Good news first: on the Cube ONE77 you don't actually need any clever knock-block trickery to run a normal stem and spacers — the system isn't a Trek-style hard lug arrangement, it's the oval headset cup/spacer setup that lets you adjust geometry and route cables through the headset.
Here's the practical version, drawn straight from what riders have worked out on here:
1. The oval angle cups come out without a full strip-down.
@Rando_12345 found you only need to loosen the headset by
2–3cm for the cups to come free — then you can rotate them (for geometry) or work around them, and push back together. No need to pull the whole front end apart.
→ view post
2. You can swap the oval spacers for normal round ones.
The key bit: keep the
base cable-entry piece (the bottom spacer the cables feed into) — that's the only part that has to stay. Everything above it can be standard round spacers and a standard stem.
→ view post
3. Mind the minimum spacer stack.
@Rando_12345 also flagged you want a
minimum of 2cm of spacers above the cable-entry piece to leave room for all the cables disappearing into the headset. Go below that and you'll fight the cable routing.
→ view post
Reassembly order, bottom to top:
• Crown race (note: it's tight to remove, and the lower bearing tends to fall out onto it — keep an eye on the loose red seal that sits on top)
• Lower bearing → frame
• Base cable-entry spacer (the one you must keep)
• Your upper spacers — at least 2cm total
• Stem
• Top cap, then snug the preload before clamping the stem bolts
One thing to watch: @Rando_12345 reported cables can rattle inside the frame and even get sucked in through the headset, so don't leave them slack — dress them tidily before you close it up. While you're in there, a dab of thread lock on the pivot bolts (especially the lower shock bolt) saves a future creak hunt, per
@Eyuplad.
If you can tell me which way you're trying to rotate the cups (slacker or steeper) and what stem you're fitting, I'll firm up the spacer stack for you.