Moguls. We’ve all experienced them and, it’s safe to say, that none of us are fond of them. Moguls are the entire reason that trail groomers for snowmobile trails exist. Over time every trail will fall victim to the mogul, but understanding the mogul can actually help you reduce their frequency and aid in their destruction.
There are multiple factors that contribute to the formation of moguls but they all pale in comparison to the main culprit, snowmobiles themselves.
First let’s look at one of the smaller contributors to mogul development: trail surface. Many people believe that an uneven trail surface with natural dips and bumps in the terrain contribute to mogul development and to some degree they are correct. An uneven surface causes the suspension of the snowmobile to rise and fall as it tries to compensate for the uneven terrain, therefore when the suspension falls down into a dip in the trail the track naturally digs its way out of the hole, displacing snow at the bottom of the hole and piling it up behind it, further defining the “bump” in the trail, the next sled will then compress that mounded up snow, reinforcing the bump and subsequently falling into the hole and digging itself out as well, when the track comes out of the hole it is still digging and creates a new smaller hole following the previous hole before it fully recovers to being on flat surface, creating a new “bump in the road,” this constant expansion and contraction of the suspension continues the pattern and after a while you create a series of bumps aka moguls. An ungroomed trail on a naturally uneven surface will most definitely create moguls and these moguls will persist regardless of snow depth as the peaks of these bumps will be hard and the valleys soft so even when they are covered by new snow the process will continue. The good news is that once the snow has reached a depth to fill in uneven terrain a groomer can eliminate these types of moguls by putting a solid surface of trail over the top of them, therefore those that believe the underlying cause of moguls is an uneven trail surface are only partially correct, that is indeed the case until a groomer does its work and then what terrain lies underneath the snow matters much less than how the trail surface is prepared by the groomer.
So now we have a beautiful flat trail created by the hard work of your local club but after a full weekend of use we are back to moguls again, how did this happen? There are two answers to that question: #1 the snowmobile rider and #2 the snowmobile suspension. Many snowmobilers try to blame the power and speed of modern snowmobiles for mogul development but it is not the snowmobile that is the problem, it is the rider. Remember that any deviation in the surface of the trail affects the suspension. You will often notice that moguls first form before and after corners and before and after road crossings. The reason for this is that any sudden decrease or increase in speed makes the track spin or rapidly changes its rate of rotation which makes it dig into the surface of the trail creating a small mound of snow, the next snowmobile over that mound compresses it and the suspension reacts and digs out a little bit of snow after the bump creating another bump and so on. In short, if you hammer the throttle after a road crossing you create a mound of snow and therefore create moguls, when you hammer the throttle after a corner you create moguls, add paddle tracks, high horsepower and the modern suspension and you amplify these conditions. In short if you managed to keep an even speed you would dramatically reduce the number and frequency of moguls, any time you radically change speeds on the trail you contribute to the mogul problem.
There is a myth out there that back in the days of lower horsepower sleds that moguls were less common, that myth is 100% false. Whether it be bogey wheels or slides, 10 horsepower or 150 horsepower, moguls have always existed. Don’t agree? Try riding a trail after a vintage ride that had nothing but vintage sleds on it, trust me, you will see some of the worst moguls ever, this is why grooming equipment came into existence. First it was an old box spring mattress towed behind a snowmobile. That helped initially but it became evident that although this mattress set up smoothed things out for a little while, the moguls quickly returned, that is because all that was happening was the tops of the moguls were being knocked down into the ruts, but the snow in the mounds was still hard while the snow in the dips was soft and after a few sleds rode by the dips were quickly dug out again. This led to the development of modern grooming equipment with a series of blades designed to cut the tops of the mounds off and churn the snow adding moisture to it so as it settles into the dips the snow is compacted by the drag and the moisture in the snow freezes forming a solid base. It is essential for a groomer to get down to this solid base when grooming to help prevent new mogul formation. This is also why groomers operate over night, because it is essential for that trail to have time to set up/ freeze. When a snowmobile goes over a trail that has just been groomed without allowing the snow time to set the base weakens and makes it easier for the mogul process to begin again.
The battle against moguls is a never ending task, but there are two things that you as a snowmobiler can do to help prevent them. First, be courteous and try to keep an even speed throughout your day on the trail especially trying to avoid any sort of activity that results in you creating a mound of snow and second, join a snowmobile club and become a groomer operator, that way you can be sure to have great trails every time you ride!