Ratio Mech rear derailleur review: The best mechanical shifting I’ve ever experienced
When you want the shifting performance of electronic but don’t want to charge batteries.
UK outfit Ratio Technology made a name for itself with aftermarket ratchet kits for SRAM DoubleTap road levers, but it revealed far grander ambitions when it announced its Mech rear derailleur for mountain and gravel bikes last year. A showcase of local CNC-machining and 3D-printing technology, the Mech promises a mechanical system that rivals the precision and consistency of electronic systems, but with more reasonable costs, less weight, and better repairability than battery-operated systems (and of course, no batteries to recharge, either).
Truth be told, the Mech isn’t for everyone. However, if what you’re after is outstanding shifting performance and you prefer the tactility and mechanical simplicity of a cable-based system, look no further.
This is how mechanical shifting should always be.
A matter of fidelity
Modern electronic drivetrains were originally conceived not as a way to speed up your shifts or reduce weight, but rather as a means to gain consistency in shifting performance. As component brands started packing ever more cassette sprockets on to the same amount of freehub body space, it naturally became more difficult to maintain the level of precision required for reliable chain movement.
Consider the numbers: For modern 12- and 13-speed cassettes, each shift comprises less than 4 mm of cable movement. The exact figure also varies not only by component brand and model, but by specific sprocket position, and worst of all, it’s the climbing gears where you’re often putting out the most torque (and when you’re least tolerant of skipping) where the cable pull tolerances are often the tightest.
Now consider that those sub-4 mm “signals” are transmitted via a meter-long piece of wound steel cable sliding inside a plastic-lined housing. Steel cables and housings are prone to wear and/or can get contaminated with water and grit, derailleur pivots can develop slop or corrode, and steel ratchet rings and pawls shifters can get gummy and stick. Add it all up, and it doesn’t take long before the mechanical signal sent by your fingers can degrade substantially by the time it gets to the derailleur at the other end. A difference of just 0.5 mm – about 0.05% of the total length – can easily mean the difference between a solid shift and a missed one.
In essence, mechanical shifting is like a game of telephone played out on your bike, and the message heard by your derailleur may not always be exactly the same as what the shifter sent.
Electronic shifting was designed to remove that uncertainty, replacing that mechanical cable movement with a digital signal to ensure that the command received at the derailleur is always the same as what was requested by the shifter. Tens of millions of electronic systems later, it’s clear that that signal was received loud and clear in the enthusiast marketplace, too.
But is electronic the only way to get that sort of signal fidelity? What if you could instead optimize a mechanical system to either remove or minimize those signal distortions such that you could get the reliability and consistency of an electronic drivetrain, but with the tactility and field serviceability of a mechanical setup?
That’s precisely what the folks at Ratio Technology in the UK have set out to do with its Mech rear derailleur (and yes, I understand that essentially translates to “derailleur rear derailleur” in certain markets, but so be it).
The Mech, dissected
In many ways, the Mech isn’t all that different from SRAM’s long-standing 12-speed Eagle mechanical stuff with its straight-parallelogram layout, a pulley cage clutch built into the lower knuckle, and a large offset to the upper pulley to maintain a proper chain gap across the full cassette range. Ratio has even incorporated a tool-free cage lock for easier wheel removal and installation (apparently without violating any SRAM patents).
Where the Mech sets itself apart from the norm is in Ratio’s obsessive approach toward eliminating slop and flex.
For example, while nearly every derailleur on the market relies on an array of solid bushings and pins for the body pivots, the Mech’s parallelogram links instead rotate on Enduro stainless steel cartridge bearings that are secured with larger-diameter threaded bolts and shafts. Similar to how placing your feet further apart is inherently more stable than a narrower stance, the pivots themselves are also very widely spaced for more inherent stiffness. Even the machined aluminum pulley cage plates are fully triangulated and well-braced to minimize flex between the oversized 14T upper and 16T lower narrow-wide machined acetal (more commonly known as Delrin) jockey wheels.
It’s a decidedly burly-looking thing visually, or as burly as a rear derailleur can get, I suppose. But from a functional standpoint, the upside to all of that is a big reduction in slop, bending, and friction as compared to what you’re probably used to seeing from cable-actuated rear derailleurs. If you’re thinking to yourself that much of this seems similar to what SRAM has already done with its Transmission rear derailleurs, you wouldn’t be entirely wrong. Stiffness was certainly a major goal there, and a big reason why those rear derailleurs shift as well as they do (as well as why they tend to be so heavy).
Ratio has also gone with a modular approach for Mech to accommodate a broad range of shifter and cassette applications. Every configuration features the same main body, but swappable mounting arms are available for either traditional or UDH-style dropouts; there are both long- and medium-cage options for mountain- and gravel-sized cassettes; and although the Mech is only designed for 1x drivetrains, there are eight different cable “fins” to ensure proper shifting for almost any combination of Shimano and SRAM shifters and cassettes you decide to run.
Want to run a SRAM 12-speed trigger? Of course – and Ratio has fins to handle SRAM 12-speed XPLR, Eagle, or Transmission cassette spacings. Looking for a new rear derailleur for your gravel bike with Shimano GRX levers and an XT 10-51T cassette? No problem. Combined with one of Ratio’s retrofit lever ratchet kits, you can even run an older SRAM DoubleTap road levers with the latest 13-speed XPLR gravel cassettes. Ratio says additional fins are in development, too.
That modularity affords another big plus: Ratio not only says that Mech was conceived from the outset to be repairable, but it’s designed to be fixable in the field using nothing more than a common multi-tool. It’s not just pulleys and cage plates that are available, either. Ratio has nearly every small part available for purchase (including links, upper mounting arms, knuckle assemblies, springs, clutch guts, and so on) – for reasonable prices, no less – and there are even tutorial videos on its web site that guide you through the replacement process step by step.
There are lots of clever details, too. Visual guides are incorporated into several plastic parts to help ease setup and adjustment, the cable fin includes a handy slot that tidily tucks the cable out of harm’s way, and laser etchings on the back of the cage plate offer a built-in reference for gauging the B-gap so there are no separate jigs required. Even the cage lock function is elegantly designed, featuring no moving parts.
Not to be overlooked is where Ratio is making the Mech. The company is proudly based in the Lake District of northwest England, and nearly every piece of the Mech is either made in-house or sourced from nearby. All of the machining is done directly at Ratio HQ (including all of the aluminum bits, the pulley wheels, and clutch internals), and while the 3D-printed nylon parts are made further south in Kent, it’s still the American equivalent of having stuff trucked over from the next state.
Despite the oversized proportions, Mech isn’t all that heavy. With UDH-compatible mounting arms, a long pulley cage, and a Shimano 12-speed cable fin, my sample came in at 370 g. Granted, that’s a substantial 130 g heavier than an XTR RD-M9100-SGS mechanical rear derailleur, but Shimano’s unit is also a lot flexier and flimsier. A closer comparison would be SRAM’s much beefier Eagle 90 Transmission rear derailleur, which is about 25 g heavier than the Mech and not built to the same level of attention to detail.
Alternatively, if you want to compare to the SRAM XX SL Eagle Transmission electronic rear derailleur, the Mech is a scant 10 go or so lighter once you account for the requisite cable and housing, or about 40 g lighter if we’re looking at GX Eagle Transmission.
Nor is the cost quite as bad as you might expect, either.
Ratio prices the Mech at £288 / US$384 / €330 / AU$555 (without VAT for applicable areas), which is decidedly premium for a mechanical rear derailleur when you compare to a Shimano XTR or even the similarly boutiquey Madrone Jab. But yet it’s almost the exact same price as a Vivo Cycling Enduro (and a lot less expensive than Vivo’s new Air model), and compared to a SRAM XX SL Transmission or Shimano XTR Di2 electronic rear derailleur, the Mech starts to look like a downright bargain.
Whatever the price, what you unfortunately won’t find on the Mech are color options – at least not yet. Ratio teased blue-anodized variants during the prototype phase, but currently the Mech is only offered in black. Silver versions are on the near horizon, though
On the trail
Alright, let’s get into the part you really want to hear about: how’s the Mech perform out on the trail? TL;DR version: This is the best cable-actuated shifting I’ve ever experienced – and I’ve used almost everything.
The holy grail of mechanical shifting is set-it-and-forget-it: the idea that you can do your initial setup and adjustments, and then never touch it again with no degradation in performance throughout. With the caveat that it’s been an extraordinarily dry past few months in Colorado (though ultra-fine dust can be just as detrimental to shifting performance as water and mud), the Mech has certainly fit that description. I paired my test unit with a Shimano XTR trigger shifter, XTR chain, and XTR 10-51T cassette, Yokozuna slick stainless steel cable, and Shimano SP41 housing on a Pivot Switchblade trail. Compared to an all-XTR drivetrain, the Mech-enhanced version has been far less finicky with not a single tweak of the barrel adjuster required since that initial installation.
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