1engineer
Moderator
I've had rocks kicked up by trucks that were more than 10 lengths ahead of me.
At 70 mph you cover your "10 lengths" in less than two seconds.
Sure, the windshield angle has some effect that will ultimately determine the maximum force of the impact.
What is just as important is the angle, mass and velocity of the projectile, in this case a rock. I have had many many vehicles over the years and this 4Runner on average has been struck by a rock in the windshield about the same as the other 20+ vehicles I have had. Call it what you want: Fate, Luck, Kharma or anything else. Everyone think for a minute:
In order for a rock to strike your windshield requires much more than the angle of the 4Runner windshield.
To the guy above who says bugshields worked for his buddy: Haha. They don't even keep bugs off the windshield much less change the trajectory of a rock by causing a different airflow pattern.
I put 29K on my 4Runner the first year. It has been hit several times by rocks, but not more than any other vehicle.
If you get a rock to hit and crack your windshield, especially from 4 lanes over, go buy a lottery ticket because you beat the odds that day. On second thought, go home and go to bed. With the odds you just beat, you might get struck by lightning too!
The only things that will change the odds are:
1. Drive less miles
2. Do not drive behind any vehicle
3. Drive really slow
Good luck!