Cracked windscreen....but not bits....dangerous?

[cheeryble]

Hi

years ago I think I caused a crack in the top corner of my windscreen from thumping a mozzie to hard.

Couple years later got another one the other top corner.

No problem at all no leaking no edge to wear wipers so I left it (pretty old car BTW)

Recently a long crack's appeared in the middle from the top down.

Again, it doesn't bother me in the least.

A friend said the windscreen should have shattered and I must have a dodgy screen.

I doubt this as I bought the car like new very low mileage genuinely owned by two sisters and the Suzuki garage had the full history.

So, why didn't the screen shatter into many bits and can long cracks travel like this? (obviously they can)

So the first friend says it can break and hatchet my face and another friend says no the shape of the screen puts it into compression with wind and just tightens it all up.

I'll probably change it at last but just interested. Kinda seems like 4000 down the drain when I don't really care about it and the vehicle is a purely functional 4WD not a tart trap.

(BTW thats the Dang Som Pratu price I presume it's good?

Edited January 30, 2016 by cheeryble

[richard_smith237]

A long crack (i.e. 8") can happen... I experienced it a couple of years ago.

Your windscreen will shatter into tiny pieces (cubes) of glass should an impact be strong enough, in this case it was enough to start a small crack which I guess propagated though normal stress on the windscreen.

I'm not sure if this will make sense.... The crack is holding itself together preventing the catastrophic 'shattering' of your glass which will happen at some point. Additionally some / many screen are laminate, maybe only the outside layer is cracked.

It would be best to get it changed lest you find yourself on the road and it spreads and thus stuck...

[cheeryble]

U think they're not all laminated or otherwise treated Richard?

[cheeryble]

Just found this interesting bit on wiki.....labour intensive so would think they might do here in LOS

Size and depth

Repair of cracks up to 61 cm (24 in) is within permissible limits, auto glass with more severe damage needs to be replaced. Dependent on State and Local laws.

Type

Circular Bullseyes, linear cracks, crack chips, dings, pits, and star-shaped breaks can be repaired without removing the glass, eliminating the risk of leaking or bonding problems sometimes associated with replacement.

Location

If the damage is in the driver’s line of sight or very near the windshield’s edge, usually it cannot be repaired.

Some damages are very difficult to repair, or cannot be repaired:

on inside of the windshield

deep damage on both layers of glass

damage over rain sensor or internal radio antenna

damages that reach into the driver’s critical viewing area

complex multiple cracks

very long cracks (i.e. over 18–24 inches (46–61 cm) long)

contaminated cracks

edge cracks and chips

In cracked windshield repair, air is removed from the damaged area on the windshield with a specified vacuum injection pump. Then using the injection pump, clear adhesive resin is injected to replace the air in the windshield crack. The resin is then cured with an ultraviolet light. When done properly, the damaged area’s strength is restored, as is 90–95% of the clarity. Auto glass chip repair usually take about 15–20 minutes.[5]

[pgrahmm]

Spot repairs are usually only good on bulls eye/rock chip repairs....Almost like welding they have to be done correctly to not crack further....

What you are describing is a travelling stress or flex crack....If you put the tip of a ballpoint pen in the crack and follow it somewhere within the crack the pen will stick and this would be the point of impact of a pebble or other object that hit the windshield - usually close to the edge/trim/frame......If there is no impact point it is almost worse as that means body flex and possible water intrusion.....

The laminated glass is actually a sandwich of pliable plastic between two hardened piece of glass - I'd say replace it at this point as it is like anything molded once the integrity is breached....

A few years back I located a hard to find car to restore/update and flew halfway across the US to inspect and buy it.....It had like ladder cris-cross cracks in the windshield but seemed ok to drive....Driving across Texas at the 85mph speed limit I saw a one pole gas station sign that looked like the pole was bending in the middle.....As it was a strong headwind I thought it must be really windy to move that sign so many feet off center - until I looked out the side window and the 18" pole was straight !!!! It wasn't the wind it was the windshield bending inward making the sign APPEAR to be bent at the pole.....What my mind saw would have been impossible without the pole shearing and bending/breaking....But it didn't register right away....

When I got to Las Cruces NM I called a mobile shop and they came out and replaced the windshield for me the next morning......Relieved the windshield wouldn't collapse on me at freeway speeds......

As luck would have it I made it about 7 miles and about 5 minutes into the journey home.....As soon as I got on the freeway from the on ramp a pebble from a passing truck hit and broke my under an hour old windshield in the extreme upper right corner.....Making a bulls eye and a newly started flex crack.....

Moral of the story - replace your windshield.....

Edited January 31, 2016 by pgrahmm

[Jitar]

Cheeryble the windscreens that shattered in to small blunt fragments were toughened glass. One impact and these would break, if your screen has cracks it is probably not one of these.

Toughened glass windscreens have mostly been replaced by laminated windscreens in modern cars. Laminated screens can get large cracks and remain OK but eventually can become unstable as pgrahmm described. The windscreen is also stressed in some cars which exacerbates this. If the crack has been there for some time and is not growing, you might be able to get away with it for a while. If it is growing quickly, time to change.

Edited February 1, 2016 by Jitar

[cheeryble]

Cheeryble the windscreens that shattered in to small blunt fragments were toughened glass. One impact and these would break, if your screen has cracks it is probably not one of these.

Toughened glass windscreens have mostly been replaced by laminated windscreens in modern cars. Laminated screens can get large cracks and remain OK but eventually can become unstable as pgrahmm described. The windscreen is also stressed in some cars which exacerbates this. If the crack has been there for some time and is not growing, you might be able to get away with it for a while. If it is growing quickly, time to change.

I figure the shape of the screen means the air pressure compresses it into place.

But then i try to get away with anything.

It's a 16 yo car now but these 4WD Vitaras with he Jap 16valve engine are good.....especially when you have land up a hill with a dirt track......and at 191cm tall I have plenty of headroom.

I have decided even at 250,000km to repair rather than replace, and bring up to scratch a few things.....aircon, new clutch, big dent, camshaft belt, re-upholster driver seat (fabric still fine just needs stuffing again) etc......and will likely do the windscreen.

Edited February 1, 2016 by cheeryble