If you’ve ever had a BMW feel slightly different session-to-session (or even lap-to-lap), there’s a good chance the rear alignment isn’t staying exactly where you set it. On performance road cars, track builds, and anything running aggressive geometry, the rear eccentric adjusters can shift under load, which means your toe and/or camber can move without you touching a spanner.
XC3 lockout shims are a simple, bolt-on way to remove that variable and make your rear geometry repeatable.
The problem
BMW uses eccentric bolts to adjust rear toe and camber. They work, until they don’t.
Under heavy cornering loads, track use, or aggressive alignment settings, an eccentric can slip. That gives you:
- inconsistent rear-end balance
- unpredictable mid-corner behaviour
- tyre wear that doesn’t match your setup sheet
On cars fitted with adjustable toe/camber arms, the eccentric adjuster is also redundant, you’re adjusting on the arm, but still relying on an eccentric interface to stay clamped.
Signs your rear alignment is moving
- Car feels “different” from one session to the next
- Rear toe changes between alignments without any obvious reason
- Steering wheel correction mid-corner where you didn’t need it before
- Accelerated inner-edge tyre wear after a geometry change
- You’ve installed adjustable rear arms and want the alignment to be set-and-stay
Options compared
1) Keep the OEM eccentrics
Fine for stock-ish road use, but it’s still a friction-based system that can move when loads rise.
2) Mark & monitor (paint pen, witness marks)
Helps you detect movement - doesn’t stop it.
3) Lockout solution (XC3 shims)
You remove the eccentric “slip point” and replace it with a fixed, repeatable interface, while still keeping the adjustment on your aftermarket arms.
The XC3 solution: lockout shims (toe + camber)
XC3 lockout shims are designed to do one job properly: hold your rear geometry exactly where you set it. They’re stainless, laser-cut for accurate fitment, and supplied with upgraded hardware so you can clamp everything correctly.
Product highlights
F8X / G8X Rear Toe Lockout Shims (M2/M3/M4)
- 4mm stainless steel, precision laser cut
- Laser-engraved XC3 logo
- Upgraded replacement hardware (12.9 tensile spec)
- Lifetime warranty
F8X / G8X Rear Camber Lockout Shims (M2/M3/M4)
- 5mm stainless steel, precision laser cut
- Laser-engraved XC3 logo
- Replacement hardware (10.9 tensile spec)
- Lifetime warranty
E9X / E92 Rear Toe Lockout Shims (M3)
- 4mm stainless steel, laser cut for accurate fitment
- Laser-engraved XC3 logo
- Replacement hardware (10.9 tensile spec)
- Lifetime warranty
E9X / E92 Rear Camber Lockout Shims (M3)
- 5mm stainless steel, laser cut for exact fitment
- Laser-engraved XC3 logo
- Replacement hardware (10.9 tensile spec)
- Lifetime warranty
Fitment
BMW M2 / M3 / M4 (F8X 2016–2021, G8X 2020–2025): toe + camber lockout shims available
BMW M3 (E9X / E92): toe + camber lockout shims available
Who it’s for
Track-day cars that need consistent balance and tyre wearAnyone fitting adjustable rear toe arms and/or camber arms and wanting the alignment to stay locked
Takeaway
Rear alignment should be a known quantity, not something that quietly shifts as loads increase. Locking out the OEM eccentric interface is one of those small changes that makes everything else (setup, tyres, driver confidence) more consistent.
If you want repeatable rear geometry, choose the correct lockout shim kit for your chassis:
F8X/G8X Toe Lockout Shims -> View Product
F8X/G8X Camber Lockout Shims -> View Product
E9X/E92 Toe Lockout Shims -> View Product
E9X/E92 Camber Lockout Shims -> View Product