SRAM AXS Drive Train

When I heard leaks about this new family of components from SRAM, all I heard about was the stuff we’re conditioned to notice: the 10-tooth 1st position cog, the 12-speed cassettes; the new chain ring options. But there’s more to all of this. Having said that…

Yes, SRAM RED is 12-speed now. And the 1st cog has 10 teeth. This is the meat and taters of the new AXS ecosystem. But there’s much more to this new groupkit. Below I’m going to write about the chain and everything it touches.

Among what SRAM introduced: 3 new cassettes; and 3 new chain ring pairings. This is the heart of what it calls its X-Range gearing. The chain ring options are: 50/37; 48/35; 46/33. These are what SRAM is offering now for its road groupkits. So, no (obviously) these are not built around any traditional spider or bolt pattern. In fact these are direct mount chain rings and they’re bolted to the crank via 8 T20 Torx bolts. These chain rings come in pairs (except for the 1x rings).

And to be clear, these are road cranks. MTB cranks increase the Q factor and therefore your stance width by about 25mm (an inch). If I want a stance width like that I’ll ride a horse. These new cranks are spaced the same as SRAM’s existing road cranks.

But these rings are too small! Yes. If the 1st position cog had 11 teeth. But SRAM’s X-Range gearing relies on a 10t first position cog, and 12 cogs in the rear. The 3 available cassettes are: 10-26; 10-28; 10-33.

What’s the net result? If you’re running 53/39 and 11-25 on your tri bike right now, then you’d run 50/37 and 10-26 in X-Range shifting and you’d have an exact overlap, except a slightly higher and slightly lower gear than you’ve got currently.

What’s the point here? What’s the benefit to this? Several. First, it’s 12 speeds rather than 11 of course; second, that there are more 1-tooth jumps as you shift from cog to cog. The overall breadth of a gearing range is greater. The front derailleur shifting is better due through reducing the chain differential to a standard 13 teeth; and there aren’t any long cage RDs anymore, so, whatever noise those cages caused in the shifting is gone.

And finally, the capacity is there to make the gearing even lower, because direct mount chain rings can be made in any size (though this groupkit is already going to stretch the adjustment range of some existing frames that use a fixed FD tab).

What about efficiency? Doesn’t fewer teeth mean more friction? Well, marginally. Maybe. I’d like to see the data on that. Besides, as I did the rough math on this, I think I might end up running more total teeth, more of the time, if I’m in the big ring more often.

I mostly ride either a tri bike or a gravel bike. Right now I’m riding 50/34 on both bikes, an 11-28 on my tri bike, and an 11-32 on my gravel bike. I don’t have a gear low enough on the gravel bike. With this new groupkit I’d have a slightly lower using the 46/33 and 10-33. But I’m only trading in a 34x32 for a 33x33: 2 teeth lower. Fine, I’ll take whatever I can get.

Just, how about a 43/30, gents? I’d certainly run into FD tab issues with a chain ring set like that; bike makers would have to anticipate this. I just don’t think very many companies have awakened yet to the imperatives gravel demand. That said, SRAM with this launch offers some compelling 1x solution and I’ll talk about these later. Yes, you can mix and match cassettes with chain rings in this new groupkit.

There’s a new chain, it’s called the Flat Top. The hourglass shaped plates are gone. Why? If you’re going to make the chain thinner, you’ve got to add back that material somewhere to regain the strength. (Oddly, while the chain is thinner, there’s actually more space between the outside plate of the chain and the next cog than with 11 speed systems.)

There’s still a master link for joining (as you can see above), but there’s a new piston-press chain tool required to shorten the chain (to take links out). It’s a Park CT-3.3, replacing the 3.2. This tool is backward compatible for other chains, but the Flat Top’s bushings make your existing chain tool not compatible. Was this SRAM being overly conservative, as this company tends to be about spec that doesn’t tow its precise line? I called Park Tool. Yes, you pretty much do need this new chain breaker. If you’re in a huge hurry, tho, the tool itself is not quite ready. Park says March 1. Park Tool’s MLP-1.2 pliers will work on the master link.

The new RED rear derailleur underwent some big changes. It’s got oversized ceramic bearings and you can’t swap out the cage. Ceramic Speed is going to have to figure a workaround. But what’s more notable is that there’s a damper in this baby. Not a clutch. A fluid damper. It’s sufficient to be used as a 1x derailleur. What SRAM says is that a damper is not a clutch, but a clutch is a damper. SRAM just figured out how much you could build down the damper and yet get rid of chain slap. The net? At the RED level there is only now 1 derailleur, for both 1x and 2x SRAM systems.

The RD is, according to SRAM, faster, the shifting intervals are more precise. Just, when I had this in Sequential shifting there’s still the same thing as with Shimano’s Synchro shifting: the FD does its thing first, then the RD. This means when you shift to the small ring you’re spinning like a son of a gun until the RD downshifts a couple of cogs. I can shift my mechanical Campagnolo derailleurs simultaneously. This is the one thing about Sequential/Synchro that I don’t like. Somebody please eventually solve this. Speaking of shifting…

Let me say something here that I’ve never said before: SRAM’s shifting, with this new group, in Sequential, is at least Shimano’s equal. I’ve always felt Shimano had it over SRAM, particularly in front derailleur shifting. This new group closes the gap to zero, at least in Sequential (versus Synchro) mode, and I could find very little fault with SRAM’s shifting in any mode.

However, SRAM achieves this by taking some things away from you. Remember, SRAM’s new shifting is solved in part by removing options, such as the capacity to choose the tooth-interval between the 2 chain rings. One reason the SRAM-equipped bike I’m riding does better than my current bike with Di2 is that SRAM has the luxury of saying: You must have 2 rings, which we sell you only as a pair, and they must have a 13-tooth differential. No variance from that. My existing tri bike has a chain stay 2 centimeters shorter than the SRAM-equipped gravel bike I’ve been riding, and it has a 16t chainring differential. Nevertheless, SRAM’s shifting was impressive. Also remember…

I’m old enough to have heard this limited-gearing-option complaint before (and maybe I complained myself). Decades ago Shimano repented from allowing me to slap any cog I wanted on a cassette body, replacing this with discrete cassettes. One cassette. One range. No mixing/matching cogs of my choice. Why? Boiling it down, the shifting improved. Both Shimano and SRAM have made these calculations: remove options, increase shift performance. With that preamble, in SRAM’s case, when you look at the available X-Range gearing – and if you go through a gear inch exercise – this new system does not leave me wanting any options I previously enjoyed.

There’s a new driver, the XDR, for this drive train. The new SRAM cassettes require this driver. Most hubs today accept drivers and end caps that make them both thru axle and XD driver compatible. I spoke to a couple of wheel companies and they’d been apprised of this a while ago, and have already made their versions of XDR drivers. If you have existing wheels that are reasonably late model there’s a better than even chance they’ll accept an XDR driver. Just about all wheel companies now will accept an XDR driver.

Pricing! Well, it’s not cheap. But then it’s RED. Its electronic, hydraulic, ceramic pulleys, built-in Quarq and so forth. Groupkits start at about $2,800 and go to $4,100 depending on 1x or 2x, rim or disc break, power meter or no. These are retail aftermarket prices (and the groupkits are available now). Depending on how frugal you are on the frameset, handlebars, stem, seat post, saddle, wheels and tires, I could imagine seeing bikes outfitted with this groupkit selling in the $6000s for a 2x hydraulic, and then up from there. We’ll soon see. A number of bike companies are spec’ing the group already. I don’t know the downstream schedule, but Force in the AXS family by next year is not out of the question (this is me guessing).

What I cover in separate articles (not in this article) are: what AXS is, and the AXS app; SRAM’s new 1x offerings as a result of this launch; the implications of this new product line for tri (including what Zipp has done with aerobars); and Quarq (this brand has made the biggest wholesale change of all).