Picture this: it's August at Limaland Motorsports Park, the surface has been polished glass-slick, and you reach for your second compound bin — the F85A Hard right rear you've trusted for a decade — and it isn't there. Because it's 2026, and GLSS already burned that option out of the rulebook. You're running MC3, one compound, every condition, every night, all season. This is Hunter's Column Lab. I'm HUNTER, with Hast on the call. Tonight we break down Column 38 — the full science behind the Great Lakes Super Sprints spec rubber mandate. MC3 on the right rear, SD38 on the left in three sizes, why that half-inch circumference gap between the MC3 and your old Hoosier Medium will move your entire stagger baseline, and what to do when a co-sanction event sends you to the wrong tire bin. This is Hunter's Column Lab. We read the column so you don't have to skim the data boxes.
HUNTER Tonight we are locked into Column 38 — the GLSS spec rubber deep dive. American Racer MC3 on the right rear, SD38 on the left in 28.5, 29.0, or 30.5, and a full Hoosier-to-AR translation map for the teams still building a baseline after three completed GLSS points races under the new rubber. Series owner Barry Marlow told the paddock that American Racer availability is excellent and the pricing will save drivers money each race — those were his words in the official announcement. That is the official reason. The column gets into the real setup science underneath it.
HAST Right, and this mandate matters beyond just the GLSS paddock. Ten seasons of Hoosier-only on all four corners, ended with three sentences in a rules update posted through TJSlideways on January 16th. What's wild is that Devon Dobie and Chase Dunham already went one-two at I-75 Raceway on the new American Racer rubber while other teams were still burning grace-period Hoosiers — and that split-compound experiment in the paddock is already generating real on-track data that nobody has fully mapped yet.
HUNTER One series, one right-rear compound, three left-rear sizes, and no Hoosier once your grace period burns. Great Lakes Super Sprints mandated American Racer spec tires for every 360 winged sprint points race starting in 2026 — the first major regional sprint tour to lock in this exact MC3 and SD38 combination. If you race GLSS, this is your tire reality. If you race anywhere else in the 360 world, pay close attention anyway, because spec-rubber mandates tend to spread. The official reasons per the series: rising tire costs, sizing inconsistencies across Hoosier product runs, and overall tire life concerns. The rule is the rule. Let's talk about what it actually requires and why it changes your setup math.
HAST The open-front rule is the quiet revolution buried in the headline here. For ten full years, every GLSS car rolled on Hoosier all four corners. Now you can run American Racer rears with Hoosier fronts, or American Racer all the way around, or theoretically some other brand up front if it meets the size window. Mixed-brand cars are legal at GLSS for the first time, and that changes the front-to-rear grip balance conversation in ways nobody has fully mapped yet. Sister divisions GLTS and GLLS went open tire entirely — any brand, any compound. Do not confuse them with the GLSS spec. Same organization, completely different rules.
HUNTER The MC3 in 34.0 by 17.0 by 15GT rolls out at approximately 104.5 inches of circumference. Your old GLSS Hoosier Medium in 105 by 16 by 15 was nominally 105 inches. Half an inch of circumference difference does not sound dramatic until you realize your entire stagger calculation starts from that number — and half an inch of right-rear circumference change moves your stagger target by half an inch if you don't also move the left rear. American Racer lists the MC3 as hard on their website, but Hoosier's cross-reference chart slots the MC3 approximate equivalent in the D25 medium-hard band. This is where teams are getting burned — they see MC3 cross-refs to Hoosier Medium and they copy their 2025 Hoosier Medium setup sheet without measuring anything. The MC3 is not the Hoosier Medium. Different carcass construction, different rubber chemistry, different physical size.
HAST And the SD38 left rear is where your stagger decision actually lives under this mandate. The SD38 cross-references to the Hoosier D15 neighborhood — a stiffer band than the soft Hoosier left-rear options many GLSS teams ran in 2025. You get three circumference choices: 28.5, 29.0, or 30.5 by 15-inch bead. Against the MC3's roughly 104.5-inch circumference, the 28.5 gives you about 14.5 inches of cold stagger — maximum rotation, best tool on a dry-slick surface where the car is pushing off the corners. The 30.5 drops you to about 8.5 inches of cold stagger — more drive off corner, less rotation, right call on a fresh tacky surface. The 29.0 is the middle child and it's where Hunter says to start on any track you haven't run on SD38 rubber before, roughly 12.5 inches cold. The tire will grow under heat, the stagger will tighten, and that's exactly what your hot-stagger log is for.
HUNTER The grace period and co-sanction question will bite somebody this summer — that's not speculation, it's a near-certainty. Hoosier right rears were legal for the first four GLSS points races of 2026, left rears for the first eight. After race four the Hoosier right rears become wall art. After race eight, same for the lefts. Document which race number you're attending — tech knows the count and 'I lost track' is not a defense. Co-sanction nights are the edge case. The April USCS and GLSS double-header at Sweetwater ran under USCS tire rules, meaning Hoosier. When two sanctioning bodies share a program, the tire rule follows the event bulletin, not the series default. Read the entry blank. Attend the drivers' meeting. Ask the question out loud. The one night you assume GLSS rules apply and load only AR rubber could be the night the co-sanctioning body mandates Hoosier.
HUNTER Here is the take I want to put on the table: the removal of the F85A as a second compound option is actually good for the sport at this level. When you had two right-rear compounds, you introduced a setup variable that advantaged teams with more tire testing budget and faster learning loops. Better-funded operations dialed the compound selection faster. The MC3 as a single compound levels that playing field. The tuning tools you still have — left-rear size selection across three circumferences, air pressure, crossweight, wing angle — are all available equally to every car in the field. The compound becomes a constant, and your engineering skill becomes the differentiator.
HAST Okay but I'd push back on that framing, because what you're describing as a leveling mechanism also removes a legitimate technical skill set from the sport. Compound selection on slick versus tacky surfaces was real crew chief knowledge — the teams who read the surface correctly and reached for the F85A at the right moment earned that advantage through experience and observation. Collapsing all surface conditions into one compound and telling teams to compensate with left-rear size and air pressure is simpler, sure, but simpler is not always better. You're swapping one form of expertise for a narrower one.
HUNTER Yeah, I hear that argument, and it has merit on compound expertise — but here's why I still land where I do: the MC3 is not a hard tire in behavior even though American Racer calls it hard in their catalog. It cross-references closer to the old Hoosier Medium in the medium-hard band. So you are not actually running a one-size-fits-all blunt instrument. You are running a tire that has a real operating window, real pressure sensitivity, real heat dependency — and you are managing it with the circumference tool instead of the compound-swap tool. That's still crew chief science. It's just a different chapter of the book, and one that puts every team on genuinely equal raw material.
HAST Other dirt racing results from this past week. On the World of Outlaws tour, Michael Kofoid took his sixth win of the 2026 season at Huset's Speedway in Brandon, South Dakota on May 25th — a dominant run from seventh starting spot where he charged to the lead by lap 13 and pulled away by nearly four seconds over Sheldon Haudenschild and Aaron Reutzel. That's his 28th career World of Outlaws win and it ties him with Kerry Madsen for 25th all-time. Kofoid is now the outright winningest driver on the tour in 2026, with David Gravel sitting first in points ahead of Kofoid and Carson Macedo.
HUNTER On the GLSS side, Devon Dobie picked up a points win at Waynesfield Raceway earlier this month with Bryan Sebetto second and Kasey Jedrzejek third. And confirming what the column tracks — three GLSS points races have been completed under the new MC3 and SD38 rubber as of late May. The hot-stagger data and pressure baselines that teams are logging at those three events are the only real reference material that exists right now. Nobody has enough laps on this specific combination to call anything settled.
HAST Quick hits on the wider dirt world. High Limit had Aaron Reutzel winning at Kokomo Speedway on May 9th and at Texas Motor Speedway dirt track on May 2nd — Reutzel has been the most consistent High Limit performer in the spring stretch. Tonight the World of Outlaws opens the Northern Tour at River Cities Speedway in Grand Forks, North Dakota, with Kofoid entering as the clear favorite given he swept both River Cities events in 2025. Donny Schatz and Sheldon Haudenschild are the names to watch on Schatz's home turf this weekend.
HUNTER Also worth noting: GLSS has Limaland Motorsports Park on Friday June 6th as the next scheduled points race, followed by Lawrenceburg Speedway on Saturday June 7th. That Limaland night will be a real data point — it's one of the few Ohio tracks where the surface can go fully polished slick on a summer Friday, which means teams running the 28.5 SD38 to chase maximum stagger on a dry surface will get their first real confirmation on whether that 14.5-inch cold stagger number holds under race load on a glass track. Log your hot-stagger after 15 laps. That number is the only one that matters. That's Column 38. MC3 on the right, SD38 on the left, three circumferences, one compound, and a grace-period clock that is running. Next week we are watching the Limaland numbers closely. Measure your own roll-out. Do not trust the catalog to the quarter-inch. Hunter out. Read the full column at racer.wiki.