One derailleur hanger to rule them all, one standard to tie them all together?
The derailleur hanger is a sacrificial part that connects the rear derailleur to the hanger. In the event of an impact, the derailleur hanger is designed to bend or break, protecting your rear derailleur and frame.
For many years, derailleur hangers were frame specific. If you broke one, it often meant a trip to the bike shop, where the shop would rummage through hanger drawers for a replacement – or they would have to order one.
That changed when SRAM released its Universal Derailleur Hanger (UDH) standard in 2019.
In this guide, we’ll walk you through what exactly SRAM UDH is, how it works, bike compatibility, and how to remove and install the mount.
We’ll also explain how it differs from Shimano’s direct mount standard and SRAM’s latest T-Type Eagle Transmission drivetrains.
What is SRAM UDH?
SRAM UDH is designed to unify derailleur hanger standards.
SRAM claims that consolidating different bar designs makes it easier to replace a bent bar and helps optimize shifting because there are fewer variables.
Like many other handlebars, the UDH is made up of two parts – the handlebar itself and what SRAM calls the “UDH bolt,” which secures the handlebar to the dropout.
On some frames you will need to use a “UDH frame washer” between the bracket and the bolt. It’s worth checking with your frame manufacturer to see if this is necessary, although it’s typically used on split-pivot designs from brands like Devinci, Orbea, Salsa and Trek.
You’ll also need to make sure you’re using a compatible thru-axle to attach the rear wheel. SRAM specifies that thru-axles should use an M12x1.0 thread pitch and 12.7mm thread length.
SRAM has made the UDH design an open standard. Aftermarket brands such as Wheels Manufacturing offer anodized options, with different color options to match your bike.
You are also not limited to using only SRAM rear derailleurs. The UDH is compatible with other MTB groupset manufacturers, such as Shimano.
Many brands have adopted the standard on their mountain bikes since the announcement of the UDH. Knowing that a hanger will almost certainly be available at most bike shops is much easier than having to scour the internet and find your specific derailleur hanger.
SRAM UDH is also starting to find traction on some gravel bikes, such as the Berria Belador Allroad, ENVE MOG and Scott Solace. However, it has yet to fully take off and is rarely seen on road bikes.
What happens to SRAM UDH if your chain gets stuck?
Rather than simply breaking or bending, SRAM designed the handlebar to pivot rearward in the event of a chain bind. It can also slide back slightly to help absorb an impact if the handlebar is hit.
If the handlebar pivots backwards, it can be pushed forward, often without having to loosen the thru-axle.
It also sports a hooked lip to push the chain back onto the smallest cassette sprocket if it slips. This prevents the chain from getting caught between the dropout and the cassette.
SRAM UDH compatibility: Which bikes use SRAM UDH?
Only bikes designed around SRAM UDH will work with the standard.
Unlike other cycling industry standards, such as bottom brackets or helmets, adoption of SRAM’s UDH standard among brands has been rapid. The standard was announced in 2019 and many performance mountain bikes now use it, such as the Trek Fuel EX, Scott Scale RC and Canyon Neuron.
SRAM has a bike finder on their website so you can check if your bike uses the standard.
How to install or replace a SRAM UDH on your bike
Step 1
Run the chain through the smallest sprocket. If your rear derailleur has a clutch mechanism, disable it.
2nd step
Remove the rear derailleur.
Step 3
Remove the thru axle from the rear wheel.
Step 4
Loosen the UDH mounting bolt on the outside face of the drive side bracket. Note that the bolt is reverse threaded.
Step 5
Remove the UDH from the inside face of the drive side tab.
Step 6
Thoroughly clean the tab with a rag and isopropyl alcohol.
Step 7
Install the UDH into the frame. Rotate it fully forward until the stopper contacts the frame.
Step 8
Install the bolt. If your frame requires a washer between the bracket and the bolt, be sure to install it before installing the bolt. Note SRAM specifically says not to apply prep to the bolt threads.
Step 9
Since the UDH bolt is reverse threaded, tighten it counterclockwise. Using a torque wrench, tighten the bolt to 25Nm, ensuring it is fully seated in the frame.
Step 10
Reinstall the wheel and rear derailleur.
SRAM UDH versus Shimano direct mount
SRAM wasn’t the first brand to try to unify derailleur hanger standards.
Shimano introduced their direct mount standard in 2012 when they released their Shadow style mountain bike rear derailleurs. This eventually transferred to the road when the brand released Dura-Ace R9100 and gravel with GRX.
Direct mount was designed to create a stronger connection between the frame and the rear derailleur to improve shift quality. Shimano also claimed to have sped up wheel changes.
Shimano has included a “B-link” to connect the rear derailleur to a conventional hanger as the Shadow derailleurs are positioned further back.
A direct mount handlebar sees the B link removed and the rear derailleur bolted directly to the handlebar.
Although a number of aftermarket products were available to fit a variety of bikes, the standard never really caught on in popularity.
Shimano appears to be developing a universal derailleur hanger similar to SRAM T-Type, according to a patent application filed in 2022. The patent shows a hanger that fits on either side of the hanger and is held in place by the axle.
SRAM UDH and SRAM T-Type
In March 2023, SRAM launched its T-Type Eagle Transmission MTB drivetrains.
Eagle Transmission does away with the derailleur hanger completely, mounting the derailleur hanger directly to the frame.
Although SRAM UDH was not required for these new suspensionless drivetrains, it did lay the groundwork for them.
This is because Eagle Transmission drivetrains are only compatible with bikes designed to the SRAM UDH standard.
In addition to ditching the derailleur hangers, Eagle Transmission drivetrains do away with the limit screws and B-gap adjustment on the rear derailleur.
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