What is a clinometer, and how do you use it for trail building?

Trail builders have a wide range of tools at their disposal, from heavy machinery to hand tools. One tool that might not be familiar to most people is the clinometer.

Singletracks spoke with a few trail builders to understand what clinometers are and how they are used in trail building.

What is a clinometer?

David Renko, a senior foreman with Progressive Trail Design, described a clinometer as a handheld tool used to find the grade of the run of a trail or an area. Renko noted that they can be either mechanical (using a type of heavy liquid, such as the liquid in a level) or digital. He personally uses digital clinometers when building trails in backcountry areas.

To use a clinometer, Renko said that you first need to zero it out by either using a grade stick (a six- to seven-foot-tall measuring stick with inch measurements on it) or another person. You point the clinometer at a point on the stick or the person’s body to establish a frame of reference, and then you can point it at an area of land to determine the grade.

Jeremiah Stone, the principal of Unearthed Trails LLC, offered similar instructions on calibrating a clinometer. “I have a friend with me, and I stand toe to toe with them and see where the clinometer lens is on their physical body. Then, I have them stand in potential lines so I can measure using that reference point.

When Stone is by himself, “I can hang my flagging tape at eye level and use that as a reference point. I’ve even used a pocketknife handle stabbed into the tree bark at eye level to measure against.”

How trail builders use clinometers when constructing new trails

Nat Lopes has been building trails since 2007 with his company, Hillride Progression Development Group LLC. He says clinometers are one of the most important tools for ensuring trails are truly sustainable. He primarily uses it when building trails in steep or moderate terrain, as well as for creating flow trails and jump lines.

When it comes to steep terrain, Lopes said that “clinometers are crucial for laying out trails when side slopes are exaggerated.” In this instance, “it is easy to lay out trails that are too steep for comfortable climbing or require heavy braking on descents.” In areas with super subtle, moderate terrain, Lopes said, “it can be challenging to design trails within the moderate grades required to meet the half rule and ensure proper drainage.” The “half rule” recommends that builders keep the grade of the trail less than half the grade of the side slope so that water will run over the trail and continue down the side of the hill, instead of running down the trail and causing erosion

Lopes says clinometers are also essential for designing flow trails and jump lines. They help builders “maximize the available elevation, provide the consistent trail speeds needed for progressive jump lines, minimize the speed when heading into tighter turns, and minimize the need for excessive braking.”

Typical use cases for clinometers

Lopes shared some examples of building scenarios where clinometers are particularly useful. “If you are working in areas with gentle hills, it can be really tricky as the trail grades will be much closer to the grades of the side slopes and it is easy to just punch a trail up a hill as it won’t be super steep, but the trail just won’t drain and will stay wet in the rain and erode out much faster.”

When building climbing trails, clinometers are important because the percentage of grade can determine the pedal cadence. “If you keep the trail grade at a 5-7% grade, which is not very steep, you can keep a much higher pedal cadence and keep a faster cruising speed in a higher gear, which is a more comfortable and fun way to climb and gain elevation,” said Lopes. “As you go steeper, you will have to start to downshift, and it turns into more of a grinder of a climb, and as you get to about 50%, you are reaching a max grade for sustained climbing in terms of traction and pure output.” 

For flow trails, Lopes said that 5-7% downhill grades are ideal. This allows the rolling speeds to be in the 15-20 mph speed range, which is great for extended sections with jumps and to create extended runs that utilize every bit of available gravity. “The steeper you go from there, the more braking you will have, which will cause erosion, and dreaded brake bumps. For any downhill trails, if you can reverse grade before your turns, you can minimize braking forces [and] brake bumps and create more dynamic movements.” 

When it comes to downhill trails, Lopes said that clinometers aren’t as necessary because going steep is the point. “One of the craziest trails I have ever ridden is Mount Seven in interior BC. It drops 4,000ish feet in 7.3km at an average grade of 50% and steeper sections going even over-vertical at points.”

Clinometers are also helpful in other situations

“I find the clinometer most helpful when I’m dealing with less-than-obvious build situations or a line where timing is crucial, such as jumps,” said Stone. When he’s building in terrain that appears flat, “the clinometer can help me find and address dead spots and adjust my line so that it has the momentum and flow I’m looking for.”

When building trails according to IMBA guidelines or contract specifications, Stone said that clinometers are an important tool to have. “There’s a place for trial and error in trail building, but I try to avoid it when someone’s paying. Metrics help me do that by getting things right the first time rather than finding out after risking life and limb in the first flow check that something needs to be drastically moved or changed.”

Renko echoed Stone’s sentiments, stating that clinometers are a good tool for building in foreign environments or when the build must meet specific requirements, like those of the Americans with Disabilities Act. He also said that clinometers come in handy when trail builders need to keep a trail within the grade required for the soil type they are working with, ensuring the trail is sustainable.

Clinometers have been around for centuries, but they are still valuable to today’s trail builders

Though accounts vary, the clinometer is believed to have been in existence in one form or another for several hundred years. For trail builders, it is an important tool to have.

While Renko noted that smart levels and laser transits offer a greater level of accuracy for applications requiring finer tolerances, such as building trails in urban areas or bike parks, clinometers still have a place in a trail builder’s toolkit. Indeed, a clinometer might be responsible for the sustainability and flow on your favorite local trail.