Campagnolo is already there, and we’ve heard rumors another “S” has something in the works. Somewhere between vaporware and actual product, though, is a prototype SRAM Red eTap 12-speed that’s been flying across the interwebs lately.
One big difference between the two is the small cog on the cassette. Campy’s sticks with a standard 11-tooth cog and freehub body. SRAM’s doesn’t, opting to go with the smaller 10-tooth cog similar to what’s on their Eagle mountain bike groups.
The only way to create a cog that small is to reduce its inside diameter, which means the outside diameter of the freehub body must shrink, too. And that’s what XDR Driver bodies offer.
They also make cassette installation a lot easier because individual cogs and spacer rings aren’t used. Instead, they’re clusters or one-piece units that slip on easily and then lock into place using a traditional cassette lock ring and tool. No need for different axles or other standards, and you’ll still use a chain whip to take it off. For what it’s worth, that’s how the new Shimano XTR Micro Spline design works, too.
SRAM sent us a quick note to say that adoption of their XD and XDR freehub driver bodies continues to grow. Which is obvious if you’re a mountain biker since it’s the only way you can run their Eagle groups. And Eagle groups are everywhere now. However, roadies may not know as much about it yet. They’re about to.
This patent drawing shows how the cassette’s smaller cogs fit onto the reduced diameter section at the end of the Driver Body.So what’s the difference between XD and XDR? It’s pretty simple, the “R” basically just means it’s for “Road”. That’s because they’re different widths and designed to accommodate the different cassettes used for road and mountain. Here’s SRAM’s description:
“The XD interface is designed for mountain bike applications and maintains the same hub spacing and flange locations used for 8, 9, and 10-speed compatible HyperGlide® freehub bodies. The XDR interface is 1.85mm longer than XD and is designed for road hub applications. XDR maintains the same hub spacing and flange locations used for 11-speed road compatible HyperGlide freehub bodies. XDR driver bodies are compatible with all XD cassettes when the cassette is installed with a 1.85mm spacer behind it.”
SRAM set up this explainer page (and video above), and we shot another video (below) with them that runs through it all.
If you look at the quick progression of Eagle groups to cover all price points, we wouldn’t be surprised to see a complete suite of 12-speed road groups from SRAM by MY2022 (assuming that 12-speed eTap group is real, of course). And SRAM charges nothing to license the design, so any hub manufacturer can offer it.
So this “news” should really only serve to comfort you that if they do indeed go to 12 speeds, wheels will likely be available from all your favorite brands. Because the hub spacing and all is the same, it means you should be able to sub in an XDR unit onto your existing 11-speed compatible road hubs as soon as that brand makes one, so you won’t even need a new wheelset.
