Friday, 25 May 2012

SRAM XX1 revealed (kind of)

As press releases go, this one from SRAM is notable for its brevity:

ALL NEW SRAM XX1 FAMILY

  • New 1X MTB drivetrain
  • Designed for Enduro and XC racing
  • Innovative chain management technology including TYPE 2
  • Grip shift and trigger shifter
  • Widest range cassette available
And there are some pictures. And that's it. Which means I get to squint at the pictures, read between the lines, pontificate wildly and probably end up looking faintly daft in July when full details are promised. Let's take each point one at a time...

Fear not, there is a shifter, you don't have to push the mech with your finger
Here's a pic of the new group mounted on the Cannondale Jekyll of enduro specialist Jerome Clementz. Clearly the pic's meant to look like a cheeky long-lens spy shot, but it's SRAM's picture -- they're just good at not revealing too much too soon. So, checklist:

New 1X MTB drivetrain/Designed for Enduro and XC racing

This is obvious, and clear to see. It makes perfect sense, being exactly what increasing numbers of riders have been doing themselves without the aid of specific components for a while. There are even a few non-DH bikes available off the shelf with 1x10 setups -- certain Specialized Evo bikes and the Genesis Fortitude Race spring to mind. A couple of things to note from that first pic -- there's no sign of a chain guide, generally considered essential for homegrown single-ring setups, and the big sprocket on that rear cassette looks massive. By a happy coincidence, those are the two bits that SRAM has seen fit to supply slightly more detailed photos of.



Chainring molars?

Innovative chain management technology including TYPE 2

I'll deal with this one in reverse order. TYPE 2 we know about (although I've never mentioned it, because I'm slack) -- it's SRAM's roller-clutch rear derailleur tech to stop the cage flapping about over rough ground, reducing chain slap and minimising the risk of unwanted chain sheddage along much the same lines as rival Shimano's Shadow+ setup. That alone isn't going to be enough to keep the chain on, though, which is where the "innovative chain management technology" comes in. In this pic you can see the rather interesting teeth on the single chainring, which look like they're designed to engage with the chain links to stop it leaping off. I'd speculate that this may rely on a specific chain to work. UPDATE: See how the fat bits are on every second tooth? I think (and it's making my brain hurt a bit) that if SRAM sticks to even-numbered chainring teeth then the fat teeth while always line up with the wider gaps in the chain. It's certainly cleaner-looking (and should be less faff to set up) than a conventional chain guide setup. And it frees up bike designers, too -- there are some fairly elaborate ways of mounting a front mech out there that could be done away with completely.

Grip shift and trigger shifter

The existing XX group recently gained a grip shifter, a technology that it had appeared that SRAM was quietly putting out to pasture. Love them or loathe them, grip shifters are really light, so having one in a group pitched partly at XC racers is no great surprise. Both shifters will be new for XX1, though, for reasons that are about to become clear.

Insert own Spinal Tap reference here

Widest range cassette available

Another not-very-close close-up, but with some CSI-style zooming in (and squinting) this is clearly an eleven-speed cassette. There'll be howls of anguish from those of a retrogrouchy persuasion, but it was inevitable that someone would do it sooner or later. And if you want to keep a decent spread of ratios with just one chainring then more sprockets is helpful. Plenty of people are using 1x10 quite happily, but even with an 11-36 10 spd cassette you have to compromise a bit at one end of the range or the other (or a bit of each, for a kind of compromise compromise).

Another sprocket gives plenty of options. With one ring you'll be wanting range over closely-spaced ratios, and I certainly wouldn't expect the XX1 cassette to have substantially bigger jumps than existing 10spd setups. I'm pretty sure that that's a 10spd top sprocket on there -- extrapolate from there with similar ratio gaps and you end up with a 38 low. I reckon (yes, I'm waving a finger in the air) you could get away with a 40 without excessively unpleasant leaps.

You'd imagine if you're just having one chainring that it would make sense to have either what used to be the middle of a triple or something between the inner and outer of a double, which would be something in the 32-34 range. The one in the picture looks like it might be a 39 or 40, though, based on more squinting and counting teeth. I'm guessing again, but I'd expect a choice of rings -- a gravity enduro specialist is going to want bigger gears than an XC racer, and I further suspect that there's not much scope for different cassette options -- anything wider than a 10-40 is going to start having big jumps in it even with 11 sprockets. So I think there'll be smaller chainrings available. [UPDATE: Apparently it's a 10-42, and there'll only be one cassette option but chainrings from 28-38]

It'll be interesting (for certain values of "interesting") to see what the numbers actually are. Clearly there are things here that'll cause controversy -- 11 speed, proprietary chainrings/chain, can it really work without a chain guide? -- but I like the idea. Current 1x setups are all a bit of a lash-up to some extent (although they work), and a low-faff, off-the-peg option would be welcome. More details as they appear...

Commercial Break
Browse SRAM components at Chain Reaction Cycles, Wiggle, Evans or Merlin.

1 comment:

  1. If it's an even numbered tooth count on the chain ring, and a single ring, then yes, it'll be outside plates (I really want to say 'flange' here, by the way) on alternating teeth of the chainring predictably. so having alternating 'fat' teeth than somehow interact with these outside (as opposed to 'inny' plates) makes sense. Maybe some sort of rubber or Teflon coating for the fat teeth to retain the chain a little more than a normal chainring, but not enough to result in lots of friction. Or something.
    Either way, I wonder how easy it will be for aftermarket manufacturers to replicate these fancy new rings.

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