Help Understanding Rear Suspension in Deep Snow

[AKSNOWRIDER]

If you read your owners manual..it says right in there the softer you can run your suspension the better it will go in powder...with that said..I couldnt stand the frt end 2-3 ft off the snow in a steep climb..to the point of the sled almost stopping due to the near vertical aproach angles...what I found to work best on my 08 D-8 with a 163 stock was frt track shock in lower mnt, (and stock low pressure), rear track shock pressure raised 10 pds over stock and frt shocks stock pressure...sled would hold the ski's about 1 foot off the snow..last year I went to float 2 ski shocks and the original holz skid with carls valved floats..much better everywhere then stock..trail, bumps, jumps and all powder riding..

 

[craigvansickle]

If you read your owners manual..it says right in there the softer you can run your suspension the better it will go in powder

I picture the skid moving through powder - floating up and down in the chassis - encountering different depths and densities of snow: it makes sense that softer settings would allow the skid to react to subtle changes it encounters - staying on "step" to use a boating term. You can definatetly feel a big change while riding when your sled begins to break through and cavitate rather than float. If in a climb you begin to pass that point and take a less steep line you can also feel a big change as the sled climbs back on top.

last year I went to float 2 ski shocks and the original holz skid with carls valved floats..much better everywhere then stock..trail, bumps, jumps and all powder riding..

So from what everyone has said it sounds like the quality aftermarket mountain suspensions poses the following characteristics:

Better geometry for staying on top of the snow and keeping the front end down.

Better shocks - allowing the skid to react appropriately to large inputs as well as subtle ones.

last year I went to float 2 ski shocks and the original holz skid with carls valved floats..much better everywhere then stock..trail, bumps, jumps and all powder riding..

Can someone explain how valving affects how a shock operates?

 

[trailtoy1993]

Can someone explain how valving affects how a shock operates?

Valving is quite simply the control of the fluid inside the shock. The entire operation of the shock is dependent on how the shock is valved. A shock typically has two different operating parameters, high speed and low speed. In low speed operation shock oil flows through tiny holes in the face of the piston inside the shock as the shock moves up and down, changing the size of these holes determines how much resistance the shock has to movement. In high speed operation, like landing off a big jump, the holes cannot flow enough fluid fast enough to keep the shock from "locking up" so they posses a spring loaded "valve" that opens to allow more fluid through. All of these things are changeable in a shock to make it stiffer, softer, in all parameter of operation low-speed, high-speed, compression, rebound. You can effect your "perceived" spring rate with your dampening rate as a stiff shock will make the spring "seem" stiffer but that is really not a good way to be, the spring should be the right rate, and the shock should be valved accordingly.

Is that what you were after?

 

[craigvansickle]

Valving is quite simply the control of the fluid inside the shock. The entire operation of the shock is dependent on how the shock is valved. A shock typically has two different operating parameters, high speed and low speed. In low speed operation shock oil flows through tiny holes in the face of the piston inside the shock as the shock moves up and down, changing the size of these holes determines how much resistance the shock has to movement. In high speed operation, like landing off a big jump, the holes cannot flow enough fluid fast enough to keep the shock from "locking up" so they posses a spring loaded "valve" that opens to allow more fluid through. All of these things are changeable in a shock to make it stiffer, softer, in all parameter of operation low-speed, high-speed, compression, rebound. You can effect your "perceived" spring rate with your dampening rate as a stiff shock will make the spring "seem" stiffer but that is really not a good way to be, the spring should be the right rate, and the shock should be valved accordingly.

Is that what you were after?

Thanks Brad. That was a very understandable description. I assume when members on the forum refer to "custom" valved shock they are referring to one that has been specifically tuned for its specific application?

 

[Dartos]

I picture the skid moving through powder - floating up and down in the chassis - encountering different depths and densities of snow: it makes sense that softer settings would allow the skid to react to subtle changes it encounters - staying on "step" to use a boating term. You can definitely feel a big change while riding when your sled begins to break through and cavitate rather than float. If in a climb you begin to pass that point and take a less steep line you can also feel a big change as the sled climbs back on top.

There has to be a point that too soft and the suspension collapses too quickly and you begin to drag the chassis/running boards through the snow.?.?.?.?

 

[craigvansickle]

There has to be a point that too soft and the suspension collapses too quickly and you begin to drag the chassis/running boards through the snow.?.?.?.?

I think you are right. Its interesting to look at information regarding the progressive nature of an air spring vs a standard coil spring. (see image bellow) They posses the ability to have a soft, smooth resistance for the beginning of their stroke but stiffen up drastically as they reach the last 1/3 of their travel. They can "float" keeping the track, ski, or wheel in constant, even contact with the ground. Allowing you to maintain traction and steering over ever changing terrain. If you watch videos of those long travel baja racing trucks, just sitting still the suspension is compressed quite a bit. They need to be able to handle huge hits, but also have the tires follow the terrain to maintain traction and control. I wonder if a snowmobile skid in deep snow is much the same. The progressive nature of an air spring would also seem to be of great advantage with limiting excessive weight transfer.

 

[craigvansickle]

Allowing you to maintain traction and steering over ever changing terrain. If you watch videos of those long travel baja racing trucks, just sitting still the suspension is compressed quite a bit. They need to be able to handle huge hits, but also have the tires follow the terrain to maintain traction and control.

See 1:20 - 1:45 in the video bellow.

http://www.youtube.com/watch?v=rFS8tKU1ve0

 

[BigTruck]

This is all great info/input! Ive truly enjoyed reading this thread. The truth of the matter is that alot of people set there mountain sleds up to handle the rough trail. They think that stiffer springs held keep the sled from bottoming out on the big bumps. This is correct. However, it also takes away from the suspensions capability to "work" in the deep powder. If the suspension is in an extended position all the time it doesnt react to the changing terain. I am a 260 lb guy that rides a 600 155 and a 800 155 (both non Dragon's) with the stock springs and shocks. The sleds dont do all that good going down the whooped out trail. But get them in some POW and they work extremely well. The front ends are light when climbing from the rear suspension transfering the weight of the sled to the back. I am a beleiver that in deep snow a little softer skid goes a long way.

My .02 worth...

 

[hilinerider]

i notice nobody mentioned a limiter strap setting????????????????????

 

[AKSNOWRIDER]

i notice nobody mentioned a limiter strap setting????????????????????

good catch hilinerider, on stock skid with the frt. track shock laid down, I had mine all the way out...on the holz skid it is set at 6 inches(upper arm shaft to rail top)...

 

[craigvansickle]

Work pulled me out of town for most of 2010. I put 0 miles on my sled last winter. Did a bunch of flat land riding in the arctic, but the rmk sat back home. Looking forward to picking back up on sled tweaking. Suspension and clutching still fascinate me.

 

[Clarke673]

Alright, that makes a lot of sense to me.

When I look at the photo I posted above a couple things jump out at me:

a steep ramp angle(where the track exits the driver and descends to meet the rails) would possibly increase the tendancy to claw at the snow rather than climb on top.

A steep ramp angle may also cause the sled have more of a tendancy to rotate backwards under high power on a slope in deep snow.

Are these statements accurate?

Yes you are. A good example of that is to simply let your limiter strap out... or ride a short track IQR with a modded 800... that will help you out too.

 

[440dart]

AK what did you notice with changing your limiter from tight to loose, i ran mine on the tightest setting and recently changed it to the center hole just seem to handle better, but ive had a horrible problem with when going extremely slow when i nail the gas and it trenches the skis come way up the the sled gets really really tippy so i tried to keep them tight to keep the skis down.

 

[korythigpen]

need some help and info

so i am new to the snowest forum. i have a 2010 rmk 800 and,a 2010 dragon 800, they are the same machine, same chassis, same body but the dragon has the fox floats, i don't know why but my rmk will high mark the drogon by 10 fold and after reading every ones comments on the suspension it got me wondering, is the dragons suspension causing the problem so if any one has anything for me that would be great

 

[MORSNO]

Are the tracks the same also? My vote would be the clutching or rider for that much difference if they are identical sleds.