Solution For Rear-View Mirrors That Keep Falling Off- Permatex Ultra Grey

If you have a rear-view mirror that won’t stay fastened to the windshield, this may be an extra tough solution.

Our rear-view mirror also holds an aftermarket back-up camera screen/rear-view mirror combo. This places extra weight on the rear-view mirror bond and causes the mirror to come crashing down every 18 months (or so). This was often brought on by very cold weather or rough roads.

After the latest failure, we searched for an extra-tough rear-view mirror glue. We contacted the good people at Permatex to see if they had any recommendations. Permatex produces rear-view mirror adhesives for the commercial and consumer market. They are also a world-leader in automotive and industrial bonding agents and sealants.

We lucked into a conversion with an extra-helpful technician at Permatex. He gave us the scoop on a trial being performed with one of their gasket-maker products tested as a rear-view mirror glue. He hinted that this product may actually do a better job in this application than their commercially available rear-view mirror adhesive kits. That product is Permatex “Ultra Grey”. We do not sell this product and have no relationship with Permatex.

Permatex describes Ultra Grey as a “rigid, high-torque RTV silicone gasket maker”. Our contact at Permatex raved about the abilities of Ultra Grey and offered that testing in this alternate duty as a rear-view mirror adhesive had been very promising. We were eager to give Ultra Grey a try.

The Process To Re-attach Your Rear-View Mirror To Windshield With Permatex Ultra Grey

1. Use a painter’s razor blade to strip off old rear-view mirror glue from the windshield surface.
2. Remove “button” from mirror assembly. The button is the part that is bonded to the windshield. Most buttons simply twist off of the mirror assembly. If unsure, search the internet for the mirror button removal procedure for your vehicle.
3. Sand button on flat surface to remove glue. Any grit of sand paper will do.
4. Clean glass and button with Dawn or Palmolive dish soap and warm water. Rinse thoroughly with clean water. Do not use alcohol or Windex to clean this area as they are astringents. They will leave a residue in the pores of the glass.
5. Allow glass and button dry thoroughly.
6. Apply a healthy dot of Ultra Grey in center of button.
7. Press button firmly onto glass and hold for a few minutes.
8. Secure button with painter’s tape. Do not install the mirror onto the button yet. 
9. The Ultra Grey instructions suggest that the product will fully cure in 24 hours. Note that 24 hours is not long enough for this application. We waited a full 48 hours (in summer weather) for Ultra Grey to cure before installing the mirror on the button. We wanted to be 100% sure that the product was fully cured in order to give this trial an honest chance. 

Still Holding

The mirror has been holding now for over seven years and counting (Update: still holding as of January, 2024). With Ultra Grey’s ultra-wide operating temperature range (-65°F to 500°F), we hope that winter-induced failures are a thing of the past. Hopefully it also provides extra security on rough roads.

We will post future revisions to this topic in this space. We certainly hope that we never have to revisit this task again.

Ultra Grey also seems to do a great job fastening door seals and body trim. This seems to be a very versatile and competent product.

Ultra Grey is available at most auto parts stores. Note: We do not sell Permatex Ultra Grey.