January 24, 2019

Where has all the Butyl Tape gone?

This 1970 El Camino had a ‘tape in’ windshield using Butyl tape

Many of our customers ask about butyl tape- either the vehicle they’re restoring used it originally or they heard that they should use it to set their windshield. Most are surprised that we offer a very long list of windshield and rear windshield gaskets but do not carry butyl tape. Here’s why.

Originally, auto manufacturers installed the front and rear windshields with a rubber gasket. That took a lot of time on the assembly line so in the mid 60’s, General Motors made the switch to using butyl tape to speed up the process and it worked well. The rest of the auto manufacturers soon followed suit.

In the mid 60’s cars started changing from having a body over a frame to unibody style construction (where the body also served as the frame of the vehicle- with added support around the engine, of course). Unibody construction made rigidity more important than ever and while butyl tape was really great at sealing, it offered little strength. On a unibody frame, the front and rear windshield had to be strong as they now served as part of the structure of the vehicle so a better solution for attaching them was needed.

Body over frame vs. Unibody

During this time period adhesive technology had made major improvements and urethane adhesive became the better choice. It offers excellent sealing and strength all while still providing some flexibility/movement. The 3M website says “Urethane structural adhesives are two-part formulations that react when mixed and do not require moisture to cure. They are relatively flexible when cured and therefore tend to have excellent impact and vibration resistance” making it perfect for this application.

In the mid 70’s the gradual switch to urethane adhesive for bonded windshields and rear glass began.  By the 1980’s it was standard operating procedure on all the assembly lines to use a urethane adhesive.

3M Urethane Adhesive

Butyl tape is still out there on the market (it’s used for many things) but here at Steele, we always recommend urethane adhesive for this application. We carry the 3M Brand (3M part number 8693) but you can also purchase it at any local auto parts store. It comes in a caulk style tube for easy application and typically cures in 24 hours.

To use it to set your windshield or rear windshield simply run a bead on the edge the glass sits on, push the glass down on it and leave it to cure (you’ll also want to use spacers to get the glass lined up just right and hold it in place till the adhesive cures).

Urethane adhesive can also be used to attach universal beltline or beltline weatherstrip with no tabs on it. Simply run a bead on the gluing surface, push the beltline on and use some wooden clothespins or wood clamps to hold it on. Remove the clamps after 24 hours and you’ll be ready to go!

Danny shows you how to attach Beltline Weatherstripping using Urethane Adhesive

Have more questions about butyl tape or urethane adhesive? Comment below and let us know how we can help.

Steele not only has all the products you need but all the knowledge you need to get the job done right, too. If you have questions about Rubber Parts or Weatherstripping on your Classic Car, Truck, Hot Rod or even your boat, trailer or RV, feel free to reach out to us! You can call us at 800-650-4482, contact us through our website or comment on this post and we’ll get you answers as quickly as possible. Check out our YouTube channel for our full library of how-to/installation videos.

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