What is a Universal Derailleur Hanger? (UDH)

UDH is short for Universal Derailleur Hanger and is a system developed by SRAM with the aim of standardizing hangers across all mountain bikes. The UDH was launched by SRAM in 2019, and since then many mountain bike brands have adapted to this new standard.

SRAM's Universal Derailleur Hanger is made of two parts. The hanger itself and the UDH bolt, which secures the hanger to the dropout. Some frames also require a UDH frame washer, so it is best to check with your frame manufacturer to see if it is required.

The UDH is a thru-axle specific hanger. As a result it is important to make sure you have a compatible thru-axle to secure the rear wheel. SRAM says that thru-axles must use a M12x1.0 thread pitch with a thread length of 12.7mm.

Why Was the Universal Derailleur Hanger Developed?

The main issues with the old system prior to the UDH was that mountain bike brands would all develop their own hangers. Some brands would even have multiple incompatible hangers across their own models. With hundreds of bike brands doing this it created a huge problem for riders who would break their hanger and have to find a replacement. The hangers were oftentimes hard to source. If you broke one you would typically have to go to a local bike shop. If they didn't have a replacement in a parts bin, they would often have to order one in.

The UDH is meant to simplify this. SRAM says that if a rider has a bike with a UDH compatible frame and they break their hanger, it means they will be able to go into almost any bike shop and pick up a replacement UDH hanger. They are also readily available to order from a lot of online bike parts retailers.

What is the Purpose of a Derailleur Hanger?

The main purpose of a derailleur hanger is to be a sacrificial part in order to save the expensive derailleur if a strike were to occur. The derailleur hanger is typically designed to bend or break in the event of a hard impact. This protects your rear derailleur and frame, which helps with increased longevity and saves you money. For example, a SRAM UDH retails for around $23CAD, compared to SRAM rear derailleurs that can range from around $150CAD to over $400CAD, depending on the model. It's definitely a better option to replace the UDH instead of a rear derailleur.

UDH Design is Open Standard

By allowing the UDH design to be open standard, bike brands can sign up for a free licence. SRAM says the license gives the licensee the right to use the UDH patent and the UDH trademark. A bike brand can make a slightly different derailleur hanger with different features, but they must conform to UDH frame and hanger specification. This ensures that if a rider breaks their hanger, it can still be replaced with a standard UDH hanger. A benefit of this is that after market companies can produce universal derailleur hangers with anodized options, with a wide range of colours to match your bike.

Compatibility

With the UDH you are not limited to using only SRAM rear derailleurs. The Universal Derailleur Hanger is compatible with other mountain bike groupset manufacturers, such as Shimano and Box. This is a huge benefit to consumers since they are not limited to using just SRAM components with the UDH. By doing this SRAM has allowed the UDH to be even more universal and widespread throughout the industry. Since the launch of the UDH in 2019, many mountain bike brands have adapted to this new standard. Most major mountain bike brands now produce bikes that are UDH compatible, as it becomes more and more universal.

To make things even easier, SRAM has a bike finder on its website so you can check to see if your frame uses the UDH standard.

Advantages of a UDH

The Universal Derailleur Hanger has some advantages over a "traditional" hanger. SRAM has designed the hanger to pivot backwards in the event of your derailleur taking a hit. This feature could help save your derailleur and the hanger itself, and that is exactly what it is intended to do. Over time this will help save money as your derailleur won't break as often.

Additionally, the UDH has a feature that will prevent the chain from falling off the smallest cog. It has a hooked lip that will push the chain back onto the smallest cog if it slips off. This prevents the chain from jamming and results in a smoother and more efficient ride.

Our Take

After many years of having so many different hangers from a variety of bike manufacturers, it is nice to see a universal standard that is becoming more and more widespread. The parts are more readily available for consumers, and it creates less confusion at the same time. Since 2019 the UDH has taken off and we hope that it only continues to get more and more mainstream. The additional features that SRAM has included in the UDH also make the drivetrain more efficient. It seems like a no brainer for more bike manufacturers to produce bikes using the Universal Derailleur Hanger.

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