A mud-terrain is the correct tire for an early Bronco built to wheel hard rock and deep mud, and on this short, light chassis it is startlingly effective. It is also the tire that writes checks the rest of the truck has to cash: 3.5 to 4 inches of lift, cut fenders, a mandatory regear, likely stronger axle shafts, and a wet-pavement grip penalty on a vehicle that has neither ABS nor much brake. If your terrain is mixed, the all-terrain is the smarter tire. If your terrain is rock and mud, read the whole bill below before you order.
The difference between an all-terrain and a mud-terrain is void ratio — the proportion of the tread that is open space. An MT runs large, widely spaced lugs so that mud packs in and then throws clear as the tire rotates, instead of filling the tread and turning the tire into a slick. That self-cleaning behavior is the whole point, and no all-terrain replicates it.
On rock, the gain is different and comes from two things: aggressive shoulder and sidewall lugs that grab when the tire is aired down and rolled onto its edge, and a heavier three-ply casing that survives sharp granite. On a 4,000-pound early Bronco aired down to 12 to 15 psi, a mud-terrain wraps a rock in a way that is genuinely hard to believe until you have driven it.
The Bronco's light weight is an advantage here that heavier rigs do not share. It floats over ground that bogs a full-size truck, and the short 92-inch wheelbase lets the aggressive tread find purchase on ledges that a longer rig has to attack at an angle.
Lift and body work. A 33-inch mud-terrain generally measures slightly taller and wider than a 33 all-terrain of the same nominal size, and its stiffer sidewall bulges less under compression. Plan on 3 to 3.5 inches for a 33 MT, and 3.5 to 4 inches plus aggressive trimming for a 35 — often with a body lift or a radius-arm drop strategy to buy the rest. The tire sizing reference has the full matrix.
Regear, and treat it as mandatory. Factory ratios on these trucks are 3.50, 4.11, or 4.57. A 35 on 3.50 gears makes a 302 feel gutless, runs hot, and abuses an automatic's torque converter. The documented early Bronco baseline is 4.56 with 35s; a 33 lands at 4.11 to 4.56; a heavy 35 behind a small V8 sometimes wants 4.88. Both axles get the same ratio, or the Dana 20 binds. See the regear guide.
Axle shafts — and a correction worth reading. Every early Bronco from 1966 through 1977 came from the factory with a Ford 9-inch rear axle, not a Dana 44. The Dana in these trucks is the front: a closed-knuckle Dana 30 through 1971, then a closed-knuckle Dana 44 from mid-1971 to 1977. This matters practically, because it changes what you should spend money on:
Steering and brakes. A 35-inch mud-terrain weighs 68 to 75 pounds and has enormous rolling resistance at parking speeds. On a manual box this is genuinely unpleasant; budget the power steering conversion. If the truck still has front drums, the disc conversion stops being optional.
BFGoodrich Mud-Terrain T/A KM3 — the current benchmark for rock. Excellent sidewall durability, strong aired-down behavior, and better street manners than a mud-terrain has any right to have. Expensive.
Nitto Trail Grappler — the quiet one. Noticeably less road drone than most MTs, which matters if the Bronco drives to the trail. Slightly less aggressive in deep mud than the KM3.
Cooper Discoverer STT Pro — strong in mud and soft ground, good value, a bit louder.
Maxxis Trepador — a dedicated rock tire in the classic sizes. Sticky, aggressive, and short-lived on pavement. For a trailered or trail-primary Bronco.
Falken Wildpeak M/T — the value entry, and a reasonable choice if the truck sees moderate use rather than hard rock.
Wet pavement is the real safety tradeoff, not noise. Large tread blocks mean less rubber contacting the road and channels that evacuate water poorly at speed. A mud-terrain on a wet highway, on a truck with drum rear brakes, no ABS, and a 92-inch wheelbase, is a meaningfully longer stopping distance and a twitchier truck. Slow down in the rain, and treat this as the reason a street-driven Bronco should stay on all-terrains.
Snow and ice are worse still unless the tire carries the three-peak mountain snowflake rating. Most classic mud-terrains do not. Large voids pack with snow and the compound stiffens in cold.
Wear and balance. Expect 30,000 to 40,000 miles, versus 50,000-plus from a good all-terrain. Aggressive tread also invites cupping if alignment or shocks are tired, so rotate on a schedule and get a road-force balance — on a light truck with a solid front axle, an out-of-balance 35 will find a wheel-hop resonance you cannot ignore.
Run five, not four. Behind a locker, a mismatched spare loads the differential and the driveline. Buy the fifth tire with the set, and settle the carrier before the tires arrive — see the rear bumper and tire carrier guide.
Air down further than you think. These tires are designed to work deformed. On a light Bronco, 12 to 15 psi on rock is where the sidewall lugs start earning their money. Carry a way to air back up.
The honest total for putting 35-inch mud-terrains on an early Bronco correctly — tires, gears, and shafts — lands between $3,300 and $4,700, before the lift and before any steering or brake work. That number is why so many well-sorted early Broncos end up on 33s. Built around properly, though, the mud-terrain is what makes a short-wheelbase Bronco a genuine rock rig, and there is no substitute for it in mud.
| Part | Vendor | Est. price |
|---|---|---|
| Mud-terrain tires, set of 5 (33x12.50R15) | BFGoodrich KM3 / Nitto Trail Grappler / Cooper Discoverer STT Pro | ~$1500 |
| Mud-terrain tires, set of 5 (35x12.50R15) | BFGoodrich KM3 / Nitto Trail Grappler / Maxxis Trepador | ~$1750 |
| Mount, balance, and new valve stems (per tire) | local tire shop | ~$40 |
| Chromoly rear axle shafts, 31-spline, large-bearing conversion | Currie / Yukon / Moser | ~$650 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.
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