Frameless Rear Vent Glass and Integrated Pillar Guides
Unlike fixed quarter glass on a hardtop, the rear side vent window on this convertible is a fully retractable, frameless pane that drops vertically inside the rear fender quarter cavity. The defining mechanical characteristic of this glass is the factory-bonded vertical division channel running along its leading edge. This guide pillar does double duty: it stabilizes the pane during travel and holds the critical rubber run-channel that seals directly against the trailing edge of the front door drop-glass. Whether replacing the left side (dealer reference 51357365771) or the right side (NAGS part FQ26988GT, dealer reference 51357365772), the piece is manufactured from AS2 green solar tempered safety glass shaped to integrate cleanly with the folding fabric roofline.
Because the unit operates on a motorized internal cable-and-track regulator rather than sitting in a fixed urethane bed, physical damage or regulator failure often leaves the cabin vulnerable to the weather. If a broken window leaves the interior exposed, I typically get to your location about an hour after you book so the car is not left open to elements or theft. This glass serves identical dimensions across the Cooper, Cooper S, and John Cooper Works (JCW) trims, meaning the mechanical clearance challenges behind the rear interior quarter card remain consistent across the model run.
Sealing the Three-Way Junction at the Roofline
Replacing this rear side glass requires precise spatial alignment because of how many movable parts meet at a single point. When fully raised, the top edge of the glass presses into the soft-top side weatherstrip seal, the bottom drops past the exterior lower beltline waist moulding, and the bonded front guide must mate parallel to the frameless front door window. If the glass sits tilted by even two millimeters on its regulator clamps, high-speed cabin buffeting or water leaks quickly develop along the fabric edge.
| Glass Specification | Left Rear Quarter / Vent | Right Rear Quarter / Vent |
|---|---|---|
| Glass Structure | Frameless tempered drop-glass | Frameless tempered drop-glass |
| Factory Solar Tint | AS2 Green Tint | AS2 Green Tint |
| NAGS Number | FQ26987GT | FQ26988GT |
| OEM Reference | 51357365771 | 51357365772 |
| Hardware Feature | Bonded leading division pillar | Bonded leading division pillar |
Owner Inspection After Quarter Glass Service
Once the replacement glass is secured to the internal regulator carrier and the interior quarter panels are buttoned back down, verify that the mechanical interfaces and rubber profiles seat without binding:
- Leading Edge Vertical Seal: Inspect the seam where the front door window meets the rear quarter pillar guide. The door glass must slide smoothly into the vertical rubber channel without catching or folding the lip when closing either door.
- Soft-Top Upper Interface: Raise the convertible roof completely and confirm the top edge of the rear vent glass seats firmly inside the upper fabric weatherstrip without gaps or pinching.
- Beltline Waist Moulding: Check that the glass drops clean through the outer rubber beltline moulding without scuffing the green solar tint or dragging the exterior weatherstrip downward.
- Full Stroke Travel: Cycle the window down into the rear quarter cavity and back up to confirm the internal cable mechanism operates quietly without popping or tilting off-axis.
