View Full Version : Mirror to glass. Seriously, WHY is it hard?

September 21st, 2017, 13:13
I have a question for the collective mind...

Mirror to glass. Easy, right? Buy a kit, follow the instructions, bam.

Except, no.

I follow the directions implicitly- I've tried every product for the purpose at Oreilly/Autozone/Advance. None of them work for more than a week.

The glass is cleaned very well with 91% alcohol. I scrubbed it off with a razor blade first, then the alcohol. I gloved up so finger oils don't get into things. I took the mounting puck and removed all the old adhesive, then took sandpaper on a piece of glass to it to make sure it's flat and has some tooth.

Followed the instructions (all of which are similar (press and hold for a minute, then leave it in place for at least 12 hours before hanging mirror)... except I've left the darn thing there for a week without anything on it. I hang the mirror and if I'm lucky it doesn't immediately fall off.

Glass is brand new. I thought I had some sort of chemical contaminant on the old one, and it was broken anyway so I replaced the windshield. The new one came with a preattached puck. Figured it would last a good long while. Nope- fell off in traffic.

Sometimes they stay till I try to adjust the mirror- then donk, off it goes.

I'm tempted to try Super Glue, but I think that will just cause issues down the line.

Anyone got ideas?

The mirror pucks that come with the adhesive tape are a joke- who thinks that would work? Not me...

Hmmm.. then again, I DID use some 3M trim tape to hold an old radar detector and a large GPS on the window, and that worked out quite well.

It's the simple crap that's kicking my butt... :firedevil:rattle::sure:

September 21st, 2017, 13:40
What are you using now? Every button I've ever applied required a primer on both surfaces then adheasive. Never had one fall off, they will usually break the glass if I tried to remove it!

September 21st, 2017, 13:41
On one of my other cars the mirror attaches to the glued on piece using tiny ball bearings and a weird plastic piece. I guess the engineers wanted the most complex and likely to fail solution.
Sorry, nothing usedul to add other than maybe scuff the glass a bit to give the glue a chance to bite?

September 21st, 2017, 13:50
As I said, I've used the products available at several LAPS- So Permatex, Loctite, Surehold, et al.

I've razored off the glass, then scrubbed it with alcohol or lacquer thinner. Scrubbing to abrade the glass isn't a good idea.

That said, I HAVE scrubbed the button/wedge/PITA metal bit, to create a flat crosshatched clean spot.

If a primer was included, I used it.

Followed the directions implicitly. I even used a stopwatch to make sure I let it sit the 2 minutes or aas required in the instructions.

I'm thinking humidity may be the issue. Maybe I need to wait till winter

September 21st, 2017, 15:15
I used JB Weld after the DIY kits failed again. Abrade both surfaces, clean both surfaces with Acetone, press gently so you don't squeeze out all the epoxy, and hold the part in place with some duct tape. Several Midwest winters and summers and the mirror remains stubbornly mounted to the glass. You could always stop by the local auto glass shop and have them do the job for you.

September 21st, 2017, 15:58
I had the same problem when I lived in MI - every time I went to the airport the mirror would fall off my Scirocco (the roads were really that bad there)

Solution was to move out of MI.

September 21st, 2017, 16:33
Shield it from sun for 24 hours? Leave the windows open for a day? No idea...

September 21st, 2017, 17:06
I know they are temp sensitive not sure about humidity.

September 21st, 2017, 18:29
I have put it back on again with another permatex kit, using a BIG drop. I will let it cure overnight and try again. If it fails, jb weld time!

September 21st, 2017, 18:50
Are you just gluing the botton or the whole mirror?

September 22nd, 2017, 01:14
Seriously? I said I was gluing the wedge.

September 22nd, 2017, 04:05
I've never had much of an issue with them. The original may or may not fall off after years, the replacement usually lasts for years.

I do use wet and dry sand paper, about 220 grit. Use a little tape to keep from sanding too much. Acetone to clean the glass.

I did have one fall off after installing a new one. I figured the glue in the kit was junk. Used Loc Tite epoxy the next time.

The glue that comes with the kits seems to have a bit of flex in it, kind of soft. Best guess is for temp changes and windshield flexing.

If all else fails buy yourself some jewelers epoxy, No flex in it, but few things hold as strong. A little pricey.

September 22nd, 2017, 06:17
Good info there, 8Mud. This is what I was after.

I've had three of you now mention sanding the glass. Guess I will do that if this present iteration doesn't work. I would have thought it would be a really bad idea, but on further research seems I was wrong. Won't be the first time!

Thanks much!

September 22nd, 2017, 06:32
I ran across this:


It's literally a site that tells you what glues to use to stick different things together.

Dropped down metal to glass, found they even suggest JB Weld. They also suggest a Loctite UV Bond glue, but this particular windshield has a sticker or something laminated into the glass to mark where the wedge goes (rather stupid if you ask me). This prevents the adhesive from curing if you're using a UV glue, because it will mask the bulk of the area.

If this last attempt doesn't work (I used the Permatex kit, sanded the wedge, followed instructions implicitly, and used he entiretyy of the adhesive contained in the kit, not just "a small drop"), I will use JB weld. Appearance isn't super important as I have that thing masking the back side, and a UV glue wouldn't work in that application.
Of course, with the JB Weld, it will be there forever. Well, that's fine.. that's kinda the ruttin' idea! :)

September 22nd, 2017, 07:32
I've found that a little more pressure than tape helps. The last one I did I cleaned, preped, sanded, primed and pressed and it fell off after a week. I then repeated the process but applied pressure, I used a broom handle between the wedge and the seat to apply pressure for about 12 hours. It stayed for years after that application and was still on when I sold that truck. Not sure if it was the pressure or extended cure time that was the trick. Anyway it's a pain and because of it my rear view mirror is sitting on the backseat of the Jeep right now because I don't want to fool with it.

September 22nd, 2017, 08:00
I agree, pressure certainly helps. I was thinking about putting a rare earth magnet on the other side of the glass to hold it for a while.

I put the new wedge (well, since I'm having to put it back up I'm going to go ahead and put in my Gentex 261 mirror, requiring a different wedge) in last night at 1900. It's now been in place for 16 hours, I'm going to lunch and see if I can't hang the mirror.

If this SOB comes off, I'm going to JB Weld the @#%%er.//

September 22nd, 2017, 09:10
Well, that went over like a fart in church...

Put the mirror back on. Tightened it finger tight. No problem.

Adjusted the mirror. Hey, this is looking good.

Drove off. Hit a bump.

Mirror in the floor.


Bought Clearweld from JB Weld. It's made for glass to metal, and other materials. If I can find some masking tape I'll go back out and put it up...

September 22nd, 2017, 09:34
Found some duct tape ion my ruck. Plan!
Stuck it up there with the JB stuff, held it in place for the 5 minutes it takes to set. It says for best bond wait an hour.

I get off in 3 hours, I may at least pull the duct tape off and let it sit for a while, maybe overnight. At the very least I want to make sure the stuff around the sides dries well, lest I end up with the mirror bonded to the window as well (which honestly, at this point, I'd settle for!)

September 22nd, 2017, 17:30
Here's my $0.02. Windshields have a coating of wax on them- I know from experience, I compounded my windshield when I was just 16, which made the windshield unusable, dirt collected in the pores like mad, and the light from oncoming vehicles was terribly reflected on it. Many long hours of re-waxing it ensued.

By this information, I would surmise that you might get better results in making sure the wax is well removed to allow the glue to settle in the pores- I used high-grit turtle-wax compound.


September 22nd, 2017, 19:32
I used lacquer thinner. Pretty sure that will remove wax...

September 23rd, 2017, 17:12
A buddy of mine used loctite 312 and loctite 736 when installing radar trancievers in police cars. They were affixed to the glass in the same manner as the rearview. (Read: metal wedges) he told stories of chaos when removing said wedges.

I've discovered that the DIY kits sold today are useless wastes of time and money. I wish that bean counters would quit controlling the world and let the quality come back.

September 23rd, 2017, 17:55
You said a mouthful in that last bit there. I really do think that is the problem.

However, using the JB Clearweld seems to be the cat's ass. I even smacked the mirror around a bit today without any issue whatsoever.

September 24th, 2017, 12:46
Just an FYI :

Cleaning with acetone, lacquer thinner, paint thinner, etc will leave a residue on the cleaned surfaces.

Only denatured alcohol will leave a residue free cleaned surface.

September 24th, 2017, 16:51
Great point !!!

September 24th, 2017, 19:44
Yes, but as I've pointed out repeatedly, I used the solvent called for in each adhesives directions. That's what I meant by 'followed the directions implicitly'.

You will never convince me that the adhesives purpose made for this job are anything near what they used to be. I've been driving for 32 years. I've replaced many mirrors over the years (girlfriend's cars, friends cars, my own cars. Many over the years.) I've NEVER had a problem until the last 3 years or so.

Quite possibly, the EPA has gotten their fingers in the game and forked it up. They certainly screwed the pooch in the gas can arena. I've never spilled so much fuel as I have since trying these new overcomplicated abortion jobs they require be sold now.

Luckily, the solution there was a jiggler siphon.

The solution here is epoxy. Namely, JB Clearweld. Credit where it is due.

Green XJ Jeep
September 25th, 2017, 06:25
Quite possibly, the EPA has gotten their fingers in the game and forked it up. They certainly screwed the pooch in the gas can arena. I've never spilled so much fuel as I have since trying these new overcomplicated abortion jobs they require be sold now.

Makes you question the safe part in safety can doesnt it?

September 25th, 2017, 09:06
Makes you question the safe part in safety can doesnt it?

You're preaching to the choir, brother...