Affiliate disclosure: 2500hd.com is reader-supported. Some links below are affiliate links, so if you buy through them we may earn a commission at no extra cost to you. As an Amazon Associate I earn from qualifying purchases.
My Toyo Open Country R/T Trail 37×12.50R20s
I’ll be honest: I didn’t lift my truck. I bought it that way. My white 2021 Silverado 2500HD with the 6.6L gas V8 came from the previous owner already lifted and sitting on 37s, and the first time I walked up to it I was sold. It fills out the wheel wells the way an HD should. He also put in High Country leather seats and upgraded speakers, and the cab sounds fantastic. Under all that it’s still a simple truck with a real metal key and none of the fluff sensors I don’t want. I love it.
Owning a lifted truck you didn’t build teaches you fast what a “just add 37s” setup changes. Here’s everything I’ve learned, with sources, so you can do it right the first time.
My setup: 2021 2500HD, 6.6L gas (L8T), white, Toyo Open Country R/T Trail 37×12.50R20 tires, lift installed by the previous owner (brand and height unknown to me). Tiresize.com lists that tire as an LT 126Q, Load Range E (10-ply) tire with a 36.5-inch actual diameter, about 74 lb each, and a 65 psi max (>Tiresize.com). I love how they look and drive.
The 2020+ HD has torsion-bar independent front suspension and rear leaf springs, which gives you three main routes.
Option 1: Leveling kit + modifications (cheapest, most compromise)
Torsion keys (often 2–3 inches of front lift), sometimes with a rear block. Injected Motorsports, a GM HD shop, says 37×12.50s on negative-offset wheels need a bumper spacer kit or aftermarket bumper to clear in the front at about 2.5 inches of front lift (>Injected Motorsports). Owners report 37s on 3-inch leveling setups with trimming and spacers, but with rubbing at full lock (>GM-Trucks forum). Cognito rates its 3-inch kit for up to 35×12.5, and Zone Offroad’s 2- and 3-inch HD kit fitment also tops out at 35×12.50 (>Zone Offroad).
Option 2: 5-inch lift (the sweet spot)
Zone Offroad lists 37×12.50 tires on 20×9/22×9 wheels with 5–5.5″ backspacing for its 5-inch HD kits (>Zone Offroad). BDS also makes a 5-inch kit for 2020–2026 HD 4WD trucks (>Jack-It, BDS766H).
Option 3: 6–6.5-inch lift (cleanest 37 fitment)
ReadyLIFT’s 6″ MAX2.1 system (SKU 42-30640) for 2020–2024 GM HD is rated for 37×12.50 on a 20×9, 0-offset wheel with no rub, lists for $3,359.95, and has an estimated install time of about 12 hours (>ReadyLIFT). BDS’s 6.5-inch kit lists from $2,545.53 to $3,151.45 (>BDS).
Bought one already lifted, like me? Look for brand stamps or stickers on the knuckles, crossmembers, and shocks, and measure ride height at the fender lips. That tells you what you have before you buy parts.
Let’s Talk About Rubbing (Mine Rubs Some)
My 37s rub a little. That’s normal for a lot of 37 setups that weren’t built around a specific kit’s tire chart. Here’s where rubbing comes from and the usual fixes, from least to most invasive:
Full-lock rub on the inner liner or frame. Common on leveled trucks. Owners usually live with it or trim the liner. Wheel offset and backspacing play a big part.
Front bumper/air dam at full lock. This is the one Injected Motorsports calls out. The fix is a bumper spacer kit or an aftermarket bumper.
Mud flaps and plastic liners. Trimming or removing the flaps and trimming the liners is the cheap first step.
Rub under compression (bumps, loaded bed). This points to too little lift for the tire or the wrong offset. The real fix is matching wheel specs to your kit’s chart.
Always check that rubbing isn’t damaging tire sidewalls or brake lines, and recheck after any alignment.
GM’s 2021 2500HD trailering guide lists 3.73 axles behind the 6.6L L8T gas and 3.42 behind the Duramax (>2021 trailering chart). Confirm yours on the glovebox RPO sticker.
Effective ratio = axle ratio × (stock tire diameter ÷ new tire diameter)
Using a 275/65R18 (about 32.1 inches) as the stock example and my Toyos’ listed 36.5-inch actual diameter: 3.73 × 32.1 ÷ 36.5 ≈ 3.28 effective. Use the measured diameter, not the nominal “37,” for this math. That’s a big step down for a gas engine, and you’ll feel it when towing and on long grades. Mine has not been regeared. It’s still on the stock 3.73 gas axles, and that’s exactly the 3.28-effective setup above. Regearing both axles is a driveline-shop job, so if you tow heavy or climb a lot of grades, get quotes and pick a ratio that suits your tire size and towing.
MPG on mine: I averaged 11.4 mpg when I bought it. It’s now around 12.5, and I’ve seen up to 13.5 since fixing a failed fuel pump module (here’s that story). These are my numbers from the truck’s display, not a controlled test.
Speedometer and Odometer Recalibration
Using the 32.1-inch example, my 36.5-inch Toyos are about 14% taller (36.5 ÷ 32.1 ≈ 1.14). An uncorrected speedometer showing 65 mph means you’re doing roughly 74, and the odometer and trip MPG under-count distance by the same amount.
For gas trucks:
Rough Country Speedometer Calibrator 90045 ($259.95) fits gas and diesel 2020–2023 Silverado/Sierra 2500HD. Rough Country says it updates the speedometer, ECM shift points and stability control. It’s not for sale or use in California and doesn’t fit the refreshed 1500s (>Rough Country).
The Hypertech 730129 is listed for the L5P Duramax, not the gas L8T (>DmaxStore).
My speedometer has been calibrated for the 37s. I don’t know which tool or method was used, so I won’t pretend it was one of the products below. I’ve checked it against GPS and it reads accurate. Whatever you use, verify it against a GPS speed app afterward.
My 2021 2500HD 6.6 gas, bought already lifted on 37s
Ball Joints, Upper Control Arms and Steering
Lifting or cranking the torsion keys changes the angle of the factory upper control arm (UCA) and its ball joint. Injected Motorsports “highly recommends” aftermarket UCAs and correct-length shocks on leveled HD trucks, and suggests keeping at least a thumb-width of clearance between the UCA and the frame jounce stop (>Injected Motorsports). Kryptonite’s UCA kit for 2020–2026 GM HD (SKU KRUCA20) lists at $699.99 (>Kryptonite). Heavy 37s also load up the tie rods, so check for play at every rotation, and align after any front-end change.
Bigger, heavier tires mean more rotating mass and more leverage against the brakes. My Toyos are listed at about 74 lb each (>Tiresize.com), and ReadyLIFT notes most large aftermarket truck tires are 10-ply or more (>ReadyLIFT). I don’t have stopping-distance data for this truck, so I won’t invent any. Do fresh fluid, towing-rated pads, and quality rotors, and re-set your trailer brake gain.
TPMS: move or replace the sensors, and set pressures for your tires, not the door-placard size. (Fun fact: the truck can flash a turn signal at you when a tire is low. Here’s how Tire Fill Alert works.)
Headlight aim shifts with height.
Warranty: The FTC says your warranty stays in effect with aftermarket parts, and a dealer must prove an aftermarket part caused a failure before denying that claim (>FTC).
If you’re still deciding what to run, I put together my picks for the best tires for the 2500HD. And once a truck is lifted, the hitch sits higher too, so I wrote up the drop hitch I tow with.
FAQ
Can a 2020+ 2500HD fit 37s with just a leveling kit?
Owners do it with spacers or aggressive offset, trimming, and bumper work. Expect some rub at full lock.
Why do my 37s rub?
Usually full-lock contact with liners, the frame, or the front bumper, or not enough lift or the wrong offset for the tire. Trim first, then fix wheel specs.
Do I need to regear a gas 2500HD for 37s?
The factory 3.73 drops to about 3.28 effective on a 36.5″-actual 37×12.50R20 (from a 32.1″ stock tire). Gas trucks that tow feel it most. Some owners regear; mine is still on the stock 3.73s.
Which speedometer calibrator fits a gas 2500HD?
Rough Country 90045 lists gas and diesel 2020–2023 2500HD fitment. Hypertech 730129 is listed for the Duramax.
Will lifting void my warranty?
Not entirely. The dealer must show the aftermarket part caused the specific failure.
Prices are as listed by the retailers in October 2026 and may change.
Glitchy intermittent wipers, flaky Bluetooth, turn signals flashing on their own, and dead batteries on 2020–2024 Silverado/Sierra 2500HD: the GM bulletins, recalls, and owner fixes.
A rear turn signal blinking on its own on a 2020+ Silverado/Sierra HD is often Tire Fill Alert flagging a low tire. How the feature works, how to use it, and TPMS tips from the owner’s manual.
My 2021 Silverado 2500HD 6.6 gas lost its fuel pump module at 65k miles. Symptoms, the GM bulletins, why my VIN didn’t qualify for a recall, parts, and real cost ranges.
