Has anyone successfully ran the SRAM Red XPLR 13 speed on a XC MTB for racing? What problems did you run into, what fixes did you figure out? Pro’s/Cons? My thoughts are just the Cassette, And rear derailleur, which would also mean a new XDR DT Swiss freehub. Would like to still run the XXSL crankset 34t w/powermeter. Are there going to be chain compatibility issues?
A reverse mullet! 
The cassette is only compatible with a Flattop 12/13 speed road chain, so as long as you use that chain and your chainring is compatible with that chain, you’ll be good. Using an Eagle or T-Type chain isn’t officially compatible. If you’re running that $600 Red cassette, I’d say stick with the right chain and chainring.
Edit: Wolftooth makes chainrings that work with all SRAM chains (Dropstop B): https://www.wolftoothcomponents.com/pages/chain-compatibility-by-chainring-tooth-profile
I think the main question is how do you get an XDR freehub onto your mtb wheels. If solved, everything else will be pretty straightforward I assume.
Can you just change the free hub body?
There are XDR drivers for the DT Swiss 180 hubs with end caps for the 148mm spacing, that should be an easy fix if I’m not mistaken.
Can you post some links? Last time I tried to research this I threw in the towel because I couldn’t deal with DT swiss’ website
Freehub xdr body for 240 and a 148 endcap is what I’d need.
edit: nvm, does that soubd plausible?
1. The Hub & Freehub (The “Road-to-MTB” Gap)
The Red XPLR 13-speed cassette (XG-1391) requires an XDR freehub body. While you have a DT Swiss 240 hub, which is highly modular, there is a nuance with spacing:
• The Problem: Most XDR freehub bodies are designed for 142mm road/gravel spacing. If you just slap a standard road XDR body on a 148mm Boost hub, the cassette will sit too far inboard, and your endcap won’t provide the correct total width.
• The Solution: You need the DT Swiss XDR Freehub Kit for Ratchet EXP (or Ratchet, depending on your 240 version) specifically for 142/148mm. DT Swiss makes an “XDR” conversion kit that includes the required Boost-specific drive-side endcap.
• Note: Ensure you get the version for your specific 240 internals (Ratchet vs. Ratchet EXP).
2. Chain and Chainring Compatibility
This is where most “reverse mullet” builds (road groupsets on MTB frames) get tricky:
• Chain: The 13-speed XPLR cassette requires a Flattop chain (Red or Force E1).
• Chainring: You cannot use a standard Eagle T-Type or older Eagle chainring with a Flattop chain. The tooth profiles are different. To keep your current cranks, you will likely need a chainring specifically designed to be compatible with SRAM Flattop chains (e.g., Wolf Tooth “Drop-Stop B” or SRAM’s own road/gravel specific rings).
And
For the DT Swiss 240 hub with Ratchet EXP internals, you need a specific kit that includes both the XDR driver and the correct endcap for a 12mm thru-axle.
Because DT Swiss uses the same drive-side endcap for both 142mm and 148mm (Boost) hubs in the EXP system, the standard “12x142mm” XDR kit is exactly what you need for your 148mm Boost Epic 8.
The Part You Need
• Official Part Number: HWYABL00S5401S
• Description: DT Swiss Ratchet EXP Freehub Body Kit - SRAM XDR (Aluminum) includes 12mm Thru-Axle End Cap.Important Installation Notes
1. EXP vs. Standard Ratchet: Double-check that your 240 hub says “EXP” on the shell. If it is an older 240s (non-EXP), this part will not fit, and you would need part HWYAAX00S8888S instead.
2. Tool-Free Swap: The beauty of the 240 is that you don’t need tools. You can literally pull the old freehub and endcap off by hand (or with a firm tug using a cloth for grip) and slide the new one on.
3. The “Boost” Confusion: In the DT Swiss ecosystem, the drive-side offset is the same for 142 and 148. The extra 6mm of “Boost” width is built into the hub shell itself, not the endcaps. This is why the kit labeled “12x142” works perfectly on your 148mm frame.
Yeah, I wouldn’t trust AI to get parts compatibility or parts numbers correct. I’d go straight to the source: Product Support | DT Swiss . I ordered a 240 wheelset recently, and the DT Swiss support site helped me find the correct 12x100 conversion kit for my 15x100 hub.