UDH - Standard or Scam?


UDH. Is it the future of derailuers? Or a scam to get everyone to convert to SRAM and carbon fiber bikes?



Possible Hangerless Interface design variants.pdf (781.4 KB)


  • hanger is readily available
  • hanger is cheap $10 vs $30 for typical alloy hanger
  • compatibility with future SRAM drivetrains


  • the hanger fin pushes the SS outboard a non-trivial amount
  • dropout must be at least 29Ø to handle the bore
  • UDH is clearly a standard for carbon bikes. Metal bikes need to jump through hoops to get it to fit.

What does the future holds?


  • Standard or Scam from big derailleur?
  • Let’s see your metal solutions!
1 Like

I made my own with the collaboration with Peter from Daambuilt. We wanted a simple not too expensive steel alternative, which at the time was almost none. It is made frome 17-4ph stainless and I really love it.

Right now I do not think it would work the the coaxial derailleur, I would need to make a few modifications.

I think having a universal hanger is really great, no one needs that much unique parts on bicycles.


Here’s a plate style I whipped up. Roughly 68g without the hanger. I’d want to press in the nub and insert to save time but not sure if the laser cut plate’s tolerance would allow it. Other option is to oversize the plate holes for sweating or welding the bits in. All parts should be stainless. SendCutSend says it’ll be $6.84 for one 316 stainless plate 4.7mm thick and get cheaper for multiples. Not yet sure the cost for the machined insert and nub.

The real trick is creating a matching NDS dropout. Ideally, one that could work with flat and post mount brakes. Working on it and using the recent Fairlight dropout design for inspiration.

As far as whether I like UDH, I’d rather tell customers that yes they can use the fancy new Sram derailleurs than argue with them why it’s not ideal for metal bikes. Gotta pick your hills to die on.


My experience? UDH is a scam for metal bikes. The price and availability of hangers are amazing, but they just introduce so many design compromises to metal dropouts. I have tried MANY times. All the dropouts end up big, ugly, and overpriced

The problem is the fin pushes the SS outboard 5-6mm compared to traditional dropouts. It results in a really clunky-looking system.

One way to get around the SS problem is to extend the dropout above the fin. But then you end up with a large, heavy, expensive dropout.

The only design I have been happy with is a 3D printed system:

The only reasons why it looks OK:

  • the NDS dropout is actually smaller than the DS to look proportional
  • the SS’s are printed on, so you don’t need any room for welding and brazing on the dropout
  • the SS’s flare from round to rectangle, to make more space on the dropout

However 3D printing is viable for everyone. The dropouts end up costing ~$200 and take a lot of time to customize for different sizes and models.


Classic lines and simple aesthetics are a big draw for custom frames. UDH ends up making the dropouts big, heavy, ugly, and expensive. We can’t compete with weight, technology, and futuristic look of carbon frames. I would rather we create our own well engineered, universal standard for metal bikes.

One last hot take :fire: :fire: :fire: 100% my opinion: I don’t like SRAM’s engineering culture. They don’t value the compatibility and longevity of their products. They create new standards whenever it best suits them. Here are some examples:

  • SRAM went on a marking blitz touting the engineering behind their brakes and defending their use of DOT fluid, only to quietly launch a mineral oil brake.
  • Instead of adopting a spindle standard, SRAM always makes their own. Why is GXP 24mm AND 22mm?
  • SRAM didn’t have the foresight to make XD compatible with road cassettes. So instead, they just created the XDR standard
  • For road groupsets, they pushed the XDR standard for the 10t cog. Smaller cogs on road bikes don’t make sense, and the pro teams, who would be strong enough to push a 10t agree
  • Sram’s 12s road and mountain bike chains are inexplicably not compatible
  • When Shimano released their 10-51T cassette, SRAM responded by releasing a 10-52T cassette that requires a new lunar derailleur standard

I think UDH is a great idea, but I just have a beef with SRAM :rofl:




When the 44mm headtube came out people stated is was “big and ugly”,. “too chunky”, “looks horrible”. But I’d say now we’re all a custom to it and it looks “normal” now. A chunkier dropout will look normal soon enough.


Melovelo Tech has their version available.

I was quoted $4.20 per dropout and 8.5 per hanger with a MOQ of 100. Less than MOQ is 2x price.


Allotec has a version also.

Allotec C82

No MOQ and quoted $5.40 per. No hanger option.


To me, it looks like the hanger is so beefy you’d lose the benefit of sacrificing the (cheap) hanger to save the expensive derailleur. Am I wrong? Or do we not use hangers for that purpose anymore?


It was a stop gap to the new direct mount and the active clutch in the AXS was designed to take the impacts rather than break a hanger. I don’t think they care about how non electric mech’s handle the impacts.

The next gen AXS will looks like it will break away from the mount on a large enough impact.


Also a info piece to be added on UDH is that the Sram made hangers are co-molded plastic and aluminium. These should have some more give to them than a full metal version that most of the alternate brand replacements are.


Good info. I’m assuming all mid/high end bikes will be electronic within the next few years, so it’s likely the smaller parts (ie us) of the bike industry will have to be adopt this (along with whatever proprietary thing Shimano comes up with).

I have yet to do a udh bike, will be interesting to see if it becomes a popular request.


Great suggestion! This might be the dropout that Chromag uses (or very similar):

I think the style of UDH dropout works looks good for bikes with a shallow SS and CS angle.

My post from the other dropout forum on a recent set of UDH drops I made.

I brazed a spacer on the face of the dropout plate to get the depth, then a friend with a CNC bored the hole more precisely. They work great so far. I think it would be possible to make this design with only laser cut parts and hand finishing (for about $12).

The next iteration is a bit better with a shouldered stainless piece brazed into the dropout plate, and I’m also going to recess the UDH 2.5mm into the plate to absorb some of the depth.

I really like the potential standardization of the UDH, but it is clunky and obviously designed for plastic bikes where the whole body could be absorbed into the stays. As noted above by Daniel, the UDH is so thick it pushes the drive-side so the stays are asymmetrical (at least in my basic design).

One more gripe to add to the list from @Daniel_Y - the UDH uses 1.5 thread pitch. The only axle I could find for my fat bike was a clunky option from Robert Axle Project, which I had to modify to shorten. Granted, not much industry support for fat bikes but it seems like 1.5 pitch on rear ends is unusual?

In defense of SRAM: in my experience RockShox forks have always been great at compatibility, serviceability and support.



The Allotec and Melovelo both look like decent options.

@Daniel_Y’s design looks really, really nice!

Here are more pictures of the Allotec ones.


The Chromag one is different, closer in shape to the Melovelo ones but have drillium in the backside.



Chromag uses their own proprietary machined SS dropout.

I have certainly struggled trying to come up with a more universal hanger that suits UDH however I am about to hit print on two custom jobs which I found it really nice to design around. Plus, how nice is it that you can have your clients get a hanger from any local bike shop instead of sourcing through Paragon or BFS when one gets bent? I am far from a fan of SRAM introducing new standards but I do think this is a good direction and I am hoping to get a few nice options out there soon.


I don’t think its a scam as such as its a better solution for making carbon frames. The big guys aren’t worried about enabling the small guys. Building mass produced plastic bikes is cheap and is how everything will be geared towards. Coming up with a design in metal thats not 3D printed is really difficult, but Ive come up with a plate style that suits my full suspension frames and Ive adopted a similar style for my road bikes. Ideally laser cut, final machine to braze in the DS and NDS inserts and slot stays for a very strong joint.


Great execution with those laser cut dropouts!

Does your insert on the non drive side offset the hub the same 7mm from the plate face as the UDH hanger on the drive side?


It’s great to have your own signature dropouts but the main reason Paragon is so great is they are a great price for what it is and they will support things into the future, like hangers and axles. Not to say things won’t get phased out but they won’t just suddenly disappear and will give us time to prepare.
If you’re sure the Cannondale or UDH hanger is going to be around in 5 or so years… have at it! But even though the PMW flat mounts are not a stunning work of art there is a non stainless paragon that is $63 plus $23 for the hanger unless you go stainless or Ti, so not too bad.

There’s a reason many bigger custom builders use hooded with the 5/8” bosses, but the process has to be so dialed especially in Ti when welding causes so much distortion they’re hard to keep “flat”. It’s so much easier and faster to use the Paragons and wait for the next “standard” that will hopefully be nicer to build with and look better too! :joy: