Plenty of guys buy a truck and never once put a trailer behind it, and that almost seems like a shame. A GMC Sierra Denali is posh and comfortable, sure, but the real strength is in what it can drag down the road behind it. The problem is that most of us treat the how-to part as an afterthought until the day we find out we did it wrong. A few years back GMC put me through their Tow Like a Pro event, and these are the fundamentals that stuck.
What Do You Call Your "Guys Trips"?
- The weight rating printed in the brochure almost never applies to the truck sitting in your driveway.
- Tongue weight is what keeps the trailer following the truck instead of shoving it around.
- There is a point where a standard ball hitch stops being enough, and it arrives sooner than most guys expect.
- Adding tires, a lift, or a bigger hitch changes your real capacity, and nobody sends you a new sticker.
- The yellow label in your door jamb overrules the tow rating you bragged about at the dealership.
Towing is one of those skills that looks like nothing until the first time a loaded trailer pushes you through a stop sign. The fundamentals are learnable in an afternoon, and most of the mistakes guys make hauling a boat up to the lake for a weekend come down to skipping one of the steps below.
Understanding How Much You Can Safely Tow
Every truck has a maximum trailer rating, and plenty of owners have never gone looking for theirs. It is printed in your owner's manual, not in the ad you remember. It matters because the damage from towing past it does not show up on the drive home. It shows up later as a cooked transmission, a bent frame, or brakes that quit on the one grade where you needed them.
The trucks we ran at the event were brand new 2018 Sierra Denalis, and they were fantastic to drive. Back then the Sierra 1500 topped out at 12,500 pounds and the Sierra HD at 23,300. Today a Sierra 1500 will go to roughly 13,300 pounds with the 3.0L Duramax, and a 3500HD is rated as high as 36,000 with a fifth wheel. Those ceilings keep climbing every few model years, which is the best argument I know for ignoring headline numbers entirely and looking up your own truck.
Two things move your real number away from the brochure. The first is configuration: cab, bed length, drivetrain, axle ratio, and tow package all change the rating, and the maximum always belongs to one specific build that is probably not yours. The second is anything you bolted on afterward. Aftermarket hitches, larger tires, and lift kits all shift your capacity, and nobody mails you an updated sticker when they do. If you have modified the truck, or you are deciding what to modify, our breakdown of how to set a truck up to tow covers where the money is worth spending.
Gross Vehicle, Gross Trailer, and Gross Combination Weight
Towing math sounds worse than it is. There are four figures, they stack on top of each other, and naming them correctly is most of the work.
Gross Vehicle Weight
This is what your truck weighs right now, fully loaded - the vehicle itself plus fuel, passengers, tools, coolers, and whatever has been living in the bed since spring. It gets measured across two points:
- Front Axle Weight - the share of that load carried at the front axle
- Rear Axle Weight - the share carried at the rear axle, which is where tongue weight lands
Gross Trailer Weight
This is the trailer and every bit of cargo on and in it. It also breaks into two numbers:
- Tongue Weight - the downward force the loaded trailer puts on your hitch ball
- Trailer Weight - the trailer plus its full load, measured at the trailer's own axles
Gross Combination Weight
Add Gross Vehicle Weight to Gross Trailer Weight and you have Gross Combination Weight: the entire rig, truck and trailer together. Your truck has a rated ceiling for this, and it is the figure guys forget. Knowing your trailer weight is not enough on its own, because the truck has to haul itself up the same hill.
What Kind of Hitch Is Right for Your Truck
Most light-duty trucks like the Sierra 1500 use a standard weight-carrying hitch, and for a lot of loads that is the correct answer. Our trailer at the demonstration carried two four-seat Polaris RZRs and came in around 7,000 pounds on a standard ball-and-socket setup, which is well inside what that hitch is built for. Small boats and camping trailers live comfortably in the same range.
Go heavier - large farm equipment, horse trailers, RVs, toy haulers - and you move into weight-distribution or gooseneck territory. A weight-distribution hitch spreads tongue weight across both axles of the truck instead of hanging it all off the back bumper. Too much tongue weight squats the rear of the truck, lightens the front end, and takes away the steering and braking authority you were counting on.
For a conventional hitch, aim for 10 to 15 percent of your loaded trailer weight on the tongue. Gooseneck and fifth-wheel setups run higher, 15 to 25 percent, because that load sits over the rear axle instead of behind it. Once you have the right hitch picked out, our step-by-step on how to safely hitch a trailer walks through the coupling, chains, and cables in order.
Your Pre-Trip Towing Safety Check
An improperly configured trailer is not only a risk to your cargo and your truck, it is a risk to everyone sharing the road with you. Walk the rig before you pull out, and walk it again at every stop.
Mirrors - set them so you can see the end of the trailer, not just the side of it.
Lights - signals, taillights, and above all the trailer's brake lights. Have a buddy stand behind you and confirm each one.
Brakes - GM's guidance is that any trailer over 2,000 pounds loaded needs its own brakes behind a full-size truck. In the Sierra you can adjust the trailer brake gain from inside the cab, which helps in stop-and-go traffic and takes some of the shove out of a hard stop.
Tires - check pressure on the truck and the trailer, cold, against the numbers on the placard. Trailer tires age out on a calendar rather than a tread-wear basis, and our guide to trailer tires and rims covers load range and the DOT date code that tells you when they are done.
Hitch and Safety Chains - confirm the coupler is latched and the chains are crossed under the tongue with enough slack to turn.
Wires and Cables - rough road bends and breaks wiring. Check the runs feeding your brakes and lights.
Load Security - balanced side to side, strapped down, and unable to shift. A load that moves in transit changes your tongue weight while you are driving.
Plan the route while you are at it. A mountain pass that is nothing in an unloaded truck becomes a different drive with a trailer behind you, and our hauling safety tips get into route planning and driver fatigue.
Towing Tips for the Road
Driving with a trailer is normal driving with every input exaggerated. Accelerate and brake gradually so you are not cooking the engine and brakes. Take turns wider and slower than feels necessary, because the trailer cuts the corner tighter than the truck does.
Leave far more following distance than you would solo. GMC's own advice is to stay at least twice as far back as you normally would, and in practice four seconds of gap to the vehicle ahead is a workable floor on the highway.
Watch your tire speed ratings too. You might be comfortable at 75 on an open interstate, but trailer tires are frequently rated to 65, and running past that number builds heat until something lets go.
If the trailer starts to sway, hold the wheel steady, ease off the accelerator without stabbing the brakes, and use the manual trailer brake control to pull the trailer straight from the front. Then find somewhere safe to stop and figure out what caused it, because sway is a symptom - our full breakdown of how to prevent trailer sway covers the loading and pressure problems that start it.
The Manufacturer's Sticker Is The Source Of Truth You Should Trust Before Trying To Tow A Heavy Load
Payload usually runs out before tow rating does, and that catches guys who thought they had done their homework. Tongue weight does not count against your trailer rating - it counts against your truck's payload, right alongside the passengers, the gear in the back seat, and the cooler in the bed. A 7,000 pound trailer at 13 percent puts about 900 pounds on the hitch before anybody climbs in.
Your payload figure sits on the yellow tire and loading information label inside the driver's door jamb, and it is often well under 2,000 pounds on a half-ton with a nice trim package. Go read yours before your next trip. It is the one number that decides whether the truck you already own is the right truck for the trailer you are about to buy.