Technical Why do side windows break?

Walking around car shows and cruise nights, it was always puzzling to me why so many of the cars have one or more cracked windows. Nice cars, too, not just old rusty beaters. And it seems like it's always the back ones.

Now it's happened to me. I noticed today that my left rear window in my '37 has a crack. It wasn't there last week. I've rolled it down and up a few times (original regulators), and driven a few miles, but nothing I'd expect to crack a window.

Why?

 

Getting the channels and fuzzies in just right, and getting it all adjusted, and having the glass cut properly, are all challenging things to do. Especially on a 70-80 year old car.

 

they get broken the same way my socks get stolen out of the dryer

 

It's because the window glass in the old cars is laminated. Laminated glass is much weaker and cracks very easily because it can't be tempered.

 

Really!

 

Something likely put a load on them,the trick is finding what? Often its the tracks they slide in have lost padding or become out of line from a track bracket broken letting them flex

 

In newer cars the windshields are laminated to keep objects from coming through them, where side windows and back glasses are tempered to allow you to break-out in case of emergency.

Most auto glass shops don't have tempering equipment so they only use laminated glass when doing vintage cars.

 

Yes really, in our old cars the glass is cut from laminated glass, don't like slamming doors or movement, tends to crack.

 

That's why I get my side glass from a place that can do them in tempered. Especially on chopped cars!

 

Not sure when they started laminating side glass but the OG door glass in my Ford was laminated and cracked.

Now I have new glass, all the vent seals, channels and fuzzies. I'm good for another 56 years...

 

Many times it can be traced to where a rivet or screw interferes with the window channels and fuzzys or the glass is in a bind.

Slamming a door can also play a part in a cracked window.HRP

 

I always watch as kids (and unfortunately) uninformed adults slam the living daylights out of car doors. Call me old school but I would have gotten a severe scolding when I was a kid if I SLAMMED a car door shut. I get annoyed with people who ride with me, get out, turn away, and slam my door. It calls for a bit of "counseling".

 

I'm an ex-Autoglass guy.
Side laminated glass usually cracks because either a screw or rivet is sticking out of the fuzzy, a small chip along the edge of the glass, or glass not set right in the channel.
I use to cut laminate for Case tractors and other heavy equipment manufacturers. They were strict on having perfect, chip-free glass...because to them chip=crack.
When I put new chip-free laminate sidelites in, I made sure that I marked on the old glass the position where it's on channel for reference. That way I'm sure its not going to bind and have smooth operation.
I never used rivets or screws for the fuzzies. Instead, I would pre fit, apply urethane on the door where fuzzy meets door. Then roll up window to hold fuzzy in place and let it sit overnight.
Never had problems with cracks.

 

Yeah, Non old car people automaticly think they need to slam the door on a old car, or maybe its just the adrenaline rush taking affect and causing a unrealized overpowering door slam after taking a awesome ride in a old car.

 

My glass guy always does tempered glass for the doors and laminated for the fixed glass. Avoids the problem of broken glass from slammed doors etc by the "uninformed"

 

Coupes been built since 96. No broken glass yet. The slamming of doors is a big killer. Screws are another. I use a tiny wood screw that sinks deep into the fuzzy. No cracks in several years of doing this.

 

All of the glass channel and fuzzies on my Ford, the ones where it was not possible to staple or adhere the clips, I used countersunk head pop rivets. So I know they're below the surface and won't touch the glass.

I have one son, I finally broke him of his door-slamming habits. This was on my OT car, he got sick of me saying "don't slam the door!" when I dropped him off at the train station.

 

Chevy started in the early 60s. 1961 was all laminated, 1965 was all tempered...somewhere in between, they made the change.

 

lothiandon1940 has got it right. Non car people think you close the door on an old car as hard as you can.

Gary

 

So true. My windshield on my OT 88 GMC cracked right down the middle just sitting in the driveway.

Pat

 

Then you get twist and shake that doesn't help much either.

We were chatting about that exact thing last night, the engine we have in the T roadster twists the frame pretty good (even though the frame is boxed) well duh it went from the 15 or 20 HP that it had originally to 400 plus from the maybe 25 pound feet to 440+

 

Yea, many, many years of extreme hot and cold cycles, and door slam'n morons.

 

Modern vehicle doors have tight hinges and cushy weather strip acting like a shock absorber ..And yes laminated glass is pretty much just float glass so it cracks easily

 

Another bunch of reasons I like roadsters.

 

Thank you. That's good information. Slammed shut or just closed it really bugs me to see people shut a hard top door by the glass. -Dave

 

...................That's true for the glass protection but, new cars are so tight you can blow out a speaker, especially if it's in the door by slamming it too hard, and never mind the annoying rattles it can cause.

 

On a hot day you can blow the glass right out of them too. Seen it happen more then once.

I have discovered a little trick about these old heaps that we drive. Lexan makes good side glass.

its that damned cold air down the back of my neck that I don't like. You can thank my big sister for that.

hey while I got your attention I got a couple of Bruce questions if you don't mind. Check your mail please?

 

Just go some new side glass for a cracked 1/4" laminated window. Shop recommended tempered when I pick them up I used a caliper to see if it was 1/4" it measured 6mm just a little thinner, they side in the fuzzes easier may be to loose. Shop said the don't make 1/4" tempered only 6mm.
Any one know about this.
Mike

 

6MM is inly .013678 less that 1/4. I wouldn't want crank clearances to be that much too loose but I wouldn't think that it would make that much difference on glass.

I am going to fathom a guess here, economical availability verses production. Maybe they make 1/4 but the shop you're dealing with can't get it or can't get it at a price they are willing to pay.

 

The fuzzies should make up for that little difference by not crushing as much.