Ratio 1×12 Upgrade Kit Review: Drop-bar Eagle has Landed

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The Ratio 1×12 Wide Upgrade Kit allows you to easily hack an 11-speed SRAM road shifter to work with a 12-speed Eagle MTB derailleur. We installed and tested one with a well-used Rival 1 mechanical shifter and an equally worn Eagle X01 derailleur and cassette. Find details and our review here…

Over the last two years, we’ve been tinkering and experimenting with all kinds of hacks and Frankenstein mashups to enable a wide-range 1x drivetrain on a drop-bar bike. As we see it, road and gravel 1x drivetrains always seem to fall a bit short, both in range and the fact that they never have enough of a low climbing gear for loaded bikepacking. There are options, such as parts and tricks to make road shifters work with mountain derailleurs, and solutions to modify road derailleurs to work with larger cassette cogs. We’ve covered many of them in detail here. However, aside from the pricey AXS wireless group, there hasn’t really been a perfect solution to the 1×12 dirt-drop drivetrain conundrum.

Truth be told, I was a little burnt out on tinkering with mullet drivetrains after that big post last year. Alas, my friend Rusti, who’s also a local bike mechanic, told me that I had to try the Ratio 1×12 Wide Upgrade Kit. Unbeknown to me, on the day we posted the news release back in late October, he ordered one, installed it, and has already put a fair share of miles on it. He claims it was simple to install and works flawlessly. So, I got one of my own to resurrect some very well-used Eagle X01 parts and modify my Rival 1 DoubleTap shifter.

Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review


As most of you know, neither SRAM nor Shimano allow their DoubleTap or STI road shifters to interface with their 12-speed MTB drivetrains. This is quite frustrating and leads to a common remark on our website and elsewhere, “C’mon Shimano and SRAM… give the people what they want!” That is, for road shifters to work with mountain bike derailleurs. This would be a sure-fire way to get a perfectly functioning 1x drivetrain with all the range and low gearing that we need. Fortunately, the wizards at Ratio Technology in Cambridge, UK, made it happen.

Ratio Technology was founded in 2018 by Cambridge Engineers Tom Simpson and Felix Barker. During the course of another project, the two found themselves having to modify SRAM road shifters. As Tom put it, “It was a fairly hefty amount of R&D work to get everything working smoothly, and about the same time I was riding 1x with an 11-32 cassette (inherited from Felix!) on my cross bike. That’s just not enough range on a bike that I was also using on the road, so it was a simple step to realise the potential of using our shifter modifications to hook up road and MTB drivetrains.”

How the Ratio 1×12 Upgrade Kit Works

SRAM uses two different pull ratios on their mechanical groupsets. Exact Actuation is used on road and older mountain bike components, and X Actuation is employed on the newer 1x mountain bike components. X Actuation derailleurs require more cable to move across the cassette. The difference isn’t huge, but it’s enough that road shifters don’t have the capacity to pull that much cable. That means in order to use a road shifter, you have to drop the pull ratio down to Exact Actuation for it to be able to operate an Eagle derailleur. By adjusting this pull ratio at the derailleur and adding another speed to the shifter ratchet, Ratio was able to make this work with a variety of SRAM components. “Obviously we could have picked another arbitrary constant, but it makes sense to make our kit as cross-compatible as possible,” Tom adds.

  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review

Parts and Install

The Ratio 1×12 Wide Upgrade Kit comes with all the parts necessary to modify Red, Force, Rival, Apex, and S Series shifters (with both mechanical and hydraulic brakes) to operate Eagle X01, GX, or XX1 derailleurs. The kit includes a Ratio 12-speed ratchet, Ratio cable fin, Ratio cable adjuster, Spare cable fin circlip, M2.5 screw for shifter ratchet replacement (for use only on hydraulic brake levers), an emergency piece of mint candy, a couple of stickers, and a well-done, detailed instruction sheet that is written with both pro and home mechanics in mind.

The two main components are the shifter ratchet and the derailleur cable fin. The cable fin is what transforms the Eagle derailleur to work via Exact Actuation; it’s essentially a smaller version of the original, engineered to change the pull ratio. According to Ratio, the fin is made of 3D-printed nylon that has similar mechanical properties to injection-molded nylon. It was pretty painless to install on the derailleur and took only a couple of minutes.

  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review

The other main component is the shifter ratchet, which is the crux of the kit and replaces the 11-speed ratchet at the heart of the DoubleTap shifter mechanism. The Ratio ratchet is additive manufactured from stainless steel and essentially has the same overall design with one additional ratchet tooth to transform the same DoubleTap shift mechanism into a 12-speed shifter. The Ratio ratchet is stainless steel so it won’t corrode in wet conditions, unlike the SRAM version, but generally looks quite similar, aside from the now-ubiquitous and recognizable 3D-printed texture. According to Ratio, they’ve recently changed to a shot-blasted finish that is a little more smooth. The upgrade kit requires a few steps to modify the shifter. It’s not as easy as the fin replacement, but it’s not overly painstaking, either.

As you can see in the photos above, the install went fairly smoothly, all things considered. Ratio did an excellent job of providing detailed written instructions and three easy-to-follow and well-executed videos (see below). The most difficult part was step 2, removing the cover. There are four tiny screws that require a small, sharp, and thin bit to access. They strip easily if you don’t have the right bit, but I was able to remove them mostly unscathed. The rest of the process is fairly simple. I was able to install the Ratio upgrades in about an hour, and that included stopping and taking photos. It took about another hour to cable the bike and tune it up. It’s also worth adding that there aren’t too many dangers in the install process. It’s pretty straightforward and easy to mitigate any risk of bits and pieces sproinging out all over the place, or any other such calamity. As mentioned, the biggest potential issue is stripping the cover screws.

Ratio 1x12 Upgrade Kit Review


I must admit, this is hands down my favorite mechanical drop-bar drivetrain I’ve used to date. Most of the “hacked” mullets suffered in some manner—either the shifting wasn’t quite as smooth as I wanted, or the range and gearing were a little off. This one is dialed. But before I get to how it feels, note that I paired the X01 derailleur and cassette with a GX chain, flawless White Industries M30 cranks, and a Wolf Tooth Camo chaining system, which is great for being able to swap rings on the fly.

  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review

Although I’ve only had the Ratio 1×12 Upgrade Kit installed and in use for a short period of time, I was immediately blown away at how well it works. It feels the same as Rival 1 in the lever, and the shifting at the derailleur is crisp, precise, and as perfect as X01 was on my mountain bike. In addition, the 10-50T cassette offers a decent progression that works well for a variety of riding, ranging from road spins to gravel, and from singletrack to steep forest roads.

You might be concerned about durability, but after fiddling with and installing the parts, I didn’t feel there was much to be worried about. I suppose materials will need to stand the test of time for a true assessment, and I’ll make sure to update this down the road, but it’s worth noting that Rusti has about 500 miles on his and hasn’t had any issues whatsoever.

Worth the Upgrade?

Alright, let’s look at the cost. Obviously, if you have parts lying around, the Ratio 1×12 Upgrade Kit makes a lot of sense. It’s about 100 bucks, easy to install, and works really well. However, if you’re looking to build a drivetrain from scratch, you’re probably already doing some math to figure out if it fits your budget. So, let’s consider the roster of components in a few kit options:

GX Eagle + Apex 1 Mechanical (HG driver)

$125 – Eagle GX Derailleur
$100 – NX 11-50T Cassette
$162 – Apex 1 Shifter/levers
$100 – Ratio 1×12 Upgrade Kit
TOTAL: ~$487 (w/o calipers)

GX Eagle + Rival 1 Mechanical (XD Driver)

$125 – Eagle GX Derailleur
$215 – GX 10-52T Cassette
$170 – Rival Shifter/levers
$100 – Ratio 1×12 Upgrade Kit
TOTAL: ~$610 (w/o calipers)

GX Eagle + Rival 1 Hydraulic

$125 – Eagle GX Derailleur
$215 – GX 10-52T Cassette (or 10-50)
$410 – Rival 1 Shifter/levers (w/ brake calipers)
$100 – Ratio 1×12 Upgrade Kit
TOTAL: ~$850

X01 Eagle + Force 1 Hydraulic

$225 – X01 GX Derailleur
$385 – X01 10-52T Cassette
$620 – Force 1 Shifter/levers (w/ brake calipers)
$100 – Ratio 1×12 Upgrade Kit
TOTAL: ~$1,330

Obviously, the price varies significantly depending on what you have on hand and how fancy you want to get. In my opinion, the Rival 1 mechanical option makes for one of the best “mullet” drivetrains you can get. We’ve put thousands of miles on Eagle GX derailleurs and they seem invincible. In addition, the actuation and feel of Rival 1 shifter levers is paramount. But, then again, $615 is nothing to blink at. Even so, it’s really not too far off the mark from other well-known 1x drivetrains.

Ratio 1x12 Upgrade Kit Review
  • Place of Manufacture United Kingdom
  • Price £74.50 (~100USD)
  • Manufacturer’s Details RatioTechnology.com


  • Works perfectly to connect the venerable Rival 1 shifter/lever with reliable Eagle derailleurs
  • Enables a relatively affordable “mullet” 1×12 drivetrain—perhaps the best I’ve tried
  • Easy to install with Ratio’s perfectly executed instructions and videos


  • The price has increased since its introduction; it could be a hair cheaper
  • Ideally, the kit would include a precision Phillips bit for the tiny cover screws

Wrap Up

When I first heard about the Ratio 1×12 Upgrade Kit, I was a little hesitant and thought there might be a catch. I’ve tried a lot of hacks and tweaks, and there has always been a con or two. None of them are perfect. And I can’t quite say this one is perfect either, as Eagle components aren’t cheap, after all. However, this is about as good as it gets, in my opinion. It’s pretty easy to install, works flawlessly, and you get the quick, crisp shifting and excellent gear progression that Eagle is known for, as well as the reliability that comes with it. In addition, if you prefer SRAM’s DoubleTap lever mechanism to STI shifters, as I do, this solution is the bee’s knees. Now, we just need the price of GX components to come down a bit…

  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review
  • Ratio 1x12 Upgrade Kit Review


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