Aside from a crash, a mechanical failure, or an encounter with Sasquatch, the last thing you want when barreling at mach speed through a rock garden is to have your chain bounce off. Catastrophes aside, the distraction anxiety of chain slap also ranks high on the Unwanted List. Finally, protecting your one and only chainring from inevitable impacts on rocks and logs is mission critical in the middle of nowhere, and mission really-nice-to-have even when you're close to civilization.

Mountain Racing Products (MRP) has built a solid reputation for solving such issues, initially developing dependable, lightweight chainguides and bashguards for the gravity market, then iterating the designs for the trail ride and all-mountain segments as well as cross country use. They even have a cyclocross-specific 1x guide. The versatile G3 cuts a fairly wide swath across the gravity side of the spectrum with intentions ranging from aggressive all-mountain riding and enduro racing to downhill and freeride.

MRP adds better serviceability to proven formula

The G3 features MRP's proven three-point retention/protection matrix of an upper guide, a lower guide/chain tensioner and a bashguard or "skid" as the company calls it. New to the equation is the integration of the skid and lower guide into a single part, paving the way for Swingset--a clever pair of pivots designed to improve drivetrain serviceability, chainring swaps, and fine tuning. Throw the thoughtful use of just one hex bolt size (4mm) for all mounting and adjustment hardware, and you begin to see how well MRP thinks things through.

In addition to better serviceability, the sleek, integrated design of the skid and lower guide makes the G3 lighter and stronger than previous designs where these parts were separately bolted to the backplate. Made of durable polycarbonate, the lower guide comes with a sealed-bearing idler pulley installed. Fine-tuning the idler is as simple as loosening the mounting bolt and sliding it fore or aft then re-tightening. A captured nut on the back of the guide make these adjustments thankfully fumble-free and easy. MRP also includes the optional G-Slide block, a slippery urethane slider with no moving parts that can be swapped with the pulley for muddy conditions.



Since parts of both the upper and lower guides overlap the chainring to keep the chain secure, prior designs required full removal to get at the parts underneath. To change a chainring on the G2--this guide's predecessor--you'd end up with a hand full of small parts, bolts and washers which were fiddly to reinstall. With Swingset, you simply remove one fixing bolt from the lower guide and it pivots away. Remove one more bolt to open the upper guide and you have access to everything. The parts remain installed, vastly simplifying the act of servicing or changing the chain, chainring and cranks.

The nylon upper guide is also keyed to the backplate so it holds itself up during installation, eliminating the multi-finger balancing act of lesser designs. It too employs captured hardware, so the mounting nut is always at the ready. A small amount of adjustability is built-in for fine-tuning the guide's angle to help further minimize chain rub. A short piece of soft plastic tubing on the guide's tail quiets up-and-down chain slap against the unit itself. Finally, MRP took care to etch the backplate with a height adjustment guide based on chainring size. All one need do is align the top of the guide with the corresponding tooth number--in my case 33--and tighten the bolt. Simple.

G3 targets wide range of bikes, gearing options

According to MRP Marketing Manager Noah Sears--a pro downhill and enduro racer himself--the G3 is made for single-chainring bikes using 8-, 9-, 10- and 11-speed cassettes with standard-tension rear derailleurs. For newer clutch-style mechs--SRAM's Type 2 and Shimano's Shadow Plus--as well as for trail bike use, Sears recommends the company's AMG guide which eschews the lower guide for a slightly lighter, lower-friction setup.

The G3 is compatible with a wide range of current bikes, most of which are listed along with their mount type on the MRP website's Tech and Fit section. If you don't see your bike listed, call the company at (970) 241-3518 for compatibility info.

Aluminum, carbon and multiple mounting options available

The standard G3 features an aluminum backplate and is available in three mounting configurations--ISCG-05, ISCG and bottom bracket mount. It also comes in two chainring ranges--the 170 gram G3 Mini for 32-36 tooth chainrings, and the 190 gram G3 Mega for 36-40 tooth setups. Both are available in black or white and retail for $150.

MRP also offers a $200 version of the G3 with a carbon backplate in either ISCG-05 or ISCG mountings. The carbon not only knocks 50 grams off the standard version, but adds unexpected durability to the package. While carbon has a reputation for brittleness, MRP uses a special blend that flexes and returns after impacts. It's similar to the carbon used in outer space satellite dishes which are crumpled for deployment but spring back to their original shape when released in orbit.

The carbon backplate is available separately as an upgrade, but at $125, it makes more sense to buy a complete carbon G3 from the get-go if you're going to go the composite route.




G3 flaunts bomb-proof trail manners

I put the G3 through it's paces on my all-mountain sled--a 160mm travel Santa Cruz Nomad Carbon equipped with a SRAM XO 10-speed (non-clutch) rear derailleur, and a Shimano XT (2X) crankset hosting a single, 33-tooth Praxis Works chainring.

Across a wide range of trail and urban conditions, dislodging the chain proved impossible--even when doing stupid things to encourage such. Not only did the chain stay put during the course of more than two months of aggressive all-mountain rides, but drivetrain clatter was remarkably minimal.

"...the G3 handled the rough stuff like the Honeybadger handles a snake..."


Sessioning rocky, rough trail sections with the rear suspension intentionally locked-out did more to rattle my dental work than upset the drivetrain. Whether big hits or rapid-fire staccato stutter, the G3 handled the rough stuff like the Honeybadger handles a snake--which is to say, it don't care. In urban drop-to-flat scenarios, the results were the same--rock solid retention and chain slap-free performance. The G3 also performed flawlessly in more realistic trail-ride situations, impervious to disruption no matter the pedigree--uphills, flowy sections, and small to mid-size jumps and drops produced no ill effects.

Installation trials keep guide a few millimeters shy of perfection

So given the G3's awesome performance, light weight, smart features and reasonable price, what's not to like? Well, nothing MRP has any control over, and nothing that's not commonplace on any chainguide. Following the G3's instructions precisely, I set the spacing between the frame and the guide's backplate using the prescribed amount of spacers for the Nomad's 73mm bottom bracket shell. Unfortunately, once I had everything reassembled, the chain rubbed significantly against the upper guide when the chain was in the two highest gears. Figuring it perhaps needed to wear itself in, I left it that way for a few rides until I realized the rubbing wouldn't subside on its own.

In an attempt to remedy the situation, I added another spacer behind the backplate to push the unit away from the frame--MRP includes washers of varying thickness for this purpose. This simply moved the rubbing to my low gears at the other side of the cluster. After grinding up a couple extended steeps, I concluded it was worse than my original setup because it introduced more drag when I could afford it least--while climbing.

Frustrated, I finished my ride and gave a call to MRP's Mr. Sears who patiently and thoroughly explained the many variables effecting installation. The facing and/or alignment of ISCG tabs and bottom bracket shells can vary slightly in depth, influencing the side-to-side alignment of the crank, and ultimately the chainring in relation to the guide. Things like spindle length and chainline--which is different between 2x and 3x cranks, incidentally--come into play as well, and can easily account for the kind of rubbing issues I was having. The best manufacturers can do is give users a reasonable starting point and suggest some experimentation. In my case it took four variations of spacer combinations to get acceptable results--which is now a small but bearable amount of rub in both the largest and smallest gear.

Despite the huge advantage of MRPs Swingset for regular maintenance, there's no getting around the trial-and-error portion of the initial setup. During my four attempts, I dropped the spacers several times resulting in extended cussing and multiple do-overs. Note to MRP or Park Tool or somebody: Please make a (magnetic?) tool shaped like a BB wrench with ISCG-patterned washer perches you can use to hold spacers in place until you get the mounting bolts threaded--thanks.

The bottom line on the G3

Despite the setup niggles, the G3 is an excellent, well-designed, functional and lightweight chain retention and bashguard solution for aggressive riding. While my testing did not include true downhill use, its flawless performance in aggressive all-mountain environments suggests the discipline's heightened rigor would be well within its capability. With the likes of the Trek World Racing and Giant downhill teams, as well as all-time gravity legends Cedric Gracia and Brian Lopes putting time and input into the G3, you can ride assured it performs at a world class-level. Of all the stories I've heard from the World Cup circuit, Danny Hart scrambling away from Sasquatch after throwing a chain is not one of them.

Pluses:
  • Flawless performance
  • Quality construction
  • Smart, considered design
  • Swingset makes service a breeze
  • Lightweight
  • Excellent phone and on-line customer support
  • Sasquatch-resistant
  • Reasonable price
  • Carbon option
Minuses:
  • Potentially finicky initial setup
  • Minor chain rub
Pricing Configuration:
  • G3 with aluminum backplate in ISCG-05, ISCG or BB mount in Mini (32-36 tooth) or Mega (36-40 tooth) configurations, $150
  • G3 with carbon backplate in ISCG-05 or ISCG in Mini (32-36 tooth) or Mega (36-40 tooth) configurations, $200
More info at: mountainracingproducts.com; 970-241-3518