MGB RD Windshield Installation Tip

Installation Tip: MGB RD Windshield Glass Installation into the Windshield Frame

Installing a windshield into an MGB Roadster windshield frame is one of the more precise restoration tasks on the car. The frame clamps directly around the glass using a rubber glazing seal, so proper alignment is critical. The biggest challenge is getting the frame sections fully seated while keeping the seal properly positioned and avoiding unnecessary stress on the glass.

Product Note:

Windshield glass for classic British sports cars has benefited from having multiple manufacturers supplying replacement products over the years, giving restorers more choices than many other restoration components. However, through decades of sourcing windshield glass from these suppliers, Moss has observed that not all replacement glass is manufactured identically.

Although the glass may be sold under the same well-known brand name, production has often taken place in different countries using different tooling. As a result, slight variations in overall dimensions, edge profiles, and curvature can exist between manufacturers from the same brand. While these differences are typically very small, they can affect how easily the glass fits into the original windshield frame.

Moss first documented these manufacturing variations more than 20 years ago and continues to see them from time to time. For this reason, some installations may require more patience and minor fitting adjustments than others. This does not necessarily indicate a problem with the windshield frame, seal, or glass, but rather reflects the manufacturing tolerances inherent in reproduction components.

Professional Installation

Installing an MGB windshield into the frame can be completed by an experienced do-it-yourself restorer with the proper tools and careful attention to detail. However, because the windshield glass is clamped directly by the frame, improper assembly or excessive force can result in glass breakage.

If you are uncomfortable performing this procedure or do not have access to the appropriate tools and a suitable work area, Moss recommends having the windshield assembled by a professional automotive glass installer or an experienced British sports car restoration shop. The cost of professional installation may be less than the expense of replacing a damaged windshield.

What You'll Need

New windshield glass

New windshield-to-frame seal (glazing rubber)

Silicone spray lubricant

Rubber mallet

Screwdrivers

Appropriate sockets and wrenches

Plastic trim tools (optional)

Clean padded work surface

Painter's tape (optional)

Before You Start

Remove the complete windshield frame assembly from the vehicle.

Place the assembly on a clean, padded work surface to protect the frame and glass.

During disassembly, note the location and orientation of all brackets and screws.

The top rail-to-pillar brackets are handed and must be reinstalled on their original sides.

Keep the long and short screws separated so they can be returned to their original locations.

Disassembly

Remove the top rail by unscrewing it from the windshield frame and both side pillars.

Remove the left-hand (LH) and right-hand (RH) top rail-to-pillar brackets.

Note the position of each bracket and its mounting screws for reassembly.

Unscrew and remove the bottom rail assembly.

Carefully pull the LH and RH side pillars away from the windshield.

If the lower pillar brackets are in good condition, they may be left attached to the pillars.

Remove both side pillars.

Installation Order

For best results, assemble the windshield frame beginning with the bottom rail and working upward.

1. Install the Windshield Seal

Install the new glazing seal completely around the edge of the windshield.

Installation Tip:

Apply a light coat of silicone spray to the outside of the seal immediately before installing each frame section. This helps the frame slide over the rubber without binding.

2. Install the Bottom Rail

Position the bottom rail over the windshield and seal.

Tips:

Verify that the seal remains fully seated as the rail is installed.

If necessary, use a rubber mallet to gently tap the bottom rail into place.

Never strike the glass directly.

3. Install the Side Pillars

If previously removed, reinstall the bottom rail-to-pillar brackets onto the pillars.

Important:

The brackets are handed.

Install each bracket on the correct side and in the proper orientation.

Slide each pillar bracket into the channel in the bottom rail while ensuring the windshield and seal seat fully into the pillar channel.

Steps:

Install one mounting screw on each side, leaving them loose.

Install the remaining bottom rail screws.

If necessary, use a rubber mallet to help align the threaded bracket holes with the mounting holes in the bottom rail.

Do not fully tighten the screws at this stage.

4. Install the Top Rail

Slide the top rail brackets into position and align them with the side pillars.

Install the top rail over the windshield and seal.

Tips:

Start every mounting screw before tightening any of them.

Make certain the long and short screws are installed in their original locations.

5. Tighten the Frame

Once every screw has been started:

Tighten the fasteners gradually.

Alternate from side to side to pull the frame together evenly.

Verify that the seal remains properly seated as the frame is tightened.

Avoid forcing the frame together with the screws. If alignment becomes difficult, stop and verify that the seal and brackets are positioned correctly.

Final Inspection:

Before reinstalling the windshield assembly onto the vehicle:

Verify the windshield is evenly seated around the entire frame.

Confirm the rubber seal is not pinched or folded.

Ensure the metal frame does not contact the glass directly at any point.

Verify all brackets are correctly installed and all fasteners are securely tightened.

Clean any excess silicone lubricant from the frame and glass.

Important MGB Roadster-Specific Tips

Protect the Glass:

Always support the windshield on a clean, padded surface during assembly. Never place pressure directly on the center of the glass.

Lubricate Sparingly

A light application of silicone spray is all that is required. Excess lubricant can allow the seal to shift during assembly.

Don't Force the Frame:

If the frame sections do not fit together easily, determine the cause before tightening the screws. Excessive force can crack the windshield.

Use a Rubber Mallet Carefully:

Light taps can help seat the frame sections and align mounting holes. Never strike the glass or use excessive force.

Work Evenly:

Starting every screw before tightening any of them allows the frame to align naturally and minimizes stress on the glass.