After spending a year going back and forth between bikes with and without SRAM Transmission, Travis came to a realization. In today’s Dust-Up, he writes about why Transmission compatibility will be mandatory on his next bike purchase, why that worries him, and why he needed that asterisk.
As you read the title of this Dust-Up, don’t picture me pumping my fist in triumph. Picture me shrugging my shoulders in blithe acceptance. It is what it is. To be clear, that doesn’t mean I’ve soured on SRAM Transmission in the slightest. I still think it is an utter marvel. I loved it immediately during my first-ride review. And after a year of ownership, I’m loving it in new, unexpected ways. But I also have new unexpected concerns.
If you need a refresh, Transmission is a drivetrain system made by SRAM, where the rear derailleur mounts directly to the frame and rear axle instead of to a replaceable derailleur hanger. It makes for a stouter connection and a derailleur that’s much harder to be knocked askew. Until recently, this concept would have been nearly impossible because there was no standard dropout or axle configuration that would allow one derailleur to mount so intimately onto so many bikes. But years before Transmission was introduced to the public, SRAM convinced several bike brands to redesign their dropouts so they would fit a universal derailleur hanger of SRAM’s own design called “UDH.”
At the time of its unveiling, UDH was sold to consumers as a way to solve a very real problem: The enormous variety of proprietary hangers often made them expensive and hard to find in a pinch. A UDH, on the other hand, is a fraction of the price of a specialty hanger and is stocked at most shops. UDH successfully fixed those problems for a lot of us, but we know now that it was primarily a way for SRAM to broadly standardize dropout design to their own specifications, ensuring Transmission compatibility on hundreds of bike models.
Despite the controversy around UDH and Transmission, I don’t think it could have been approached any other way. There needed to be a wide install base to justify the development and production costs of building an army of fundamentally new derailleurs that would be available for sale on launch day. And I do think it is a win for most consumers, at least in the short term. But it’s all pretty murky, to say the least. And my year with Transmission, however blissful, has crystalized some of its complex implications into tangible realities. It all started when I decided to build a new bike.
Using mostly spare parts, I wanted something dedicated to trail-work days and multi-day rides. I want a low standover so I could use the huge top-tube bag I just made for my primary bike. I want it to fit a 130 mm fork, ‘cause I had a pretty special one (and plan to write about it soon, hence the censor). And I wanted it to be affordable. That’s a lot of parameters, but I knew there’d be plenty of options … until I remembered UDH. Of course, any frame would work with my cable-actuated GX Eagle derailleur. But if I really like this bike, I’ll want to upgrade to Transmission someday. So, I guess this frame will have to be UDH compatible. In fact, I guess every bike I buy from now on will, too.
Truth is, the Transmission derailleur has spoiled me. It’s never gotten bent. It’s never developed ghost shifts or hesitations. And the unique T-Type cassette shifts better under load and works better with my frame’s 55 mm chainline. Lastly—and I’d argue leastly—Transmission is wireless. I would be very happy with a cable-actuated Transmission derailleur if SRAM ever releases one, though I’m not holding my breath.
*Editor’s note: Soon after publishing this, spy photos started circulating of a mechanical Transmission-type SRAM derailleur out in the wild. That doesn’t indicate when or if one will come, but it does indicate SRAM is putting resources into making one. If we hear official news about it, you’ll be the first to know … once SRAM lifts the press embargo.
In the meantime, I’ll delight in the fact I’ll never need to replace my cable and housing. But like so many upgrades, I find I appreciate Transmission’s benefits the most when they’re gone.
Sometimes I ride my touring bike or my bike-park bike. Sometimes a non-Transmission-equipped test bike crosses my desk. And I never turn my nose up at any of them. I’m extremely fortunate to have a collection of diverse bikes, and a career that gives me temporary access to countless more. I’m not thinking about the rear derailleur when I pull a bike down from its hook. But sometimes, I’m thinking about it on the ride.
The advent of wide-range cassettes has made hanger and derailleur straightness and adjustment more important than ever. It’s only a matter of time before something gets bumped just hard enough to cause issues way out at those 40- to 50-tooth rings. I have a hanger alignment gauge, a healthy stock of fresh cable and housing, and 18 years of shop experience. And yet, problems still arise. But so far, not on my Transmission-equipped bike. I can hear the rumbling in some of the audience. That we’ve survived a century without $400 derailleurs. That adjusting a derailleur once in a while is not a big deal. That I must just be a bad mechanic. And they have every right to rumble. But I’ve seen the other side, and I don’t want to go back. And if enough people feel the same way, I don’t know if I like what that means for bike design.
Adopting UDH was sort of a no-brainer for mainstream brands. They have to cast a wide net to survive. But many small brands survive by offering things that the mainstream doesn’t. And some of those things aren’t compatible with UDH.
“I like a universal hanger, I like the fact that a Transmission mount is sturdier. I think hangers should have been a lot stiffer from the beginning.” Nick Neuhaus is founder of Neuhaus Metalworks, one of those small brands. “What I don’t like is the widening of everyone’s bikes.” Neuhaus just released a UDH-compatible gravel bike, and their UDH dropout is one of the most compact I’ve seen. But I can tell he’s more than a little conflicted about the whole thing.
That Neuhaus dropout was designed by Daniel Yang of ARTEFACT. But in the video above, he compares it to another custom dropout he made, with a custom hanger. It’s more flush and compact. With designs like these, made with rigid steel or ti frames in mind, the dropout doesn’t stick out as far and the driveside chainstay can move inward. And if you care about symmetry (which most craft cyclesmiths do), the non-driveside chainstay can, too. That allows for better heel clearance and a narrower Q-factor. I have zero opinion on Q-factor, which is a good thing. Given where modern mountain bikes are trending, I also have zero choice.
“You can tell the UDH hanger was built for a full suspension mountain bike,” Neuhaus says. And I see what he means. It’s a chunky little thing, and the dropout around it needs to be chunky, too. The aluminum- and carbon-dominated full-suspension market is not afraid of chunky parts, nor the frame-design gymnastics required to accommodate them. They already have tubes and yokes and rockers and pivots going in every which way. There’s no perfect diamond shape to preserve. “It’s easy to hide asymmetry on a full suspension bike,” Neuhaus says. “Or to just own it.”
And anyway, the full-suspension market’s quest for stiff pivots and wide tires has overruled the quest for narrow Q-factors. Transmission’s default 55 mm chainline overruled it even further. If steel and ti makers like Neuhaus want to offer Transmission compatibility, they’re forced to fit into the same box that aluminum and carbon makers have been fitting in for years.
And fitting ain’t easy. I discussed this with Calvin Norstadt. He’s the son of the founder Mark Norstadt and current CEO of frame-parts supplier, Paragon Machine Works, who offers multiple styles of UDH dropouts for small frame makers. On top of being forced into those size, symmetry, and style compromises, builders need to jump through a lot of hoops just to be compatible. “The precision with which you have to build your bike has taken it one step further,” Norstadt tells me. “You need to hold tolerances within 1,000ths of an inch. That was a big change.” And the demands aren’t just on a micro scale. UDH compatibility imposes limitations to dropout shape that, no matter how slowly and clearly Norstadt explained them, went totally over my head. I can only imagine how frustrating it must be for framebuilders who were used to much more creative freedom.
There’s also the dwindling number of chainstay-length flip chips. Many bike brands are adopting size-specific rear-center lengths, but for some riders, rear-center length is about preference, not fit. Christoph Süße is der Unternehmensinhaber / Geschäftsführer at Sour Bicycles. Sour also recently added UDH compatibility to their bike lineup, and also has reservations. Süße talked about all the same stuff Neuhaus and PNW did, but echoed my mourning of the dropout flip-chip “And I have not even started with adjustable chainstay length as it is rather common on the longer travel mtb crowd,” explains Süße.
But here’s the thing. None of this really matters to me. I don’t make frames. I don’t need a narrow Q-factor. There are plenty of bikes with chainstay lengths I like. And most importantly, I couldn’t care less how my dropouts look, nor that they look like everyone else’s. A common complaint you’ll hear about UDH from ti and steel frame manufacturers is that it’s ugly. I just don’t get it. Who decides what’s ugly? And why does it matter?
Aside from the Q-factor and flip-chip arguments (which I think effect a relatively small minority), I haven’t been convinced during my brief reach across the aisle that this UDH bloodless coup is making any bike meaningfully worse. But I still have a bad taste in my mouth, and not because I’m recovering from COVID. If I had to explain what’s so unsettling about my newfound allegiance to Transmission, I’d have to go back to my first iPhone.
That humble little 6s could seamlessly integrate with my laptop, my coworkers, and my coworkers’ laptops. My Samsung could not. In the years since, I’ve formed relationships with other Apple products. I use Apple Wallet, FaceTime, and Air Drop … when it works. And I use a Macbook. Owning an iPhone makes my life easier in ways no other phone ever will. And for years, Apple has been taking steps to keep it that way.
These are the patent-application drawings for the SRAM Transmission direct-mount derailleur (left), and a yet unreleased Shimano direct-mount derailleur (right). I don’t know the ins and outs of patent law, but I do know that Shimano’s design requires an entirely new dropout shape. SRAM understandably took steps to keep other brands from using UDH’s hard-won ubiquity to sell competing takes on the direct-mount derailleur concept. They did the same thing with their XD cassettes. The freehub body is open source, but e*thirteen had to find a loophole in the patent to make their own XD-compatible cassette. SRAM was probably more careful in their patent wording this time around. This is going a bit beyond the scope of this Dust-Up, but I think it’ll be a long time before we see a worthy competitor to Transmission with as wide an install base as UDH, if we ever see it at all.
I hope we do see a competitor, though. If we don’t, maybe I’ll regret writing this. We wouldn’t have Transmission if it weren’t for the decades of leapfrogging that preceded it. If that’s able to continue, I can’t even imagine what’s going to come next. And whatever it is, if it doesn’t require a Transmission-compatible frame, I still stand by the title of this Dust-Up. That’s what the asterisk was for.
If you’re new to this series, welcome to The Dust-Up. This will be a semi-regular platform for Radavist editors and contributors to make bold, sometimes controversial claims about cycling. A way to challenge long-held assumptions that deserve a second look. Sometimes they will be global issues with important far-reaching consequences; other times, they will shed light on little nerdy corners of our world that don’t get enough attention.
