2018 Polaris 800 RMK Assault 155 Review

Do you feel the AXYS Pro-RMK 155 is not brawny enough for you? We feel it is burly enough for any Rocky Mountain slug fest. But, if you want a bit more stout and a chance to fly up a hillclimb course, then the 2018 800 RMK Assault is the big-hit powder player you want. It may be tough as an NFL fullback, but it is as gorgeous as a Hollywood starlet.

In Polaris’ media push, this is what the company states about the RMK Assault: “The Backcountry Original. Tough-As-Nails for Extreme Conditions.” Polaris stated this for 2017 and it continues for 2018.

Polaris’ 2018 800 RMK Assault comes to market in 2018 as it did in 2017, with the only changes being some color choices for the Spring-buy.

Being the RMK Assault is built on Polaris’ AXYS platform, it makes the RMK Assault a light and strong snowmobile that has excellent lift in powder. “Lift” is a keyword from Polaris’ where the AXYS chassis has the ability to launch – move forward – in deep snow with minimal underside drag; weight transfer is properly maintained and handling and control is not compromised.

Snowy or sunny days, it does not matter, the RMK Assault will plow through the deepest snow, making use of its AXYS RMK heritage.

“Lift” comes by way of the low AXYS chassis and within this chassis, the RMK Assault’s fuel cell and components are positioned low near the drivers. This gives the 800 RMK Assault (and every Pro-RMK) its lift while maintaining a low center-of-gravity at its center mass. As Polaris states, “The AXYS RMK features a patented, raised chassis that increases clearance and reduces drag to keep you on top of the snow.”

The 2018 RMK Assault is a blend – somewhat – of the AXYS Pro RMK, AXYS SKS Pro with a few components from the Pro Ride RMK Assault, last built in 2015.

To understand the 2018 800 RMK Assault is to understand it is an aggressive competitive hillclimber, a flight chief and long cornice dropper. Now you may wonder, can’t the Pro-RMK 155 do all this? Well, yes it can. But when you feel your companion hit master needs more robust shocks up front and at the rear suspension, and a chaincase to handle the buzz when the track freewheels in flight and momentarily stops at impact, then the RMK Assault is designed by Polaris for you. It is the power tool of all power tools.

Inside the 800 RMK Assault is Polaris’ CleanFire 800 High Output two-stroke twin-cylinder motor. This electronic fuel-injected motor delivers quick throttle response and gives the RMK Assault a fairly decent power-to-weight ratio. The motor has three-stage electronically controlled exhaust valves and an electronic oil pump, which takes drag off the motor. VForce Reed intake valves assure the fresh air intake charge is plentiful and does not back out on the compression stroke.

Three track options are available for the RMK Assault. First is the single-ply Peak, which has 2.25-inch tall paddles; this is basically a trimmed down Series-5 track. It is not tall, but suited for marginally deep snow and some hillclimb competitions; this track really makes the RMK Assault more crossover-like, one step ahead the 800 AXYS Switchback Assault. Second is the Series-6 2.6-inch paddle track, which as Polaris states is the best all-purpose mountain track. This is the track we recommend for this vehicle. The third track, for early Snow Check customers, is the Series-7 which has 3.0-inch paddles. This track is tall and best for crazy deep powder. The motor can spin this track with no hesitation, but our experience with the Series-6 and Series-7, is we consider the Series-6 to be the best track and agree with Polaris, it “is the best all-purpose mountain track.” Remember, the 800 RMK Assault comes only in a 155, shorter or longer lengths are not available.

In its Snow Check Select colors, the 2018 RMK Assault 155 is menacing. It is all business and play with Walker Evans shocks and optional Series-6 2.6-inch track.

The H.O. 800 motor is mated to Polaris’ P-85 drive clutch and a TEAM LWT driven clutch. These clutches are Polaris’ traditional clutches for this model and have proven reliable for mountain action.

Absent from the RMK Assault is the Low-Inertia Quick Drive belt drive system. The Assault, per racer input, uses a chaincase as professional hillclimbers want the ultra-toughness a chaincase delivers. Big-drop and long-flight boondockers that equip their Assault with a turbocharger also demand a chaincase. The chaincase is shared tech with the AXYS SKS and all RMKs with Series-7 track.

The 800 RMK Assault has the same raised front as the AXYS Pro-RMK, but does not rely on the Pro’s forged aluminum A-Arms. The RMK Assault uses the A-arms first used on the 2015 RMK Assault. Again, racers demand these for their brutal strength. These are heavier than the Pro-RMK’s A-arms (but not by much).

Ski stance for the RMK Assault is an adjustable 41.5 to 42.5 to 43.5 inches. It uses Walker Evans Needle Shocks and the reliable Gripper ski. The RMK Assault, unlike the Pro RMK does not have a sway bar. With a wider ski stance, the Assault compensates for the width by dropping the sway bar. Hence – nimble. This too is a racer’s demand. We recommend the 41.5-inch ski stance, which is similar to the RMK Pro’s narrowest. Front suspension travel is 10 inches.

Action-ready Assault with Walker Evans shocks.

Under the tunnel is the light and rigid RMK Coil-Over rear suspension that rides, at the rear track, with Walker Evans Needle shocks. Rear travel is 16 inches. The rigid rear skid is designed and built to control pitch and improve weight transfer. Polaris claims “the rigid suspension delivers power directly to the snow.”

Like its Pro-RMK siblings, the RMK Assault’s slide- and hyfax-rail helps lift the rear skid while driving it forward. The rails add strength and use material only where needed, via computer-aided design first, then second, by years of field testing.

Polaris believes its RMKs are meant to run through narrow-spaced trees and be smartly-balance on edge when ripping across a hillside.  Therefore, Polaris’ RMK and SKS engineers designed the AXYS chassis to be narrow and flush at the lower panels, especially behind the A-arms and near the toe wells and runningboards. A narrow profile minimizes “paneling out;” which is when the side panels prevent the track from locking into a hillside. Yes, the RMK Assault’s side panels are flush with the PowderTrac runningboards and are inside the skis’ outer edge. With the raised platform and narrowed-in side profile, the RMK Assault is dirt bike skinny.

The RMK Assault comes with Polaris’ PowderTrac runningboards, Pro Lite seat, ProTaper handlebars and can be fitted with the “Interactive Digital Display” instrument pod that feature GPS mapping and Bluetooth mating. Early Snow Check buyers can opt-in bounteous color, the Interactive Display and storage bag options.

Smooth flight and controlled landings. The 800 RMK Assault with its hillclimber bloodlines and chaincase driven track drivers will hop up over a large pillow with ease.

The ProTaper bar comes with a low center mountain strap that is out of the way. Current boondockers do not rely on the mountain strap much, so minimizing its height is valued. Snow Check buyers can choose one of three handlebar post heights, low, medium, high.

From the cockpit, the motor’s throttle lever is easy to press and does not fatigue the right thumb. The motor breathes well at high-altitudes. In the conditions we rode – much powder – the RMK Assault with Series-6 2.6-inch track, was delightsome. In marginal deep-powder on tree-infested ravines with steep slopes, the RMK Assault proved a playful vehicle. The RMK Assault has a wicked streak – it likes to hit the junk. With its Walker Evans shocks and properly set chaincase gear ratio, the RMK Assault throws it down.

The RMK Assault we tested was set in at its 42.5-inch stance (remember, no sway bar on this RMK), and had its lowest built ProTaper handlebars – it was crazy fun. Depending on track type, the 155 RMK Assault is 418 pounds to 427 pounds (dry weight).

The chassis does not panel out. We had some days with ultra-deep powder to test the RMK Assault’s “lift,” its weight transfer and hill ascents, and we confidently state, the 800 RMK Assault delivers on all its engineered-in promises. One may assume, the RMK Assault on hardpack snow, with its “lift” concept, would tail walk up a hill. It defies this and maintains a flat presence up a hill. But, owners can manipulate this through rear suspension shock pressure and limiter strap length.

It takes to flight like it takes to powder play. The 2018 RMK Assault likes it when it is driven hard and put away wet.

Snow Check buyers got to choose color, bar height, windshield color, standard or Interactive instrument pod, graphics, and storage options, and could build their dream RMK Assault. For buyers who wait until the Fall harvest is done, and the money is counted, then the in-season RMK Assaults come mechanically equipped as the spring-buy Snow Check special, minus the optional painted tunnel, bar height choice, optional Series-7 3.0-inch paddle track, storage bags, Interactive Display instrument pod, and various hood colors. Regardless, it is an RMK Assault none-the-less, nasty- and sexy-looking, and all lightweight brawn, as we declared in our opening statement.

Yes, the RMK Assault is a deep powder player that too is a monster hill killer. On the trail, it is precise, especially set at its widest ski stance.

Yes, the AXYS Pro-RMK LE 155 delivers. It is a phenomenal snowmobile. Yet, for those riders who compete in hillclimb circuits, drop off railroad bridges for a videographer, or like the name “Assault” then take a summer day’s break and lay down some greenbacks for a 2018 800 RMK Assault 155.