arteeex
TY 4 Stroke Master
What you're doing is not going to get you where you want to be. You can estimate the change at the upper a-arm/spindle pivot point by tan(theta) = (length of upper a-arm) / 17mm. Then tan(theta) X 17mm will give you the approximate change in length from the a-arm pivot point on the sub-frame to where the plane of the spacer and bolt center intersect (If you know the dimensions of the ball you can do the same math to get center of the ball). The point is; this is a miniscule change to the system. If the upper a-arm is 400mm (my guess) then you’re looking at about 1mm of difference in the neutral position.
You would see the same effect if you had reduced the height of the mounting point by 17mm in this system.
The better method would be to keep the a-arms parallel and shorten the upper. But this would probably take you in the direction of a more specialized setup that may not have the same range of utility on all the trails you ride.
You would see the same effect if you had reduced the height of the mounting point by 17mm in this system.
The better method would be to keep the a-arms parallel and shorten the upper. But this would probably take you in the direction of a more specialized setup that may not have the same range of utility on all the trails you ride.
I'm curious about this mod but seeing how it is being done to the "improved" '09 FX2 geometry pretty much shows the Nytro front end needs some MAJOR tweaking of the a-arm, tie rod and spindle geometry to gain any worthwhile improvements to handing and reducing bump steer.
This mod may improve things a tiny bit but I want a front end that actually goes through the bumps without doing anything weird (excessive twitchiness, bump steer, head shake, lifting the inside ski, not dart at high speed, not wiggle the bars back and forth in the stutters, not cause the sled to drift from side to side when running through rough terrain at high speed) well you guys get the idea. Polaris has this type of front end, so does Arctic Cat, so does Ski-doo. Even my daughter's '03 Polaris Indy Lite 340 has a front end that is more stable and handles better than my Nytro.
I think it is awesome that people are trying to improve the flawed handling of our Nytro's but I don't see it being 100% fixed when the stock inner mounting points of the a-arms and tie rod ends are not changed.
This mod may improve things a tiny bit but I want a front end that actually goes through the bumps without doing anything weird (excessive twitchiness, bump steer, head shake, lifting the inside ski, not dart at high speed, not wiggle the bars back and forth in the stutters, not cause the sled to drift from side to side when running through rough terrain at high speed) well you guys get the idea. Polaris has this type of front end, so does Arctic Cat, so does Ski-doo. Even my daughter's '03 Polaris Indy Lite 340 has a front end that is more stable and handles better than my Nytro.
I think it is awesome that people are trying to improve the flawed handling of our Nytro's but I don't see it being 100% fixed when the stock inner mounting points of the a-arms and tie rod ends are not changed.
00-NUKE
Expert
Miniscule?
I wouldn't call it a 100% fix by any means. Mostly because the forward position of the front suspension could be improved as well. That is more costly that I would like to attempt. OFT Racing has a prototype that may or may not fix that. The forward position is also the #1 cause for the hard steering.
The added 17mm vertical position is miniscule. The change is the carbides horizontal position pre and post compression of the suspension is reduced considerably.
Explination: The distance from the lower ball joint to the upper ball joint is almost exactly the same as the distance from the lower ball joint to the base of the spindle. This gives each end of the spindle about a 1 to 1 camber ratio from top to bottom with the lower ball joint being the pivot point. If you want, take a measurement from the base of the left spindle to the base of the right spindle as well as the top of the left spindle to the top of the right spndle during pre and post compression of your stock suspension. I think you will be shocked at the amount of camber change that is applied to your spindle. It's been months since I figured out my results so I will remeasure and submit hard numbers after this weekend.
NOTE: I have about 150 miles on my sled with this change and so far it's made a considerable improvement to my XTX with the bump steer. I ran out of time at the end of the season to perform further testing with different geometry. So far 10mm and 17mm bushings have been tested and 17mm seems to have the best results.
arteeex said:
I wouldn't call it a 100% fix by any means. Mostly because the forward position of the front suspension could be improved as well. That is more costly that I would like to attempt. OFT Racing has a prototype that may or may not fix that. The forward position is also the #1 cause for the hard steering.
The added 17mm vertical position is miniscule. The change is the carbides horizontal position pre and post compression of the suspension is reduced considerably.
Explination: The distance from the lower ball joint to the upper ball joint is almost exactly the same as the distance from the lower ball joint to the base of the spindle. This gives each end of the spindle about a 1 to 1 camber ratio from top to bottom with the lower ball joint being the pivot point. If you want, take a measurement from the base of the left spindle to the base of the right spindle as well as the top of the left spindle to the top of the right spndle during pre and post compression of your stock suspension. I think you will be shocked at the amount of camber change that is applied to your spindle. It's been months since I figured out my results so I will remeasure and submit hard numbers after this weekend.
NOTE: I have about 150 miles on my sled with this change and so far it's made a considerable improvement to my XTX with the bump steer. I ran out of time at the end of the season to perform further testing with different geometry. So far 10mm and 17mm bushings have been tested and 17mm seems to have the best results.
00-NUKE
Expert
That's what I think is funny! If you notice Ski-doo, and Polaris run their upper and lower A-arms parallel from each other. Arctic Cat used to and now their new A-arms actually have a gradual increase of angle to the spindle. I started this project on a whim, but now that I'm seeing some results, I can't believe that Yamaha would overlook something soooo simple. Perhaps they did it to be different??? I don't know. All of the other brands run their skiis fruther forward as well. Their is a reason for that. The sleds weight is carried behind the ski and the skiis are actually pulling the sleds weight through the turn. The 2008 Nytro's were horrible at pushing corners because there is too much weight on top of the ski and the few little improvements Yamaha made to the front end in 2009 were to aid with that issue, however it did nothing for the bump steer. I've owned a 2008 and a 2011 Nytro. If their motors weren't so damn awesome, I would have gone back to ski-doo by now.AKrider said:
TurboJamie
TY 4 Stroke God
00-NUKE said:
Engines are awesome no question handling is not. I have to say my 1200 renegade does everything to my liking, however I couldn't resist a new kitty with a turbo from the factory.
I'm glad you posted the results of your mod. It got me thinking and I recall they did the same thing on the Ski-doo RS 600 race sleds.
If you look closely at the upper arm you will see a spacer sitting on top of the spindle. I was reading a post on Doo-talk and this mod was done to get the sled to corner better, but it didn't mention a problem with bump steer.
Here is a link explaining what creates bump steer and how the a-arms and tie rod all need to point to the instant center. If they don't you'll have bump steer. This is why I don't see how a kit can fix the Nytro's handling if it doesn't change the hard mounting points of the a-arms or tie rods. There can be some improvement I'm sure, but unless the geometry is improved significantly, the Nytro will never handle as good as the other three OEM's. http://www.circletrack.com/chassistech/ctrp_1001_bump_steer_explained/index.html
If you look closely at the upper arm you will see a spacer sitting on top of the spindle. I was reading a post on Doo-talk and this mod was done to get the sled to corner better, but it didn't mention a problem with bump steer.
Here is a link explaining what creates bump steer and how the a-arms and tie rod all need to point to the instant center. If they don't you'll have bump steer. This is why I don't see how a kit can fix the Nytro's handling if it doesn't change the hard mounting points of the a-arms or tie rods. There can be some improvement I'm sure, but unless the geometry is improved significantly, the Nytro will never handle as good as the other three OEM's. http://www.circletrack.com/chassistech/ctrp_1001_bump_steer_explained/index.html
Here is another link I found useful in explaining bump steer and front end geometry. http://www.mustangandfords.com/techarticles/suspension/mufp_0611_bumpsteer_explained/index.html
When Yamaha was racing the Nytro their factory supported racers got to run prototype front ends that consisted of a modifed front clip, raked back shock angles, 3" increase in wheelbase and heim joint equipped upper and lower a-arms that could be adjusted for camber and caster. The front end I got to look at was modified from the stock front subframe. Yamaha also produced aluminum front ends that were used in sno-x and XC events. I think many have seen the pictures of the sno-x sleds with that front end.
I suspect there must not be any money in offering an aftermarket front end that uses a revised and strengthened subframe and improved geometry? That's what it would take to put the Nytro front end on par with a Cat, Polaris or Doo. I'd then install a rear skid out of a Polaris and you'd have a much better riding and handling Nytro. Thing is, it is much easier to just buy a new F1100 (assuming you'd want a 4-stroke) than spend the time and effort trying to make a 5 year old Yamaha design even equal to a Polaris IQ consumer chassis.
When Yamaha was racing the Nytro their factory supported racers got to run prototype front ends that consisted of a modifed front clip, raked back shock angles, 3" increase in wheelbase and heim joint equipped upper and lower a-arms that could be adjusted for camber and caster. The front end I got to look at was modified from the stock front subframe. Yamaha also produced aluminum front ends that were used in sno-x and XC events. I think many have seen the pictures of the sno-x sleds with that front end.
I suspect there must not be any money in offering an aftermarket front end that uses a revised and strengthened subframe and improved geometry? That's what it would take to put the Nytro front end on par with a Cat, Polaris or Doo. I'd then install a rear skid out of a Polaris and you'd have a much better riding and handling Nytro. Thing is, it is much easier to just buy a new F1100 (assuming you'd want a 4-stroke) than spend the time and effort trying to make a 5 year old Yamaha design even equal to a Polaris IQ consumer chassis.
It would be interesting to measure how much bump steer is present in the Nytro front end. The '09 geometry was to have reduced bump steer but it wasn't enough.
RJH,
You got me thinking about the old Indy's and their front ends with parallel, equal length radius rods had bump steer but it wasn't a big deal. They handled great and to this day offer more high speed stability than a Nytro. Yamaha's trailing arm V-Max chassis used the same set up as the Indy but I've never ridden one to see how it did.
I'm thinking there must be some additional factors that makes the Nytro handle like so bad. I think the caster angle is too steep. I lowered the back of my sled and the high speed stability improved. This would have lessened the caster angle. I also did the 2.5 mm ball joint mod and it did improve the high speed stability a little bit but also caused the sled to push in the corners and not bite as hard in the corners.
RJH,
You got me thinking about the old Indy's and their front ends with parallel, equal length radius rods had bump steer but it wasn't a big deal. They handled great and to this day offer more high speed stability than a Nytro. Yamaha's trailing arm V-Max chassis used the same set up as the Indy but I've never ridden one to see how it did.
I'm thinking there must be some additional factors that makes the Nytro handle like so bad. I think the caster angle is too steep. I lowered the back of my sled and the high speed stability improved. This would have lessened the caster angle. I also did the 2.5 mm ball joint mod and it did improve the high speed stability a little bit but also caused the sled to push in the corners and not bite as hard in the corners.
Simply take the front shocks off...place a steel rule on the floor under the ski tips...lift the front with a power lift or jack.
Lower the front from full height at watch the ski tips move. That is bump steer.
The problem was the steering arm , on mine, was not on the same plane as the suspenion arms. I fixed that.
I would think the Polaris was not the same. They selected 80's Indy to run oval. They call it the Formula 500 class. They are on rails...on the turns.
I happen to drive the first ever attempt by Yamaha to build an independent front suspension on an oval sled. Not good. But HP ..OH MY
Yes..I did drive the Nitro..it was not good...no comfort balance at all. But again..the factory sled the next year..had the best I had seen.
Lower the front from full height at watch the ski tips move. That is bump steer.
The problem was the steering arm , on mine, was not on the same plane as the suspenion arms. I fixed that.
I would think the Polaris was not the same. They selected 80's Indy to run oval. They call it the Formula 500 class. They are on rails...on the turns.
I happen to drive the first ever attempt by Yamaha to build an independent front suspension on an oval sled. Not good. But HP ..OH MY
Yes..I did drive the Nitro..it was not good...no comfort balance at all. But again..the factory sled the next year..had the best I had seen.
Crewchief47
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Re: Testing
I'm going to split hairs with your mod for a moment. What you've done is actually change the moment centers in the front end which will affect the amount the chassis rolls in the corners. The change possibly had a minimal effect on actual bump steer. I can see an improved moment center assisting in that twitchy feeling the Nytro is known for.
You'd get more change in bump steer by adjusting the height location of the steering heims.
00-NUKE said:
I'm going to split hairs with your mod for a moment. What you've done is actually change the moment centers in the front end which will affect the amount the chassis rolls in the corners. The change possibly had a minimal effect on actual bump steer. I can see an improved moment center assisting in that twitchy feeling the Nytro is known for.
You'd get more change in bump steer by adjusting the height location of the steering heims.
I got curious about the bump steer in my Nytro so I removed the springs from the shocks and reinstalled the shocks. I then checked my ski alignment and it was 1/16" toed out with a strap keeping a light tension on the front of the skis. I then measured toe at full droop and then full compression. The toe changed 13/16". That is a lot of toe out change. The '08 front end toes out as it compresses and when you think about it, it makes sense that the front end darts all over in the bumps because each ski is trying to turn into each bump. From what I've read about bump steer in race cars, they recommend no more than 1/16" of toe change. I measured my toe out change the front of the skag on C&A skis.
I also have an angle finder and checked the caster angle. This was a tricky because there is no perfect spot to set the angle finder. I used the top of the spindle and had to avoid the slight raised portion at the front of the spindle. You also have to make sure the sled is level. I found my caster was different from one spindle to another. My right side was 20 degrees while my left was 22.5 degrees. The 22.5 degrees doesn't concern me because the back of my sled is lowered down a little bit which would slacken the caster angle. I'm pretty sure the stock '08 caster is supposed to be 22 degrees and the '09 was slackened to 26 degrees.
I'm now going to check to see if my subframe is bent.
I'm really beginning to wonder if the Nytro front end is not as bad as I first believed? I feel bump steer the the cause of all the handling problems most of us have been complaining about. The caster angles are not super steep, at least compared to what is common on mountain bikes. A downhill mountain bike uses a slack head angle of around 68 degrees. The same as the '08 Nytro. The '09 Nytro geometry is more slack and is a 64 degree head angle which is known to create slow steering in mountain bikes. I've read posts and ride reviews where people have noticed the '09 geometry is slower to turn and respond. If we can tune out the bump steer both front ends should work as good as the other OEM's. The '08 would turn out to be the sharper handling of the two.
Edit: Had to double check my methods, particularly with caster
I also have an angle finder and checked the caster angle. This was a tricky because there is no perfect spot to set the angle finder. I used the top of the spindle and had to avoid the slight raised portion at the front of the spindle. You also have to make sure the sled is level. I found my caster was different from one spindle to another. My right side was 20 degrees while my left was 22.5 degrees. The 22.5 degrees doesn't concern me because the back of my sled is lowered down a little bit which would slacken the caster angle. I'm pretty sure the stock '08 caster is supposed to be 22 degrees and the '09 was slackened to 26 degrees.
I'm now going to check to see if my subframe is bent.
I'm really beginning to wonder if the Nytro front end is not as bad as I first believed? I feel bump steer the the cause of all the handling problems most of us have been complaining about. The caster angles are not super steep, at least compared to what is common on mountain bikes. A downhill mountain bike uses a slack head angle of around 68 degrees. The same as the '08 Nytro. The '09 Nytro geometry is more slack and is a 64 degree head angle which is known to create slow steering in mountain bikes. I've read posts and ride reviews where people have noticed the '09 geometry is slower to turn and respond. If we can tune out the bump steer both front ends should work as good as the other OEM's. The '08 would turn out to be the sharper handling of the two.
Edit: Had to double check my methods, particularly with caster
Here is a video of a Honda 450R showing the toe change on a tire resulting from bump steer. http://www.youtube.com/watch?v=GFi9E5KmCAI
Here is another link with a suspension geometry calculator. http://www.racingaspirations.com/?p=286
I've been playing around with it and it is interesting to see how different length a-arms, spacing of the a-arms and angle of the a-arms all influence how much scrub and camber change happens at the spindle. Then lengthen the spindle like on the new Arctic Cats and see what happens.
I've not been able to find a free calculator that also allows you to input the tie rod. If someone can find one then it will be a simple manner of inputing all the Nytro measurements and it will be evident whether the front end can be improved or not.
I've been playing around with it and it is interesting to see how different length a-arms, spacing of the a-arms and angle of the a-arms all influence how much scrub and camber change happens at the spindle. Then lengthen the spindle like on the new Arctic Cats and see what happens.
I've not been able to find a free calculator that also allows you to input the tie rod. If someone can find one then it will be a simple manner of inputing all the Nytro measurements and it will be evident whether the front end can be improved or not.
00-NUKE
Expert
Re: Testing
I'll look into that. My whole idea is to keep the co$t down. If I can develop something for the height of the steering heims and it works, I'll post it. I would like to factor in the heavy steering issue as well. Mine handles better than it ever has but still has heavy steering. I wish Yamaha would have applied that power steering to the Nytro's. I have a buddy on Yamaha's sales team that says Yamaha has a new lineup they're pushing to have ready by 2013. If that's the case, it might be the end of the Nytro????
Crewchief47 said:
I'll look into that. My whole idea is to keep the co$t down. If I can develop something for the height of the steering heims and it works, I'll post it. I would like to factor in the heavy steering issue as well. Mine handles better than it ever has but still has heavy steering. I wish Yamaha would have applied that power steering to the Nytro's. I have a buddy on Yamaha's sales team that says Yamaha has a new lineup they're pushing to have ready by 2013. If that's the case, it might be the end of the Nytro????
