UDH is the big bike buzzword these days with SRAMs latest direct-mount Transmission derailleurs requiring it but Sour thinks theyve found a better way to future-proof their steel bikes. Instead of fully adopting the universal hanger standard, Sour tweaked it a bit so they could still make a lightweight dropout well-suited for small-diameter steel tubes, but with T-type direct mount derailleur compatibilitySour goes Not-UDH for Transmission compatibility(Photos/Sour)OK I know, I know we finally got a universal derailleur hanger standard that brands were whole-heartily adopting, and these steel bike builders decided to screw with it and make another standard! What are they thinking?Sour Not-UDH left vs. SRAM UDH right (Bikerumor composite)Well, what they are thinking is that UDH was really optimized for the flat dropouts of carbon bikes. It requires a 13mm thick dropout with a pretty big 30x40mm flat area on the inside and 25mm diameter flat spot on the outside. Transmission derailleurs simply require ~30mm in diameter flat on both sides. Thats pretty common on carbon bikes anyway. Alloy bikes with big machined dropouts can also easily make that work. But many quality steel (and titanium) bikes use much smaller and often hooded dropouts, optimized to weld or braze-on small diameter seatstays & chainstays. And they simply dont have enough free real estate to work with UDH. Yes, its possible to make it work. Some steel bikemakers have switched to bigger or interchangeable dropouts, rearranged layout of their stays to fit, and some have come up with a good UDH-ready compromise.Sours solution was just to tweak the standard a bit.Whats that mean?That means, the Sour Not-UDH is pretty much the same as a regular UDH, just with a bit of that inward-facing plastic upper fin chopped off. Sour says its about 25% smaller overall. That lets them fit it into a compact hooded dropout, and doesnt get in the way of their integral rack/fender mount. And on the outside, theres just a spacer since steel dropouts arent 13mm thick. Sour Not-UDH left vs. SRAM UDH right (Bikerumor composite)Plus, unlike the SRAM UDH which is half plastic, the Sour Not-UDH is entirely made of machined aluminum. So, much like the Robert Axle Projects replacement, the Sour one might actually offer more precise shifts.And in the end, it is 100% Transmission compatible, since SRAM direct mount derailleurs dont need the space of the fin anyway.Sour Not-UDH AvailabilityAll new made-in-Germany Sour frames welded after the middle of next week will feature the new Not-UDH dropout. Sour says the new dropout & hanger is also a bit lighter than their previous dropouts, even with the added compatibility.But no, you cant just fit a regular SRAM UDH to your new Sour bike (without a little modification). So Sour will deliver all of their new steel bikes with an extra spare hanger, as well. (And it sounds like you could use it as a replacement for your regular UDH-equipped bike if you damage a hanger there.) Pick a Sour steel gravel or hardtail mountain bike if you want wide mountain climbing Transmission gearing. Or, now that Red went Xplr 13-speed, you can get a tighter-spaced 1x race setup for a gravel or all-road Sour.Sour.bikeThe post Sour Shifts to Transmission-Ready Not-Quite-UDH Dropouts For Lighter Steel Bikes appeared first on Bikerumor.