September 13, 2026 Colby Hill

Where the Spare Goes: Full-Size Spares, Carriers, and Clearance

Here is how it usually goes. You fit a bigger tire, everything clears, the truck finally looks the way you wanted it to, and then six months later you pick up a sidewall cut forty minutes from pavement. You drop the factory spare out from under the bed and it is the original tire — two or three inches shorter, a different tread, and sometimes a different bolt pattern than the aftermarket wheels you bought along with the new rubber. Now you are limping out on a tire that is actively fighting the other three.

Almost nobody plans for the spare. It is the last thing in a build and the first thing skipped, because the stock one is still bolted under there and it feels like it counts. It mostly does not. Here is what changes when you upsize, what your real options are, and what to measure before you spend money on a carrier.

Why a mismatched spare is a real problem, not a cosmetic one

A spare with a different diameter than the tires on the ground rolls a different distance per revolution. That one fact causes a chain of problems, and how bad they get depends on where the odd tire ends up and what drivetrain you have.

Open differentials tolerate it, up to a point. An open diff lets the two wheels on an axle turn at different speeds, so a slightly undersized spare will not hurt the axle itself. It will scrub, wear faster, and pull the truck slightly under braking.
Limited-slip and locking diffs do not. A clutch-type LSD sees a permanent speed difference and slips continuously, which generates heat and shortens its life. An automatic locker will chatter and load unevenly. If you are not sure which one you have, our rundown of lockers, limited slips, and open diffs explains how to tell.
Full-time 4WD and AWD systems are the least forgiving. A center differential fed two different front-to-rear speeds absorbs that difference continuously. Manufacturers generally want the difference held to a fraction of an inch of diameter, and less across a full-time system. A spare three inches short is well outside that.
Electronics get confused. ABS, traction control, and stability control all infer what the vehicle is doing from wheel speed sensors. A different rolling circumference reads as permanent slip on that corner. Expect warning lights and, worse, intervention at the wrong moment.
It may not even fit. This is the one people forget. Add a lift plus wider wheels with less backspacing and a narrow stock spare on a stock wheel sits somewhere quite different in the wheel well, where it can foul a trailing arm or a brake line.

The short version: a stock spare will get you home on pavement at reduced speed. It is not a trail spare, and on a full-time 4WD system it is not something you want to drive on for a full day.

Where the factory put the spare, and why it stops working

There are three common factory arrangements, and each one fails in its own way once you upsize.

The underbody hoist

Most pickups and body-on-frame SUVs carry the spare under the rear on a cable winch, held in a shallow cage. That cage is sized for the largest tire the manufacturer ever offered on the platform, usually well short of what you just bolted on. A larger tire either will not seat at all or hangs so low it becomes the lowest point on the truck, eating departure and breakover clearance and offering itself to the first ledge you back over.

The tailgate or rear-door carrier

Wranglers, Broncos, and older body-on-frame SUVs hang the spare off the rear door. The hinges are engineered around the stock tire's weight with a margin, but not a huge one. Hang a heavy tire on a stock hinge and you get sag, a door that no longer latches cleanly, wind noise, and eventually cracked sheet metal at the hinge mounts. This is the most common failure people create for themselves.

The interior well

Some unibody SUVs and crossovers stow the spare under the cargo floor. No version of this accepts a significantly larger tire — the well is a fixed shape, usually sized for a temporary spare in the first place.

The four real options for carrying a full-size spare

1. Keep it underneath, if it will go

Before you spend anything, measure. Some platforms take one size up in the factory hoist, especially if you run the tire face-down, or if the wheel has enough backspacing to let the tire nest deeper into the cage. A few aftermarket extension kits drop the hoist slightly to make room.

The tradeoff is clearance. A tire hanging below the frame rails is not armor; it hooks on ledges, and the cable winch is the part that gives. If your trails involve real breakover, this option gets worse as the tire gets bigger.

2. A rear bumper swing-out carrier

This is the purpose-built answer, and for most people running large tires it is the right one: a steel arm pivoting on a spindle, integrated into a replacement rear bumper, that carries the tire vertically behind the truck and swings clear of the tailgate. Weight goes into the bumper and then the frame horns, not into a door hinge.

What separates a good carrier from a bad one is the pivot and the latch:

The spindle. Better carriers pivot on tapered roller bearings that can be preloaded and re-greased. Cheaper ones use a bolt through a bushing, which works fine when new and develops slop over a season — a rattle on every washboard road.
The latch. It needs to pull the arm tight against a stop, not just hold it closed. Any free play lets a hundred pounds of tire hammer back and forth, and that load goes straight into the spindle.
Where the weight sits. A tire on a swing-out is cantilevered well behind the rear axle — a long lever on the frame, and a rearward shift in weight distribution that shows up on off-camber terrain and in crosswinds.

Carriers come as part of a bumper, so you are making a bumper decision at the same time. Material matters more than usual here, since the tire weight stacks on top of the bumper weight — our breakdown of steel versus aluminum bumpers covers that tradeoff directly. Browse what fits your platform in bumpers.

3. In the bed

For a pickup, the cheapest workable answer is a bed mount: a plate bolted to the bed floor or bulkhead, tire upright, usually just behind the cab. It costs a fraction of a carrier, adds no length, keeps the weight ahead of the rear axle where it does the least harm, and cannot rattle a door hinge.

What it costs is bed space. A large tire against the bulkhead takes a real bite out of usable floor and fights with a bed rack, a tonneau, or a drawer system. If you are planning bed storage, work out the layout before you buy either piece — truck bed gear and our guide to bed racks and bed storage are the place to start.

4. On the roof, mostly as a last resort

People do it, and it looks the part, but the roof is the worst place on a vehicle for a heavy object. An assembled tire on a steel wheel is serious mass sitting above your center of gravity, and a spare plus the rack itself eats most of a roof rack's dynamic load rating. Then there is the practical problem: getting it up and down, alone, in the dark. The weight math behind roof racks and payload is worth reading first.

The measurements to take before you buy a carrier

Carrier fitment is where people get burned, because sidewall numbers are marketing sizes, not measurements.

Actual mounted diameter. Measure the tire mounted and inflated on the wheel you will actually use. A tire sold as a 35 can measure anywhere from about 34 to over 35 inches depending on brand and wheel width, and cage openings are unforgiving.
Section width at the widest point. On a swing-out, this determines whether the tire clears the body when the arm is closed and whether it fouls the taillight.
Wheel backspacing. Backspacing decides how far the tire stands proud of the carrier's mounting plate. Less backspacing pushes the whole assembly further out, which lengthens the lever on the spindle and can put the tread past the bumper's outer edge. If backspacing is still fuzzy, our offset and backspacing explainer is short and worth ten minutes.
Bolt pattern and center bore. Most carriers use a bolt-on hub plate. Confirm the pattern matches your wheels and that the plate either indexes on the center bore or supplies a ring — a spare hanging on the studs alone with no centering will work the studs loose over time.
Assembled weight. Weigh it if you can. This is the number that determines whether your hinge, plate, or spindle is adequate, and it goes into your payload budget along with everything else you added.
Swing radius. Measure how far the arm sweeps open, then check it against your garage and the space behind the truck when parked nose-in at a trailhead.

The parts that fail, and the things a carrier breaks

A carrier changes more about the back of the vehicle than people expect. Plan for these:

The third brake light and license plate. A tire on a swing-out blocks both. Most good carriers include relocation brackets. Confirm yours does before you find out at a traffic stop.
The backup camera and parking sensors. A tire directly behind the camera makes it useless and can trigger constant sensor alerts. Some carriers offer a camera relocation mount.
Fasteners working loose. A carrier lives under constant vibration with a heavy cantilevered load. Torque the hub plate studs, spindle preload, and bumper-to-frame hardware after the first few hundred miles, then check them at every trail inspection — it is on the list in our post-trail inspection walkthrough for a reason.
Your jack. This is the quiet one. The factory jack was specified for the factory tire diameter. With a lift and taller tires it frequently cannot raise the axle far enough to get the flat off and the spare on, especially with the wheel at full droop. Check it in your driveway, not on a side hill.
Your lug wrench. Aftermarket wheels often use a lug nut the factory wrench does not fit. Carry a socket that works and a breaker bar with enough leverage for lugs torqued by an impact gun.

A short sanity check before you order

Is the spare the same size, same construction, and the same bolt pattern as the four on the ground?
Does the mounting location survive a rock ledge, or is it now the lowest point on the truck?
Is the weight carried by the frame, or by a door hinge that was never meant for it?
Does your jack lift far enough, and does your wrench fit your lug nuts?
Have you added the assembled weight to your payload number along with the bumper, the rack, and everything else?

None of this is exciting, and that is exactly why it gets skipped. But a matching spare is the difference between a thirty-minute inconvenience and the end of your weekend, and it is one of the few upgrades that only matters on the day it matters completely.