Ski-Doo’s Gen 4 REV models feature a new front suspension, the RAS 3 front suspension. Similar in design to the already stable and precise RAS 2 front suspension found on the REV-XS models (to maintain toe-out ski orientation upon maximum compression for precision), the even more precise RAS 3 has been made possible with the all-new vacuum die cast aluminum front bulkhead found on the Gen 4 REV platform.
The RAS 2 front suspension was about as good as Ski-Doo engineers could deliver with the limitations of the REV-XP/XS bulkhead design. It was a very good step in the right direction, but demonstrated they could in fact do even better if they had the luxury of relocating the bulkhead mounting points, or attachment locations, of the a-arms to the bulkhead. On the new Gen 4 REV platform, they were given this exact opportunity to delivery and even more precise front suspension geometry.
Another major benefit here is the addition of more stroke, or suspension travel. MX Z sleds with the wider front end see another inch (25mm) of stroke, and the narrower Summit sleds get 0.8” (20mm) more stroke, or travel. The RAS 3 is slightly lighter as well, to the tune of 300 grams, or 0.7 of a pound, and the new vacuum die-cast aluminum front bulkhead is 634 grams (1.4 lbs.) lighter and much stronger.
For added precision, the total elimination of bump steer and less feedback through the handlebars, MXZ X and Renegade X package sleds feature an all-new rack steering system. Instead of the single pitman arm found on the MX Z TNT and Renegade Adrenaline models. Why two steering systems? We tend to believe this was done to provide some type of difference between the in-season models and the Spring-only X-packages. You know, incentive to order early. Logically and mechanically it would make sense to do them all the same, thus the incentive theory.
The new RAS 3 seems to be all about reducing bump steer and bump feedback, getting the sled to track straighter through the bumps and be even more predictable to the rider through even rougher terrain. The RAS 3 now provides a constant caster angle of 22 degrees, where the RAS 2 would vary from 18-19 degrees up to 23-24 degrees through the suspension travel. Caster angle refers to how straight up and down the ski spindle is as viewed from the side of the sled. It is always raked back at the top, with the ski slightly forward. This angle, or positioning, is now held constant through the suspension travel. Bump steer refers to the variation in ski alignment as the suspension moves through its travel. Instead of having the ski alignment changing as the suspension strokes, the skis and runners are now held even closer to perfect alignment, especially with the rack steering on the X-packages. On the TNT and Adrenaline models there is slightly more bump steer, but chances are riders will feel more of a difference from the different skis on these models than they will the steering system, as they are fitted with the Pilot 5.7 skis where the X-packages with Quick Adjust get the adjustable Pilot TS skis. X-package models without the Quick Adjust option package still come with the Pilot 5.7 skis, which we are perfectly happy with, and actually prefer for snow conditions other than hardpack, you just can’t adjust the runner depth on them like you can with the Pilot TS.