My windshield keeps getting cracked. Could it be my own tires flinging rocks?

[Noleftist]

I have the Continental ECF tires in 315/30-19 size on a 2022 Mach 1 with handling package. Somehow my Windshield keeps getting cracked every so many months. I’m starting to wonder if it’s due to my own tires flinging rocks up somehow and come down and crack in my windshield? Have you heard of or experienced this problem? It happens on and off track and seems to happen when I’m going straight. At times there’s nothing in front of me to fling rocks I could be 20 cars back from somebody. It happened at VIR going down the front straight and I was pretty far behind the two vehicles in front of me and all of a sudden I heard a loud noise and figured it was a hard hit from a big rock. Another time I was beside a 18 wheeler and my windshield somehow got cracked. It happened again a couple days driving on the highway. Thank you guys have a good day.

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[zenwhipper]

If you're standing still spinning the tires it is possible a rock could fly up and fall back down on the car. This assumes your tires poke out beyond the wheel wells in the upper arc of rotation - basically the upper half of the wheel well. Under regular driving conditions the answer is - highly unlikely. The reason being is an object (say a rock) on an object spinning in rotation (tire) at the moment that rock breaks free, the centripetal force instantly drops to zero - and the object travels, from the tire, at a 90 degree angle of departure. The rock flies away and behind you as your car moves down the road.

But I'd like to know how exposed your tires are that, while highly unlikely, they could possibly launch a rock to hit the windshield as you drive down the road. It would have to be quite low speeds and the right rotational timing of the rock coming off the tire, the flow of air over the car etc etc.

 

[NightmareMoon]

There's no straight path from the tire to the windshield without ricocheting off something else.

If a rock did get tossed up and then fell back down, its relative velocity would be pretty low because it would have to be moving almost the same horizontal speed as your car (you can't just toss a normal small rock from your wheel to your windshield and break it. Pretty sure anyway, I'm not going to test it

I think it was most likely a rock from the cars ahead on track, the 18 wheel right next to you, and whatever other traffic on the highway.

Sorry for the bad luck.

 

[Noleftist]

If you're standing still spinning the tires it is possible a rock could fly up and fall back down on the car. This assumes your tires poke out beyond the wheel wells in the upper arc of rotation - basically the upper half of the wheel well. Under regular driving conditions the answer is - highly unlikely. The reason being is an object (say a rock) on an object spinning in rotation (tire) at the moment that rock breaks free, the centripetal force instantly drops to zero - and the object travels, from the tire, at a 90 degree angle of departure. The rock flies away and behind you as your car moves down the road.

But I'd like to know how exposed your tires are that, while highly unlikely, they could possibly launch a rock to hit the windshield as you drive down the road. It would have to be quite low speeds and the right rotational timing of the rock coming off the tire, the flow of air over the car etc etc.

It is happening at slow speed between maybe 60mph but more often I guess 90 to and 130mph or so usually.

There's no straight path from the tire to the windshield without ricocheting off something else.

If a rock did get tossed up and then fell back down, its relative velocity would be pretty low because it would have to be moving almost the same horizontal speed as your car (you can't just toss a normal small rock from your wheel to your windshield and break it. Pretty sure anyway, I'm not going to test it

I think it was most likely a rock from the cars ahead on track, the 18 wheel right next to you, and whatever other traffic on the highway.

Sorry for the bad luck.

I was spitballing and trying to think of all possibilities.
How often do the rest of you get your windshield broken?
Thank you Nightmaremoon.

 

[NightmareMoon]

It happens. Only lost 1 in this car, Three feels like a lot, but dice roll funny sometimes.

I try to avoid following semi trucks. Anybody on the shoulder (on track or on road) can kick up a lot of crap.

 

[Skye]

Race track. 18 wheelers. I mean. Yes. You'd be surprised how far some things will travel.

I've struck my own side and back glass, but that involved a truck, A/T tires and a flat back windshield. In my car, no. Behind the tires and along the rocker panels, previously, yes.

If you don't have rock guards, those should be installed, wide enough to cover the entire surface width of the tire.

https://www.mustang6g.com/forums/threads/mudflaps-rockguards…-do-they-work.229074/

PPF across the windshield is something I've encountered more and more. In the beginning, people who owned high-end cars were getting it installed. It made sense versus paying for a new factory glass. Now, people commuting in areas of high construction are sometimes using it.

You'd have to get a quote and do a cost/benefit analysis. Discuss with an installer in your area the expected service life. It will last no more than a few years. Wipers will wear the material. If you use your wipers often like in the Pacific NW, PPF might not be worthwhile.

Edit,

Cracks don't always happen with one strike. Sometimes, one hit will create a small point of weakness or deviation. Now, the flexing of the glass as the car moves and temperature changes work on it, the glass then cracking, especially with a second strike.

 

[Unbridled5.0]

Race track. 18 wheelers. I mean. Yes. You'd be surprised how far some things will travel.

Yep. I was hit on the side of the face with a small piece of clag (balled up rubber from a race tire) when I was way up in the grand stands at a Nascar cup race. It flew up, and over the safety fence and several hundred feet, at least, before it hit me.

 

[DRIVEN]

Do you use any treatment on your windshield ? Like a vision blade (ppg) or other treatments that are similar.

 

[WItoTX]

My wife got 3 screws in her tire in a week. Hasn't had one in numerous years of ownership.

Sometimes it's just luck. I'd bet those rocks came off other vehicle tires.

 

[HoldenSSVandGT350]

As others have stated, likely debris strikes in those situations. However, it could be a structural issue due to an imperfect mating surface. Many possible reasons, none likely. If the windshield glass body attachment surface has a paint high section or any deviation from opening specifications that are outside of the - tolerance side it could be causing spontaneous cracking due to chassis flexing that pops the windshield that has no expansion room. But, that would likely lead to crack propagation from outward to inward and be obvious. Good luck going forward.

 

[Garch]

I cracked a windshield from truck stone travelling in opposite direction on 6 lane highway. I move over to inside lane and stay clear of dump trucks and stone slingers now.

 

[Hack]

Are you using OEM windshield replacements?

 

[screaminrevs]

Check your Drive Mode settings. Make sure rock atTraction Control is set to minimum, or off. You know how those things tend to reset to default all the time

But seriously, tires ahead of you can kick stuff pretty high and wide, and if you are traveling at the right speed and direction, you are lucky enough to be there just before it would have hit the ground. It has happened to me too, but not quite so frequently.

 

[G.T.]

As others have stated, likely debris strikes in those situations. However, it could be a structural issue due to an imperfect mating surface. Many possible reasons, none likely. If the windshield glass body attachment surface has a paint high section or any deviation from opening specifications that are outside of the - tolerance side it could be causing spontaneous cracking due to chassis flexing that pops the windshield that has no expansion room. But, that would likely lead to crack propagation from outward to inward and be obvious. Good luck going forward.

Thinking similar to this. What do the cracks look like?

Are they always in the same place?

Do the cracks have impact marks consistent with something hitting and causing the cracks?

 

[tom_sprecher]

It happens...three times to my car. Now I buy glass replacement coverage after the first time.

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