MRP AMg Chainguide
Test Locations: Washington & British Columbia
Test Duration: 4 months
Compatibility: Bikes with ISGG-05 tabs and 28 to 36-tooth round or 26 to 34-tooth oval chainrings
Blister’s Measured Weight (including mounting bolts):
AMG SL, Small: 119 grams
- AMG SL: $99.95
- AMG SLR: $159.95
Reviewer: 6’, 170 lb (183 cm, 77.4 kg)
MRP has been making chain guides for decades, dating back to the days when setting them up was frequently a major headache. The chain guide market as a whole has gotten vastly more refined in the years since, but MRP still saw some opportunities to make their AMg upper guide + bash guard easier to set up and use, and the latest version has some clever new features to streamline the whole process.
Design and Compatibility
MRP offers three different versions of the AMg, spanning a range of materials, weights, and price points. The most basic AMg CS uses a stamped steel backplate but also features a different upper guide design than the updated AMg SL that we tested, as well as the top-spec AMg SLR. The latter two just differ in terms of backplate material, with the AMg SL getting an aluminum one, and the SLR subbing in carbon fiber to save a claimed ~30 grams. Since the AMg CS uses a substantially different design from the two fancier variants, and we’ve not tested it, we’re going to focus on the AMg SL and SLR here.
Both the AMg SL and SLR are offered for ISGC-05 tabs only and feature an adjustable upper guide that wraps over the top of the chainring to keep the chain in place, and then a fiber-infused plastic bash guard underneath to protect it and the chainring. The bash guard is available in two sizes, with the Small size covering 28 to 32-tooth round chainrings (26 to 30-tooth oval ones) and the Large handling 32 to 36-tooth round / 30 to 34-tooth oval rings. The backplate and upper guide are shared across both sizes, so you only need to replace the bash guard itself if you want to swap sizes down the line. The backplate doesn’t protrude above the upper guide no matter the chainring size setting (for cleaner looks), and the upper guide sits lower and (at least in my opinion) looks a lot better than the prior-generation AMg.
On The Trail
I’ve run the AMg on several different bikes over the summer and it’s been quiet and generally trouble-free, with no dropped chains during my time with it (despite deliberately running the derailleur with the clutch turned off for a while, for testing purposes). The bash guard has done its job admirably, taking some big rock strikes without issue. Going into the test, I’d wondered if the relatively small set screws that secure the sliding mechanisms would be up to the task, or if they’d come loose at some point, but I’ve had no issues there, either — everything has been very set-and-forget.
MRP has been making mountain bike chain guides for longer than just about anyone, and their latest iteration of the AMg does its job well. I’ve had no dropped chains, it’s quiet, the installation and setup are very easy, and the bash guard has shrugged off some big rock strikes without issue. The couple of times that I’ve gotten a small pebble wedged in the upper guide were a small irritation, but I think those were much more a flukey confluence of factors rather than an issue that is going to crop up for most people. It’s a good guide that’s notably easy to set up and comes in at a respectable weight and price.