Do I need the spacer on an 8/9/10-speed freehub?

No. The cassette was designed for that body and sits flush without it.

Can I use a different 1.85 mm spacer?

Any 1.85 mm cassette spacer does the same job. The one in the box is the right thickness; keep it.

Why does the Defy page say "unknown" if the freehub and the speeds both match?

Because the cassette also requires a derailleur that reaches a 50-tooth cog, and the largest-cog limit of the derailleur fitted to the Defy is not on file. Two matches and one missing fact is "unknown" — not "probably".

Fit, explained · At the bench

The 1.85 mm spacer: the cassette that confuses everyone

The bench · July 21, 2026 · 4 min read

An 8/9/10-speed cassette and its 1.85 mm spacer on a workbench

Every few weeks someone brings in a wheel with an 11-speed road freehub and a cassette meant for a 10-speed body, and asks why the lockring will not tighten. The answer is a 1.85 mm ring that was in the box and is now in a drawer.

Shimano made the 11-speed road freehub body about 1.85 mm longer than the 8/9/10-speed one. A cassette built for the shorter body sits flush on it; on the longer body there is a gap behind it, and the spacer fills exactly that gap. Our vocabulary says it in one line: the 11-speed road body accepts the 8/9/10 body, one hop, with a spacer — and the resolver reports that hop as "match with a spacer", never as a plain "match".

The spacer that ships in the box. It goes on the freehub first, then the cassette. — Atelier 700

One cassette, two bikes, two honest answers

SRAM PG-1230 — freehub required	Shimano HG, 8/9/10-speed body (also 11/12-speed MTB HG cassettes)
SRAM PG-1230 — rear speeds required	12 speeds
SRAM PG-1230 — largest cog the derailleur must reach	≥ 50 t
Giant Defy Advanced 2 (2025) — freehub on file	Shimano HG, 11-speed road body (+1.85 mm)
Giant Defy Advanced 2 (2025) — rear speeds on file	12 speeds
Giant TCX Advanced Pro 2 (2023) — rear speeds on file	11 speeds

Take the SRAM PG-1230, a 12-speed Eagle cassette for the 8/9/10 body. On the Giant Defy Advanced 2 the freehub line reads "match with a spacer" and the speed count matches — and the verdict still reads "unknown", because the third thing the cassette needs, a rear derailleur that reaches a 50-tooth cog, is not on file for that bike. On the Giant TCX Advanced Pro 2 the answer is shorter: an 11-speed bike and a 12-speed cassette — "does not fit". Neither verdict is typed; both are computed from the rows above.

Fitting it, step by step

Fit a 10-speed-body cassette on an 11-speed road freehub

Clean the freehub Wipe the splines; old grit under a cassette is what makes a lockring feel tight when it is not.
Fit the 1.85 mm spacer It goes on the freehub body first, flat against the shoulder. If you skip it, the lockring bottoms out before the cogs are clamped.
Slide on the cassette Line up the wide spline; the loose cogs and their thin spacers go on in the order they came out of the box.
Torque the lockring The usual figure is 40 N·m — check your cassette maker. Hand-tight is not enough; the cogs will creak and eventually notch the freehub.
Check the chain line Shift to the smallest cog and look for the chain rubbing the frame or the derailleur cage; if it does, the spacer is missing.

If the lockring stops before the cogs are tight, you are missing a spacer — not a tool.
— The bench

SRAM PG-1230 Eagle cassette 11-50T, 12-speed — The cassette in question: freehub settled with a spacer, derailleur limit still unknown on the Defy.

Giant Defy Advanced 2 (2025) — The 11-speed-road-body bike: "unknown" on this cassette, for the reason above.

Cassette — Giant Defy Advanced 2 (2025)

Do I need the spacer on an 8/9/10-speed freehub?: No. The cassette was designed for that body and sits flush without it.
Can I use a different 1.85 mm spacer?: Any 1.85 mm cassette spacer does the same job. The one in the box is the right thickness; keep it.
Why does the Defy page say "unknown" if the freehub and the speeds both match?: Because the cassette also requires a derailleur that reaches a 50-tooth cog, and the largest-cog limit of the derailleur fitted to the Defy is not on file. Two matches and one missing fact is "unknown" — not "probably".

What to remember

An 11-speed road freehub body is 1.85 mm longer than the 8/9/10-speed one; the spacer fills the gap.
The resolver records that as "match with a spacer" on the freehub dimension — a positive answer with an extra part, never a plain match.
A verdict needs every required fact: a settled freehub and a matching speed count still read "unknown" while the derailleur limit is missing.
A lockring that stops early means a missing spacer, not a stripped thread.

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