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Corner weighting and balance of suspension

jaegerc

Newbie
Joined
Jun 21, 2007
Messages
17
Location
Denver, CO
Hi all,
Been reading a lot of posts for quite some time and have a question I would like to open up the topic about sled weight and balance. I come from the world of race cars and know a lot about suspension setup and weight balance/transfer. I know there is a lot of people out there that bash on Yamaha owners about weight, I won't go into arguments for or against but I would just have to say that for most all situations what's more important, IMHO, is the balance of the sled and the ability of the rider to make the sled to what the rider wants. After watching Schooled Again, I am more convinced that while weight is important weight balance and transfer is more. Also talking to Chris Burandt helped although he didn't give away his seutp.

Example: Brother owns a big bad Ski-DOO with a lot of mods (nice sled, tons of power, traction blah blah blah.) Rode that for about an hour and by the end all I wanted was my Apex back. Sled may be light on the scale but rode like it weighted 800lb. Now I see why some people want a 20" handlebar riser!
Preface: I do not want to bash anybody elses system for sled setup or suspension settings. To me the best race car setup you had was the one that won you races (doesn't matter how you got there just that you liked it and it worked for you). Same goes for sled setup, if it works for you great I am looking for information to make my setup work for me and this is how I know how to do it.
To the point; some of the posts that I have read have setup advice that recomend setting preload with the suspension in full droop. This is a VERY BAD idea, it will vary too much sled to sled and doesn't tell you anything about how the spring or damper work when in motion. Also people will say to loosen or tighten a limiter strap to help one problem or another but this is a band aid and is too general, it doesn't take into account what the bottoming setting is or what the spring rates or static weight distribution of the sled is. This type of setup may work but you probably don't know why and if you tried to do to another sled it probably wouldn't work.
What I would like to do: I would like to (and am going to) weigh my sled as I rode it last season. I like it a lot, worked well for me but I of course had some complaints and found situations where I didn't know what would help.
1.) I am going to corner weight the sled and get an idea of what moving my body back and forth on the running boards does for weight bias in %. Including wrong foot forward versus standard stance.
2.) Jack the rear skid down or make a dummy spring to simulate the rear traveling and hitting the transfer stop. I've read in too many posts about people adjusting this or using different shims to change weight transfer. I simply do not think that many people know what happens when you switch a 5mm spacer for a 2.5mm spacer. Many people say it helps with weight transfer which is a misleading statement. Weight transfer is caused by acceleration or the rider changing position. Thus adjusting this doesn't change weight transfer, it simply allows more travel which can change CG location which can chagne sled attitude. Remember Weight Transfer and Weight Bias are very different things. You NEED acceleration to cause weight transfer.
3.) Adjust the front preload independently, I will end up trying to figure out how much raising and lowering change the front rear distribution.
4.) I'll figure out what else I want to do when I get there.

Problems that I need help with: There's a reason I am posting in the Apex MTN section; because I ride an Apex MTN and because I am only interested in how the sled performs off tral in the trees and tighter places or deeper snow. I have no interest in making this sled fast on the trails, fast trail sleds get people hurt and I don't need that extra 3 mph in the corner, I need the sled to turn like I want it to, once again that's the most important thing for a suspension system to do, what you want it to do.
1.) I need to figure out if I am going to use 3 or 4 scales for this. I feel that I will need 4: 2 for the skis and one for the front of skid and one under the rear axle. It would be nice to figure out some sort of center of pressure for the skid using 4 scales but I am concerned that in most scenarios the 3rd scale will just cause a false reading of weight transfer. Opinions and arguments needed here.
2.) Your recomendations or any backround information about how you set your sled up. Once again I'm looking for people that have adjusted springs or damper settings and have good reasoning why they did it.
3.) Why do people say a different skid like the timbersled is better? Is this simply because of progressive rate springs due to Fox Floats? It can't simply be the weight, It must have to do with weight bias or travel or the progressive rate.

P.S. Anybody in Denver, CO with scales that they want to lend me (Like the Intercomp Circle Drag setups) would be nice.
 

I agree with you that its not the weight of the sled but how it works at it's weight. i got all caught up in the whole light weight thing with my 2003 RX1. I took over 150 pounds off of the sled, 85% of which came off of the back. Even though the sled was way lighter, it never handled right after that because the weight bias shfited to the front a bunch and made it feel even heavier in the front than stock. The only way that sled worked right after that was putting 5 galons of gas on the rear of the tunnel.
First thing to do is find your owners manual if you have it. In with the owners manual was a laminated card that described the process to set the proper sag for the rear of the sled. if you can't find it, PM me and I can email you the suspension tuning guide fron the most recent Yamaha tech update. I think i may have posted the tuning giude a year or so on this site as well.
Modern sled suspensions are very similar to dirtbikes in that the handling of the machine is all based off of proper rear sag and spring rate.
You set the sag by sitting or standing on the sled with gear on in your "normal" riding position and messuring the gap at the transfer rods. Change rear spring preload up or down to get the specified gap. I think it's 35mm for the apex.
This is the first and most important adjustment to be made to the suspension. If the proper setting can not be reached with the springs on your sled, you need to get different springs. Yamaha offers harder and softer springs.
The rear sag and spring rates need to set properly before any other tuning is done. Otherwise your wasting your time.
Do not move the transfer rod nuts to get the gap you need! These nuts are for fine tuning transfer as one the very last steps in tuning. 1mm up or down on these nuts is a huge change in transfer. Also make sure the rear skid mount is in the upper hole on the rear drop bracket.
After you get the rear sag right then its time to play with the other setting to get the sled to handle like you want it. No two sleds or riders will like the same setup.
I've found in general that the Yamahas work best in powder with the limiter straps all the way out and the center shock preload higher than stock setting. I agree with you that sucking the limiter straps up a bandaid fix for a poorly setup sled. Some guys have had good luck with mounting the front arm of the rear skid a 1/2 inch lower in the tunnel to get more weight off of the front.
Yamaha spends a lot of time and money tuning and developing suspensions to work well in all situations and you can make it work for you with some tuning.
 
Thanks for the bit of insight. I am with you about setting sag. I guess what I am trying to get at is mostly an understanding of what the weights look like "At proper sag". I think that if I can make a correlation of weight balance of a sled it should work at getting me close on another sled the end goal beign some form of "Magic Number".
I think that setting sag is a good place to start but I also want to make a setup that isn't defined by spring rates or preload but one that is based on balance and mass positioning. The problem in my mind is that if my 165lb self has set sag and so has a 220lb rider with a stiffer spring we can't talk about what balance and ski pressure and track loading numbers.
In general my Apex rides great and my RX-1 rides Okay, and my M6 is difficult to initiate a side hill but is great once in it. I'm hoping to find balance and load profiles for my "Ideal Compromise" setup and then use that to dial in other sleds. I will use this setup with "Magic Number" to base spring rate and preload settings off of. This is the method I have used for setting up race cars and it has worked very well car to car for the same track or very similar type of track.
As for the drop bracket comment I am very intrigued because I set mine to the lower hole because that's what the owner's manual says to do for "Mounting/ deep snow" riding. Do you use the upper hold for an angle of attack adjustment?
Last year I found that my sled worked the best and had a good compromise once I set the front spring to nearly full preload and set the torsion spring to "Hard". I know that made the sled work better but it may have violated the sag rule and I didn't know how much I was changing anythign which is why I started to think about doing more research to Mountain Setup.
What I seem to gather was that front spring takes pressure off the skis and puts it below the "Normal riding stance". The rear spring is just for rider weight and to start sucking up the bumps. Like I said I set mine to "Hard" because I felt it was bottoming too hard through woops on my way to power riding and I would rather make the spring work rather than bounce off the bottoming adjustment all day.
I know the proper solution is a re-valve of the rear shock and to set the rear spring to the proper rate so that I have proper sag and track pressure in riding gear but I still want to know what that skid pressure is.

If yours rides right I would be curious to put scales under it and see what it is with you on it. Not only would it give us a weight to go off of but I could make my setup match yours and still have proper sag. I would also be curious if you notice that your sled turns better one way than another and you simply do not have matching ski pressures.

Remember matching height doesn't mean matching pressures.

Thanks

C
 
I dont think there is a magic weight disrtibution number that can be used univeraslly. Different riders and different sled will work best at different numbers. A 2-stroke sled needs a differnt setup than a 4-stroke. I'm a stand up rider who weighs 210 without gear. Even on the same sled, a sitdown or knee in the seat rider at my same weight will need different setups. Tuning your suspension is starting with the basics and then riding it and adjusting to make work for you. The setup you run on your car is not the same as the guys you are racing.
The suspension on your sled is much more like a birt bike than a car. I say that because the sled reacts to changes like a bike does. If you are not a dirtbike or sportbike rider then this may be tougher to grasp. So the setup procedure is similar to a bike in the fact that all tuning starts with proper rear settings. Some of the best people i have been around for sled tuning are those who have raced dirt bikes at high levels and really understand how suspensions work.
Take Holz or Ezryde rear skids for an example. Both companies are experts at understanding suspension. They use very specific and detailed install and tuning instructions. Both want to know the sled its going in, rider weight and riding style so they can spring and valve the shocks correctly. Both have very detailed tuning instructions that start with setting the rear ride height correcty and then riding the sled and making small changes and checking and resetting rear sag every time a change is made. That tells me that rear sag and proper rate is the critical part.
As for the rear mounting hole, I wish Yamaha would take that out of the bracket and manual. By using the lower hole, that raises the rear of the sled up which puts more weight on the skiies of a sled that is already heavy up front. Doing that may work fine for those who climb hills in areas were the snow is firmmer than here or for the boosted hill climbers. It does not work for powder or tree riding here in colorado.
As for your sled bottoming through the whoops, are you sure it bottoms and not just coupling when the transfer rod gap goes to 0. Many poeple mistake the clunk they hear or feel as bottoming instead of the suspension coupling through the last few inches of its stroke. Chances are, if it is bottoming in whoops, that you need to increase preload on the center shock instead of the rear. That would be felt through your feet.
I'm not trying to get in an argument with you, but setup is different for everyone and every sled and you need to start with what the OEMs recommend, and then fine tune the sled the old fashion way, by riding the sled and making small adjustments, one at a time and evaluating if the change is positive or not.
I think you would really benifit from the Yamaha tuning giude. It is very comprehensive, model specific and goes over theeffect, pros and cons of each adjustment. PM and I will email it to you.
P.S., I did post the tuning giudes on sledmods.com in the Yamaha section
 
Hi all,
Been reading a lot of posts for quite some time and have a question I would like to open up the topic about sled weight and balance. I come from the world of race cars and know a lot about suspension setup and weight balance/transfer. I know there is a lot of people out there that bash on Yamaha owners about weight, I won't go into arguments for or against but I would just have to say that for most all situations what's more important, IMHO, is the balance of the sled and the ability of the rider to make the sled to what the rider wants. After watching Schooled Again, I am more convinced that while weight is important weight balance and transfer is more. Also talking to Chris Burandt helped although he didn't give away his seutp.

Example: Brother owns a big bad Ski-DOO with a lot of mods (nice sled, tons of power, traction blah blah blah.) Rode that for about an hour and by the end all I wanted was my Apex back. Sled may be light on the scale but rode like it weighted 800lb. Now I see why some people want a 20" handlebar riser!
Preface: I do not want to bash anybody elses system for sled setup or suspension settings. To me the best race car setup you had was the one that won you races (doesn't matter how you got there just that you liked it and it worked for you). Same goes for sled setup, if it works for you great I am looking for information to make my setup work for me and this is how I know how to do it.
To the point; some of the posts that I have read have setup advice that recomend setting preload with the suspension in full droop. This is a VERY BAD idea, it will vary too much sled to sled and doesn't tell you anything about how the spring or damper work when in motion. Also people will say to loosen or tighten a limiter strap to help one problem or another but this is a band aid and is too general, it doesn't take into account what the bottoming setting is or what the spring rates or static weight distribution of the sled is. This type of setup may work but you probably don't know why and if you tried to do to another sled it probably wouldn't work.
What I would like to do: I would like to (and am going to) weigh my sled as I rode it last season. I like it a lot, worked well for me but I of course had some complaints and found situations where I didn't know what would help.
1.) I am going to corner weight the sled and get an idea of what moving my body back and forth on the running boards does for weight bias in %. Including wrong foot forward versus standard stance.
2.) Jack the rear skid down or make a dummy spring to simulate the rear traveling and hitting the transfer stop. I've read in too many posts about people adjusting this or using different shims to change weight transfer. I simply do not think that many people know what happens when you switch a 5mm spacer for a 2.5mm spacer. Many people say it helps with weight transfer which is a misleading statement. Weight transfer is caused by acceleration or the rider changing position. Thus adjusting this doesn't change weight transfer, it simply allows more travel which can change CG location which can chagne sled attitude. Remember Weight Transfer and Weight Bias are very different things. You NEED acceleration to cause weight transfer.
3.) Adjust the front preload independently, I will end up trying to figure out how much raising and lowering change the front rear distribution.
4.) I'll figure out what else I want to do when I get there.

Problems that I need help with: There's a reason I am posting in the Apex MTN section; because I ride an Apex MTN and because I am only interested in how the sled performs off tral in the trees and tighter places or deeper snow. I have no interest in making this sled fast on the trails, fast trail sleds get people hurt and I don't need that extra 3 mph in the corner, I need the sled to turn like I want it to, once again that's the most important thing for a suspension system to do, what you want it to do.
1.) I need to figure out if I am going to use 3 or 4 scales for this. I feel that I will need 4: 2 for the skis and one for the front of skid and one under the rear axle. It would be nice to figure out some sort of center of pressure for the skid using 4 scales but I am concerned that in most scenarios the 3rd scale will just cause a false reading of weight transfer. Opinions and arguments needed here.
2.) Your recomendations or any backround information about how you set your sled up. Once again I'm looking for people that have adjusted springs or damper settings and have good reasoning why they did it.
3.) Why do people say a different skid like the timbersled is better? Is this simply because of progressive rate springs due to Fox Floats? It can't simply be the weight, It must have to do with weight bias or travel or the progressive rate.

P.S. Anybody in Denver, CO with scales that they want to lend me (Like the Intercomp Circle Drag setups) would be nice.

A good place to start.
 
Wow awesome vid and resurrecting a thread from 6 years ago LOL. I was JUST thinking about this for my summer mod plans was how to balance the sled better, this video was awesome. I was going to do a simpler method based on center of gravity but never thought about center of transfer. Cool!
 
Wow awesome vid and resurrecting a thread from 6 years ago LOL. I was JUST thinking about this for my summer mod plans was how to balance the sled better, this video was awesome. I was going to do a simpler method based on center of gravity but never thought about center of transfer. Cool!
His technique works. You put the scales under the points of contact and move yourself around the sled and you can see the weight transfer to the different points, front to back and side to side.
 
Has anyone weighed a apex with this method and figured out how balanced it is stock vs modified?
I put my friends 14 XTX Apex on scales and he was heavy on the front but he is running Simmons ski up front with coil over Yamaha shocks with clickers. I think that with a little more seat time and some little tweaks I will lose him in the corners with my Viper RT-X. His Apex is fast and it will come down to carrying speed thru the corners. I am much lighter on the front and transfer quicker to the skid. Watching the weight transfer around to the different contact points when on the scales translates directly to handling on the trail. Very helpful, helps set up for different types of snow conditions. Every sled will weigh in differently when stock. Depends on rider weight and shock setup, limiter strap ect......
 
Do you remember the numbers? I'll post mine when I get the scales!!


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I remember the front was at 190lbs each side with him middle of the seat. His sled has EPS and the wider ski up front. We didnt change any thing on his sled yet.
 
I finally got a chance to weigh mine on 4 scales and it was a very interesting process. I have the ZX2 rear suspension in 151" length. I put a scale under each arm just like the video in the above link. The ZX2 has no shocks on the front arm. Look at how much weight is being carried there! Also my hyfax is completely wore through in that same location (duh right?). It may explain why I noticed very little difference going from 121 to 151 Zx2 in the trails. There simply isn't much weight applied back there. This is the opposite of a mountain skid like it showed in the videos. Weird.
Lightweight mods from stock Apex:
Head ligh pod replaced with LED lights
ZX2 is about 52lbs all dressed so lighter
Lighweight Hood from CR racing
MPI stock heavy battery PC545 Odyessy (~12lbs)
Stock exhaust, stock seat, tool box full of tools
Gas tank almost empty with low fuel light ON. (be fun to try it full of fuel)
 

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I finally got a chance to weigh mine on 4 scales and it was a very interesting process. I have the ZX2 rear suspension in 151" length. I put a scale under each arm just like the video in the above link. The ZX2 has no shocks on the front arm. Look at how much weight is being carried there! Also my hyfax is completely wore through in that same location (duh right?). It may explain why I noticed very little difference going from 121 to 151 Zx2 in the trails. There simply isn't much weight applied back there. This is the opposite of a mountain skid like it showed in the videos. Weird.
Lightweight mods from stock Apex:
Head ligh pod replaced with LED lights
ZX2 is about 52lbs all dressed so lighter
Lighweight Hood from CR racing
MPI stock heavy battery PC545 Odyessy (~12lbs)
Stock exhaust, stock seat, tool box full of tools
Gas tank almost empty with low fuel light ON. (be fun to try it full of fuel)
I was thinking that you may want to get your front left/right a bit closer when loaded. I am a lot heavier on my front shock than the rear but the weight is reduced significantly under acceleration do to the transfer to the rear shock or contact point. Front or forward shock weighted under deceleration allows some what of a pivot point in a corner however I do find that to much weight on forward shock can create excessive ski lift. I am currently having a new shock package from Hygear installed so after 3000 miles I will be starting all over again. I decided to go coil-over rather than air for the simple reason, consistency.
 
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Mike P are you concerned with the balance of the sled front to rear? Everyone says the Apex is nose heavy but according to this and if we what a 50/50 (do we want that??) I'm at like 38/62. When standing it goes to 40/60. I was expecting the opposite. I am toying with moving my skid mounting locations forward to help lighten the front but not sure now.

I'm actually not sure what conclusions I can draw here. I have a pile of lightweight parts I was going to install, custom tunnel, and push more weight to the rear, but i'm really torn after seeing these results on what I can actually do. The main issues I have is it trenches, and plows straight in deep snow off trail.

Trail manners are impeccable, I can and have outrun most any other sled in the tight twisty woods with it. Its a Ferrari on trails. Its also a top speed master with the narrow track it REALLY has long legs and will do 150+ on dream meter (like 130ish on radar). I don't really want to wreck any of that.

What would you do with it?
 

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