You walk back to the trailer after the feature and you say the track changed on you. No. The track did not change on you. You never knew what the track was. Eldora Speedway sits on a Celina silt loam — an Aquoll — and that native substrate holds moisture three hours longer than a sandy Udipsamment track 90 miles east. Nobody told you that. Tonight we fix that. This is Hunter's Column Lab. I'm HUNTER, with Hast on the call. Column number thirty is our biggest yet — the three-layer soil model, USDA SSURGO substrate data, what promoters actually amend, and what your boots tell you during the track walk. Plus: Brandon Sheppard coming into Ohio red-hot, the World of Outlaws Blaster 57 Special at Mansfield kicking off tonight, and David Gravel strangling the sprint car points lead with three-hundred-eighteen points of daylight. This is Hunter's Column Lab. We read the column so you don't have to skim the data boxes.
HUNTER Tonight's column is number thirty — 'The Dirt Under the Dirt' — and it is the framework column, the one I have been building toward since we started tracking substrate data. We have SSURGO measurements on 557 of 598 tracks in our dataset, that is 93% coverage, and tonight we walk through exactly what those numbers mean for your right rear tire pressure. On the racing side, the World of Outlaws Late Model Blaster 57 Special is live tonight and tomorrow at Mansfield Speedway in Ohio — Brandon Sheppard enters as the clear setup favorite after sweeping three straight World of Outlaws appearances at Wayne County just a few years back, and he grabbed the Lonewolf 40 at Wayne County just two nights ago on Thursday.
HAST Right, so Sheppard is the name to beat in Ohio, full stop. On the sprint car side, David Gravel holds the World of Outlaws points lead at thirty-three sixty-four — that is one hundred eighteen points clear of both Michael Kofoid and Carson Macedo, who are tied at thirty-two forty-six. And Aaron Reutzel has been absolutely on fire in High Limit action, taking a twenty-thousand-dollar payday at Grandview earlier this month. Hudson O'Neal has already stacked up ten wins on the year in late models, which is a number that should make everyone else in that hauler very uncomfortable about their spring-rate decisions.
HUNTER Every Saturday night somebody walks back to the trailer and says the track changed on me. No. The track did not change on you. You never knew what the track was. You were reading the top eighth-inch of a system that goes down four feet. The surface you drove on tonight is layer three of a three-layer stack, and if you do not understand layers one and two, you are guessing. You have been guessing. That ends today. Wikipedia will tell you dirt track racing happens on clay. It will not tell you that the native soil under Eldora Speedway is a Celina silt loam — an Aquoll with a saturated hydraulic conductivity of 4.2 micrometers per second and a drainage class of somewhat poorly drained. It will not tell you that this is why Eldora holds moisture three hours longer than a track 90 miles east sitting on Udipsamments — sandy, excessively drained soil that bleeds water like a screen door on a submarine. It will not connect any of this to your right rear tire pressure. I will.
HAST So the three-layer model fits on a napkin and it is the single most useful framework in the column. Layer one is substrate — the native soil under the track, geological timescale, nobody controls it. Layer two is the racing surface — what the promoter imported, blended, and maintains, timescale seasonal to annual, the promoter controls it. Layer three is race-night condition — tack, slick, rubber, moisture gradient, timescale hours — it changes between your heat and the feature. This is the layer most racers think is 'the track.' It is not the track. It is tonight's weather report on a surface built on a substrate you have never looked up. Three different data sources, three different timescales, and every setup mistake I have ever seen comes from confusing which layer the driver is actually reacting to.
HUNTER The USDA NRCS has mapped the soil of the United States at a resolution that would make a race team's data acquisition system jealous. Every square meter has a map unit key tied to taxonomic classification, particle-size distribution, drainage class, available water capacity, and saturated hydraulic conductivity. The system is SSURGO. The farmer interface is Web Soil Survey. The API our dataset uses is Soil Data Access at SDMDataAccess dot sc dot egov dot usda dot gov. Same data agronomists use to decide whether to plant corn or soybeans. We use it to understand why your 410 goes slick in 14 laps at one track and holds moisture for 30 at another. A track sitting on 85 percent sand — Udipsamments, common in Florida and the Sandhills — drains water almost instantly. A track sitting on 22 percent sand, 45 percent silt, 33 percent clay — Aquolls, common in the Ohio and Indiana river bottoms — holds moisture for hours. Saturated hydraulic conductivity over 40 micrometers per second means rain drains through fast. Under 4 means water pools and perches, and after a heavy rain the promoter may need 4 to 6 extra hours to get the surface right.
HAST And here is the mistake that 90 percent of racers make — the clay percentage at the SSURGO pin is the native soil. It is not what you are racing on. A track in central Florida might sit on 87 percent sand substrate. Pull up Web Soil Survey, look at the pin, and you would think the track could not possibly support a dirt-racing surface. But the promoter trucked in 200 loads of Hawthorne clay from a pit in Alachua County, blended it with the native sand, and built a racing surface that runs 31 percent clay in the top six inches. SSURGO says sand. Your tires say clay. Both are true. They are measuring different layers. The target for most racing surfaces is 28 to 35 percent clay content in the amended layer — enough cohesion to hold moisture and rubber, enough silt for a smooth polished surface when it slicks off, enough aggregate structure to resist breaking into dust too early.
HUNTER Layer three is the layer most racers live in. It is the only layer you can read with your boots. And it is the layer that changes fastest — sometimes between your heat race and the feature, sometimes between turns one and three on the same lap. Your track walk gives you five data points. Footprint depth — walk the racing groove and check how far your boot sinks. Less than one-eighth inch: slick, polished, low grip, the track has already transitioned. One-quarter to one-half inch: tacky, moisture is present, your crossweight window is wider and your right-rear spring rate choice matters more. Surface color — darker means wetter. Tack sound underfoot — a sticky pull as you lift your boot means calcium chloride is active and surface chemistry is working in your favor. This is the column that ties it all together. SSURGO tells you what the earth is. The promoter tells the earth what it is going to be tonight. Your job is to figure out which one is winning.
HUNTER Here is the take I want to put on the table: substrate data is the most underused variable in all of dirt racing setup science. Teams spend four figures on shock valving, they argue spring rate within fifty pounds, they dial crossweight to the half-percent — and then they show up at a track built on Udipsamments and run the exact same tire pressure they ran at Eldora. That is not a shock problem. That is not a spring-rate problem. That is a soil-taxonomy problem, and it costs you track position every single time the surface transitions faster than your setup expects.
HAST Okay but let me push back on one thing, because I think there is a real limit here that the column does not fully address. SSURGO data is static. It tells you what the native soil has been for thousands of years. It does not tell you what the promoter did with 200 loads of clay last winter, or whether they switched calcium chloride suppliers, or whether the track sat under six inches of rain two weeks ago and the sub-surface is still saturated at depth. You can have perfect SSURGO data on a track and still be completely blindsided on race night because layer two changed on you in the off-season with zero public documentation anywhere.
HUNTER That push-back is exactly right, and it is precisely why the column frames all three layers as a system, not a single lookup table. SSURGO gives you the baseline behavior — what the substrate will do when pressure is applied from above, how fast it drains, what the capillary buffering capacity looks like. But you are correct that layer two is the blind spot in most datasets, including ours. That is why the column calls for promoter records, soil notes, and documented surface clay sources as the layer-two data source. The honest answer is that the industry does not publish that data consistently, and until it does, substrate science plus a disciplined track walk is your best available tool. Use the baseline. Adjust at the track. Mark your inferences clearly.
HAST Other dirt racing results from the past week: Brandon Sheppard took the Lonewolf 40 at Wayne County Speedway in Orrville, Ohio on Thursday, May 28th — which matches the World of Outlaws Late Model schedule exactly where we expected him to be dominant. On the sprint car side, David Gravel picked up the Morgan Cup at Williams Grove Speedway earlier this month, and Kasey Kahne scored his first World of Outlaws sprint car win of 2026 also at Williams Grove in a duel with Sheldon Haudenschild. Hudson O'Neal sits at ten wins on the late model season, which is a pace that puts serious crossweight pressure on every other team trying to figure out what that Longhorn Chassis is doing differently lap to lap.
HUNTER Anthony Macri took a significant back injury after a Friday night crash at Williams Grove and that reshapes the northeast sprint car picture for the near term — a tough break for a guy who was running up front consistently. On the High Limit side, Aaron Reutzel cashed a twenty-thousand-dollar payday at Grandview and continues to be the name in May for that series. Tonight and tomorrow the World of Outlaws Late Model Blaster 57 Special runs at Mansfield Speedway — tomorrow night's purse is fifty-seven thousand to win, two hundred forty thousand total, which is a significant event. Sheppard has history there including the Dirt Million in 2019, so watch that setup sheet closely.
HUNTER Quick hits: the USAC Corn Belt Clash at Knoxville is running tomorrow night — non-wing sprint car fans, that is your watch. The MARS USA World 50 at Paducah is also tomorrow with ten thousand to win on the late model side. Northern Allstars made a May 29 to 30 swing for ten-thousand-to-win events at Bloomington and Brownstown in Indiana — actual competitive setups on those Udoll substrates in the river bottoms, which should produce a very different track character than the sandy Florida tracks everyone tuned on in February.
HAST Dexton Koch is stepping up to the WISSOTA Late Model division in 2026 after 100 super stock wins in four seasons — worth watching to see how a crossweight and stagger toolkit built on super stocks translates to a full late model four-link, because that transition is exactly the kind of chassis-science story this show lives for. And the DIRTcar Sportsman Series had a full Memorial Day weekend swing across the northeast — good baseline data on how those weekly-class setups perform on different county-fair substrates if you are looking for layer-one comparisons in the dataset. That is column number thirty. The three-layer model is on racer dot wiki right now with the full substrate table, the Ksat values, the AWC ranges, and the promoter amendment breakdown. Next week we go deep on calcium chloride — how much is too much, what it actually does to your tire wear rate in the first five laps, and why tracks on Udipsamments are the heaviest users. Hunter out. Read the full column at racer.wiki.