Amid the circus of Trojan hangers and load-bearing derailleurs, few of us paid any mind to SRAM Transmission’s humble front chainring. All it got was praise for its two removable bash guards, and scorn for its eight-bolt interface. But the T-Type chainring reflects some fascinating choices. Choices that prevented you from using any competitor’s chainring, and by extension, any competitor’s crank … until now. Wolf Tooth recently released Transmission-compatible chainrings that can be paired with many common cranks. Travis Engel talks about why that matters, even though his Cane Creek eeWings aren’t exactly common.
Photo: Josh Weinberg
Here we are, six months into a post-SRAM-Transmission society, and the world did not end. The Transmission (AKA T-Type) drivetrain has joined the party, and after a piercing record-scratch and a brief stunned silence, the room is again filled with a thousand different conversations about a thousand different things. Not unlike so many disruptive technologies that came before it, Transmission is becoming just another functioning, living, hopefully evolving part of the industry. And products like the Wolf Tooth Drop-Stop B chainring are a small but important part of that process.
If you’ve had better things to do than study the nerdiest aspects of SRAM’s new drivetrain, let’s uncover, layer by layer, why the chainring is nearly as controversial as the derailleur. First, there’s the tooth profile. Transmission’s road-style flat-top chains use rollers that are slightly larger than those of a traditional Eagle 12-speed chain. There’s also an updated chain-link profile that helped achieve Transmission’s “yes-you-actually-can-shift-under-load” performance. So, the chainring teeth needed to be shaped differently.
Next layer is the chainring’s 8-bolt direct-mount interface. The only non-e-bike chainrings with that new tooth profile are 8-bolt, not the long-standing 3-bolt SRAM has used on their mountain cranks for nearly a decade. SRAM’s road cranks currently use 8-bolt, as do their Quark power meters. Going 8-bolt meant SRAM won’t have to manufacture a unique, power-meter-compatible crank within the Transmission ecosystem, as they do for non-T-Type drivetrains.
Below that layer is the 55mm chainline. If you want to take a detour, have a read of my story on it. In a nutshell, the T-Type derailleur and cassette are optimized around the chainring sitting 55mm outboard from the bike’s centerline, not 52 mm like most Boost-148-dropout-spacing bikes. This allowed some frame manufacturers to add tire clearance, chainring clearance, and beef up the area around the bottom bracket. To accomplish that, SRAM’s T-Type cranks have a longer spindle, putting that direct-mount surface 3 mm further out than most 3-bolt cranks did.
The final layer is the chainring offset. That’s the chainring’s “dish,” allowing the teeth to sit on a different plane than the mounting surface. Before Boost, when we had 49mm chainlines, SRAM’s direct-mount rings had a 6mm inboard offset. In the Boost days, it was 3 mm. Now, because T-Type crank spindles are wider, a 3mm offset nets a 55mm chainline instead of 52mm.
This seems like a bunch of hair-splitting, but so much of what makes Transmission work so well (and it works really goddam well) is the precision of all of its interconnected elements. Does that mean it’ll all go to pot when it starts to wear out in a year? Maybe. Hell if I know. Ask me in a year. Bottom line is, for everything to function as intended, you need a T-Type chain to work with Transmission shifting, you need a T-Type chainring to work with the T-Type chain, and you need a T-Type crank to work with a T-Type chainring.
But here’s how the Wolf Tooth chainring unravels all that (it’ll be quicker this time): It’s got a 0mm offset, which means you can use a traditional-width crank and still get the required 55mm chainline. And it uses the old 3-bolt SRAM interface, which a lot of the traditional-width cranks in circulation are gonna have. And finally, Wolf Tooth used their Drop-Stop B tooth profile, designed to work with Transmission’s flat-top chain.
And it works great. I wish I had more interesting stuff to say about the actual function of the chainring, but it’s, ya’ know, a chainring. It holds the chain. And it does a fine job at it. There’s not any noise or friction you might sometimes worry about with non-standard components. And I never dropped a chain, though I can’t remember the last time I did. The only version of this chainring that I could use to bump my word count would be the oval one, but I opted for the round version. I have ridden Wolf Tooth’s oval rings in the past, and I’ve gotten along with them better than ovals from SRAM, Absolute Black, or Rotor. Mainly because they feel a bit more subtle. For me, those too-oval ovals are not a big deal at very slow, high-torque situations, but I get some bounce spinning them at even a moderate pace. Wolf Tooth’s shape keeps things a bit more calm. But whichever configuration you go with, as you’d expect from Wolf Tooth, the fit and finish is superb. These feel like any other U.S.-machined aluminum component you’d put on your bike. You put it on with some pride.
And that pairs well with what got me so excited about this chainring. Since I started my long-term review of the new GX drivetrain, I’ve had to leave my Cane Creek eeWings on the sidelines. That was hard. For years, I’ve been recovering from the trauma I suffered during the square-taper era by always having some type of fancy cranks. Whether they were Profile BMX or Race Face North Shore or all manner of XTR, from 952 to 9100. I’m sure the T-Type GX crankset could last me forever, and the DUB spindle was the first good new bottom bracket standard to catch on since Hollowtech II over twenty years ago. But I missed my eeWings. They’re the only things on my otherwise soulless bike that hold real emotional value.
And I’m not alone on this. Cranks have become an unlikely outlet for self-expression in bike spec. Look at the staying power of White Industries and Hope and even Middleburn. And the fascination with 5DEV and INGRID and Appleman. Only two of the boutique cranks I’ve mentioned (Cane Creek and 5DEV) use this chainring’s SRAM 3-bolt standard, but Transmission drivetrains are here to stay. I’d be very surprised if every small crank maker doesn’t follow Wolf Tooth in finding a way to work with it.
One thing this chainring won’t necessarily do, unfortunately, is make converting to a Transmission drivetrain significantly cheaper. You’d think that if you already have a standard-width 3-bolt SRAM crank, you’d save money if you don’t have to buy an 8-bolt T-Type crank. But it’s not that simple. SRAM offers a package deal for the Transmission derailleur, cassette, chain, crank, shifter, battery and charger. At the GX level, that’s $1,099. If you bought everything but the crank individually, that’s about $970. Add $76.95 for the (U.S.-made) Wolf Tooth, and you’re barely saving $50. Similar issue at the XO level, when this chainring plus everything but the crank goes for about $1,500 a-la-carte, and SRAM’s package deal with the crank goes for $1,599. So, why drag you into reading a story about a product with such limited applications? I guess because it’s a step in the right direction. It’s a way to give riders a little more freedom of choice. Maybe you like your crank’s narrow Q-factor. Maybe it’s worth spending extra not to give up on your carbon arms. Or maybe you’ve got eeWings.
- If you like your current SRAM-direct-mount crank, you can keep your current SRAM direct-mount crank
- Outstanding oval options
- Made in USA
- Have a different crank? (like Race Face Cinch) Wolf Tooth may make what you need!
- Doesn’t really bring down the price of a Transmission upgrade
- Black only, for now
- Some direct-mount interfaces still not served (Shimano, Hope) … yet.
See more at Wolf Tooth