Open the caliper.
Inspect the retention roles.
Separate native caliper exteriors, opposed piston/seal envelopes, pads with bored ears, shims, springs/pins, mounting screws/lock tabs and bleeder/banjo roles replace the coarse caliper and pad groups on both sides. Rotor, hub, bearing and wheel stations remain unchanged.
The right-side references mirror the construction geometry. Mirroring is a drawing choice, not proof of fitted handed details.
Factory topology and owner evidence
Factory PDF p. 142 and p. 143 separate handed calipers, GBP108 pad set, four shims and split pins, two pad springs, four mounting screws and tab-locking hardware for the car. The supplier front-brake listing corroborates the opposed two-piston caliper architecture and separate service roles. No listed caliper, pad, piston or hardware has been identified as fitted.
Existing owner underside views provide wheel/suspension context rather than calibrated disassembled caliper, pad or hose-end measurements. No new direct owner dimensions are applied. All new sections, profiles, bores, pockets and fixing maps remain estimates.
What the new geometry exposes
| Relationship | Construction and limits |
|---|---|
| Caliper / upright | Two estimated 4.5 mm-radius caliper bores share the old ear/web endpoints with new bores in two upright carrier meshes. Sixteen other kingpin-source meshes remain identical. Mounting screws and flat two-hole lock-tab envelopes do not establish fitted thread, torque, locked bending, seating or support strength. Positive cast/web contacts remain. |
| Pistons / pads | Blind 18 mm-radius pockets, 17.5 mm-radius piston-cup and unloaded seal envelopes clarify opposed piston roles. These are construction dimensions, not a verified hydraulic bore, pressure/seal design or service fit. The caliper stays one exterior assembly; no bridge-bolt separation or overhaul sequence is encoded. |
| Pad retention | Estimated ears grow from the old pad backing envelopes and share new retaining bores with the caliper. A bridge window exposes the spring/pin region. Smooth split-pin stems/loops, shim and spring envelopes do not reconstruct installed bending or spring force. The opening is not a verified pad withdrawal path. |
| Rotor gap | The old 1 mm gap on each rotor face is retained for display. It is not running clearance, piston setting, adjustment or wear allowance. The original rotor dimensional comparison and hub/wheel datums are preserved. |
Keep hose variants separate
Factory p. 167 distinguishes GBH139/GBH157 hose branches at GAN6-162565, banjo bolt 11D5264/gasket 3H550, and locking hardware explicitly linked to earlier GBH111. This car’s fitted hose branch remains unselected. Caliper mounting lock tabs are distinct from hose-locking hardware.
The new banjo eye, hollow-bolt and uncompressed washer envelopes expose a catalog connection role. Their bore, thread, valve/flare seating and orientation are estimates. The eye center lies 5 mm inboard of the retained network endpoint; the existing hose route is not moved to manufacture a sealed join. No hidden fluid channel or complete pressure circuit is inferred from open local passages.
Retained carrier contacts
| Source part / carrier, per side | Intersection |
|---|---|
| opposed caliper exterior blind pockets and mount bores swivel carrier | 4823.92 mm³ |
| flat two hole mounting lock tab comparison swivel carrier | 0.0015 mm³ |
| open bleed screw exterior comparison swivel carrier | 4.8395 mm³ |
| banjo eye and unassigned hollow bolt envelopes swivel carrier | 89.7472 mm³ |
| two uncompressed banjo washer envelopes swivel carrier | 4.0984 mm³ |
The same values are recorded independently for the mirrored right side. The 0.0015 mm³ tab contact is a numerical-scale source result, not a physical interference diagnosis. Larger casting and fitting contacts still prevent installed seating or access claims. These are reconstruction discrepancies, not evidence of damage or actual interference on the car.
Workshop boundary
Select, isolate and illustratively separate pad, retention, mounting and hose roles. Valid source solids and open bores do not establish pressure safety, loaded sealing/locking, tool access, hydraulic release or bleeding order, hose travel, steering/suspension sweep or verified replacement/removal paths. No brake service setting or operating motion is supplied.
Native files
Thirty source meshes contain fifty-six valid STEP solids. Construction checks cover mounting/retention bores and nonintersection of the rotor comparison with friction pads, shims, spring and retaining-pin envelopes. Viewer checks cover metric placement/picking, shared caliper/carrier and pad bores, fixing/pin occupancy, isolation, declared display movement, source counts, links/downloads and mobile layout. They do not certify fitted brakes.