Trailer tires for snowmobile trailers are NOT all created equal! You can find several tires of the exact same size, yet with widely varying load ratings and number of plies (internal layers). For example, a popular two-place snowmobile trailer tire (18.5 x 8.5 x can be found with load ratings of 590 pounds, 770 pounds and 940 pounds from a single tire supplier.

With sleds weighing in at over 600 pounds (some even top 700 pounds each full of liquids), you should quickly realize when you factor in the weight of the trailer you can easily exceed or be close to the rated load capacity of some of the “lesser” tires. Anytime you approach the load capacity of a tire, it becomes even more critical to have the tire pressurized to its full pressure rating. Any trailer tire that is under inflated will have a reduced load capacity, which translates to an increased risk of tire failure.

How often do you check the pressure of your trailer (and tow vehicle) tires? Tire inflation pressures change due to time and temperature. According to the tire experts at the Tire Rack (www.tirerack.com) tires lose about 1 psi per month due to air escaping through the rubber as it stretches. If you were to check your tires only every six months, it would not be uncommon to find them underinflated by as much as 6 psi (six pounds)!

Tire inflation pressures also fluctuate with changes in outside air temperature, a HUGE consideration when it comes to pulling a trailer in sub-zero environments. This occurs at a rate of about one psi for every 10° F (plus OR minus). So the trailer tires you set correctly with an ambient temperature of 50° F will be underinflated by seven psi at -20° F!

If you add the variations of time and temperature together, it is easy to understand why a tire’s inflation pressure should be checked frequently, especially when you consider how close you may be to the tires rated load capacity on a fully-loaded trailer.

According to the Tire Rack, tire pressures should ideally be checked once a week, in the morning before the tires have been used (heated) at the coldest time of the day. The heat of the day and/or driving more than a few miles will cause an incorrect cold pressure reading.

If the tires are warm the general logic is that the pressure will be approximately four psi higher than the cold pressure. NEVER let air out of warm tires (those that have been used for over one mile within the past three hours) to arrive at a desired cold pressure specification. However, you can ADD air to warm tires if they do not have the specified cold pressure. Again, NEVER let air out of warm tires to reach your target pressure, as this can result in a low pressure, but it is OK to add pressure to warm tires to reach your target. Recheck the pressure again when cold.

Next time you’re shopping for a spare or a new set of trailer tires, pay attention to the load capacity and number of plies, which will also increase the tires resistance to puncture and overall failure rate. And yes, they do cost more, but one flat tire out on the highway in the middle of the night at –20 will forever cure you from being a cheapskate.

Several astute SnowTech readers cried foul when a competitive snowmobile magazine proclaimed they were “the only magazine that’s ever gone to the trouble of quantifying weight for the enthusiast market” and that “no other competitor responded by either doing the same thing or implementing something similar”.

SnowTech has for years weighed a number of PRODUCTION snowmobiles using a method known as “Wet, no gas”, using actual production machines, not one-of-ringers or pre-production prototypes that may or may not be representative of the actual production models sold on dealer’s showroom floors.

The manufacturers will list “dry weight” in their specifications, but these are glorified numbers that remove any and every drop of liquid from the sled, rendering it useless (inoperable). This is how heavy a sled is with no gas or oil or coolant or battery electrolyte or lube in the chaincase or oil in the shocks. Looks good on paper this way, but fairly useless information for making an accurate decision.

So, we weigh sleds in a state that they can be operated, ready to go, but with no gas. Why no gas? A fully loaded figure may be valuable, but since gas weighs the same per gallon for all brands of machines, we prefer the no gas routine to take away the ability to tamper with weight numbers. At eight pounds per gallon of gas, all a sled maker has to do to make their sled sixteen pounds lighter is to make their gas tank two gallons smaller. We highly value extended range, afforded by a larger tank, and consider this to be a more valuable attribute than a lighter weight number on paper. Our readers are smart enough to figure out the wet weight differences with some simple math (REVs and RX-1s will all be lighter with their 10 gallon tanks compared to sleds with 12 gallons). Key here is to use the same method for all comparisons. We believe this method is the most accurate to make fair and unbiased comparisons.

The snowmobile manufacturers have for years banned measurements of their pre-production units during spring testing events held for the snowmobile press, and have just recently included “weight” in their list of banned measurements (which includes noise levels, radar testing, top speed runs, etc.). Why? Because the units available for testing are many times not accurate representations of future production units. Therefore, SnowTech will continue to provide real-world testing of actual production models, as close to what you can walk into any dealer and buy, so the information is as accurate as possible. Granted, the timing is an issue here, as purchase decisions need to be made well in advance of production machine availability. If pre-production weights were CLEARLY identified as such we could have some good data to consider, but these weights are commonly passed on as actual-factual, which it is not.

One of the best analogies to the classic question, “Which is the best snowmobile for me”, is that snowmobiles are like gloves. Most of us all own numerous pairs of gloves of all sorts and types. And most of us would admit that, depending on exactly what we’re doing, each pair of gloves has a situation where it is the “best” pair of gloves for that job. Not any one pair of gloves is necessarily “bad”, it’s just that some work better than others in various environments.

Like with snowmobiles. Each one will work better at a specific application than another. The key is to determine which pair of gloves (or snowmobile) and its set of features and attributes best matches YOUR requirements and particular situation. If you could only select ONE pair of gloves from your arsenal, would you choose the pair that works acceptably well across the widest range of conditions, or would you select the pair of gloves that works best in a narrow set of conditions that you most frequently encounter or consider to be the most important? There is no right or wrong answer here – this choice is yours to make. But this analogy perhaps best demonstrates the selection process we all must labor through in the selection of your next purchase, be it gloves, snowmobiles, or just about anything you spend money on.

Examples? The obvious ones would be if you’re an off-trail deep snow rider, then a longer track with deep lugs is going to generally be the better performer. But as the frequency of riding in hard packed conditions increases, or you do a fair amount of groomed trail riding, you may go with a shorter track or one with not-as-tall lugs to compensate for the wider set of conditions. If ultimate flotation in bottomless snow is your paramount concern, then the greatest amount of track on the ground will be your primary consideration. If all you do is motor around on groomed trails then you select a short track sled. This doesn’t make the longtrack machine “bad”, it just isn’t well suited for that particular application.

You have to ask yourself what is truly most important to you – the broadband (shotgun) approach, or the narrow focus (rifle) selection. This is exactly why the “crossover” segment of sleds with “medium” track lengths have gained tremendous popularity recently. These machines work fairly well in a wider range of conditions than do the long or short track models. Even so, a long track will always work better in the deep and a short track will always work better on tight, packed groomed trails.

Snowmobiles equipped with detonation (knock) sensors, both two-stroke and four-stroke, automatically compensate for various fuel quality and octane ratings. The ignition timing and in some cases amount of fuel delivered is varied to avoid damaging detonation. This also means that the engine will make more power when fed higher octane fuel, and less power as the system compensates for lower quality fuel.

For example, the T-660 Turbo Arctic Cat four-stroke will run safely on 87 octane fuel, but will make more power on 92-octane.

On the other hand, four-stroke engines not fitted with knock sensors (like the Yamaha RX-1) that are designed to run safely on 87 octane fuel see little advantage to the use of high octane fuel other than cooler operation. In fact, the power output may be reduced with the higher-octane fuel.

Two-stroke engines not fitted with knock sensors generally benefit from the use of higher-octane fuel as a measure of insurance against detonation, as detonation is typically more damaging to a two-stroke than a four-stroke. Most two-stroke snowmobile engines run fairly high compression levels, thus generally require higher-octane fuels. Some Polaris models feature a two-position key switch that allows the user to manually select a different timing curve, better suited to the use of each fuel type.

How about using lower octane fuels at higher elevations? This is common in the automotive world, as you can find lower octane fuel out in western states (higher elevations) in the 84-85 range. The air density is lower at higher elevations than in the Midwest or eastern areas. This means less air to squeeze during the compression stroke, which also means less heat and pressure in the combustion chamber. Therefore, most engines can safely run a lower-octane fuel at higher elevations. Some riders who run 91-92 in the Midwest safely run 89 out west, and this is also why western riders who ONLY ride at higher elevations can stack on even more compression yet remain safe on pump gas. Yet these same sleds, if brought down in elevation, require an increasingly higher octane fuel.

Chaincase Chain Tensioning
So, when was the last time you checked the tension of the chain in your chaincase? Unless you ride an Arctic Cat, you’d better be saying something like 500 miles ago, or so. Big power sleds need more frequent attention, and if you ever put your sled into the air this becomes even more critical. Loose chains don’t like the shock load input from a spinning track that lands hard on the ground with a spike in load feedback through the drive train.
Most Arctic Cats have a spring loaded auto-tensioner that does a pretty good job at keeping the chain tensioned properly, but this can lead to complacency in performing inspections and changing the oil. On Yamaha and Polaris models you need to loosen the locking nut on the adjuster bolt protruding out of the front side of the chaincase and tighten it by HAND, then back off about 1/8 turn. Hold the bolt head in this exact position and tighten the lock nut to maintain this setting. Don’t reef on it, just snug it up with your fingers and back it off slightly.
On most Ski-Doo models there is no lock nut, and the adjuster is on the backside of the chaincase, making it far easier to get at in most cases. Remove the locking pin (key) and again, tighten by hand (with your fingers, NO tools). Back off just until the holes line up in the bolt so you can get the pin back in. If the holes line up really close to the point you end up when finger tightening, you need to make a judgment call. You need to back the bolt off slightly from “finger tight” before locking it with the pin. If the holes line up but you can’t back it off at all, don’t put the pin in. This is worse than going 1/2 rotation out to get it in. That amount of slack is far better than being too tight.
Main thing is to not ignore your chaincase. The cover should be removed at least once a year, preferably at the end of a season, for an actual inspection. Bolts and nuts can and do come loose, and gears do chip and chain plates come loose. All of the contaminants need to be removed, so an oil change is always welcome at this time. Normally you don’t want to mix different types of chaincase lube, but stick with a name brand product here.
Since you’re in here, there are usually some serious weight savings to be gained by replacing the cheap, heavy OEM gears with some high quality ones from EPI (Erlandson Performance). EPI’s Pro Lite sprockets reduce the rotating weight of the gear by about 30%. For example, a Pro Lite 41 tooth gear can reduce the rotating mass by 3 1/2 pounds! The performance potential of this change alone is similar to something like 25 pounds! That’s how much energy it takes to accelerate rotating mass!