Which Freehub Body for My Cassette? HG, HG+, Micro Spline, XD, XDR and Campagnolo Explained

Start from the cassette, then check the body. 7- to 10-speed Shimano and SRAM cassettes fit the classic HG body; Shimano 11-speed sits on HG/HG+; Shimano 12-speed with a 10-tooth cog (SLX, XT, XTR, and the 12-speed road groups) needs Micro Spline; SRAM Eagle MTB uses XD; SRAM 12-speed road uses XDR; Campagnolo needs its own N3W body (N3W-BT for 13-speed). None of these is interchangeable with another without changing the body or the wheel.

Whether you are refreshing a worn sportive cassette or speccing a new wheelset for a trail bike, the logic is the same. This guide sets out the rules from L'Atelier's compatibility guides (la-telier.com), flags the two points where those guides contradict each other, and ends with a five-step check you can do in the workshop.

Why there are now six standards

For years there was one freehub standard. Then came 10, 11, 12 and 13 speeds, plus a race for wider ranges and ever smaller sprockets. A 10-tooth or 9-tooth sprocket physically cannot sit on a body as large as HG, so each brand designed its own answer. The result, in L'Atelier's words, is six main standards that are not interchangeable.

Campagnolo does not appear in that grid because it does not share a body with anyone: Campagnolo 9- to 13-speed cassettes only go on Campagnolo bodies.

Road bikes: HG, Micro Spline, XDR or N3W

On the road, the body tells you which ecosystem the wheel was built for:

• Shimano 11-speed road (105, Ultegra, Dura-Ace 11sp) and SRAM Rival/Force 11-speed: HG. An 11-speed road cassette needs a slightly longer body than 8/9/10-speed, so very old wheels may not accept one.
• Shimano 12-speed road (R7100 onwards): Micro Spline, according to L'Atelier's quick table.
• SRAM 12-speed road (Red, Force, Rival): XDR, which is 1.85 mm longer than the MTB XD body.
• Campagnolo 12-speed (Chorus, Record, Super Record): N3W, with specific splines smaller than Shimano HG. N3W also takes 11-speed Campagnolo cassettes, via an adapter or directly depending on the model.
• Campagnolo 13-speed (Super Record Wireless, 9-36): N3W-BT, physically identical to N3W but paired with a thinner 9-tooth small sprocket.

Campagnolo also has its own lockring tool for N3W (UT-FT001), different from the Shimano lockring tool. If you are switching between Campagnolo and Shimano, plan to change the freehub body, or the whole wheel if the body is not interchangeable.

Mountain bikes: the 12-speed split

On MTB the confusion is all about 12-speed. Shimano Micro Spline was introduced in 2018 with XTR M9100: 23 fine splines instead of HG's 9 asymmetric ones, which is what allows a 10-tooth sprocket and the 10-51 range. SRAM XD takes Eagle cassettes with a 10- or 9-tooth smallest sprocket that threads straight onto the body (GX, X01, XX1 Eagle). The two are not cross-compatible: "12-speed" on both boxes means nothing for fit.

HG and HG+ are worth separating too. HG+ keeps HG dimensions with one wider spline to cope with 11- and 12-speed torque. HG+ cassettes fit standard HG bodies but dig harder into aluminium, and Shimano recommends a steel body for HG+. If your aluminium body already shows notches from the sprockets, that is the known weakness of HG at work.

Spacers, adapters and when a new wheel is unavoidable

1. 10-speed cassette on an 11-speed body: fit the 1.85 mm spacer behind it, otherwise the lockring will not tighten the cassette properly.
2. XD Eagle cassette on an XDR wheel: fine with a spacer. The reverse (XDR road cassette on an XD body) does not work.
3. Swapping body: DT Swiss sells conversion kits (HG, Micro Spline, XD, XDR, Campagnolo); Hope offers interchangeable bodies on Pro 4 and Pro 5 hubs; Mavic uses ID360; Fulcrum and Campagnolo offer adapters depending on the model.
4. Fixed bodies: some entry-level hubs cannot change body, so a new standard means a new wheel.
5. Freewheel hubs: a threaded freewheel (1 to 7 speeds) cannot be converted to a cassette; the hub, and usually the wheel, has to go.

Once the right cassette is on the right body, tighten the lockring to the specified torque. L'Atelier's chart gives 40 Nm, the same for Shimano, SRAM and Campagnolo, while reminding you that the value printed on the part or in the manufacturer's manual always takes precedence.

Moving from 11- to 12-speed Shimano: the body is only one part

A new freehub body is often the trigger for a wider upgrade. L'Atelier's migration guide is clear that Shimano 12-speed (Deore M6100, SLX M7100, XT M8100, XTR M9100) is not simply "one more sprocket": with a 10-51 cassette it offers a 510% range, but several parts change at once.

What you can keep: the frame (same mech hanger), the wheels if the hub accepts a Micro Spline body, a narrow-wide 11-speed chainring (it works with a 12-speed chain), plus brakes and cables. The good news on the gear side is that all Shimano 12-speed groups share one cable pull ratio, so a Deore M6100 shifter works with an XT M8100 mech. Never mix 10-, 11- and 12-speed shifters and mechs, though: the indexing will not line up.

On the road side, the same logic applies to a 10- to 11-speed conversion. L'Atelier's article on the subject points out that the frame is not the issue: the three real blockers are the freehub body length, the rear mech (a 10-speed mech does not have the right cable pull for 11-speed) and the shifters (a 10-speed shifter will never give you 11 gears).

A five-step check before you order

1. Cassette or freewheel? A splined lockring means cassette; a notched centre nut means freewheel. Turn the sprockets backwards by hand: on a cassette, only the sprockets turn while the body clicks inside the hub.
2. Smallest sprocket: 11 teeth or more is usually HG/HG+; 10 teeth means Micro Spline, XD or XDR; 9 teeth means SRAM XD or Campagnolo N3W-BT.
3. Exact cassette reference (CS-M8100, XG-1299 and so on), not just the groupset name.
4. Hub model, to see which bodies its maker offers.
5. The other three drivetrain parameters: speed count, derailleur pull ratio and derailleur capacity. If any one of the four does not match, the drivetrain will skip, mis-index or simply not fit.

If you are stuck on a specific combination, the L'Atelier bike mechanics base answers questions such as "Which freehub bodies are compatible with the Shimano CS-M8100 12-speed cassette?" and quotes the guide it relied on.