Harvest Season and Why Gravel Damage Spikes in September

From late August through October the traffic pattern in Weld County changes completely. Silage trucks run corn to the feedlots, beet trucks work the fields north and east of Greeley, and grain carts move between farms on roads that were quiet in July.

Most of that traffic is heavy, loaded, and running on gravel. It is the worst combination for windshields that exists here, and it is the reason September is consistently one of our busiest months for chip repair.

What is actually happening to your glass

A loaded silage truck puts a lot of weight through tyres with deep, aggressive tread. On a gravel surface those tyres pick up stones, hold them in the tread, and fling them backwards as the wheel comes around. The stone leaves at close to the vehicle speed, and you are driving towards it at yours.

That closing speed is the whole problem. A stone thrown back at 40 mph, met by a car doing 40 mph, arrives with the energy of an 80 mph impact. Laminated glass handles a surprising amount, but not that, and not repeatedly.

This is also why the damage clusters where it does. Most harvest chips land in the upper two thirds of the windshield, driver side, because that is the line the spray takes from a truck ahead of you.

Why it is worse on county roads than on the highway

Weld County has a large grid of numbered county roads and a good share of them are unpaved. Those roads are the direct route between field and feedlot, so that is where the trucks go.

Three things make them worse than pavement. There is loose material available to throw, which a paved road mostly does not have. The trucks run closer together in convoys during harvest. And the roads are narrow enough that you pass oncoming traffic with very little lateral separation, so you catch spray from both directions.

Freshly graded roads are the worst of all. Grading brings loose aggregate to the surface, and for the first week after a grader passes that road throws stones far more than it did before.

How to drive it

You cannot avoid these roads if you live or work out here. You can change how much glass damage you take.

• Following distance is the entire game. Six to eight seconds behind a loaded truck on gravel, not the two or three that feels normal. Stones lose energy fast, and distance is what buys you that.
• Slow down when meeting oncoming traffic rather than holding speed. Closing speed is what does the damage, and you control half of it.
• Move right and ease off when a loaded truck comes the other way on a narrow road. A few feet of separation matters more than it seems.
• Avoid passing on gravel during harvest. Pulling alongside a loaded truck puts you directly in the spray line for the length of the pass.
• Give freshly graded roads a week, or take the paved route, if you have the option.
• Keep the washers full and use them. Dust on the glass scatters low autumn sun badly, and in September the sun sits at exactly the wrong angle morning and evening.

Fix chips before the freeze, not after

This is the part that costs people money, and the timing is unforgiving.

A chip you pick up in September sits in the glass through October. The first hard freezes arrive, water that got into the damage turns to ice and expands inside the cavity, and the chip that was a thirty minute repair becomes a replacement. We watch this happen every year, in the same order, to the same chips.

So the rule for harvest season is simple. Get the chip filled while it is still autumn. Chip repair takes under half an hour, and most Colorado insurers waive the deductible on repair, which usually means it costs you nothing out of pocket. The mechanism behind the autumn deadline is covered in detail in why Colorado temperature swings turn chips into cracks.

Farm trucks, feed trucks and fleet vehicles

If the damage is to the working vehicles themselves rather than to a car that passed them, the calculation is different. A truck off the road during harvest is a real cost, and the window to fix it is between loads.

We handle that as mobile work at the yard, the shop or the field edge. Heavy equipment and agricultural glass is its own category, covered on heavy equipment and ag glass, and multi-vehicle operations are covered on fleet and commercial glass.

If it is already a crack

A crack that reaches the edge of the glass or sits in your line of sight is a replacement, not a repair. On anything recent with a camera behind the mirror, that also means recalibration afterwards, because lane keeping and automatic braking read the road through that glass.

We cover Greeley, Eaton, Kersey, La Salle, Ault, Pierce and the rest of Weld County as a mobile service, so harvest work does not mean a trip into town. Text a photo of the damage to (970) 608-4888 and we will tell you whether it is a fill or a replacement before we set out.

More guides

• Why US 85 is hard on windshields. A freight corridor with no median and permanent roadworks.
• Oilfield traffic and what it does to glass. Lease roads, sand haulers and fleet glass as a running cost.
• What to do in the first hour after a rock chip. Keep the cavity clean and dry, and book it the same week.

Harvest damage still gets fixed from the same Greeley base. See our main service page.