Tailfin Adaptors: What they are, Why they matter, and How to pick the right one
When choosing a Tailfin Rear System for your bike, you will have two questions:
- Which axle does my bike require?
- Does it need an Adaptor? If so, which one?
Many bikes do not require an adaptor. For example, if the frame has no cap/bolt over the end of the Thru Axle and just features a 12mm opening on the driveside. This allows the Tailfin Thru Axles to be installed, just like the bike’s original axle, with no additional parts required.
What Part Does A Tailfin Adaptor Replace On My Bike?
Some bikes have an additional cap/bolt over the end of the Thru Axle, which holds the derailleur hanger and/or Thru Axle in place. These commonly have an 8mm hex opening, which is too small for the 12mm Tailfin Thru Axle to pass through. Instead, you’ll need an adaptor with a 12mm opening. Using a Tailfin Adaptor with a 12mm opening means the Tailfin Thru Axle can then be installed.
What Adaptors Do Tailfin Produce?
SRAM Adaptors
The three SRAM Adaptors are our most commonly required adaptors, largely thanks to the UDH (Universal Derailleur Hanger) standard. Introduced by SRAM in 2019, UDH standardised a part that had previously varied not just between brands, but between bike models within the same brand, and even between different generations of the same model.
Full-mount (or T-Type Transmission) derailleurs require the frame to be made with the UDH standard, but don’t require the UDH hanger itself. The attachment points are on either side of the frame and are held in place by a single bolt.
Conveniently, all three SRAM Adaptors use the same Thru Axle thread pitch of 1.0mm. You can choose the Universal Thru Axle (which includes the 1.0mm driveside part).
The Single 1.0mm Thru Axle is often too short for bikes fitted with Boost (148mm) hubs or full-mount/T-Type Transmission derailleurs. The Universal Thru Axle addresses this with the option to add one or two 8mm central extenders, making it suitable for wider hubs, hooded dropouts, or protruding brake callipers. The extenders should be added to the non-driveside part before threading the non-driveside and driveside parts together.
The Universal Thru Axle includes 4 thread pitch types (1.0mm, 1.5mm, 1.75mm, and Speed Release/Double Lead) – in case you want to use one axle across different bikes.
See our Complete Guide on the Universal Thru Axle for more information.
UDH Adaptor
The UDH Adaptor is the most commonly required adaptor among our customers. The SRAM UDH (Universal Derailleur Hanger) is a derailleur hanger which features on many frames, including those running Shimano or other non-SRAM groupsets. The UDH is a frame standard, not a groupset one, so don’t assume it only features on bikes with SRAM groupsets.
To check whether your bike has a SRAM UDH and therefore requires a Tailfin UDH Adaptor, look at the bolt covering the end of your axle on the driveside, which holds the derailleur hanger in place; if it has ‘UDH’ printed on it, you have the genuine SRAM part.
We worked with SRAM themselves to design a UDH Adaptor to specifically fit the genuine SRAM UDH and replace the original bolt.
If the bike is not fitted with the genuine SRAM part, you’ll need to use the derailleur hanger provided in the Tailfin UDH Adaptor Set to fit the UDH Adaptor.
You will need to swap the non-SRAM hanger for the Tailfin one provided in the Tailfin UDH Adaptor Set. Examples of brands producing their own versions of the UDH are Sonder, Cervélo and Santa Cruz; however, this may apply to other brands, too.
GX Transmission Adaptor (SRAM-A)
The Tailfin GX Adaptor is for bikes which feature SRAM’s Eagle GX T-Type Transmission/full-mount derailleurs. This Adaptor is also required for bikes with other SRAM rear derailleurs such as the Force 13-spd, Rival 13-spd, Eagle 90, Eagle 80 & S1000.
XX/XO Transmission Adaptor (SRAM-B)
The Tailfin XX/XO Adaptor is for bikes which feature SRAM’s Eagle XX/XO T-Type Transmission derailleurs. The SRAM RED XPLR (13-spd) derailleur also requires the XX/XO Adaptor.
There are no third-party full-mount/ T-Type Transmission derailleurs or bolts, as these are supplied with the SRAM full-mount or T-Type Transmission derailleurs. Just swap the existing bolt for the correct Tailfin Adaptor.
Choosing The Correct SRAM Adaptor
What’s included with the Tailfin SRAM Adaptor Set?
1 x UDH Adaptor
1 x GX Adaptor (SRAM-A)
1 x XX/XO Adaptor (SRAM-B)
1 x Tailfin Universal Derailleur Hanger (UDH)
1 x Washer (to use with UDH Adaptor)
1 x Hex Reducer (12-8mm)
The SRAM UDH Adaptor Set includes all the required adaptors you may need for a bike made to the UDH standard.
Other Adaptors
Some bikes require different adaptors, and these are specific to certain bike brands and models. These adaptors are not included in the SRAM UDH Adaptor Set and will need to be purchased separately. They are available on our Spares Page if purchasing separately from a Tailfin Rear System.
Locking Nuts
Locking Nuts are required on certain bikes with unusual derailleur hanger setups. The 1.0mm Locking Nut is predominantly used on some OPEN (U.P, U.P.P.E.R, WI.DE) and Santa Cruz bikes, but also occasionally on other manufacturers.
We offer 1.0mm, 1.5mm and 1.75mm Locking Nuts. These are threaded onto the Thru Axle once it’s been fitted to the bike.
Salsa Domed Nut
The Salsa Domed Nut is required for some Salsa Warbird, Warroad, and Cutthroat frames. It replaces the original part on these frames and allows you to fit a Tailfin Thru Axle to your bike. Some newer Salsa models use UDH frame standards now, so check our Axle Finder to see what your bike requires. When using the Salsa Domed Nut, you will also need the 1.5mm thread (included in the Universal Thru Axle or available as a single Thru Axle).
R.A.T. Adaptor
The R.A.T. Adaptor is for use only with bikes using the Rapid Axle Technology (R.A.T.) Axles (mainly Focus bikes). This adaptor replaces the R.A.T part on your frame and is to be used in conjunction with the Tailfin 1.5mm Thru Axle or Universal Thru Axle (which includes this 1.5mm part).
For Cervélo bikes, please contact us.
LOOK Adaptor
The LOOK Adaptor is required for certain LOOK bike models, although some newer models have moved across to UDH standards (e.g. 795 Blase RS 3 2026+).
Pearson Adaptor
Some Pearson bikes require a Pearson Adaptor to secure the Tailfin Thru Axle in the frame.
Use our Axle Finder to check what your bike requires.
Find What Axle and Adaptor You Require
We understand that choosing the right axle and adaptor isn’t easy. Bike frame standards frequently change, which can be confusing when the same bike models a few years apart require completely different axle and adaptor combinations.
If your bike uses a QR (Quick Release) Skewer, then you won’t require any additional adaptors. Just fit the Tailfin QR Axle as normal.
We designed a specific Axle Finder so you can search your bike make/model/year to check which axle and Adaptor (if necessary) are required. If you’re purchasing the axle and adaptor as part of a Tailfin Rear System order, these can be added during the configuration process* in the ‘your bike’ stage. When purchasing an axle or adaptor as a single item, these can be found on our Spares Page.
*Only 1.0mm Locking Nut and Salsa Domed nut are available in Rear System’s configuration. All other non-SRAM Adaptors are available on the Spares Page.
Can’t Find Your Bike In Our Axle Finder? Complete The Form Below:
Hex Reducer
For adaptors that require a 12mm hex/Allen key, we supply a 12mm->8mm Hex Reducer that will allow you to use an 8mm Hex key to install and remove our adaptors. The 12mm Hex size is rare on multitools, 8mm being much more common. It is important to take the Hex Reducer with you on any trip in case you need to remove your Tailfin Adaptor.
The Hex Reducer is included with your Tailfin Adaptor, but if you lose it, you can purchase it as a Spare.
Fitting Your Thru Axle and Adaptor
When fitting your Tailfin Axle, you can use our Assembly Guides for help. We also have a range of quick Video Guides.
Follow the steps below to install the UDH Adaptor:
(Skip this step if you have the genuine SRAM UDH)
FAQ
Any bike fitted with a UDH requires the UDH Adaptor. If the bike is fitted with a non-SRAM UDH, you will also require the Tailfin UDH from the UDH Adaptor Set, in order to fit the Tailfin UDH Adaptor. You can identify a bike with a SRAM UDH from the ‘UDH’ writing on the bolt.
Bikes with SRAM T-Type Transmission derailleurs will require the GX Adaptor:
– Eagle GX
– Force 13-spd
– Rival 13-spd
– Eagle 90
– Eagle 80 & S1000
See this video guide for installation.
Bikes with SRAM T-Type Transmission derailleurs will require the XX/XO Adaptor:
– Eagle XX
– Eagle XO
– RED XPLR (13-spd)
See this video guide for installation.
The torque settings for our adaptors vary, and the torque rating is included in our Assembly Guides.
If you can’t find your bike in our Axle Finder, please fill out the form underneath the Axle Finder above.
We can then use this information to help customers with the same bike in the future!
Yes, you can include the Thru Axle and Adaptor in your Rear Systems order during the configuration stage.
The Adaptors are available to order individually on the Spares Page.
Yes, the UDH Adaptor fits the SRAM UDH. This part is used on frames that run other groupsets, e.g. Shimano or Campagnolo. Bikes with a third-party UDH will need the Tailfin UDH. This is included in the Tailfin UDH Adaptor Set. Some Shimano Di2 groupsets feature a different derailleur hanger design; if so, please contact us.
