AmSnow.com is now SnoWest.com
Mono Shock suspension: Yamaha answers questionsHere are a few commonly asked questions that we have received regarding the Mono Shock RA and EC rear suspensions. The engineers at Yamaha have chimed in with a few knowledgeable answers.
Q: How exactly do clicker compression shock adjustments work and how does that translate into the RA and EC Mono Shock systems?
A: As you turn the clicker dial, the needle valve opens or closes, changing the damping rate. As you turn the clicker softer, the needle valve opens and allows more oil to flow increasingly free. As you turn the clicker stiffer, you close the needle valve, which increasingly restricts the flow of oil. The Mono Shock RA and the Öhlins Mono Shock EC adjustments work in the same way, but on different damping forces. The RA version uses a manual adjuster dial on the left side of the tunnel to make changes to the shock's rebound rate. Similarly, the EC version uses a small servo motor, operated on the left side control switch, to make its adjustments. However, the EC's thumb switch adjusts the compression damping rate. There is a manual rebound rate adjuster on the end of the EC's shock rod as well. The difference between the two systems can be easily remembered like this: RA changes rebound and EC changes compression.
Q: How do you set spring pre-load on both?
A: The Mono Shock RA has a stepped, cam-type adjuster. Consumers make spring preload adjustments using the spanner wrench included in the sled's tool kit.
The Öhlins Mono Shock EC has a threaded collar spring preload adjuster. It has a double locking nut to loosen before making the adjustment and then tighten after.
Consumers can have additional spring preload changes made on the Mono Shock RA suspension by having the shock and spring removed and repositioning the circlip. Since this is a procedure that requires a special spring compression tool, we recommend it be done at a Yamaha dealership. Yamaha also offers a stiffer spring option for additional preload calibration options.
Q: 22 clicks of compression adjustment on the RA, how many comparable clicks on the EC?
A: The Öhlins Mono Shock EC offers 16 settings of compression adjustment at the thumb switch. It also has 20 clicks of rebound via the manual adjuster on the end of the shock rod.
Q: What were the changes made in the spring (i.e. stiffness) on the coil-over sprung mono shock since its introduction?
A: In 2008 we gave the Öhlins Mono Shock EC a spring rate increase, along with the necessary valving calibration changes to match.
Q: How do you best suggest a consumer set this suspension?
A: The single most important step is to get the spring preload correctly set. Our testing has shown that this is most reliably done by measuring the spring length. In a nutshell, take the spring's measurement while the sled is either lifted or tipped on its side. Then put the rider, in riding gear, on the sled and measure the spring's length. The ideal preload setup will result in the spring compressing 40-45mm with the rider's weight. If the spring compresses less, reduce the preload. If it compresses more, increase the preload.
After the preload is correctly set, take the sled out to ride. This is the time to use the shock's rebound and compression adjustments to fine tune the ride characteristics to your personal liking.
Q: How much does it cost to retrofit a regular mono shock Apex with the electronic version?
A: There are two kits available at your local dealer. The first kit is designed for the 4-cylinder, fuel-injected models and is essentially plug and play. You install the shock assembly, plug into the wire harness and the gauge is preloaded with the functionality to use the thumb switch.
The second kit is designed for the carbureted 3-cylinder models. It will require you to install a small gauge display unit (included in the kit) on the dash to achieve the functionality. Since those models were not developed with the Öhlins Mono Shock EC in mind, there will be additional wiring work as well. However, once correctly completed, it will work the same as the Apex application. Both kits can be found on the accessories page of
www.yamaha-motor.com as well.