This site uses the 1-10 scale rating describe how technically difficult a trail is. Other sites or clubs may use the 1-5 scale, which is essentially the same, just halved. While there is no standard scale, we choose to use the 1-10 scale simply because it what most of the clubs and groups in my area use
Also note that the ratings are during optimal sunny and dry conditions. Rain, snow, wind, etc. can quickly alter a trail's rating.
A 1 rated trail is a true stock friendly trail (and by stock friendly we mean a stock Jeep). An example would be a graded dirt road. There are no obsticles and should not need to engage 4 wheel drive at all. Really any street car or truck can traverse this trail.
A 2 rated trail may includes a small rut or very small loose rocks. Sometimes a washboarded dirt road may be described as a 2 rating. Stock Jeeps will have no issue here, however it may be a bit bumpy for a car.
A 3 rated trail may add a few loose rocks or steep inclines. 4 wheel drive may be necessary to help maintain slow speeds on steep sections. However, any Jeep should be able to navigate a 3 rated trails without any difficulty.
A 4 rated trail add a few more challenges in to the mix. These trails may have steep inclines, some minor off-camber sections, and some ruts and steps or loose rocks that require more attention. 4 wheel low may be required to handle the steep slopes or crawl through small to mid-sized rocks. Stock Jeeps should be able to handle a 4 rated trail, however inexperienced drivers may want to have a little help.
A 5 rated trail may have even steeper grades to navigate, and bigger rocks and steps to get through. Moderate water crossings may be involved as well. Taking a stock Jeep on a 5 rated trail should be challenging, but not impossible. 4 wheel low is required and inexperienced drivers will benefit from good spotting. Minor bottom scraping may occur with Jeep without lifts or larger tires.
A 6 rated trail is where stock Jeeps typically hit their limit. These trails will have large rocks and steps, possibly as large as 3ft. Off-camber sections will likely exist. Spotting should be used on the tougher obsticles. Lifts and larger tires are likely required required. Lowing air pressure in tires and disconnecting sway bars should be considered a must for trails rated 6 and higher.
A 7 rated trail is typically a 6 rated trail but will add one or two more difficult obsticles. Lockers will be helpful, but may not be required. Stock Jeeps should not attempt a 7 rated trail. Excellent spotting is required. Some bottom scraping is likely, even for lifted Jeeps. These trails are only for experienced drivers.
An 8 rated trail is where we separate the men from the boys. High lift, large tires (35" or better), and lockers are required. Even with this equipment, expect not to be able to make it through the more extreme obsticles. You are likely to get some damage to your Jeep and may need to be winched out. Extreme off-camber sections may result in roll-overs.
A 9 rated trail is probably about as extreme of a trail that you will encounter. These are usually reserved for buggy type Jeeps. Should have full and securely suporrted roll cage, as the likelyhood of a roll over is extremely high. Obstacles will include giant boulders, extremely steep climbs, deep v-notches, and more. Do not attempt unless you have an extremely modified rig and willing to risk damaging it.
A 10 rated trail is similar to a 9 trail, but with one or two "impossible" obstacles. Most attempts will fail, even with the most modified of rigs. This will be the limit to which any vehicle can pass.