Caster Angle Mtn Viper

[Off Trail Mike]

Many thanks Peter:

Kinda surprised actually. Figured it was less than that just looking at pictures, but that is a pretty good number as you know..

Have started down the CAD path and have an interesting new geometry in mind for the old Nytro. Higher roll center which is good. Still have to figure out and find the approximate CG so I get a sense of how much this will really help relative to the stocker, but it will be better for sure.

Also looks like I'll be moving the direct steering post above and between the lower a-arm mounts, as opposed to behind the lower A-Arms like on the stocker). Complicated, but better I think. Now have to look for rubber boots off some other sled that will work on the Nytro body panels and figure out how to close the old holes....oh the joys of custom builds.

Going to be a busy fall...

Again thanks,

Mike

 

[Mountaintech]

Your direction sounds good. Hopefully you will have another good winter.

 

[Mountaintech]

Mike, something must have been wonky when I measured the caster on a Proclimb a few weeks ago because I just checked on a sled I installed a 38" front end on. Caster is 18 degrees, which make more sense. It was actually 16 degrees when it had the 40" front end on it.

 

[Off Trail Mike]

Thanks Peter:

Swamped at work right now so no work on the Nytro. Next month hopefully some "life" sanity will return.

Yeah, I was thinking less than 20 degrees, but wasn't sure so thanks for the confirmation. I think if you look at CMX, Doo, Cat, there seems to be some consensus around what works in the mountains and why it is different than a trail sled. Keep thinking side-hilling with longish caster (>22 deg) will cause the sled to dive (cut harder) into the mountain. I see narrower/steeper caster as a better alternative than wider/shallower caster.

My problem is I have to build the darn thing to test it!

Here's to hoping

Thanks

Mike

 

[Mountaintech]

Mike, I agree. On the Nytro chassis, more caster is better for off trail performance. I was able to verify that with my prototype arms. The sled was more controllable and smoother on one ski (carving, sidehilling). With fully adjustable arms it was easy to change settings and compare within minutes. 23-24 degrees was better that low 20's or high teens. My prototype arms are ready for the Viper. All we need now is snow!

 

[Off Trail Mike]

Peter:

Yeah...on the 38/39" front ends, the Nytro needs more caster and your A-Arms are right in the sweet spot of adjustability (21-24).

One question if you don't mind. You ever test a 36" set of your arms on your Nytro? I know CR makes one, but I've never had a chance to ride one.

The more I think about it, the more I think a general rule is that caster has to decrease as you narrow. Call it gut instinct, but to me if you don't reduce caster a bit, the front end will try to tip over too quickly and make the sled bounce thru the turn more (requiring more steering corrections to keep it going where you want it to).

I'm pretty sure powder turns work best when the ski remains relatively flat (thus the need to counter steer) during a banking corner or side hilling and the angle to the Center of Gravity of the sled needs to stay relatively consistent, or it will fall over. So narrowing ski stance changes the angle relative to CG which means you need to change Caster to compensate.

Hey, I don't design for a living and maybe I'm dead wrong but going to fun to try.

Thanks

OTM

 

[Off Trail Mike]

Forgot to ask.....Prototype arms for the Viper.....spill the beans Mountiantech!

 

[Mountaintech]

Mike, Tried 36 and 37". Boy, I had a ton of prototype arms. I just threw a whole bunch out the other week when I cleaned shop. I found 36 and 37 to be way too much of a compromise on the trail. The 38 set is nice and responsive off trail without being a hazard on the trail. If you offset the skis on the 38 kit you can adjust from 36- 40. As far as the Viper/Proclimb arms are concerned, prototypes and jigs are done, just need snow to verify a few things. They are caster and camber adjustable.

 

[turbo800]

Its interesting that you mentioned you've tried both 36 & 37" stances. I was thinking about trying a set of 36" on my Viper, but then I remembered back to the old Doo ZX days with the 37" ski stance and I hated it! I pushed mine out to 40" and loved it.

My thinking was, both the PRO and the XM both use 36" stance and they boondock very well. On the flip side, I hate their trail manners! It seems like every little bump in the hill, I was shifting my weight to counterbalance the sled. I don't know how many times I tipped it over simply because I didn't react fast enough or over compensated. It seemed I used just as much energy as a sled with a lil wider stance if not more. I've been told you just need to ride them more to get used to their handling characteristics.

Does this same logic apply to the Viper with a 4 stroke also? Or can you get away with a lil narrower stance because of the mass of a 4 stroke?

 

[stingray719]

Its interesting that you mentioned you've tried both 36 & 37" stances. I was thinking about trying a set of 36" on my Viper, but then I remembered back to the old Doo ZX days with the 37" ski stance and I hated it! I pushed mine out to 40" and loved it.

My thinking was, both the PRO and the XM both use 36" stance and they boondock very well. On the flip side, I hate their trail manners! It seems like every little bump in the hill, I was shifting my weight to counterbalance the sled. I don't know how many times I tipped it over simply because I didn't react fast enough or over compensated. It seemed I used just as much energy as a sled with a lil wider stance if not more. I've been told you just need to ride them more to get used to their handling characteristics.

Does this same logic apply to the Viper with a 4 stroke also? Or can you get away with a lil narrower stance because of the mass of a 4 stroke?

We put 38 inch front on the girlfriend's sled then spaced skis in for 37 inches. So my new Viper I set up the same as I could tell no difference on the trails we use to get to the powder. Side note I had tried both 36 and 37 (2 inch forward)on Nytro and preferred the 37.

 

[Sportsterdanne]

Stock Pro has 39" with ski in the middle position.

Its interesting that you mentioned you've tried both 36 & 37" stances. I was thinking about trying a set of 36" on my Viper, but then I remembered back to the old Doo ZX days with the 37" ski stance and I hated it! I pushed mine out to 40" and loved it.

My thinking was, both the PRO and the XM both use 36" stance and they boondock very well. On the flip side, I hate their trail manners! It seems like every little bump in the hill, I was shifting my weight to counterbalance the sled. I don't know how many times I tipped it over simply because I didn't react fast enough or over compensated. It seemed I used just as much energy as a sled with a lil wider stance if not more. I've been told you just need to ride them more to get used to their handling characteristics.

Does this same logic apply to the Viper with a 4 stroke also? Or can you get away with a lil narrower stance because of the mass of a 4 stroke?

 

[turbo800]

Stock Pro has 39" with ski in the middle position.

Poo PRO or Cat Proclimb?

I've been told the PRO is 36" center to center spindle. To me that makes sense since Doo updated theirs to match with their S36 front end kit.

Edit:
Found this on Poo's site...

Ski Center Distance (in./cm.)
39 - 40- 41 / 99.1 - 101.6 - 104.1

Not sure if that is center spindle also, or where the carbide playing into its width either!

Doo's site:

Ski stance 907 or 950 mm / 35.7 or 37.4 in

 

[Off Trail Mike]

I run both my XM and Nytro on full narrow (around 36") and I really love how they work. I don't find trail manners on either too awkward but I don't run much trail and definitely not at warp speed anymore. That said, I think the XM can get away with a slightly narrower stance because of its lower CG and lower weight up front.... The Pro RMK I tried was set on 39 and although it works very well in freshy pow, IMO it could also benefit from a 38" stance in more set up snow.

So back to the drawing board..... With my Nytro I'm leaning towards a 37" stance (spindles) with the option to go 3/4" narrower or wider using adjusting bushings. Only question is caster and that will be the $50k question.

I think the Viper MTX will be right in there at 38 - 39, which is likely a very good compromise, but will be interesting to see what the aftermarket provides as options, but I'll be it won't be wider!

OTM

 

[Mountaintech]

I run both my XM and Nytro on full narrow (around 36") and I really love how they work. I don't find trail manners on either too awkward but I don't run much trail and definitely not at warp speed anymore. That said, I think the XM can get away with a slightly narrower stance because of its lower CG and lower weight up front.... The Pro RMK I tried was set on 39 and although it works very well in freshy pow, IMO it could also benefit from a 38" stance in more set up snow.

So back to the drawing board..... With my Nytro I'm leaning towards a 37" stance (spindles) with the option to go 3/4" narrower or wider using adjusting bushings. Only question is caster and that will be the $50k question.

I think the Viper MTX will be right in there at 38 - 39, which is likely a very good compromise, but will be interesting to see what the aftermarket provides as options, but I'll be it won't be wider!

OTM

I'm sticking with 38" for the Viper MTX arms I'm developing.