M20 Platinum Spec
The current design trend toward stand-up / rider-forward positioning allows riders to more easily use their legs in big bump events …. a definite positive. It has also added new challenges in attaining quality sit down ride comfort. As the rider position and mass has shifted further forward, the same amount of mass has been removed from above the rear suspension arm. This shift in mass has forced ride engineers to concentrate more shock and spring forces at the front arm, while leaving them with less mass and mechanical advantages over the rear arm.
The mass location of a sleds weight fore and aft has largely remained unchanged in today’s rider-forward snowmobiles, while the location of rider mass has had a major shift forward. The significant reduction of rider mass over the rear arm has resulted in reduced compliance of the rear arm. In particular over what are normally considered sit down small and medium bumps. The reason is, there is less mass / weight over the rear arm acting against vertical sprung and un-sprung forces.
When Ski-doo released the XP chassis in ‘08 we found they’d lost a step on their own ‘07 REV chassis in sit down ride quality. This forward-most chassis proved particularly challenging in terms of ride quality. This prompted us to come up with somewhat unorthodox XP specific mounting geometry and air-shock calibrations. These somewhat peculiar XP specs were all aimed at improving the rear arm’s compliance and the peculiarity had generated questions and concerns for us ever since. Ultimately last winter we decided to take a more encompassing look at the XP “anomaly”.
We asked ourselves what would be the most effective way of getting the rear arm to carry more weight, more work? The answer turned out to be the simplest of solutions….remove the front arm spring, forcing the rear arm to carry the load.
Did the rear arm become more compliant…yes, was the sled more comfortable….a lot more, was there a down side….in the beginning, yes. The sled would bottom more frequently on square edged bumps at the front. But now when the rear arm pressure was raised just a bit, the suspension delivered nice gains in ride quality in small and medium bumps. Not so surprisingly there was also a gain in the sleds capability in large bumps at the rear. These improvements were….BIG!
A surprising benefit from the work was a reduction in body roll on corner exit without any noticeable reduction in traction. Our challenge would now be to overcome the not so small task of eliminating the square edged bump bottoming at the front arm.
If corrected, the benefit would be huge as would be the challenges in overcoming the unsettling front arm bottoming. So over the next couple months we pulled out all the stops. First, we increased the coupling between the front and rear arms thus shifting more of the loads to the rear arm. Next we went through many rounds of bleed and flow circuits timing adjustments in the front arm shock, making it more sensitive to speed and shock position. Next we went to work mating the rear shock to the new demands transferred back from the front arm through the additional coupling. At the rear we reduced low-speed compression valving and worked through many iterations of increased medium and high speed compression and rebound valving. Through the ambitious efforts during the test period we achieved another giant step forward in ride quality and control.
Not since the M-20s introduction had we made such a large leap forward in product development. So we were compelled to try the new spec out on other models including traditional seating models. We tested sleds both with heavy and light front ends, and sleds with light and heavy overall weights. We needed to see if removal of the front arm spring would adversely affect the balance and heaviness of steering. We installed and tested the new specifications on the following models:
- Arctic
- 2005 Suzuki Turbo 4-strokes (2 of them), 2007 F-8
- Yamaha
- 2003 RX1, 2006 Attack 136”
- Ski-doo
- 2010 XR Renegade 4-stroke 136”, 2010 GTX 4-stroke 121”, 2009 Renegade 800, 2008 XP 600, 2010 XP fan cooled
Most of the sleds had dual runner carbides of some sort with the very effective Woody’s Slim Jim being the most prominent. Except for the Skidoo GSX (which had a very un-aggressive track profile) and did exhibit a slight amount of over-steer in wet-sloppy conditions, each sled had a wonderful surge forward in bump control and noticeable improvement in cornering capability.
The all new 2012 Platinum Spec performance gains are found in the two-up riding category also. The new 2012 specification is used along with an air-spring on the center shock. This gives two-up riders the same new benefits but provides for a greater load capacity helping to control problematic two-up bottoming, without making compromising settings for one bump range over another.
In closing, we will proudly be offering this new innovation in ride control on all this years M-20 Airwave suspensions!
See the product listing
Or go straight to the store.09-27-2011
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