At the time of publishing this, the ink is still drying on our first-impressions of SRAM‘s debut boat-rocking direct-mount, electronic-shifting drivetrain concept, dubbed “Transmission.” Ever since, it’s been hard to get into a conversation with a bike nerd without Transmission coming up. Travis Engel is one of those nerds who can’t stop talking about it, so he was the perfect person to cover the surprise addition of a lower-priced GX group, which launched today. Read on to see what changed, what didn’t, and why this is such good news.
Before we start, I want to set some expectations. I have opinions about what SRAM Transmission means for the bike industry. You might even call them concerns. I’ve voiced a few of them in past stories, and I’ll probably voice more in the future. But I won’t be voicing a lot of them here. Partly because I want to focus on the news of the day. On exactly what GX AXS Transmission is, and how my experience with it went. But also because the launch of GX Transmission (GX T-Type) has softened my skepticism a bit. Part of that softening came from the eye-opening book about Transmission’s development that I got along with my test kit. But it’s mostly thanks to the GX T-Type group itself. It warms my heart that a lower-priced* T-Type drivetrain is being introduced this soon after the concept first launched at the XO and XX level. For some historical perspective, traditional (non-T-type) GX AXS wireless electronic shifting came out two years after the flagship AXS groups. The first Shimano XTR Di2 took just about as long to beget XT Di2. And the first Ultegra Di2 was three years behind Dura-Ace Di2. GX Transmission? About three and a half months. SRAM must have committed to this lower-price* option very early in Transmission’s development. They then dedicated enough manufacturing bandwidth to it that it will hit retail shelves within days of launch. Granted, GX Transmission is still just another fancy toy built for the overfed high-end mountain bike market. And it will not deliver the promises of Transmission to the masses in the same way that cable-actuated GX Eagle delivered the wide-range 1X drivetrain. But it’s a step in the right direction. And proportionately, it’s a pretty big step.*
I normally wouldn’t start a first-impressions review with pricing, but it sure was the first thing I wanted to know. Individual component prices are posted below, but $1,099 is the GX T-Type “groupset” price. That’s a rear derailleur, shift pod, cassette, chain, chainring, crank, battery, and charger. For comparison, the debut T-Type groupsets launched were XO, XX and XX SL, which started at $1,599, $2,049, and $2,199 respectively. Let’s do another history lesson to put those in context: When non-T-type Eagle AXS wireless drivetrains launched in early 2019, they were also sold in groupsets. There can be no apples-to-apples price comparisons for a few reasons, including the fact that the cassette construction has changed significantly, XX SL didn’t exist, and XO’s crank went from carbon to aluminum. But the XX tier serves as a pretty close counterpart. When it launched four years ago, an XX Eagle AXS groupset cost $2,000. Adjusted for inflation, that’s somewhere from $2,200 to $2,300 today, $150 to $250 more than its current T-Type iteration. On the GX side, it’s even harder to put in context because there was no factory “groupset” option at launch. But Amazon happens to sell a non-T-type GX AXS groupset for $1,005. That would mean about a $95 upcharge for T-Type, but we are talking Amazon.
This is a simplified price list. It does not cover the various power-meter or e-bike options. Groupset includes rear derailleur, shift pod, cassette, chain, chainring, crank, battery, and charger.
All this is to say that, though none of these drivetrains are cheap, Transmission doesn’t really appear to be ratcheting component prices up further than AXS did. And the line graph is just as horizontal when comparing complete bikes. I can’t give specific examples, but I talked to a few brands about their upcoming GX Transmission-specced builds. Most will be comparable to how you’d see a non-T-type GX AXS bike priced. For full-suspension carbon-fiber frames, alloy rims, and RockShox Ultimate or Fox Factory spec, the non-consumer-direct brands I polled will be selling their GX T-Type bikes for about $7,000. Again, not cheap, but not unprecedented.
The only bit of unfairness in the GX T-Type groupset pricing is that it still forces you to buy a crank. There are a few reasons for this, and they unfortunately require us to get into the weeds a bit: One is that Transmission was designed around a wider, 55mm chainline, a topic I recently covered. SRAM designed its “MTB Wide” crank configuration with Transmission in mind, so including the crank ensures you’re using the correct chainline. Also, the flat-top T-Type chain requires a different tooth profile than SRAM’s traditional X-Sync chainrings. All T-Type chainrings use SRAM’s road-style 8-bolt direct-mount interface instead of the MTB-style 3-bolt, so you need the matching 8-bolt crank anyway. But there’s no structural reason T-Type drivetrains need an 8-bolt interface. SRAM claims the move was made because their spider-based power meters require an 8-bolt crank, but I think the cost-conscious GX customer couldn’t care less about power meters. There’s also the possibility that SRAM will move all MTB rings to 8-bolt in the future for simplicity’s sake, but I’m disappointed that the GX T-Type launch didn’t include a T-Type compatible 3-bolt chainring. It would require some savvy on the consumer’s part because of the chainline issue, but it likely would have dropped that groupset price below $1K. Or, if you’ve got your own workaround, everything is sold individually, so let’s get granular and talk about what’s new.
At first glance, this looks just like the debut T-Type derailleurs, but it’s very different. There’s the subtle change to a steel pulley cage from XO or XX’s aluminum or carbon. But there’s a not-so-subtle change in battery position. Instead of being plugged into the rear end of the body, the GX T-Type battery is sort of docked inside the derailleur itself. It’s just as easy to get in and out, but it’s more protected from certain types of impacts.
This is related to another major structural change to the derailleur’s upper chassis; Instead of being machined from one large solid block of aluminum, it is made from multiple smaller pieces that are bolted together. This makes manufacturing it quicker and cheaper, but it also makes it heavier. Reading on, you’ll see that’s a theme throughout the updates made to the GX group. The goal was to make little or no impact on function other than adding weight. In fact, a pretty insignificant amount of weight. My GX derailleur weighed 473 grams without a battery. The XO derailleur I had on hand was only 24 grams lighter at 449 grams. I didn’t have an XX or XX SL derailleur to weigh, but SRAM claims 450 and 440 respectively. For reference, a traditional GX AXS derailleur I had on hand weighs 438 grams, but add the UDH hanger, and it’s back up to 465. Despite being unsprung weight, which has an impact on suspension performance, I’d say the GX derailleur’s added weight is worthwhile, and worth the cost savings. Many of the updates to GX T-Type make it feel like the “workhorse” group. A little more burly, but just as ready to get shit done. More importantly, the price drop was relatively significant. The XO T-Type derailleur, without battery, was $550. A GX is $400. Also, not a huge upcharge from the traditional GX AXS derailleur, which went for $390 … without a hanger.
This is a perfect example of a workhorse component. The original XO and XX Eagle 12-speed cassettes used one aluminum 50t (and later 52t) cog, riveted onto 11 other cogs that were machined from one giant steel block. It’s a beautiful hunk of metal, but very labor-intensive to produce. The XO, XX and XX SL T-Type cassettes have actually stepped back from this a bit, using a hybrid approach that machines only the smallest nine cogs out of steel billet and pins the 10th and 11th cog to the largest aluminum one. The GX cassette uses only forged, pinned-together cogs from top to bottom, though they maintain the other Transmission cassette’s use of narrow-wide X-Sync tooth shapes in all but the 21t “setup cog.” The forged-and-pinned approach does add weight, though. significantly more than the derailleur. My GX cassette weighed 445 grams. That’s 63 grams more than the 382-gram XO cassette. SRAM claims 385 grams for the XX cassette and 350 grams for XX SL. If you pair the GX cassette with the GX derailleur, that’s 87 grams of extra unsprung weight compared to XO. But it may have some metallurgy snobs cheering.
There’s a sort of “grain” to the microscopic structure of most metals. Machining metal ignores that grain, and can make for a less durable component. Pressing and forging metal is a better way of maintaining that grain. It’s one reason why, no matter the price level, Shimano has stuck to forged metal gears on cassettes and chainrings. Though a cassette’s unsprung weight is more valuable than parts found elsewhere on a bike, I think it’s worth the added durability when talking about an item so directly in harm’s way. The GX XG-1275 cassette is still pretty pricey at $250, but it’s a huge drop from the XO-level XG-1285 cassette, which goes for $400. And it’s not a huge bump from the traditional GX cassette, whose MSRP is $231.
Crank and chainring
The distinctive XO aluminum crank has a nifty little weight-saving window that resulted from a series of finite-element analysis experiments SRAM did in an effort to find out how much of the crankarm material really had to be there. The GX Transmission crank is much more traditional. Looking at it from the rear, it’s shaped like any pricepoint-focused aluminum crank. It still uses SRAM’s DUB spindle, though that spindle isn’t compatible with their less-expensive spindle-based power meter. You can get it in 165, 170, and 175mm lengths.
Again, its 8-bolt chainring interface is compatible with spider-based power meters. The direct-mount ring uses the same bash-guard interface as the rest of the T-Type cranks, and the crank comes stock with two polycarbonate guards. The ring used on GX cranks is the only direct-mount steel option in the Transmission lineup. I’ve run steel rings in other SRAM drivetrains, and they’re pretty impressive. They add some longevity without a huge weight penalty. The chainring is available in 32, 34 and 36t options, and they’re $42, compared to $74 for an XO ring. All together, in the 175mm version I had on hand, the GX T-Type crank, chainring, and polycarbonate bash guards weighed 743 grams. The XO crank I had on hand weighed 708 grams at 170mm with two guards. The GX crank is $200, compared to $300 for the XO crank.
No hollow pins, no hollow plates, this is likely as simple as a T-Type chain will ever get. It’s nickel-plated, but doesn’t have the Physical Vapor Deposition, or “PVD” coating that the XO and above chains have. That’s a high-tech corrosion-resistance measure that helps merit the XO chain’s $100 price compared to GX’s $50. I got 281 grams, plus or minus a gram, for my 112-link GX and XO chains.
Just dropping this in here for clarification. There’s no GX-specific controllers, since there really weren’t any acceptable cost-savings to be had here. The XO-level controller goes for $150. Or, you can still use the old-style GX AXS controller for $158. I actually preferred the feel of the classic shifter, but we’re getting into ride impressions, so let’s move on.
This is not a complete list. It does not include power meter or e-bike options. GX and XO weights are based on my real-world weighing on a consumer-grade digital scale. XX and XX SL weights are based on SRAM claims. All shift pod weights are based on my real-world weighing on a consumer-grade digital scale.
I’ll say it again, this is not a perfect spreadsheet. It doesn’t include all configurations, like different crank lengths, different ring sizes, power meters, e-bike configurations, with two bash guards, one bash guard, or no bash guard. but it gives you an idea of the delta between the options. And what stands out is that 123 grams is probably not going to be worth $500 for most people. Even if most of it is unsprung weight. And given how undetectable the performance difference between GX and XO proved to be, I think this will be the go-to group for most riders, and probably most bike brands.
I spent over a month on an XO T-Type drivetrain while testing the Santa Cruz 5010. And now, looking back at my time with GX T-Type, I’m realizing I can not point to any moment when I felt a difference in performance between the two. That probably shouldn’t come as a surprise. As mechanical shifters and derailleurs get less expensive, the tolerances in their component parts usually drop proportionately. As an extreme example, try clicking through the gears on a SRAM NX shifter and derailleur. Even brand new, there’s a noticeable sloppiness to the process. But with electronic shifting, there’s simply no room for jank.
Everything in my GX T-Type ecosystem responds as predictably as it does on XO. And that pairs well with Transmission’s capability to shift instantly under load. It’s an odd sensation, especially for someone who’s been trained for nearly 30 years to be kind to their drivetrain. For riders who tend to have trouble shifting with finesse, I think it’s an unquestionable win. But personally, I had to force myself to behave badly while evaluating GX Transmission. And although I was impressed when it regularly rewarded that bad behavior, it never felt quite natural. One of SRAM’s catchphrases around Transmission has been something like “The Harder You Pedal, The Better It Shifts.” I get what they’re saying. It’s certainly more encouraging the harder you pedal. I never got it to slip during my bad behavior. I just got more (or less) torque, immediately on demand. There’s also a standout improvement in the crucial, often desperate shifts into the 52t cog. T-Type cassettes have an 8-tooth gap ahead of its granny gear, as opposed to the traditional cassettes’ 10-tooth gap. That helped further forgive bad behavior, but there was no harm in shifting the old-fashioned way. Plus, unless and until I convert all my bikes to T-Type systems, it’s just safer for me to hold onto my good habits.
One bad habit I have and will probably continue to have is careless chainring-bashing. There are precious few ISCG-equipped frames that will take a bottom-bracket-mounted bash plate, and even fewer protection-equipped chainrings. In my short time on the GX T-Type crank, I had a couple otherwise troubling impacts. The polycarbonate plate slides nicely across rocks, and comes at a minimal weight penalty. Still, I’ll probably remove the one that faces the ground while I’m riding regular-foot. #goofyfoot4lyfe
Speaking of personal preference, I’m not a fan of the new controller shape. I know it’s not a GX component, but I think it bears mentioning. The two buttons are millimeters apart, and were given mirror-perfect orientation to one another. It forces me to put my thumb in position, and then think “up” or “down.” On the other hand, the revised paddle to the classic AXS shifter puts upshift and downshift on two totally different-feeling paddles in two totally different positions. It’s much easier to shift using muscle memory with the old shifter. But ask me again in eight months. I’m going to go through the summer and winter, trying to ride exclusively on this drivetrain. I’m looking forward to seeing how much an extended season will chip away at its performance.
But more importantly, I’m looking forward to seeing how much that performance chips away at me. The thing is, I really like my mechanical shifting. I like the physical understanding of how my thumb position relates to the derailleur’s position. I like the tactile feel of the double upshifts on my Shimano XT shifter. I like that, if I gently bump my knuckle on that shifter while pushing my bike up a hill, it’s not in a different gear when I go to pedal it. Transmission has introduced improvements that, as far as I understand, have little to do with electronic shifting. There’s the fool-proof installation process. The better compatibility with the increasing number of 55mm bikes. The more durable, more rebuildable derailleur. The incredible shifting performance under load. Maybe I’m just being optimistic. Maybe Transmission stops at GX AXS. But I think it’s too early to tell. It’s only been three and a half months.
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