rear springs question

[Alatalo]

Oh boy, this is sure to get some opinions going. You could be right Alatalo, for the REALLY aggresive types, but my butt dyno would have to argue with you. I would use springs strong enough to get the sag within specs. (and maybe have a little in reserve?) then use damping for control from there. In either case, just a warning for most riders. My thought is if you are going to go EITHER way (HD spring or damping), to deal with a type of bump/bottoming seen in 1% (or less) of your riding, you are calibrated incorrectly for the other 99% of the time. You'll be WAY too stiff to get any type of enjoyable ride! Guys racing, jumping, or looking for a super aggressive set up might consider this (and be willing to pay the price), but not the guy looking to be geared up good enough for good Sat pm. junk survival. A set up to control bottoming in g-outs is a set up that will rattle your teeth just about full time the rest of the time! Most riders are further ahead learning to spot them in time to get up off their azz! FWIW

I have got my opinion, you have got your opinion and I see no reason to even spend the time on arguing one or the other. However, one thing is for sure. In my riding conditions, I and everybody else have to deal with big dips and g-outs much more than 1% of the time (if you don't, I seriously doubt why you are riding a snocross replica...). In fact, big dip and g-out bottoming resistance plays quite an important role in the suspension setup. With the 1400's I can not get the bottoming resistance I want without sacrificing the comfort due to excessive compression damping. With the 1900's I can get exactly the bottoming resistance I want, combined with a small bump comfort that is smoother than any OEM sled up to date. As simple as that...

 

[nplathe]

You should call Hygear...they'll set you up with what you need.

From the Hygear website "We do not recommend using Torsion springs to control bottoming resistance."

 

[Alatalo]

No need as I am happy with my current setup.

But I find a statement like that to be very strange, especially when considering it is on the website of a reputable suspension shop. According to basic suspension theory, the spring rate used goes pretty much hand in hand with the load of the vehicle. It is obvious that the load generated by a 60 kg rider is not the same as the load generated by a 120 kg rider, thus the spring rates used should be different. Using the same rate springs, it is still possible to adjust the hydraulics for improvements in, for instance, bottoming resistance. But in order to achieve the results wanted, this means that one of the setups is going to be severely under- or overdamped, thus being pretty far from optimized. Strange statement, I would say.

 

[SledFreak]

You should call Hygear...they'll set you up with what you need.

From the Hygear website "We do not recommend using Torsion springs to control bottoming resistance."

I agree, it's in the valving of the shock.

 

[ahicks]

No need as I am happy with my current setup.

But I find a statement like that to be very strange, especially when considering it is on the website of a reputable suspension shop. According to basic suspension theory, the spring rate used goes pretty much hand in hand with the load of the vehicle. It is obvious that the load generated by a 60 kg rider is not the same as the load generated by a 120 kg rider, thus the spring rates used should be different. Using the same rate springs, it is still possible to adjust the hydraulics for improvements in, for instance, bottoming resistance. But in order to achieve the results wanted, this means that one of the setups is going to be severely under- or overdamped, thus being pretty far from optimized. Strange statement, I would say.

I think most will agree with your basic suspension theory. I do. I just believe the spring rate (including preload) piece of the theory should not go beyond supporting the static weight? Your comments sounds like you support the idea of factoring in some bottoming resistance, in addition to load requirements, when selecting your spring rate?

Regarding the damping required for bottoming resistance, you mention "one of the setups is going to be severely under- or overdamped, thus being pretty far from optimized". If we were allowed only a single damping rate (which is so typical of Yammi), I'd agree without hesitation. But that's not the case. This is a perfect illustration for the need to set up our valve stacks using mutiple/progressive rates? No?

 

[Alatalo]

Your comments sounds like you support the idea of factoring in some bottoming resistance, in addition to load requirements, when selecting your spring rate?

Yes, but only big dip and g-out bottoming resistance. The basic theory behind it is the old saying that "no compression damping in the world is going to stop a heavy load that is acting for a very long time". Simply, the compression damping is not going to stop the movement at a certain position - the compression damping is just going to slow the movement down.
Look at it through a slightly over-exaggerated example - the static weight of the snowmobile and the rider is acting for a very long time (eternity). Even if you would close the compression adjuster and install the stiffest shim stack you could find, the suspension would still bottom out if you had no spring. Simply, you need the position sensitive spring instead of the velocity sensitive damping.
Basically, I would say that most suspension engineers would include the g-out bottoming resistance as part of the "load requirements". You know the load at your 1G position. Through simulations and/or field testing, you can also figure out the load when bottoming out in g-outs. You know the stroke in between and then you can calculate the spring rate that you need.

Regarding the damping required for bottoming resistance, you mention "one of the setups is going to be severely under- or overdamped, thus being pretty far from optimized". If we were allowed only a single damping rate (which is so typical of Yammi), I'd agree without hesitation. But that's not the case. This is a perfect illustration for the need to set up our valve stacks using mutiple/progressive rates? No?

I can see what you are on about, even if I would use a slightly different nomenclature. From the dyno runs I have seen of Yamaha OEM shocks, I would actually say that the "typical" Yamaha setup is a very digressive damping force vs. velocity curve. This means that the damping rate at low velocities is huge (=overdamped) and that the damping rate at high velocities is close to nothing (=underdamped). This kind of setup is usually created by a heavily preloaded shim stack that just refuses to open at low velocities, but when eventually being forced to open it kind of opens too much. In short, a harsh ride but still no bottoming resistance.
By utilizing more open bleed / bypass flow combined with a stiffer "multi stage" shim stack, the damping constant at low velocities can be reduced and the damping constant at high velocities can be increased. This is much more in line with, for instance, BRP OEM shocks, Ohlins and Fox snocross shocks and also the shocks that I am running right now.

 

[ahicks]

Alatalo, instead of using the stiffer springs to control your slow speed/g-out scenario, why not let some coupling come in to play to "catch you" at some point? We both know that not only couples up the front and rear springs to increase spring rate big time - but it also couples up the shocks for extra damping power - and can be set so it's out of play until deep in the suspension stroke! How much coupling/at what point in the stroke the coupling occurs, is not that hard to set up on a decent skid capable of adjustable coupling. Carefuly set, I've found this is the key piece of the setup will let me run the lighter springs for a decent ride, prevent much (but honestly, not all) of the bone jarring forces in a g-out, and not being subject to springs any bigger than necessary.

Maybe you've been here, done that, and it didn't work for you, but it's very effective for me and the way I ride. FWIW -Al

 

[NyTrOMaNIaC]

Pretty sure the stock springs on the RTX models are 1900's, so 2100's are the next step up. Myself, I just put a set of X-Click aluminum 4 position torsion spring blocks on mine and it added the stiffness I was looking for. A lot cheaper than buying new springs, and I'm only on the 3rd setting. 4th position is the overload setting (20% over 3rd setting), yet the 3rd is more than stock HARD and more than enough. They replace the plastic 3 position blocks that adjust the tension on your torsion springs (S M H) and I think I paid around $60 for them.

Where did you get them from?

Here's where I bought the X Clicks. They work awesome for me, and I test them out often

http://www.hiperf.com/cgi-bin/sh000001. ... aX_2dCLICK

 

[Alatalo]

Alatalo, instead of using the stiffer springs to control your slow speed/g-out scenario, why not let some coupling come in to play to "catch you" at some point?

You are right about the fact that coupling adds spring as well as damping progression to the bottom of the stroke. I would also say that even if I have never adjusted the coupling point of the FX Nytro, I have kind of tried to use the coupling to my advantage. The 1400 Nmm/deg rear springs actually offer quite decent g-out bottoming resistance when being combined with a 32 N/mm center spring. Unfortunately, this setup tends to ride the front of the skid a little bit more (taking load off the skis) and also offers a "stopping feeling" that puts the entire sled into a small, forward-rearward pitching motion when riding fast through sections with smaller moguls. I get the same bottoming resistance but no pitching drawbacks when combining the 1900 Nmm/deg rear springs with a 28 N/mm center spring. Based on this I feel that the 1900/28 combo offers a better balance between center and rear for the same bottoming resistance, but this is not necessarily going to be the case with every rider.

Regarding the adjustment of the coupling point, I have more or less decided to leave it in the OEM position. The reason for this is basically that I am forcing myself to learn how to ride a "wheelie-happy" sled. And the more I ride it, the more I start to realize that it is actually possible to ride around the problems caused by the excessive weight transfer and actually use this to your advantage. It requires a lot of body english, ugly as hell stop-and-go type of cornering and likely a steering post relocator, but once sorted out and in the right environment, I enjoy it a lot...!

 

[ahicks]

ugly as hell stop-and-go type of cornering

Right.....giving somebody hot on your behind, that's tuned a little differently, a big easy opportunity to go right around you - if for no other reason than to roost you big time.

Have you tried a set of Poo coupling blocks on it (or something that may serve the same purpose) and tried that? Very easy to fiddle with them on a few rides! It's nice to be able to jump into the throttle prior to actually being pointed in the right direction! I've ridden the setup you're talking about. That's a lot of work. Too much for this old fat body. Or are you not doing much riding on tighter trails?

Set properly, you can still have a lot of that transfer you're talking about (fun! See avatar!) AND be able to accelerate while turning....

I understand the point regarding the heavier front skid spring having a lot of effect on your transfer. I've messed with that extensively - a major tuning tool to have at your disposal! Even if not going so far you're changing springs, just a big change in preload can make a lot of difference...

 

[Alatalo]

I have used only the standard coupling blocks and the standard rear limiter strap (which does the same job as the center-to-rear coupling blocks of other brands). As I said, the reason is simply that I want to learn how to ride a snocross replica with high center of gravity, minimal coupling and excessive weight transfer in all kinds of directions. Couple of years ago I used to be a guy that preferred tight coupling and minimal weight transfer, basically the way you would set the SRX and the Viper up. As my sleds got higher and more snocross like (I went through REVs and - believe it or not - a very cross country specialized Attak...), I realized that my riding style did not utilize the possibilities of excessive weight transfer - I simply had to change my riding style in order to stay with the current snocross replicas and in front of the SRXs and Vipers. Actually, the current Lynx models that are the reference for good suspension function around here are even more "wheelie-happy" sleds, even though their long center swingarms make them more sensitive to body positioning (if you want them not to wheelie out of corners, less body english is required compared to the FX Nytro).

Most of the trails I ride do not see frequent grooming and they can be pretty bad and bumpy in the end of the weekend. But this is just the conditions where the FX Nytro and other snocross replicas really shine. Unfortunately, my feeling is that this message sometimes gets lost in the debate on a forum like this. The FX Nytro is a good big bump sled, but not at all a good groomed trail sled. If you try to make it into a groomed trail sled, you have got too much of the basic physics (the ergos and the high center of gravity, for instance) against you and you are only going to end up with a bad compromise that is...well, good at nothing. If you are serious about flat, groomed trail racing, get the SRX, Viper or RX-1 (or possibly a low-slung Apex). Properly set up, you will fly past the FX Nytros...

 

[ahicks]

OK, I have a better idea of what you're doing. I might be a little (lying, actually a lot) jealous of somebody with the stamina to spend a day on a sled riding like that.

There are some trails in the area I ride dedicated to ATV/ORV traffic only. They aren't ever groomed either. That's the area I generally head for to check out what I have going on with the latest round of adjustments. I can identify with what you're saying.

Last thought - coupling doesn't have to be an all or nothing tuning tool - and the same goes true with transfer.....

C'mon snow!

 

[nplathe]

Do they offer the 1900 spring for the XTX?? i was looking for it under the parts catalog and couldn't find it.

 

[multi sled]

I have used only the standard coupling blocks and the standard rear limiter strap (which does the same job as the center-to-rear coupling blocks of other brands). As I said, the reason is simply that I want to learn how to ride a snocross replica with high center of gravity, minimal coupling and excessive weight transfer in all kinds of directions. Couple of years ago I used to be a guy that preferred tight coupling and minimal weight transfer, basically the way you would set the SRX and the Viper up. As my sleds got higher and more snocross like (I went through REVs and - believe it or not - a very cross country specialized Attak...), I realized that my riding style did not utilize the possibilities of excessive weight transfer - I simply had to change my riding style in order to stay with the current snocross replicas and in front of the SRXs and Vipers. Actually, the current Lynx models that are the reference for good suspension function around here are even more "wheelie-happy" sleds, even though their long center swingarms make them more sensitive to body positioning (if you want them not to wheelie out of corners, less body english is required compared to the FX Nytro).

Most of the trails I ride do not see frequent grooming and they can be pretty bad and bumpy in the end of the weekend. But this is just the conditions where the FX Nytro and other snocross replicas really shine. Unfortunately, my feeling is that this message sometimes gets lost in the debate on a forum like this. The FX Nytro is a good big bump sled, but not at all a good groomed trail sled. If you try to make it into a groomed trail sled, you have got too much of the basic physics (the ergos and the high center of gravity, for instance) against you and you are only going to end up with a bad compromise that is...well, good at nothing. If you are serious about flat, groomed trail racing, get the SRX, Viper or RX-1 (or possibly a low-slung Apex). Properly set up, you will fly past the FX Nytros...

i have come to agree with this,yammy makes a good trail sled,apex or the new vector,their mountain sleds are good what they are,face it, the nytro is a ditch banging,rough trail machine.geting it to keep up with a apex on a groomed trail is kinda fruitless in my experience, but i would like to see if i can make mine a little more deep snow useful.hey nick i see you have been talking to the hygear guys,any parts come in yet[/u]

 

[nplathe]

multi sled, yup my triple rate springs and torsion spring spacers came in last week and I should have my shocks back sometime next week. I went with the sport package.
There awesome to deal with! Any question you have for them they can answer it.