Rubber & Seals
The Parts Nobody Notices Until They're Wrong

Door & Body Seals

Door seals are the most frequently replaced rubber on any classic car. They compress under door closure, cycle through temperature extremes, and degrade with age into a hardened state that neither seals nor compresses. A hardened door seal causes water ingress, wind noise, and — because the door no longer closes against the correct resistance — a gradual loosening of door latch engagement.

Replacement door seals must match the original profile precisely. The visible cross-section is only part of the specification — the wall thickness, the hollow section geometry, and the durometer (rubber hardness) all affect how the seal compresses. A seal that is too firm prevents the door from closing properly; too soft means it collapses without sealing.

For most British classics, door seal kits are available from Moss Motors and SNG Barratt. These are generally correctly profiled and made from EPDM rubber (suitable for outdoor use and UV resistant). Avoid very cheap seal kits with no specified material — uncured or incorrect rubber grades harden quickly in outdoor exposure.

Window Glass Seals

Fixed glass seals (windscreen rubber, rear window rubber) hold the glass in the body aperture and provide the weather seal between glass and bodywork. On most classic cars these are rubber channel profiles with a specific lip geometry for the glass thickness and the body flange depth.

Windscreen rubber for common British and Japanese classics is generally available. Less common models and rare variants (coupe versions of predominantly roadster models, for example) present more difficulty. The MGA coupe rear window seal is a specific example of a profile that has been out of stock at all major suppliers simultaneously.

When fitting new glass rubber, use a proper fitting lubricant (washing-up liquid or dedicated rubber lubricant — never silicone grease, which prevents adhesion in sealed screen applications). A rubber locking strip tool prevents damage to the rubber during installation.

Brush Seals

Brush seals use a polypropylene or nylon pile insert to seal door frame corners and frameless glass edges. The pile allows relative movement without the resistance of solid rubber — critical where a frameless glass drops into the door on opening.

The MGB uses brush seals at the door frame corners (the grey brush seals at the front and rear of the door aperture). These are among the more difficult-to-source items on the MGB, with irregular availability from major suppliers. The guide on CarSpanner covers the specific MGB brush seal sourcing situation in detail.

Brush seals can be sourced by profile — the brush pile height and the carrier channel dimensions — from weatherstrip specialists, making custom short-run production possible where original equivalents are unavailable.

Mechanical O-rings & Gaskets

O-rings and mechanical gaskets are in a different category from body seals — they are standard engineering components available in any size from industrial rubber suppliers. An O-ring is defined by its inner diameter, cross-section diameter, and material (NBR/nitrile for fuel and oil; EPDM for water; Viton for high-temperature fuel applications).

Most mechanical rubber sourcing problems on classic cars are the result of not knowing the specification rather than genuine unavailability. Measure the O-ring (preferably the original — measure the groove if the original is gone), determine the material requirement, and order from any industrial rubber supplier. Parker, James Walker, and Trelleborg all supply small quantities directly.

Head gaskets, carburettor gaskets, and manifold gaskets are application-specific and must be sourced from suppliers who know the engine. Moss Motors and Rimmer Bros carry comprehensive gasket sets for most British engines.

When It's Out of Stock Everywhere

When a specific seal profile is unavailable from all major suppliers simultaneously, the options are:

• Wait for restock: Most out-of-stock items are scheduled for restock rather than permanently discontinued. Moss Motors typically provides ETA information; set an alert and check back.
• Find a custom extruder: UK-based firms including Hicks & Haas and D-Line can produce short runs of custom extruded rubber profiles from an original seal used as a template. Minimum orders are typically 5–10 metres — enough for one car with spares.
• Cross-model sourcing: A closely related model may use the same or compatible seal. Specialist suppliers can often advise on cross-model profile compatibility for specific applications.
• NOS sourcing: Original sealed rubber stored correctly (dark, cool, no ozone sources) retains its properties for many years. NOS seals occasionally appear on eBay from dealer old stock liquidation.

Rubber Preservation

Rubber seals age primarily through ozone attack and UV degradation, which strip plasticisers from the rubber and cause surface cracking and hardening. Preserved correctly, original rubber seals can remain supple for decades.

Apply a rubber conditioning treatment (303 Aerospace Protectant, or similar UV-inhibiting compound) twice yearly to exterior seals. This replaces plasticisers and provides UV protection. Do not use silicone spray — it only coats the surface. Do not use petroleum products — they degrade natural rubber.

Storing a classic car without using it accelerates seal degradation through ozone exposure. Running the car regularly, or at least moving it and compressing the seals, maintains seal condition better than long static storage.

Recommended Suppliers

Related Guides