of times that I've dropped a chain in the last three or four years. Sure, I'd probably use a guide all the time if I was racing enduros every weekend, but I'm mostly just skidding around in the forest with some buddies.
The SXg made me rethink my approach, though.
There is zero contact between the chain and any part of the SXg when you're on the trail, regardless of what gear you're in, meaning that I couldn't complain about the guide stealing any of my meager power. It's December, so my trails have more in common with a Turkish mud bath than they do with any sort of flowing singletrack, but while sticky, brown crud managed to get everywhere from down my shorts to in my helmet vents, the SXg refused to pack up. That kind of mud is often the Achilles heel for any full-sized chain guide that uses a pulley wheel at its lower slider, but the Whippersnapper continually cleared sludge that would have troubled a normal full-sized guide.
I haven't had the guide on my bike long enough to comment with any real authority when it comes to reliability, but given that once it's set up it has about as many moving parts a spoon, I doubt that it will cause any trouble down the road.
As I mentioned earlier, I rarely lose my chain, so I didn't expect the SXg to be a revelation in that regard. And it wasn't - I still didn't suffer from a single dropped chain - but I did appreciate the extra security. The bike was also marginally quieter, which is an added bonus. So, the lower slider is drag-free, isn't bothered by clumpy mud, and it also protects your expensive chain ring from smashing into things, which means that I'm running out of excuses as to why a hard charging rider wouldn't want to run a guide like the SXg. This is especially true if they were on a long-travel, enduro race bike, or if their local trails are extremely rocky and full of ledges. Pinkbike’s Take:
|Bruce Willis has starred in more Die Hard movies than the number of times I've dropped a chain over the last few years, so I'm not convinced that everyone with a single ring drivetrain should be bolting on an SXg anytime soon. That said, it's an ideal add-on for any rider who wants the security and protection that a full-sized chain guide provides but without any of the drag and complication that usually comes part and parcel with that. - Mike Levy|
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