Putting 37-inch tires on a Ford Bronco looks like one purchase. In the shop, it turns into six or seven. The taller tire needs room, so the Bronco needs lift. The tire and lift change how the gears feel, what the speedometer reads, and how hard the steering works. Then the spare gets heavier and the flares stop covering the tread. Below is each step in the order owners hit it.
In This Guide
Why One Tire Size Starts a Chain
Ford Built the Bronco Around Specific Tire Sizes
Every part of a Bronco is sized for the tire it ships with. The Sasquatch Package pairs 35-inch LT315/70R17 tires with a 4.7 final drive ratio, locking front and rear axles, high-clearance suspension, and high-clearance fender flares. Non-Sasquatch Broncos use smaller tires with 3.73, 4.27, or 4.46 axle ratios. Change the tire and those parts are working outside what they were built for.
A 37 Is About Two Inches Taller Than the Factory 35
A 37x12.50R17 tire measures about 36.5 inches tall. The factory Sasquatch tire measures closer to 34.4 inches. That's two more inches of rubber in the same wheel well. The fender liner, the suspension, and the steering all lose room they had before.
The Raptor Shows What 37s Ask For
The Bronco Raptor comes with 37x12.50R17 BFGoodrich KO2 tires from the factory, and it's 4-door only. Ford gave it an 8.6-inch wider track, stronger axles (a Dana 44 front and a Dana 50 rear), and extra reinforcement on the spare tire carrier for the heavier spare. That list works as a preview of what a standard Bronco needs for 37s.
The Tires Themselves
What a Set of 37s Costs
A 37x12.50R17 all-terrain tire from a major brand costs about $450 to $480 each at current average listed prices. Most owners buy five so the spare matches. That puts the tires alone near $2,250 to $2,400 before mounting and balancing.
Wheels Can Join the Bill
The factory 17-inch Sasquatch wheels can hold a 37. Many owners buy new wheels anyway to get a lower offset. That pushes the tire out and away from the inner fender. Wheel spacers are the cheaper way to get the same push. Five new wheels add a large chunk to the total if you want the spare to match.
Heavier Tires Change How the Bronco Drives
BFGoodrich lists its 37-inch KO2 at 65 pounds. One Bronco Raptor owner put his on a scale and got 70 to 73 pounds. All of that weight sits at the corners. The Bronco is slower to get moving and slower to stop. That extra weight is the reason most of the next steps exist.
The Lift
Sources Disagree on How Much Lift 37s Need
Some Sasquatch owners put 37s on with only a leveling kit and some trimming. One owner said TC Customs told him he'd need 2 to 3 inches of lift, and many owners agree for trail use. Both answers come from different kinds of driving. A leveling kit can get by on pavement. Full steering lock and full suspension travel on a trail are where 37s start to rub.
Non-Sasquatch Broncos Need More
A non-Sasquatch Bronco sits lower and has smaller flares. Going straight to 37s on these trims means more lift, more fender work, and wheels with the right offset. That's why many non-Sasquatch owners stop at 35s. Our post on the biggest tire that fits a stock Bronco lists the starting point for each trim.
Most 37-Inch Lifts Replace the Factory Shocks
A 2 to 3-inch lift for 37s commonly uses new coilovers in place of the factory Bilstein shocks. Spacer lifts cost less and keep the factory shocks. Our Bronco suspension and lift kit guide covers each lift type and its trade-offs.
Rubbing and Clearance Fixes
Where 37s Rub First
Owners report rubbing at the front fender liner at full steering lock. The rear body mount near the crash bar is next, and factory rock rails can need an inch trimmed off. One owner with a 3-inch spacer lift said his 37s used every inch of room the wheel well had.
Inner Fenders Open Up the Front
Bronco Forge carries the DV8 Offroad Front Inner Fenders for 2021 through 2025 Broncos at $499.99. They take the place of the plastic factory liners with a high-clearance aluminum design. DV8 says 37s need at least a 2.5 to 3-inch lift with these fenders. They don't fit the Raptor, and the install needs some minor drilling.
Body Mounts and Wheel Offset
Trim kits for the rear body mount are the other common fix. Moving the tire out with offset wheels or spacers helps too. Spacers of 1 to 1.5 inches show up in a lot of owner builds with 37s. Each fix adds parts, labor, or both.
Gearing
Why Bigger Tires Make the Bronco Feel Slower
A taller tire covers more ground every time it turns. That works like a taller gear. The engine has to push harder to get the Bronco moving, and it's most noticeable on hills and when towing. A Sasquatch Bronco with 4.7 gears feels this less than a non-Sasquatch Bronco with 3.73s.
Many Sasquatch Owners Skip the Regear
The 4.7 ratio is the deepest gear Ford puts in a standard Bronco at the factory. Plenty of Sasquatch owners put 37s on and keep it. They give up a little pull off the line and save thousands on gears. For a Bronco that sees mostly pavement and light trails, that trade makes sense.
What a Regear Involves on This Bronco
Regearing a 2021 or newer Bronco means changing the front drive unit and the rear axle gears. Ford Performance sells a complete M210 front drive unit with 5.13 gears and a locker. Ford says the front and rear ratios must match, and this unit doesn't fit the Raptor. The Bronco's computer also has to be set to the new ratio.
Regear Costs Add Up Fast
In 2023, owners on the Bronco6G forum reported new front drive units priced near $1,965 for 4.70 gears and near $2,950 for other ratios. That's before rear gears, labor, and new half shafts. Dana's Ultimate Dana 44 front unit in 5.13 or 5.38 needs 32-spline half shafts, which adds another part to buy.
Speedometer and Computer Settings
The Speedometer Reads Slow on 37s
The Bronco's computer still thinks the factory tire is on. With a taller tire, the speedometer shows a lower speed than you're going. The odometer logs fewer miles than you drive. The fix is a tire size change in the computer.
Two Common Ways to Recalibrate
Many owners use FORScan, a laptop program with a cable, to change the tire size setting. Ford Performance also sells a calibration tool that can set a tire size up to a 37x12.50R17 KO2. Both methods can leave warning codes behind until you do the relearn steps, so follow the process closely.
Calibration and Your Warranty
Changing computer settings and gears can lead to warranty questions if a drivetrain part fails later. Our guide to aftermarket parts and the Bronco warranty explains how those claims work.
Steering Parts
Tie Rods Take the Extra Load
Bigger, heavier tires push harder on the steering when they get pinned against a rock. On the Bronco's independent front suspension, the tie rods give first. Owner forums have many reports of bent or broken tie rods on Broncos with 37s. Owners name front locker use as the biggest risk.
Stronger Tie Rods Move the Weak Point
Factory tie rods act like a fuse. When one breaks, the steering rack usually survives. Stronger tie rods shift the stress to the rack's thin aluminum end cap. Many owners who upgrade tie rods for 37s upgrade the rack end cap too. One owner paid about $1,000 for billet tie rods alone.
Carry Spares on the Trail
If you keep the factory steering parts, carry a spare tie rod and the tools to put it on. A broken tie rod stops the Bronco where it sits.
The Spare Tire and Tailgate
A 37 Spare Is a Heavy Load for the Tailgate
The factory spare carrier bolts to the swing-out tailgate. Turn Offroad lists the Sasquatch spare wheel and tire at 93 pounds, hanging on a tailgate that weighs about 27 pounds. One owner weighed his 37 on an aftermarket wheel at 105 pounds. That's a lot of weight swinging on two hinges.
Ford Reinforced the Raptor Carrier for This Reason
When Ford put a 37-inch spare on the Bronco Raptor, it added reinforcement to the spare tire carrier. A standard Bronco's tailgate doesn't get that from the factory. Owners with 37 spares on the stock carrier report rattles over bumps and strain on the hinges.
The Third Brake Light Has to Move Up
A taller spare blocks the factory third brake light. Most carriers and relocation kits come with an extension bracket. It lifts the light above the tire so drivers behind you can see it.
A Carrier That Takes the Weight
Bronco Forge sells the DV8 Offroad Tire Carrier at $899.99. It takes on the weight of the spare and the tailgate door. It keeps the factory 150-degree tailgate opening and includes a third brake light extension. It works with every DV8 rear bumper. DV8 has not tested it on the Raptor.
Moving the Spare Weight to the Frame
The Turn Offroad Tire Carrier Rear Bumper is priced at $1,299.99. It moves the spare's weight off the tailgate and onto the frame. It opens with one hand, works with the factory hitch, and comes with lights and a new third brake light. It fits 2-door and 4-door Broncos, but not the Raptor.
A Tailgate Guard Rated for Most 37s
The DV8 Offroad Spare Tire Guard and Accessory Mount also costs $899.99. It braces the tailgate at several mounting points and accepts most 37-inch tires. DV8 lists wheel limits: 20 inches or smaller, no wider than 9.5 inches, and at least 4 inches of backspacing. It doesn't work with Ford's HD tire carrier.
Some Owners Pull the Spare for Daily Driving
Some owners take the 37 spare off for city driving and put it back on for trail trips. One Bronco Nation owner said pulling it cut about 100 pounds and stopped the rattles. The DV8 Offroad Spare Tire Delete at $199.99 keeps the license plate, backup camera, and third brake light mounted with the spare off.
Fender Coverage and Mud Flaps
A Wider Stance Can Push Tread Past the Flares
Lower-offset wheels and spacers push the tire out. That helps clearance. It can also move the tread past the edge of the flares. Once the tread sticks out, the tire throws rocks and water at the cars behind you.
California Law Requires Tread Coverage
In California, Vehicle Code 27600 says fenders, flares, or flaps must be at least as wide as the tire tread. They also have to cut down spray to the rear. Other states have their own rules, so check yours. Our post on California laws every modified Bronco owner should know covers the rest.
Flare Options Bronco Forge Carries
Bronco Forge carries the Turn Offroad Steel Fender Flares Kit at $649.99 for 2-door and 4-door Broncos. It has a narrow profile and comes with marker lights. The DV8 Offroad Tube Fender Flares for 4-door Broncos cost $999.99. They work with the Sasquatch Package and don't fit the Raptor or Everglades.
Check Coverage Before You Buy Flares
Narrow and tube-style flares add clearance for suspension travel. They may not cover a wide tire pushed out on spacers. Measure where your tread sits before you pick flares. Our list of fender flare mistakes Bronco owners make covers the common problems.
Mud Flaps Close the Gap
Mud flaps behind the tires are the simple way to cover the tread when flares can't. They cost far less than anything else on this list, and they're commonly the last piece a 37-inch build needs to stay street legal.
What the Whole Chain Costs
Parts Prices Before Labor
Start with a Sasquatch Bronco going to 37s with a 2 to 3-inch lift. Five tires cost about $2,250 to $2,400. A spare carrier from the options above costs $899.99 to $1,299.99. Inner fenders cost $499.99. Flares cost $649.99 to $999.99. Then add the lift, a speedometer tool, and mud flaps.
The Optional Steps Cost the Most
A regear can add several thousand dollars once you count both axles, half shafts, and labor. Steering upgrades can add $1,000 or more. Owners who skip those two steps still spend well past the price of the tires.
Plan the Whole List Before the First Purchase
Building one step at a time costs the most. A lift bought for 35s may not clear 37s later. Flares picked for one wheel offset may not cover the next. Pick the final tire size first, then buy each part to match it. Our breakdown of what it costs to build out a Ford Bronco puts these numbers next to a full build.
Where to Stop the Snowball
Stay on 35s If You Mostly Drive on Pavement
For a Sasquatch Bronco that sees mostly road miles and moderate trails, the factory 35s are the better choice. Ford built every related part around them. The gearing, spare carrier, steering, and fender coverage all stay as designed.
Go to 37s When the Trail Calls for It
37s make sense if you wheel hard terrain often and plan to lift the Bronco anyway. Budget for the whole chain at the start: lift, clearance fixes, a stronger spare carrier, fender coverage, and a speedometer fix. Plan the regear and steering upgrades as the next round so they don't surprise you.
Price Out a Raptor If You're Still Shopping
If you haven't bought yet, compare a Bronco Raptor to a built Sasquatch. The Raptor is 4-door only and costs more up front. It comes with 37s, a wider track, and a reinforced spare carrier, all covered by Ford's warranty. Our post on what justifies the Bronco Raptor's price breaks down that math.
FAQ
Do you need a lift for 37s on a Sasquatch Bronco?
Some owners fit 37s with a leveling kit and trimming, but they rub at full steering lock and full suspension travel. For trail use, most shops call for 2 to 3 inches of lift.
Do you have to regear a Bronco for 37-inch tires?
No. Many Sasquatch owners keep the factory 4.7 gears and accept a little less pull. Non-Sasquatch Broncos with 3.73 or 4.27 gears feel the loss more. A regear means matching new front and rear gears and resetting the computer.
Can the factory tailgate hold a 37-inch spare?
It can hold one, but owners report rattles and hinge strain. Ford added carrier reinforcement to the Raptor for its 37 spare. A reinforced tailgate carrier or a bumper-mounted carrier takes that load off the factory parts.
How do you fix the speedometer after putting 37s on a Bronco?
Change the tire size setting in the Bronco's computer. Owners use FORScan or the Ford Performance calibration tool, then do the relearn steps to clear any warning codes.
Are 37s legal in California if the tires stick out past the flares?
California Vehicle Code 27600 requires fenders, flares, or flaps at least as wide as the tire tread. If the tread sticks out, you need wider flares or mud flaps to stay legal.
How much does it cost to put 37s on a Bronco?
Five tires alone cost about $2,250 to $2,400. A lift, clearance fixes, a spare carrier, and flares add several thousand more. A regear and steering upgrades can add several thousand on top of that.
About This Guide
This was put together by the team at Bronco Forge. Our founder spent time as a Ford salesman before launching Bronco Forge, giving us firsthand knowledge of how Broncos are sold, what buyers get wrong, and what dealers don't always tell you. We sell aftermarket parts exclusively for the Ford Bronco and spend time in Bronco owner communities tracking what owners experience. Questions about fitment or anything Bronco-related? Reach out at contact@broncoforge.com or (909) 772-8050.
