You’ve heard that revenge is a dessert best enjoyed cold with a local craft beer? Did you know that it’s even better when you garnish it with a crisp patent, US20180265169A1 in this case, and a side of fresh marketing?
All XKCD standards references aside, SRAM has a very good reason, all entirely above board, for their Universal Derailleur Hanger (UDH) program. The little motors that drive their AXS derailleurs up and down your cassette are capable of incredible precision. So much precision that future chain designs will make it possible for them to add multiple additional cogs onto that same XD driver.
The problem then? Well, it comes straight out of a fantasy novel, as the ancient powers of magic give way to a future of science and engineering.
MAGIC
Cable-actuated drivetrains, from lowly Shimano Alivio to the last cable-pulled vestiges of XX1 Eagle are magical. On one end you have a spooling ratchet. Said ratchet pulls a cable, of an unknown condition through about five feet of lined steel housing, also of unknown condition, attached to the derailleur at the other end of your bicycle.
Said derailleur is attached to a hanger that may, or may not, be stiff & true, and who can say how much slop is in the multi-pivot mechanism itself? And at the push of a button that whole system somehow combines to move a chain – yes, also of unknown condition and maintenance – a precise number of millimeters so that it sits squarely on the next cog you’ve selected. And it does that 8, 9, 10, 11, 12 times in either direction. And usually it just all works out. It’s pretty amazing when you think about it.
SCIENCE
In comparison, sending a Bluetooth signal to the little motor in your AXS derailleur to tell it to shift gears is downright simple-science. They’ve engineered a solid system that works fantastically as long as you remember to charge your batteries and keep an eye on your friends. Also, you should probably make sure you can afford to replace a derailleur if there is a mishap because there’s no just picking up an NX option to get you through like you can with the top-end cable systems.
The problem comes down to what level of precision they can expect from parts of the bicycle they do not control. AXS works much better attached to a piece of rebar than a piece of cheese and in the world of derailleur hangers, both options are well represented.
It’s clear then that having the AXS derailleur bolted to a stiff hanger, or better yet straight to a frame significantly reduces the margin of error in the system, which in turn will allow SRAM’s drivetrain engineers a greatly reduced margin of bicycle industry quality, manufacturing, and design shittiness that they have to plan around when programming AXS for more minuscule movements.
TRUNNION & YOKED REVENGE
The thing about said bicycle industry quality, manufacturing, and design shittiness is that SRAM has been eating a ton of it over the last few years. To be fair so has every other suspension manufacturer. Between the cost in dollars and reputation providing endless “my bike’s under a year old” shock warranty services and the cost in dollars and time designing more robust rear shocks that can take the extra abuse, well, who knows how many thousands upon thousands of dollars have been thrown on the fire worldwide.
Do they ask if the back end of your yoked frame is actually close to being aligned before they replace your body, shaft, and air can because the warranty against “defects in manufacturing and materials” is a year long? No. Do they ask if your tiny Trunnion bearings are roached before they replace your shock entirely because it’s too cooked to be worth servicing? No. They eat it. They all eat it.
But the difference between SRAM and every other suspension manufacturer is they also make rear derailleurs. The rear derailleurs of choice for so many buyers in every mountain bike discipline, and especially the well-heeled purchasers of the most skeletal carbon XC & trail bikes. And in the rear derailleur, they can find retribution in the crackling lamentations of their tormentors’ framesets.
The thing about those lightweight carbon bikes, as any carbon-frame repair shop will tell you, is that they shard themselves when you proper-smoke your rock solid, UDH-held, rear derailleur. Oh yeah, especially with a bit of side-loading in the process. The more spindly the frame, the more likely you’re paying for an expensive repair, forking over for a discounted crash replacement, or demanding a warranty consideration. Replaceable derailleur hangers simply don’t save frames anymore.
But what’s common in the repair shop, is not common through the ridership. Not common enough to feel properly paid back by all those frame manufacturers for the sideways suspension slag that passes through their design, QC, and QA departments. Schwarzenegger didn’t do the job, enter Robert Patrick.
Enter the direct-mount rear derailleur. Unlike Shimano’s long past effort, this derailleur’s not direct mounted to the frame on a replaceable, bendable, knuckle. Oh, oh, no. The SRAM direct mount derailleur hard-mounts to your frame’s dropout both inside and out. Then it integrates the AXS battery like a spine between the two mounting points, just in case your derailleur develops any self-sacrificial ideas of twisting before it tears your rear axle out the back or snaps the chainstay and/or seat stay.
This beauty of a system promises you both the crispest and most perfectly precise shifts and the fractured demise of your hard-ridden rig just in time for the new colourway to come out. Sorry, RideWrap, with the Universal Direct Mount (UDM) rear derailleur there’s really no point in frame protection for plenty of rigs. On the other hand with the average frame warranty getting ever shorter and more exact the carbon repair business will be booming. With every new technology, there are winners and losers.
I, for one, have seen enough positively pillaged ‘warranty’ shocks subjected to bad designs and tolerances that I’m cheering for SRAM. And I hope their competition at Fox, DVO, CaneCreek, and every other suspension outfit is too. UDH is clearly better, and it was born this way, so if your flex-stay gets splayed that has to be the frame manufacturer’s fault at least as much as SRAM is to blame for your fully f*cked six-month-old Trunnion shock.
The wrath of SRAM. To equip your enemies, to see them ridden before you, and to hear the detonations of their framesets. UDH is the sweetest mass vengeance in the history of mountain biking. Or, I mean, I guess it could also be a good way to remove an area of particular imprecision from your bike frame.