My five year review of the MonoShock I

[redrx1rkt]

This is a review of only the MonoShock, not the entire sled.

SLED: 2006 Yamaha Apex RTX, 8,500 miles, no rear suspension modifications, spring set to stiffest setting. Rider weight 230 lbs. with gear.

The Mono, overall, gets a 'B+' rating from me. It is probably the best groomed trail riding suspension on the market. When riding an official state/provincial trail with normal but not extreme bumps, the Mono will soak them up like a sponge. However, when things start getting rough (two-three foot moguls, i.e., a Saturday afternoon on Tug Hill), the Mono cannot compete with the likes of the Polaris and Ski Doo skids. The Mono quickly gets overwhelmed, bottoms out, compresses and rebounds in a non-linear fashion and becomes difficult to control. Setting the dial to MAX HARD will improve its ability to take on large bumps, but it will still become overmatched sooner than other sled's rear setups.

I am not a suspension engineer, and correct me if I am wrong, but I believe the Mono is not well-suited to the rough stuff because of it's coil-over shock configuration. The coil spring simply cannot manage a lot of bump energy well. It cannot rebound the skid or shock quickly enough to be ready for the next series of bumps so it allows the skid to bottom out and kick back with a lot of force as it attempts to get control of all of the movement. Competitors' torsion spring systems work much better with bad trails (yes, I know Yamaha went to a torsion spring setup on the RTX in 2007). The torsion spring seems much better suited at returning the skid back to an uncompressed state much faster, and allows the whole skid to work in a much more linear fashion. A coil over and torsion spring spring set up seems to provide the best of both worlds.

The flip side is that on a smooth trail, or one with small to moderate bumps, the coil spring allows the shock more freedom to absorb these types of conditions compared to a torsion spring setup. This explains the Mono's superior groomed trail performance.

 

[Metallicat]

It's all in the shock valving. Plus the design probably doesn't offer much of a progressive rate. Torsion springs generally offer a linear or slightly falling rate of spring force. There was an article about this years ago in SnowTech. But they also generally have a very progressive shock rate controlled by the shock rods. The rear shock acts completely independent from the springs. My revalved mono is as good as a classic m10 and only bottoms in large dips that exert a lot of g force on the sled. I rate mine a 9.5 out of 10 for trail riding. I'm happy to hear you enjoy yours so much. The worst snowmobiling is when you have a crappy rear suspension on a rough trail. All of the power in the world can't make up for a bad ride when the trails are rough. I played around a LOT with springs and shocks and valving on my old ZR. The stiffest springs available will still bottom HARD if the shock valving is too weak.

 

[redrx1rkt]

My shock is 100% from the factory, no alternations. Should I have it revalved for better big bump performance? However I do not want to lose the super absorbent ride on groomed trails, where I do most of my riding these days.

I have noticed that when I adjust the damper (dial on the tunnel) to be more stiff, I sit a little higher on the sled. This surprises me because I figured the spring would be what controls the ride height, not the damper.

 

[Metallicat]

The dial has a larger impact on rebound than it does on compression dampening, so if you're using it to control bottoming you're probably increasing the rebound dampening too much and that is why the bumps are stacking up and slapping you. The revalve by Pioneer made my rear suspension even more plush. It is like the transition from small to medium to large bumps is so much more fluid, and yet it doesn't bottom out as much as it did when it was stock! It rides so much better in all conditions! When it was stock I had to have the dial set to 4 just to control the rebound, otherwise it was too quick. And in the 6" bumps there was more feedback than I liked. I like a really comfy ride. Now I have my dial set to 1 and it is perfect! I weight 180 lbs btw.

 

[redrx1rkt]

I also appreciate a plush ride above all else. What did you have Pioneer do to your shock?

 

[Metallicat]

I just had them do the standard revalve that they offer for the mono. They ask for your weight, riding style, and sled model, and then they choose the valve stack for you. I just told them I wanted a good ride with less bottoming. The revalve is $10 but they'll also have to change your shock fluid and maybe put in new seals. I think the total was $85 for mine. It was like a 3 week turn around last November but they're probably busy before December with last minute requests like mine.

 

[4x4]

Torsion springs have friction between the windings, the shaft, and the sliding block on the long end. I have seen a lot of broken torsion springs from ice in the windings and they often break from a stress concentration at the transition from the windings to the straight end. I think they are less responsive than coil springs.

 

[ahicks]

The torsion are rising rate. The long arm gets progressively shorter as the suspension collapses...

 

[4x4]

Does that mean that the variable arm is used to slow the rebound as the suspension returns to the extended position to reduce kick? The spring has little effect on whether the suspension bottoms or not.

 

[Metallicat]

The torsion are rising rate. The long arm gets progressively shorter as the suspension collapses...

True, but not quite true. Oh, it is difficult to explain. I had my old torsion ZR rear suspension off, modern vintage ZR with rear coupling blocks, and took all of the rear suspenson springs off, left the shocks on, and then mounted up a bracket to hold the suspension in place as it would sit on the sled. I could compress the rear end, then it would couple the front arm, and then somewhere down the travel of the rear the front arm would want to rebound instead of compress as I was compressing the rear end. That is how I mapped the shock travel vs. coupling efficiency. The coupling efficiency was like 80% during the first few inches of rear arm compression movement, then it was negative 40% at the last inches of travel meaning that for every inch of rear arm movement, the front arm was applying a 40% negative upword force from the spring of the front arm. Well, if you think about it, a long front arm and a short rear arm that is coupled will give this result! Hopefully this makes at least some sense to someone.

 

[berge75]

The hot set up on the mono is to install a Ohlines shock with the hyraulic bump stop installed in it. With this you can have a soft ride without bottoming.

 

[Super Sled]

The hot set up on the mono is to install a Ohlines shock with the hyraulic bump stop installed in it. With this you can have a soft ride without bottoming.

It's called the Progressive Dampening System, or PDS. I have about 600 miles on it so far. I also had a re valve done on my EC Ohlins shock. So far I'm really liking it. You cannot bottom that thing out, that's for sure.......

 

[Bigblue1]

Great comments. I too re-valved the shock through Hy Gear but I also used the stiffer spring for heavier riders. I can now run through relatively rough trails with ease. So making some adjustments to how you ride and your wieght etc. is a must for the optimal set up. The 2 foot stuff like in Central New York is better suited for the Nytro which I also had re-valved. On well groomed trails like those in Canada, however, there is nothing like that mono. It soaks up the stutter great handles the moderate stuff well and sets in awesome around the sweepers. It will be interesting to see the reports on the Mega Float as this just may be the answer, but I would guess a re-valve there may be be in order as well. To give some sense of my time on the mono, I have an 05 RX-1 with close to 10,000 miles on it.

 

[ahicks]

Oh boy, I was trying to leave the coupling and the rest of the geometry gadgetry out of it to make my comment. If you let all of that into the picture, you're going to make it much more model specific. Not even going there...

The torsion are rising rate. The long arm gets progressively shorter as the suspension collapses...

True, but not quite true. Oh, it is difficult to explain. I had my old torsion ZR rear suspension off, modern vintage ZR with rear coupling blocks, and took all of the rear suspenson springs off, left the shocks on, and then mounted up a bracket to hold the suspension in place as it would sit on the sled. I could compress the rear end, then it would couple the front arm, and then somewhere down the travel of the rear the front arm would want to rebound instead of compress as I was compressing the rear end. That is how I mapped the shock travel vs. coupling efficiency. The coupling efficiency was like 80% during the first few inches of rear arm compression movement, then it was negative 40% at the last inches of travel meaning that for every inch of rear arm movement, the front arm was applying a 40% negative upword force from the spring of the front arm. Well, if you think about it, a long front arm and a short rear arm that is coupled will give this result! Hopefully this makes at least some sense to someone.

 

[mr.pitstop]

I've said since 05 that the mono is one of the best riding suspensions on the market once setup correctly. Ive had pioneer revalve my shock, installed a heavier spring, had half baked do the beef up kit and powder coating on the arms and installed all new wheels. Mine rides great and is bullet proof now.. I ride mostly groomed trails, sometimes with a little rough stuff mixed in and the sled rides great...