4x4 Trail Rating Chart
The classes of trails below are to be considered a baseline description of an overall trail type under ideal conditions. Terrain analysis will take into account weather effects to trails and specifically note any effects that will degrade operations or require changes in operational expectations. Flatwater Overland shall rate a road or trail with the appropriate class based upon the most difficult section or obstacle encountered on the section of trail.
Class 1–Maintained unpaved road. Firm, dry improved surface, or less than 3 in. water crossing depth. Only gentle grades present similar to highway construction, 2WD under all conditions except snow. No width or trailer towing problems, at least two vehicles wide. This is a typical maintained gravel country road.
Class 2– Semi-maintained dirt road. Dry, or up to 3 in. water crossing depth; some minor ruts; slight grades up to 15 degrees; 2WD under most conditions. Rain or snow may make 4WD necessary. Road is usually one and a half to two vehicles wide to allow for passing. Road is acceptable for most types of trailers. This is typical of moderate use roads in backcountry or agricultural areas with at least annual maintenance of the roadbed.
Class 3– Unmaintained dirt road. Ruts, washes, or gulches may be present; water crossings up to 6 inches in depth possible with a firm bottom; passable mud or sand sections may be present. Grades up to 20 degrees may be encountered. Small rocks or holes may be frequent. Rock or dirt shelves will not exceed 6 inches in height. 4WD recommended but 2WD possible under good conditions and with adequate ground clearance and skill. No width problems for any typical passenger vehicles, and vehicle passing spots frequently available if less than two vehicles wide. Towing of a standard production trailer may become difficult. This is typical of a regularly traveled backcountry road that has not seen maintenance in several years. This is the last class of trail that can be traversed by a factory supplied all-wheel-drive car or crossover vehicle without damage.
Class 4– Rutted and/or rocky backcountry trail. Rock shelves or stair steps not exceeding 8 inches in height may be present, and rocks to 8 inch caliper may be encountered. Any water crossings encountered will usually be less than axle hub deep with a firm bottom. Passable mud or sand may be encountered, with moderate grades that may exceed 20 deg. Side hill camber may be moderate up to 15 deg. 4WD will be recommended under most conditions to increase control. No width problems, with vehicle passing spots frequently available if less than two vehicles wide. Only short wheelbase trailers rated for off pavement use should be towed here. This situation will be typical of backcountry forest or desert trails that see light but regular travel and only see enough maintenance to remain passable. This route should passable with any stock traditional 4x4 SUV or pickup truck.
Class 5– Rutted and/or rocky trail. Rock shelves or stair steps not exceeding 12 inches in height may be present; rocks less than 12 inch caliper may be encountered; water crossings up to 12 inch depth with possible currents but a solid bottom may be encountered. Passable mud or sand sections may be encountered. Moderate grades exceeding 20 degrees may be present with up to 6 inch deep holes present; side hill camber expected to be up to 20 degrees. 4WD required under most conditions with no vehicle width problems. This is the most difficult trail that should be attempted with a stock full-sized 4x4 or with a standard production short wheelbase trailer unless specifically rated for off highway use. Trail clearing and building may be necessary for stock vehicles to pass undamaged and brush may be an issue for full sized vehicles.
Class 6– Very rocky and rough trail. Frequent rocks encountered and may exceed 12 inch caliper; water crossings may exceed axle hub depth with strong currents. Rock or dirt shelves and stair steps may be encountered not exceeding 16 inches in height; mud sections may require checking before proceeding, sand may be loose and deep with dunes. Moderate grades exceeding 20 degrees encountered, and side hill camber may approach 30 degrees. 4WD is necessary with a stock high-clearance vehicle, and second attempts may be needed on obstacles with stock vehicles and/or minimal off road driving experience. Vehicles with locking differentials should not encounter significant trouble. Caution may be required with wider full size vehicles due to obstacle size and trail width restrictions. Driver having experience with off road 4x4 driving techniques will prevent vehicle damage; vehicle modifications with gearing, traction aids, and suspension will also be helpful. This is the last class of trail that an inexperienced driver with a stock 4x4 vehicle should attempt and the last class of trail a stock vehicle with an experienced driver can expect to traverse without damage. Only specialty off highway trailers with oversize tires and extended suspensions should be towed. Trail clearing and building may be necessary with heavy brush possible.
Class 7– Technical backcountry trail. Rocks will be encountered frequently with a 12 inch caliper and some may exceed vehicle hub height. Holes and washouts are frequent or up to 20 inches in depth. Rock shelves and/or stair steps may be encountered to 24 inches in height and in sequence. Eight inch deep mud may be present with ruts and may also be present on uphill sections. Sand encountered will be deep, loose, and large dunes are likely. Grades encountered to 30 degrees and side hill camber encountered to 30 degrees. Water crossings to 24 inches deep encountered, and may have strong currents with soft bottoms. 1 ½ vehicles wide maximum; 4WD required at all times; driver experience with technical 4x4 trails necessary and vehicle modifications in suspension, traction, and gearing extremely helpful. Multiple recovery operations possible and may require winching. This is the highest class of backcountry trail that the driver of a typical overland modified vehicle can expect to traverse undamaged and the highest class of trail a typical stock 4x4 can be expected to traverse. Custom or specialty short wheelbase, light weight, off highway trailers with large tires and custom suspensions are towable, but will likely experience damage or rollover. Trail repair or building may be necessary to traverse and heavy brush is likely.
Class 8– Technical trail with heavy rock and/or severe obstacles. Rocks exceeding hub height will be frequent with washouts and holes also exceeding hub height. Rock or dirt shelves or stair steps exceeding 24 inches in height are likely to be encountered. Deep mud and/or uphill mud sections may be present. Landscape scale dune areas and soft, deep sand present. Steep grades exceeding 30 degrees may be encountered that can also be loose and rocky. Water crossings may exceed 30 in. depth and/or contain currents and a soft bottom. Side hill camber to 30 degrees will likely be encountered on the trail, and trail will be no more than 1 vehicle wide. Frequent recovery operations requiring winching probable, and vehicle damage probable even with an experienced driver. Vehicle modifications are necessary and may be required; trail will not be passable by most stock vehicles under any conditions. Towing of even specially constructed overland trailers not recommended at this difficulty and beyond. Trail building will likely be necessary in order to traverse in modified 4x4s with likely damaging vegetation along the trail.
Class 9– Extreme technical trail recommended for specialty off road vehicles only. Severe rock over 20 inches caliper size and frequent deep holes over 24 inches in depth common on the trail. Rock or dirt shelves and/or stair steps over 36 inches high present. Mud bog conditions (long, deep, no firm bottom) requiring winching may be present. Water crossings over 30 inch depth with strong currents and a soft bottom may be present. Steep grades over 30 degrees and side hill camber over 30 degrees present on the trail and are likely to be loose and rocky. Trail building and repair probable for passage of even highly modified production 4x4s. Not passable by stock vehicles. Driver experience essential to safely traverse the trail. Frequent recovery actions including winching are to be expected. Driver should expect vehicle body damage, mechanical breakdown, probable rollover conditions, and possible personal injury. Extreme caution recommended and should not be attempted in anything but ideal conditions by experienced drivers in heavily modified vehicles.
Class 10– Severe conditions. Extreme caution recommended. Impassable by stock vehicles and most modified production vehicles, winching will be required to traverse under any conditions, and trail building will be necessary. Trail may be impassable under anything but ideal conditions in any type vehicle. Vehicle damage is probable, personal injury is likely, and extreme caution is necessary. This type of trail will not be passable by an overland prepared vehicle without extreme trail construction and is the realm of the purpose-built sport 4x4 buggy.