We Got Trencher - skid set up

[Twostroke]

Looking for some input here, I got a trencher'. Did some reading but getting mixed info, looking to improve it without increasing ski pressure, love how this thing handles other then the trenching. Climbing and deep snow it trenches bad.

Info;

IQR
151" RMK skid
155" track
pretty heavy on front track shock preload
same on front skis, maybe 1" static sag up front.
Rear torsion spring on stiffest setting
limiter straps in middle notch
front shock is "up right"

I had some consistant bottoming on the front skid shock so I cranked the preload doesn't bottom anymore and also wanted less ski pressure.

What is going to be my best process for helping with the trenching, Laying the shock down? Back off the shock preload till I'm bottoming sometimes again? Loosen limiters? It keeps the skis on the ground great now, could stand to be looser.

Here's a pic of my attack angle and set up. Consider this is a race chassis so this angle is much improved over stock and I feel that the problem lays within preload and settings.

 

[M8fever]

What track. ?

 

[mikew5945]

Dump that soft Polaris track. It was not any good new. You can see how the paddles are folding over just sitting there in the air. Your 'ATTACK ANGLE' sucks. Look where your weight is. The rear paddles have all the weight on them. It is starting a trench sitting on the trailer. You need to let the front of your skid out so it can work. Go back to the beginning. Adjust it so the skid is flat on the ground front to back. Ride it and adjust from there. You know that in this position it trenches so what will it do flat. Knowing those two positions you can adjust from there.
Is your suspension coupled?

 

[Twostroke]

The skis are on .5" glides so it fudges the pic some. With the track being soft I'd think it'd not be prone to trenching. Heck my roomies m8 with a challenger is much softer and more laid over and trenches less. So I'm more interested in opinions on my settings then my track..

Lets keep this honest and non biased. Straight up.

I see what your saying about the weight being in the back.. but..

So by saying my attack angle sucks what is your suggestion? Loosen my straps?

Were on the same team here, i'd like for this to be an informative discussion..

 

[sled_guy]

Ok, first off, to make it work in the powder and climbing you are going to give up on trail performance... are you ok with that?

Static attack angle, sitting on the trailer, doesn't really equate to on snow performance. When you wack the throttle the force into the track will try to colapse the suspension, especially at the front. That said, attack angle is important.

You say you were bottoming the front track shock out and turned the pre-load up to stop that... wrong approach. If you are bottoming out you need more dampening, not more spring.

For powder performance, lay the front track shock down, loosen the spring up until it barely stays on, let the limiters out. You want the front of that rear skid to be soft and mushy so that when you get on the gas it colapses and "climbs" up on top of the snow.

Take some preload out of the rear torsion springs too... let it sag in 3" or so and if you bottom it then dial dampening into that rear shock. Same on your ski shocks... why do you have so much preload in them?

How did you get your extra adjustment in track length using the 151 skid with a 155 track? Set the suspension back from normal position?

The snowmobile suspension is like a teeter-totter... with the pivot point being the front rear skid mounting point. If you have the front stiff and the rear/rear stiff then it won't pivot around that center point very well... so you'll stuff the machine into the snow, causing trenching. Soften things up on the preload and use the shocks' dampening to stop bottoming. The ability for the suspension, especially the rear suspension to both compress and fall out of the tunnel affects how it works both on trail and in the powder. If you have it all stiffened up then it can't compress and "climb" on top of the snow as well.

Now, as I said, if you want to make it work really well off trail and in the deep stuff then it is going to feel a little squirly on the trail.

sled_guy

 

[mikew5945]

The skis are on .5" glides so it fudges the pic some. With the track being soft I'd think it'd not be prone to trenching. Heck my roomies m8 with a challenger is much softer and more laid over and trenches less. So I'm more interested in opinions on my settings then my track..

Lets keep this honest and non biased. Straight up.

I see what your saying about the weight being in the back.. but..

So by saying my attack angle sucks what is your suggestion? Loosen my straps?

Were on the same team here, i'd like for this to be an informative discussion..

Sorry, I forgot it says Arctic Cat by my name. That being said the Sled Guy said in more detail what I was getting at and where I was going. Read what he wrote and get over the brand name bashing or post in the Polaris section. Your track needs replaced. The skid and track work together. I ride with a bunch of Polaris Pro's and they all changed those tracks. Good luck with your suspension.

 

[sled_guy]

If you are riding in Oregon concrete that probably isn't the best track.

Now if you were in the bottomless fluff we have in Utah, different story, those floppy paddles work well in the light powder.

sled_guy

 

[die hard poo]

I noticed in your pic you had your rear suspension front bolt mount in the lower hole in the tunnel. Try RAISING it to the top hole, this will decrease your suspension travel slightly, but will allow it not to trench nearly as bad because it lets your suspension get on top of the snow.
Look how the RMK suspension is mounted in the chassis and then look at a trail or race sled mount. The mtn/RMK sled will have the upper hole for better deep snow performance, but sacrifice suspension travel, where the race sled will have more travel but worse deep snow performance.

Also as others say, the more preload you put on the front track shock, the more it will trench. But IMO, if you need to increase preload on the fts, try and match it to the rear track shock. Also, I try and run the front ski shocks with the least amount of preload as possible balancing trail and deep snow performance.

 

[Twostroke]

Right now the front track shock is stiffer then the rear, a fair bit.

Sidehilling the rear spring is too soft, I think. Sidehilling the spring "pack"(ride low in the stroke) and ride lower and lower throughout the sidehill if snow is packing into the skid and on the sled. If I have no additional weight it will not do this, but the weight from extra snow it will. I want a stiffer rear torsion spring to prevent this actually. Long technicle sidehills are my favor thing to do and this hinders it or could this be because of too much front preload so it's not allowing weight transfer?

I had my mount in the higher hole at the start of last season, had to drop it, the ski pressure was unreal, it was pretty much no fun to ride, it was so heavy. I can't go back to how it was, I'd rather not ride.

With less preload on the front springs I feel like the front end plows and also will "pack" not allowing the spring to keep the shock & spring high in the stroke to keep it in the sweet spot and also bottoming out. Adding preload dramatic improved off trail handling, and on trail also. I like my sleds to pull onto edge easy. When we do ride trail the preload kept the inside ski more planted. Right now the sled is very predictable in all situations and pulls over really easy.

Two things are important to me; 1) pulling over easy, 2) minimal trenching. I could absolutely care less about trail manners.

Right now I do not think it could pull onto edge any easier, makes a mseries feel like a tank.

 

[Twostroke]

If you are riding in Oregon concrete that probably isn't the best track.

Now if you were in the bottomless fluff we have in Utah, different story, those floppy paddles work well in the light powder.

sled_guy

I do ride in Oregon, Central Oregon. We get some heavy snow but we also get some very dry snow, that would rival Utah fluff, sometimes.

I like this track better then my Challenagers I've had before, I not sure that I could justify purchasing a different track just for when it's heavier. I could though live with putting some screws in it to stiffen it up.

 

[Twostroke]

Ok, first off, to make it work in the powder and climbing you are going to give up on trail performance... are you ok with that?

Static attack angle, sitting on the trailer, doesn't really equate to on snow performance. When you wack the throttle the force into the track will try to colapse the suspension, especially at the front. That said, attack angle is important.

You say you were bottoming the front track shock out and turned the pre-load up to stop that... wrong approach. If you are bottoming out you need more dampening, not more spring.

For powder performance, lay the front track shock down, loosen the spring up until it barely stays on, let the limiters out. You want the front of that rear skid to be soft and mushy so that when you get on the gas it colapses and "climbs" up on top of the snow.

Take some preload out of the rear torsion springs too... let it sag in 3" or so and if you bottom it then dial dampening into that rear shock. Same on your ski shocks... why do you have so much preload in them?

How did you get your extra adjustment in track length using the 151 skid with a 155 track? Set the suspension back from normal position?

The snowmobile suspension is like a teeter-totter... with the pivot point being the front rear skid mounting point. If you have the front stiff and the rear/rear stiff then it won't pivot around that center point very well... so you'll stuff the machine into the snow, causing trenching. Soften things up on the preload and use the shocks' dampening to stop bottoming. The ability for the suspension, especially the rear suspension to both compress and fall out of the tunnel affects how it works both on trail and in the powder. If you have it all stiffened up then it can't compress and "climb" on top of the snow as well.

Now, as I said, if you want to make it work really well off trail and in the deep stuff then it is going to feel a little squirly on the trail.

sled_guy

I'm willing to give up all my trail performance.

When I was bottoming I do not think I had any preload. I think I did add dampening but I forget, it's been a while.

Your explaination makes sense and I should have known better. I will let the limiters out some and lay the front shock down, and add minimal preload. Will this put more weight on the skis and make it harder to lay over? Should I go all the way loose on the straps?

With 3" sag in the rear I'm affraid it will affect sidehilling, will that not create a packing condition with the rear spring.

The sled pulls over easier with more preload on the front end. really 3" sag up front? Seems like a lot, won't have much travel before I'm on the bumpstops. But I'm not affraid to try it by any means.

I have 8" rear wheels to pick up the slack of the 151" skid, stock wheels I think were 5.xx".

Looks like I'm going soft tonight, doesn't sound like a good thing on a friday night lol.

thank you for your input, and I hope it will help others who read this!

 

[die hard poo]

Right now the front track shock is stiffer then the rear, a fair bit.

Sidehilling the rear spring is too soft, I think. Sidehilling the spring "pack"(ride low in the stroke) and ride lower and lower throughout the sidehill if snow is packing into the skid and on the sled. If I have no additional weight it will not do this, but the weight from extra snow it will. I want a stiffer rear torsion spring to prevent this actually. Long technicle sidehills are my favor thing to do and this hinders it or could this be because of too much front preload so it's not allowing weight transfer?

I had my mount in the higher hole at the start of last season, had to drop it, the ski pressure was unreal, it was pretty much no fun to ride, it was so heavy. I can't go back to how it was, I'd rather not ride.

With less preload on the front springs I feel like the front end plows and also will "pack" not allowing the spring to keep the shock & spring high in the stroke to keep it in the sweet spot and also bottoming out. Adding preload dramatic improved off trail handling, and on trail also. I like my sleds to pull onto edge easy. When we do ride trail the preload kept the inside ski more planted. Right now the sled is very predictable in all situations and pulls over really easy.

Two things are important to me; 1) pulling over easy, 2) minimal trenching. I could absolutely care less about trail manners.

Right now I do not think it could pull onto edge any easier, makes a mseries feel like a tank.

So I get what you are saying with raising the front mount to the upper position, with the race sled stance, the front of the sled is also higher than a consumer sled and when you alter the front mount it puts way too much ski pressure. I ran into this issue with my IQR mtn conversion also. I would recommend purchasing a rmk front end. It won't be cheap, but it will make it handle like a dream(like a mountain sled lol) and will allow you to have much less ski pressure, narrower stance to make it easier to sidehill, allow you to put the front mount in the top hole where it will make it trench much less.

 

[Twostroke]

I guess I should have mentioned that I have a narrow RMK front end on it, 39" wide. Running revalved WE's with springs off a m1000, stock springs are way stiff.

I just got done laying my shock down, minimum preload and loosened the limiters, the limiters are tight sittin on the shop floor, seems like they should have some wiggle to them just sitting there?

roughly 2" static sag up front how it was, I'm going to leave it. was kind of tough to measure alone, could be off a little bit. I'd guess 3" rider sag in front, a little less in rear.

I noticed with my shock laid down it's seems stiffer then the rear torsion springs, considering a softer spring, this is a racer spring/revalved shock.

I don't get any sag with the rear torsion springs but they are very soft, even with the stiffest setting I can push down and basically bottom it out in back. I think they are wore out. I noticed some bend to them near the tension blocks. When I sidehill in the garage I can get the rear end(torsion spring) to almost bottom out, can't with the m8 in the garage, the M is much stiffer in the rear. This is with my torsion adjuster blocks on full stiff and the M set in the #2 spot of the torsion blocks. Think this could be my sidehill packing/rear of skid settling way low issue? When this happens sidehilling the rear end wants to wash out below me.


When you guys are talking sag numbers are you talking static or rider? Just to be clear.

 

[sled_guy]

My sag numbers are always with the rider (now that is a strange thing to say).

If you can collapse the rear completely sitting in the garage then I would suspect the springs are shot.

When riding, if the springs are good, and you experience "packing" that means you have too much rebound dampening in the shocks. Again, that is assuming your springs are good.

If the rear/front spring is stiffer than the rear/rear spring your going to get trenching I would suspect because the back of the track will compress easier than the front.

You have to have sag in the suspension. Sag means movement. Movement has to happen in both directions, both down and up, for the suspension to work right. Yes, if you take stiffness out of the front/rear shock and keep the front end stiff then you are going to have lots of ski pressure.

sled_guy

 

[Twostroke]

I'm come from the mx world so we always measure static and rider "race" sag. In MX you set your static sag, then check race. If you have too much race sag your springs are too soft, vice verse if not enough sag. I think it's odd that snowmobilers are not more techincle with suspension and spring settings. But anyway..

I rode it with the shock laid down, basically no preload, limiters all the way loose but still tight when sitting on the shop floor. Its worlds better. The snow as about 10"-12" of dry fluff on top of ice. I normally would have been able to get the sled stuck, could not the last two days. climbed amazing, nice to not have the sled limiting me. Think I'm going to pick some new rear torsion springs, as I can visiually see that they are bent. I also want to try a lighter front track spring.

 

[mikew5945]

I'm come from the mx world so we always measure static and rider "race" sag. In MX you set your static sag, then check race. If you have too much race sag your springs are too soft, vice verse if not enough sag. I think it's odd that snowmobilers are not more techincle with suspension and spring settings. But anyway..

I rode it with the shock laid down, basically no preload, limiters all the way loose but still tight when sitting on the shop floor. Its worlds better. The snow as about 10"-12" of dry fluff on top of ice. I normally would have been able to get the sled stuck, could not the last two days. climbed amazing, nice to not have the sled limiting me. Think I'm going to pick some new rear torsion springs, as I can visiually see that they are bent. I also want to try a lighter front track spring.

WOW.

 

[Twostroke]

wow?

 

[sunbather1969]

Twostroke

I have the same problem with mine let me know what you find out. Carls cycle said they could never get them to perform and thats why they don't f with them and i had erik beukelman help me, my machine is a good looking running all around machine it doesn't do anything handling wise the way a purpose mountain or trail sled should do any more. It was the funnest machine i ever had at 136 and coupled but i had to toy with it and install 2010 155 skid and 5.1 i even have big drivers , it has terrible approach angle.

 

[Twostroke]

sunbath I think this fixed my problem, just need a couple feet of fresh to really try it out, still lays over great. I was going to purchase a new skid but now I'm leaning towards a track instead, extreme or pc.