Rubbers and seals of your convertible roof: why supple rubber keeps you dry

Of all the components on a convertible roof, the rubber seals receive the least attention and cause the most damage. Not because they are expensive, as a maintenance stick only costs a few tens of euros, but because the consequences of neglect only become apparent much later, and then in a different place.

A customer of ours succinctly put it: if you have a convertible with many rubber seals and want to stay dry, supple rubber seals are a prerequisite. That's true, and it goes further than just staying dry.

 

What happens when rubber dries out

Rubber contains plasticizers. These slowly evaporate under the influence of UV, heat, and time. What remains is harder, shorter, and more porous than the original material. This has four consequences, and they reinforce each other:

• It no longer seals. Hardened rubber no longer conforms to the seal. Water finds the gap.
• It sticks. Dried-out rubber adheres to the paint and glass. When opening the roof, it tears loose, sometimes literally, sometimes taking a piece of paint with it.
• It makes the roof heavier. Rubber that sticks or jams requires force. The hydraulic system must provide this force. A roof that has been working against sticking rubber seals for years unnecessarily stresses the pump and cylinders.
• It freezes in winter. Moisture that penetrates porous rubber and freezes tears the material from within. This is why rubber damage often only becomes noticeable in spring.

 

And then the real problem: water

A leaking convertible roof doesn't just result in a wet seat. Water seeks the lowest point, and in a convertible, electronics are often located there. Roof modules, control units, and sensors are frequently found in the trunk or under the rear seat, precisely where water flows. Water damage to a roof module is one of the more expensive malfunctions we encounter, and the cause is almost always, in hindsight, a fifteen-euro rubber seal.

The drainage channels also play a role here. A convertible roof is not waterproof in the sense that water never gets in; it is designed to drain water through drainage channels. If these become clogged with leaves and dirt, the water will flow in the wrong direction, no matter how good your rubber seals are.

 

How often should you do it?

Twice a year is a good rule of thumb:

• In autumn, before frost. This is the most important treatment. Supple rubber does not freeze and tear.
• In spring, after winter. To repair any damage caused by the cold, and to check for any cracks that may have developed.

If the car is often parked outside in direct sunlight, it may be necessary more frequently. UV is rubber's biggest enemy.

 

How to do it

1. Clean. Maintenance product on dirty rubber traps the dirt. Use lukewarm water and a soft cloth; for stubborn dirt, use a mild car shampoo. Do not use aggressive cleaners or solvents: they extract plasticizers from the rubber.
2. Let dry. Completely. Maintenance product on wet rubber will not adhere.
3. Apply the product. Cover the entire rubber, including the underside and creases. It is in the places you don't see that the rubber is under the most tension.
4. Let it soak in and wipe off any excess product. A thick layer that remains will attract dust.
5. Operate the roof once. This distributes the product over the contact surfaces.
6. Clear the drainage channels. This is part of the process. Check the drains in the roof compartment and at the hinge points and remove leaves and dirt.

 

Which product should you use?

There is a difference between products that nourish the rubber and products that make it smooth. You want both, but not always the same product.

• For nourishing and keeping the sealing rubbers supple, a specific rubber maintenance product is intended. For this, we offer, among others, Rubber Care and the Gummi Pflege Stift; the latter is a stick that allows you to work precisely along the frame, which is useful for hard-to-reach areas. You can find them in our maintenance products.
• For the roof itself, the fabric or vinyl, you need something different. A RaggTopp maintenance kit cleans and impregnates the fabric without affecting the existing protective layer.
• For the mechanics, the guides, hinges, and rails, use a lubricant and not a rubber product.

What not to use: silicone spray on everything. Silicone temporarily makes rubber shiny and smooth but does not nourish it, and it can hinder the adhesion of subsequent treatments and paint or glass repairs. Also no petroleum jelly or household oil: these can damage some types of rubber.

 

Where to look

Check these areas, even if you don't have a leak:

• The seal above the windshield, where the roof closes.
• The side seals along the door windows.
• The seal around the rear window.
• The rubber seals around the roof compartment lid or trunk lid.
• The grommets through which cables and lines pass.
• The drainage channels in the roof compartment.

When checking, look for cracks, hard or glassy spots, rubber that has stretched or no longer springs back, and signs of sticking.

 

The calculation

Rubber maintenance twice a year costs you about twenty minutes and the purchase of a product around twenty euros that lasts for a few years. What it prevents: a leak that reaches the roof module, rubbers that need to be replaced, and a pump that has been working against resistance for years.

Of all preventive actions for a convertible, this one has the most favorable ratio between effort and result.

 

When to replace instead of maintain?

Maintenance does not repair rubber that is already broken. Replacement is necessary when:

• visible cracks across the full width
• rubber that is permanently compressed and no longer springs back
• parts that have detached from the carrier
• a seal that still leaks after treatment

For many models, seals are available separately through our parts.

 

Don't know which seal you need, or are you unsure about the correct maintenance product? Contact us, we are happy to help you.