BUMP STEER IMPROVEMENT

[AKrider]

Nice effort..

You need to place the board at about the end of the ski distance.

Another post above..ya I did that with my older style..moved the steeing rod to the under side of its stock position..bump steer..fixed.

As far as the racing..hmmm..the guy that drove the Yamaha finished in position X in the USA. The next year he drove another brand..tell me where he finished with that sled against the same competition.

I briefly tried to put the board near the end of the skis but because my sled is in storage, that configuration made it difficult to take the measurements. From what I've researched, repositioning the tie rod elevations appears to be the universal method to correct bump steer. It would be really cool to see how the '09 geometry plots with a laser.

What is position X? Are you talking about Robbie Malanoski or Corey Davidson?

For me, I just want my sled to handle better. If I can do it inexpensively then it will be well worth it. I don't expect it to be comparable to a Polaris IQ 600R or a Sno-Pro 600, but if it will just go down a rough trail in a straight line I'll be pretty happy!

 

[00-NUKE]

BREAKTHROUGH!

Nice effort..

You need to place the board at about the end of the ski distance.

Another post above..ya I did that with my older style..moved the steeing rod to the under side of its stock position..bump steer..fixed.

As far as the racing..hmmm..the guy that drove the Yamaha finished in position X in the USA. The next year he drove another brand..tell me where he finished with that sled against the same competition.

I briefly tried to put the board near the end of the skis but because my sled is in storage, that configuration made it difficult to take the measurements. From what I've researched, repositioning the tie rod elevations appears to be the universal method to correct bump steer. It would be really cool to see how the '09 geometry plots with a laser.

What is position X? Are you talking about Robbie Malanoski or Corey Davidson?

For me, I just want my sled to handle better. If I can do it inexpensively then it will be well worth it. I don't expect it to be comparable to a Polaris IQ 600R or a Sno-Pro 600, but if it will just go down a rough trail in a straight line I'll be pretty happy!

NOTE: First of all I would like to say that the 17mm mod I had origionally posted started out as a 17mm bushing and was shaved to a 14mm bushing on the top of the spindle along with having to shave the upper ball joint 5.08 mm. All of that was completed this last season and I had forgotten that I shaved the bushing down prior to my post. After utilizing the laser technique today I found minimal improvements with my 14mm mod relating to bumpsteer but a great improvement with consistancy of vertical plane of the spindle which was my origional objective last season and I had assumed was directly related to bump steer. I WAS WRONG. The results are as follows......

The 14mm mod results only a 2mm improvement of bumpsteer from full extension to 3/4 of full compression, and absolutely no change in scrub. However it places the "parallel" of the a-arms in the middle of the compression stroke instead of at full compression (where stock settings are) allowing the spindle stay more perpendicular to the ground earlier in the compression stroke when needed.

BUMP STEER findings are as follows. .......

I think I made a HUGE breakthrough today. After hours of measuring different settings with a laser I thought I'd try different tie rod settings. I found that mounting the tie rod further aft of the spindle made a rediculous amount of difference in bump steer. The images posted are a genaric setup used for "Testing Only". From the center of the old mounting point to center of the new mounting point ther is a 1-1/2" difference shown. This is not a fix in itself, but purely a finding. After I moved the tie rod mounting point back, the tie rod shares close to the same vertical plane of travel as the a arms - eliminating bump steer. I did not take measurements to confirm that the 1-1/2 inches is the perfect placing, but shared my findings with Scott from OFT. I'm sure he'll do what he does best! .
PROBLEM: this change of the tie rod mounting point greatly reduces the amount of steering travel to the ski.

 

[scmurs]

Laser Technique

Spent an hour on the phone with rlcofmn tonight talking bump steer and how we could all measure it, accurately with comparable results. He found a flaw in the laser method, and after some conversation, it was easy to see that the laser level is not the way to go.

We came up with an easy to perform method to determine what is happening. What we came up with was removing the skis and inserting a rod attached in each spindle where the ski would mount, pointing towards, and meeting each other in the middle of the sled. Each rod will move with its respective spindle as the suspension is cycled. Assuming that toe it set at 0" and the subframe is straight, the rods will be in-line with each other at a static ride height with the handlebars straight forward.

From there, while cycling the suspension both independently side to side or collectively with both sides together we can determine:

1. Whether or not bump steer is/is not the problem.

2. What solutions may/may not work with bump steer.

3. Are we still missing the golden egg, and what might that be?

Thoughts?

 

[00-NUKE]

Re: Laser Technique

Spent an hour on the phone with rlcofmn tonight talking bump steer and how we could all measure it, accurately with comparable results. He found a flaw in the laser method, and after some conversation, it was easy to see that the laser level is not the way to go.

We came up with an easy to perform method to determine what is happening. What we came up with was removing the skis and inserting a rod attached in each spindle where the ski would mount, pointing towards, and meeting each other in the middle of the sled. Each rod will move with its respective spindle as the suspension is cycled. Assuming that toe it set at 0" and the subframe is straight, the rods will be in-line with each other at a static ride height with the handlebars straight forward.

From there, while cycling the suspension both independently side to side or collectively with both sides together we can determine:

1. Whether or not bump steer is/is not the problem.

2. What solutions may/may not work with bump steer.

3. Are we still missing the golden egg, and what might that be?

Thoughts?

That's a good idea! I do believe fixing the bump steer is the solution for the handling woes. The other additive is the mass above the skis. My Nytro catches ruts badly due to the mass of the motor pushing directly down on the skis. I'm running C&A's which have a lot of bite and love to live in other peoples rutts. I think by moving the skis forward like you're doing with your front end kit will fix a lot of that. The C&A's give me steering, but their sooooooo heavy and catch ruts, but's it's a lesser evil than overshooting a corner when I'm on the boogie!

 

[rlcofmn]

I'm very interested to see what the new results are. On both the old style and the new style Spindle. Since the tie rod is shorter on the new style it should have less bump steer. I know Scott was planning on checking a 08 tomorrow. I'd like to see your 11 in stock form to see what the actual bump steer is. I am actually guessing that there will be much less than previously thought. I have a couple theory's/ideas for either way.

Keep up the good work guy's

 

[AKrider]

I don't understand why the laser is not a good method? The only issue I see is figuring out how to convert the measurements off the board to what needs to be done on the front end. But in reality you don't really need to since you can just tweak the adjustments and watch what the laser does to know if you are improving things or not.

I think I understand the concept behind using the bars but how do you measure what is happening? The further the suspension strokes, the further apart the bars will get due to scrub. Because nothing is ahead of the pivot point on the spindle, I don't see how toe could be measured?

00-Duke,
You are right, eliminating bump steer won't change anything in regards to motor weight effecting the handling. The Nytro will still be a lot heavier up front than a 2-stroke. It is funny you brought this up. I was talking to my buddy today who's got race experience with Yamaha and he said Yamaha spent a fortune trying to get the Nytro to handle. All the different riders, one off sleds, all the different prototype front ends could not make the Nytro equal to the 2-stroke sleds. This was true with sno-x but I think they should have focused their efforts on XC racing where the Nytro's weight is not as big of a detriment. In any case, I think many trail riders and regular guys would be thrilled if their stock Nytro didn't handle like a piece of sh!t.

 

[AKrider]

Re: BREAKTHROUGH!

NOTE: First of all I would like to say that the 17mm mod I had origionally posted started out as a 17mm bushing and was shaved to a 14mm bushing on the top of the spindle along with having to shave the upper ball joint 5.08 mm. All of that was completed this last season and I had forgotten that I shaved the bushing down prior to my post. After utilizing the laser technique today I found minimal improvements with my 14mm mod relating to bumpsteer but a great improvement with consistancy of vertical plane of the spindle which was my origional objective last season and I had assumed was directly related to bump steer. I WAS WRONG. The results are as follows......

The 14mm mod results only a 2mm improvement of bumpsteer from full extension to 3/4 of full compression, and absolutely no change in scrub. However it places the "parallel" of the a-arms in the middle of the compression stroke instead of at full compression (where stock settings are) allowing the spindle stay more perpendicular to the ground earlier in the compression stroke when needed.

BUMP STEER findings are as follows. .......

I think I made a HUGE breakthrough today. After hours of measuring different settings with a laser I thought I'd try different tie rod settings. I found that mounting the tie rod further aft of the spindle made a rediculous amount of difference in bump steer. The images posted are a genaric setup used for "Testing Only". From the center of the old mounting point to center of the new mounting point ther is a 1-1/2" difference shown. This is not a fix in itself, but purely a finding. After I moved the tie mounting point back, the tie rod shares close to the same vertical plane of travel as the a arms - eliminating bump steer. I did not take measurements to confirm that the 1-1/2 inches is the perfect placing, but shared my findings with Scott from OFT. I'm sure he'll do what he does best! .
PROBLEM: this change of the tie rod mounting point greatly reduces the amount of steering travel to the ski.

I've been thinking about what you discovered and I'm stoked you posted your findings along with pics. By moving the tie rod back behind the spindle you effectively shortened the tie rod. This is because the tie rod moved in an arc on the horizontal plane. So I'm thinking the tie rod needs to be shortened but on the vertical plane. I saw a minor improvement in bump steer by moving the tie rod upwards on the end of the spindle. I'm now thinking the toe rod needs to be moved upwards on the steering frog inside the subframe. By moving it upwards, it should "shorten it" but that isn't really a good way of describing what is happening. The tie rod cannot be physically shortened by screwing it in, but its effect on the spindle needs to be reduced by shortening it, if that makes any sense?

Basically the angle of the tie rod will effect how much it pulls and pushes on the spindle while it strokes through the suspension. I need to do some more testing and I should be able to present my findings more clearly. At this point I'm going to shy away from grinding my outside tie rod end (thanks for the offer rlcofmn !) and instead concentrate on how the tie rods mount on the steering frog.

Did I understand your post correctly that your upper a-arm mod provided better control of the spindle as it stroked through its travel? Did the spindle stay vertical through the entire stroke? That would be great if it did.

 

[00-NUKE]

Re: BREAKTHROUGH!

NOTE: First of all I would like to say that the 17mm mod I had origionally posted started out as a 17mm bushing and was shaved to a 14mm bushing on the top of the spindle along with having to shave the upper ball joint 5.08 mm. All of that was completed this last season and I had forgotten that I shaved the bushing down prior to my post. After utilizing the laser technique today I found minimal improvements with my 14mm mod relating to bumpsteer but a great improvement with consistancy of vertical plane of the spindle which was my origional objective last season and I had assumed was directly related to bump steer. I WAS WRONG. The results are as follows......

The 14mm mod results only a 2mm improvement of bumpsteer from full extension to 3/4 of full compression, and absolutely no change in scrub. However it places the "parallel" of the a-arms in the middle of the compression stroke instead of at full compression (where stock settings are) allowing the spindle stay more perpendicular to the ground earlier in the compression stroke when needed.

BUMP STEER findings are as follows. .......

I think I made a HUGE breakthrough today. After hours of measuring different settings with a laser I thought I'd try different tie rod settings. I found that mounting the tie rod further aft of the spindle made a rediculous amount of difference in bump steer. The images posted are a genaric setup used for "Testing Only". From the center of the old mounting point to center of the new mounting point ther is a 1-1/2" difference shown. This is not a fix in itself, but purely a finding. After I moved the tie mounting point back, the tie rod shares close to the same vertical plane of travel as the a arms - eliminating bump steer. I did not take measurements to confirm that the 1-1/2 inches is the perfect placing, but shared my findings with Scott from OFT. I'm sure he'll do what he does best! .
PROBLEM: this change of the tie rod mounting point greatly reduces the amount of steering travel to the ski.

Did I understand your post correctly that your upper a-arm mod provided better control of the spindle as it stroked through its travel? Did the spindle stay vertical through the entire stroke? That would be great if it did.

It keeps is strait-er throughout the transition, but focuses on one area more that the others. Due to the Upper and Lower A-arms being different lengths, you will never achieve a perfect transition. This mod helps keep it at it's straightest during more of the midrange portion travel. Think of it as a power band on a 2-stroke. Where do you want the power? Upper, Lower, or Midrange, because the geometry won't allow to stay inline from full compression to full extension.

 

[shadow44]

Great thread guys...my hat goes off to you for all of your thoughts and work on improving the handling. My question is..has anyone actually put the Nytro side by side with another brand that doesn't exhibit the Nytros traits, to closely compare the differences?

I'm also curious and Scott would be the guy wo can check..How does the stock frt suspension compare to the Skinz in this regard..is it possible to compare a stock nytro to a Skinz equiped Nytro for a comparison? Does moving the spindle 4" forward make a big change in the movement of everything?

Personally I don't experience bump steer..or it doesn't bother me enough...I've done all of the regular mods..2.5mm ball joint mod, skis, suspension settings etc and I really like how my 08 RTX handles. but further improvements are always welcome...keep up the good work guys!

 

[BETHEVIPER]

The above 1 1/2 mod is going to mess up your akermann alot. Keep this in mind when your making changes. The sled also has to go around a corner. Akermann is also changed by style and placement of rod ends on the inside as well. If this messes up the Akermann too much but fixes the bump, you could look to change the mount location inside to lessen its effect.
If you make it go straight while hitting a bump but in a corner it toes in, your not going to like that affect more than the bump steer. A little extra toe out in a corner can help the turn sometimes.

 

[AKrider]

The 1.5" mod isn't a mod as it is not practical. The steering radius becomes so decreased that it would make the sled unrideable except for straight line work or making very gradual turns in the big open field.

What it does indicate is further bump steer reduction is possible and it was done on the improved '09 geometry.

 

[scmurs]

I'm also curious and Scott would be the guy wo can check..How does the stock frt suspension compare to the Skinz in this regard..is it possible to compare a stock nytro to a Skinz equiped Nytro for a comparison? Does moving the spindle 4" forward make a big change in the movement of everything?

Next week I will be doing before and after on a stock front end with an '08 MTX and then with the SPG Concept kit on the same sled. I will be using two pieces of threaded rod, bolted through the spindle bushings and pointing at each other underneath the belly pan to see what I observe.

We were supposed to get a partial 1st delivery on the Concept kits this week, but have not seen them yet.

I will document how I do it and what I observe.

AK, rlc is supposed to be going up to Wasilla this weekend. I think he was planning on getting a hold of you to share the discussion that we had last night.

Scott

 

[shadow44]

Great stuff Scott...should be very interesting to see the differences.

 

[AKrider]

I spent some time watching the SPG videos over on Snowest about their front end. It would be really cool to see how the changes work on a trail sled. The SPG front end emulates a lot of the things Yamaha tried with their prototype front ends. One of their main goals was to get the engine weight more in the middle of the sled by increasing the "wheelbase". I think that is a pretty good idea.

My racing buddy thinks it is a total waste of time and effort to do anything to improve a stock Nytro front end. The SPG videos pointed out a number of things he mentioned to me over the years that Yamaha discovered from racing and things we noticed in the field.

Still, I'd like to ride my Nytro and experience how it feels without bump steer trying to pitch me off into the woods. The great thing is I'll be able to ride my sled by late October or early November so I'll be able to test the theorys we come up with on this thread.

 

[sgilbert]

Re: BREAKTHROUGH!

Nice effort..

You need to place the board at about the end of the ski distance.

Another post above..ya I did that with my older style..moved the steeing rod to the under side of its stock position..bump steer..fixed.

As far as the racing..hmmm..the guy that drove the Yamaha finished in position X in the USA. The next year he drove another brand..tell me where he finished with that sled against the same competition.

I briefly tried to put the board near the end of the skis but because my sled is in storage, that configuration made it difficult to take the measurements. From what I've researched, repositioning the tie rod elevations appears to be the universal method to correct bump steer. It would be really cool to see how the '09 geometry plots with a laser.

What is position X? Are you talking about Robbie Malanoski or Corey Davidson?

For me, I just want my sled to handle better. If I can do it inexpensively then it will be well worth it. I don't expect it to be comparable to a Polaris IQ 600R or a Sno-Pro 600, but if it will just go down a rough trail in a straight line I'll be pretty happy!

NOTE: First of all I would like to say that the 17mm mod I had origionally posted started out as a 17mm bushing and was shaved to a 14mm bushing on the top of the spindle along with having to shave the upper ball joint 5.08 mm. All of that was completed this last season and I had forgotten that I shaved the bushing down prior to my post. After utilizing the laser technique today I found minimal improvements with my 14mm mod relating to bumpsteer but a great improvement with consistancy of vertical plane of the spindle which was my origional objective last season and I had assumed was directly related to bump steer. I WAS WRONG. The results are as follows......

The 14mm mod results only a 2mm improvement of bumpsteer from full extension to 3/4 of full compression, and absolutely no change in scrub. However it places the "parallel" of the a-arms in the middle of the compression stroke instead of at full compression (where stock settings are) allowing the spindle stay more perpendicular to the ground earlier in the compression stroke when needed.

BUMP STEER findings are as follows. .......

I think I made a HUGE breakthrough today. After hours of measuring different settings with a laser I thought I'd try different tie rod settings. I found that mounting the tie rod further aft of the spindle made a rediculous amount of difference in bump steer. The images posted are a genaric setup used for "Testing Only". From the center of the old mounting point to center of the new mounting point ther is a 1-1/2" difference shown. This is not a fix in itself, but purely a finding. After I moved the tie rod mounting point back, the tie rod shares close to the same vertical plane of travel as the a arms - eliminating bump steer. I did not take measurements to confirm that the 1-1/2 inches is the perfect placing, but shared my findings with Scott from OFT. I'm sure he'll do what he does best! .
PROBLEM: this change of the tie rod mounting point greatly reduces the amount of steering travel to the ski.

I did this mod 2 seasons ago. wish I could find my post. put 10mi on it. damn scary when you need to steer sharp. took the extensions off and threw them in the dumpster. grew bigger arms and problem solved. would imagine eps is coming and that will be the end of this conversation