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Discussion Starter · #1 ·
Every since the 09's came out saying they changed scrub radius via wheel offset to improve steering I became curious as to what, where,why and how. After reading about adding more Caster to the older King Quad's and reducing Caster on the Brute Force to ease steering and a many hours searching on the web I discovered two ways to measure caster and camber that can be used on the Arctic cats. I also noticed via part numbers the only difference between the 09's and the older cats is the wheel and the upper A-arm. This got me thinking that they also modified caster.

The first method uses a machinist level that I taped to a bar that was long enough to reach from the edge of each side of the rim. It is held to the rim in a vertical position with a bungy cord. Once this is in place you can directly read the Camber of the wheel while the tire is pointed straight forwards, which in my case is Positive 1/2 degree. Meaning the top of the tire is tipped out 1/2 degree.
[attachment=123758:Setup.JPG][attachment=123759:Level_Camber__5.jpg]

To read the and calculate the Caster you turn the wheel exactly 20 degrees to the left and then re-center the bubble on the level and read the degrees of wheel tilt. In my case its reading about positive 2.75 degrees.[attachment=123760:Level_Left__275.JPG]

Then turn the wheel to where it is now pointed 20 degrees to the right, center the bubble and read the amount of wheel tilt (See Photo LEVEL RIGHT -125.JPG) In my case it is showing about -1.25 degrees.
[attachment=123761:Level_Right__125.JPG]

Now ignore the +/- signs on the readings and add them together for a total difference change in wheel tilt of 4 degrees. Now multiply by 1.43 and you get 5.72 degrees of Caster. Pretty simple huh? Also I did read that if you turn the wheels left and right 15 degrees you multiply by 1.5 instead. I used 20 degrees and 1.43 so it would match up better with the other method described below.

The other way is to make a direct reading plumb bob Caster/Camber gauge. Found instructions for this on the internet also. Was quite easy to build too. I printed off the drawing and sandwiched it between two pieces of 1/8" plastic. The left vertical edge on mine is 15.25 inches long to reach the distance across the 14" ITP rim. The BOB is a 243 caliber bullet center drilled and hanging of a piece of red dental floss. The distance between the fixed attachment point for the floss on the template and the bottom of the scale at 0 is critical it is also critical that the plumb bob reads ZERO when the edge of the gauge is perfectly vertical. This gauge is probably more accurate since your not estimating distances between tiny lines on a machinist level and it is definitely easier to read. To use it. You just hold up against the wheel in a vertical position and read where the plumb bob line crosses the scales. (the angled lines)

To directly read the Camber, point the wheel straight ahead and read the Camber scale on the positive side for positive camber or the negative scale for negative Camber. See where the red thread crosses the right diagonal line? Also shows almost 1/2 degree positive camber, well maybe closer to 3/8 degrees. Holding the gauge up with one hand and taking the picture with the other hand distorts the view and the angles read on the scales a little. If you eye-ball the point where the red thread crosses the diagonal lines from the same level and at a right angle view from the gauge the degrees of angle is easier to read.
[attachment=123763:Gage_Camber__5.JPG]

To read Caster once again you point the wheel left 20 degrees and read off the CASTER scale in the center which in my case shows about 4 degrees.
[attachment=123764:Gage__400.JPG]

Now turn the wheel right from centered 20 degrees and again read the Caster which in my case shows about -1 3/4 degrees.
[attachment=123765:Gage__175.JPG]

Now again ignore the + & - signs and just add these two measurements together for a total of 5-3/4 degrees Caster. Which is pretty damn close to the 5.72 degrees calculated above. This gives me some confidence in the accuracy of the gauge and the methods since both are about the same. If both your left and right 20 degrees measurements are either both positive or both negative, then you would subtract the smallest angle from the largest angle and the difference would be your castor angle. Something I don't think you would see on a cat.

If you noticed the gauge closely you can see a notch cut into it on the right hand edge. Just lay the gauge on the floor with the center of the notch aligned with the center hub of the wheel and then with a marker or chalk line extend the lines out. This makes aligning the wheel 20 degrees left or 20 degrees right pretty simple. If you look closely on the concrete you can see a red chalk line on the floor. There is another one that extends out from the front. I just aligned the tire to be parallel with the chalk lines when turning left or right.
[attachment=123767:Chalk_Line.JPG]

Below is the JPG file I used to print off and make my Caster/Camber gauge and it's instructions for use. You can ignore the scale at the top. It's there if you want to make a horizontal plumb-bob. On the Plumb bob template, you can see the plumb string attachment point. Short curved black line that is top center directly over the center zero on the bottom scale. When the left edge is perfectly vertical, the string should be centered on the bottom V. Thus showing zero degrees vertical angle.

Ok what good is all of this. Remember where the King Quads were unstable because there Caster was only 1.6 degrees. And the Brute Force is hard to steer, that is because of the large amount of positive caster built into them. King Quad and Brute riders figured out a way to make their caster adjustable, adding caster to improve straight line stability or removing caster to ease steering. It seems from what I've read on the Nyroc site, around 4 degrees Caster is a sweet spot to have the best of both. Ease in steering and good stability. With the 5.75 degrees caster on the Cat's I'm planning to decrease the amount of Caster to around 4-4 1/2 degrees to see if it steers as well as a 2009 when done. The same method those on the Nyroc site have been using on the King Quads and the Brute Force would work on the cats. To reduce Caster. The attachment of the top A-arm would be moved forwards about 1/16 inch per degree by shimming the A-arm forwards. I'll know more after I rebuild the front A-arm Bushing on my Tcat. I've got all the rear ones done with oil impregnated bronze, and have more ordered for the front.

I also suspect knowing how to check caster and camber would be a good quick method to insure the steering geometry of your ATV isn't bent up, bushings shot and having both left side caster and camber being close to the right side caster and camber for best handling. Note Toe-in must be correctly set to compare left and right wheel caster. Also when the the bars are straight, both front tires should be tracking straight minus the amount of toe-in. Air pressure should be balanced left and right and full weight on the ATV sitting on level ground. Sure would be nice if someone with a 2009 cat would follow up on this post and measure the caster and camber on their ATV so I've got a good idea of what to shoot for. Hint Hint.

Brute force caster reduction
http://www.nyrocatv.com/forum.cgi?viewcat=...earchtext=brute caster

King Quad Caster addition
http://www.nyrocatv.com/techtip.cgi?viewca...mp;viewtopic=17

Various Caster Angles found in a Nyroc thread.
Yamaha Kodiak YFM400 = 4 degrees
Yamaha Griz 660 YFM660FP = 5 degrees
Honda Rubicon TRX500 = 3 degrees
Honda Fourtrax 400ex = 6.5 degrees
Honda Fourtrax 250R = 6 degrees (for '86, '87), 4+ degrees after
Suzuki Kingquad 700 = 1.6 degrees
 

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Excellent work! Not worthy:

Front end geometry fascinates me, there's more to it than meets the eye! I understand & know exactly what you're talking about here.

It's been so many years, but the automotive courses I did was taught by a master of front end & steering geometry, he knew his stuff, as he formerly was an engineer in the automotive manufacturing industry previous to his educational profession. He taught only because retirement bored him.

At the time I wasn't as interested as I could've or should've been, at the time being a young guy with other more seemingly important obsessions on my mind... Like hot babes for example.

I don't know if you pay any attention to the sled side of ArcticChat... But when I did the AGLT front suspension project, a lot of things came back, more than I realized ever could. I could recognize what A/C engineers did, I knew what to look for, I knew what to do, I knew what would or wouldn't work... I remembered things I never knew were in my head.

:chug:
 

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Discussion Starter · #3 ·
<div class='quotetop'>QUOTE </div>
Excellent work! Not worthy:

Front end geometry fascinates me, there's more to it than meets the eye! I understand & know exactly what you're talking about here.

It's been so many years, but the automotive courses I did was taught by a master of front end & steering geometry, he knew his stuff, as he formerly was an engineer in the automotive manufacturing industry previous to his educational profession. He taught only because retirement bored him.

At the time I wasn't as interested as I could've or should've been, at the time being a young guy with other more seemingly important obsessions on my mind... Like hot babes for example.

I don't know if you pay any attention to the sled side of ArcticChat... But when I did the AGLT front suspension project, a lot of things came back, more than I realized ever could. I could recognize what A/C engineers did, I knew what to look for, I knew what to do, I knew what would or wouldn't work... I remembered things I never knew were in my head.[/b]
Thank you, couple days ago i could of said I knew nothing about steering geometry. And to be honest I don't really know 100% if my measurements and method is correct. However i decided I wanted to understand the changes they made to the front end of the 09's and wondered if I could improve my H1 & H2 without buying new top A-arms. and no I don't follow any of the sled treads at all, I gave up sleds back in 78. Seems when i had to start working in the cold, playing in the cold lost all appeal
 

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Discussion Starter · #4 ·
Finished the front end bushing replacement an reduced the caster by 1 1/2 degrees. Caster before I made the change was 5 3/4 degrees on on side and 6 1/4 on the other. (worn bushings also) Replacing all the bushings with oil impregnated bronze removes all slop, provides for smoother suspension action. equaled out the caster on both sides to now 4-1/4 degrees.

The results, much better. Much easier to steer now. For a measurement, I held a old bathroom scale centered up against one end of the handle bars noting how much pressure it took to turn the wheels. Pushing only one end. The Tcat now requires approximately 40-45 lbs of force on one bar end to turn the wheels. Compared to the 650 H1, it requires between 60-65 lbs of force to turn the wheels. Same tires, same surface, same wheel offset, same air pressure in the tires. I wish I would of measured the force on the Tcat before the Mod, but least I got good hindsight. I'll probably do the same mod on the 650 at some point. Test riding in the street and in the alleys for about 45 minutes felt very good.

To reduce the caster, the top A-arm is shimmed forwards 94 thousands of an inch. (3/32")This was done using the bronze bushings that have a thinner flange and two 5/8 washers in the back and one on the front . See pictures. I took calipers to the hardware store and found six 5/8 washers that were 94 thousands of an inch thick so I could properly shim the center bolt stud on the suspension between the frame brackets. There is less than 5 thousands gap between the washers/A-arm between the frame mount tabs, Tight enough you cannot feel any play in the suspension at all. Pictures show the shims on the A-arms top, and both bottom on the right side of the bike. Equal width shims on the bottom are 14 gauge shim washers. (about 1/8" thick)
 

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Hey Wyo.....man I'm glad your doing this!! Buddy of mine got that info from the Nyroc site and did this King Quad. Talk about a difference, its like power steering.

Been trying to find some info on Cats, but until now, haven't seen anything.

Hopefully somebody will have the tech tools to measure out an H1 and come up
with the amount of shimming needed to improve its steering.

I'll have to read your post about 20 times before it starts to soak into this old brain.
 

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Discussion Starter · #6 ·
<div class='quotetop'>QUOTE </div>
Hopefully somebody will have the tech tools to measure out an H1 and come up
with the amount of shimming needed to improve its steering.[/b]
Every thing you need is in the above, even the template to make your own tech tool, a vertical plumb bob. I describe two different ways to measure your castor and camber, either one will work. My 2006 H1 is almost identical to my 2008 Tcat when it comes to front suspension geometry. It measured out a little over 5 degrees. The bushings on it as a little sloppy also though. Shimming the top A-arm forwards 3/32 or 0.094 of an inch forward will reduce your Caster to about 4-1/4 degrees from the stock 5-3/4 degrees on a Tcat or about 1/16 of an inch on my H1 to obtain 4 degrees caster if it is 5 degrees stock with good tight bushings.

The older King Quad has the opposite problem, It has too little Caster only 1.6 degrees. This will make the steering twitchy and erratic at speed. They are adding shims on the front of the A-arm to shim it backwards to a total caster of about 4-1/4 to 4-1/2 degrees. Some older Brute Forces are like the Cats, too much Caster. They are shimming the A-arm forwards like I did my cat.

A person does not need to replace suspension bushings like I did. Mine where worn and needed replaced anyhow. I decided to try the bronze bushings to see if they hold up better for me.

If you were to cut the front shoulder flange from your stock rubber A-arm bushing to make it exactly 3/32"thinner and then place a 5/8 SS washer between the bushing and the mount point, It would do the same thing. In the attached cut-away (Crude) drawing. You would cut or grind the flange of the forward bushing (green) thinner by 3/32 of an inch and replace the created clearance by placing a 5/8 inch washer (blue) that is 3/32 thick between the frame mount and the rear bushing. This will shim your entire top A-arm forwards 3/32 of an inch and reduce the caster from approximately 5-3/4 to 4-1/4 degrees. So there you have what you asked for. Every 1/32 of an inch changes caster by 1/2 degree. If you were to find you didn't like the feel and wanted to return to stock, just replace the front bushing with a new one, or place the washer in the front instead of the back. Either way would return you back to the stock caster angle. The other drawing would be a non cut-away of the assembly showing the A-arm and attachment to the frame tabs

Using the Machinist level or building the Plumb-bob vertical level will allow to to check your work and insure you are where you want to be. Measuring also lets you know your Arms are not bent and each side is castered the same amount for the best handling.

I would suspect that if you purchased a set of new 09 upper A-arms and installed them on your 08 or older ATV you would also get improved steering. Pretty costly way of doing it though.
 

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Discussion Starter · #7 ·
Put about 45 miles on the Tcat today with the new bushings all around and the new caster setting. Steering is light and responsive. At first I was thinking I made a mistake because it was so much easier to steer. I was over steering. After I got used to it, I like it! Lots less bump steer, and a lot less tiring on the arms. In soft sand or dried out ruts where there was a lot of chris-crossed tracks, the front wheels would try to follow the ruts a little easier which at first felt unstable, but after I got used to it, I was fine. At no time did I feel out of control, but wow, what an improvement in steering effort and less bump steering.

Don't confuse bump steer with having the handle bars being ripped out of your hands, LOL Not the same cause or affect. <grin> Bump steer is caused from the arc your suspension travels from fully extended to full collapsed. This causes changes in the toe and I think maybe scrub radius of the steering that can cause a change in direction even with the wheels pointed straight ahead and without the handle bar being turned. Just the nature of A-arm suspensions, Bump steer is a issue in any vehicle with A-arm suspensions including cars, trucks, & ATV's Some are worse than others Bump steer is the common name of this issue in the automotive world. However the Caster mod or your Caster mod bushings do seem to help minimize bump steer some, since bump steer is more apparent with higher caster degree settings.

Fines Double racing had some videos on here from their Baja races. In those videos there are several times you can see the cat changing directions coming out of a hole that collapses the suspension and it changing direction of travel upon re-contact of the ground even with the front wheels pointed straight and the handle bars not being turned. That is bump steer. The rider must immediately correct steering to maintain control. I'm sure they do have a steering stabilizer installed and they do not prevent that from happening.

As for the stabilizer, What they will do if it works good is to take the jar or shock from your steering being yanked one way or the other if you hit a rock , stump log, or rut at the wrong angle. This is not bump steer, not sure what you would call it I'm sure there is a better technical name than a "Oh Crap". We used to call it Wheel Whip when off roading in the 4x4's and jeeps. Before power steering in jeeps and 4x4's one learned to drive without wrapping their thumbs around the steering wheel. If you did a Broken thumb was quite possible in the rough stuff. So maybe Bar Whip would be an appropriate name???

A Stabilizer... Sure saves on wrists and elbow pain as well as helps keeping you in control of your ATV. As I've said before Wish I had an Precision but my Shindy is a whole lot better than nothing.
 

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Excellent work! Not worthy:

Quite some time ago I when I noticed how worn the urathane arm bushings are shot & sloppy, the idea of sintered bronze bushings entered my head but haven't replaced them yet.

The stock bushings are indredibly sloppy so it's something I'm going to look at doing it this year if I find the time.

Not sure if I need to change/adjust the geometry though, but I suppose I could try just to see how it feels. I was comfortable with how it steered & felt before though. Steering was always very light because the ATV is lighter than most others (compared to ATVs with additional bolt-on aftermarket weight) and I don't drive with my weight on top of the rear wheels either.

On my sled A-arms I installed grease zerks to push the water out, as I found water creeps in, and then rust from the center bolt migrates to the sintered bronze bushings, which is like throwing sand at it... The zerk's main purpose is to be a method to push out water with grease, to prevent corrosion, as the bushings themselves are already self-lubricating.
 

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Discussion Starter · #9 ·
<div class='quotetop'>QUOTE </div>
Not sure if I need to change/adjust the geometry though, but I suppose I could try just to see how it feels. I was comfortable with how it steered & felt before though. Steering was always very light because the ATV is lighter than most others (compared to ATVs with additional bolt-on aftermarket weight) and I don't drive with my weight on top of the rear wheels either.[/b]
My plan is to lighten the steering for my Lady on the H1. That's her biggest complaint that a ride is so hard on her arms. Since all the bushings were shot on the H2 decided it would be a Guinea Pig. Other than my time, the Sinistered bronze @1.76 a piece was less than half the price then replacing with stock rubber bushings. I was riding like you normally do yesterday, 50-60 mph in the sand draws and was on gravel trails that have moguls in them up to a foot or more deep spaced every 10-15 ft apart. If you've ever been skiing you know what I mean, The reduction in the bump steer made taking these moguls at speeds over 35 easily although the Tcat was in the air more then on the ground. Yet remained straight and stable coming out of the hole much better then before.

<div class='quotetop'>QUOTE </div>
On my sled A-arms I installed grease zerks to push the water out, as I found water creeps in, and then rust from the center bolt migrates to the sinistered bronze bushings, which is like throwing sand at it... The zerk's main purpose is to be a method to push out water with grease, to prevent corrosion, as the bushings themselves are already self-lubricating.[/b]
We're thinking along the same lines here, my feelings exactly. I figure a quick shot of marine grease after washings and each oil change will prolong the life. If not, I'll replace with a tough self lubricating plastic, such as the Kevlar-Filled Nylon or Teflon. Would love to use Torlon, but at $200 a ft a little pricey. I also think grease zerks on the a-arms using the stock rubber bushings may prolong their life as well. I believe it was GWC who removed all his bushings, bolts and sleeves and coated thick with Red and Tacky grease, appears to prolonged his bushing life. So apparently the rubber is compatible with that grease.
 

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Think I'm gonna have to at least try this mod as my H1 steers like a dog!! If I was still a young stud , it probably wouldn't be an issue, but I just like to joy ride and NOT fight the steering.
Probably more than anything, it will give me something to do or shall I say play around with.
Thanks for the info, much appreciated!!

When I git er done, I'll let ya know how it turns out.

Actually I thought the drawings were pretty good!!
 

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Very interesting piece, as usual. Steering ease for my wife's machine ( 07 500) is a big topic of interest to me.

My own machine has 26x9x14" bighorns on itps, and the combination of tire and more rim offset has greatly improved steering effort. Plus I'm done messing with it for know. My wife's machine, on the other hand...

I just changed tires on her machine, from stock carlisle badlands to V 2.0 bighorns. I went with 25x8x12s on all four corners, using my old stock front rims. I want to see how much steering effort has changed with just the tire swap. My 2 mile ride seat of the pants test was inconclusive -- these bighorns hook up so well, the whole machine feels different.

I am seriously considering the a-arm shims to lighten up steering further. If it was mine, I'd do it in a heartbeat, but she does not like the feeling of a loose machine. What you said about rut following concerns me.

We have works shocks on hers, so I can tune weight transfer infinitely. I set it up so it felt like it had just a bit of push, but she still thinks it feels too free. We haven't had a chance to ride since I tuned it a little more.

Anyway, what I'm thinking, is I can take back some of the instability of reducing camber by dialing in more front spring preload -- best of both worlds.

Wyo, when are you going to spring for some works shocks? They are a huge benefit in the realm of rider comfort and fatigue. Of course they cost a little.

Mike
 

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Discussion Starter · #12 ·
<div class='quotetop'>QUOTE </div>
Very interesting piece, as usual. Steering ease for my wife's machine ( 07 500) is a big topic of interest to me.

My own machine has 26x9x14" bighorns on itps, and the combination of tire and more rim offset has greatly improved steering effort. Plus I'm done messing with it for know. My wife's machine, on the other hand...

I just changed tires on her machine, from stock carlisle badlands to V 2.0 bighorns. I went with 25x8x12s on all four corners, using my old stock front rims. I want to see how much steering effort has changed with just the tire swap. My 2 mile ride seat of the pants test was inconclusive -- these bighorns hook up so well, the whole machine feels different.

I am seriously considering the a-arm shims to lighten up steering further. If it was mine, I'd do it in a heartbeat, but she does not like the feeling of a loose machine. What you said about rut following concerns me.

We have works shocks on hers, so I can tune weight transfer infinitely. I set it up so it felt like it had just a bit of push, but she still thinks it feels too free. We haven't had a chance to ride since I tuned it a little more.

Anyway, what I'm thinking, is I can take back some of the instability of reducing camber by dialing in more front spring preload -- best of both worlds.

Wyo, when are you going to spring for some works shocks? They are a huge benefit in the realm of rider comfort and fatigue. Of course they cost a little.[/b]
We are running the same tires, 26x9x14 and ITP rims on all 4 corners also. Also the same setup on my 650H1. As for Works Shocks, yeah I'd love to have some, but there is always something else that demands were the money goes. Fixed income so I have to budget carefully. The next major expenditure will be a PCIII for the Tcat. I shimmed the A-arm forward by 3/32" of an inch this reduced caster a full 1-1/2 degree on the Thundercat, 1/16" of an inch would equal out to about a 1 degree change. If a person would come up with a method to shim maybe 1/32 of an inch at a time, then you could adjust both forwards (reduce steering effort) and backwards (increase steering effort) 1/2 degree at a time to your liking. I'm wondering just how well shimming the stock rubber A-arm bushings would work, there is some give in them which may require more shim to obtain the same difference. I also wonder if the give in the rubber adds to the inherent bump steer arctic cats have? The reduction in bump steer alone sure made this change worthwhile in my opinion. The ruts I was speaking of were hitting other deep atv tracks in packed sand or dried out mud at speeds over 50 mph where the ruts were deep at an angle. In such conditions my worn out stock bushings were probably worse. At the time, I also had my steering stabilizer set at minimum where I usually have it pretty stiff. The new suspension is tight enough and handling improved enough where I was getting a little ****y. I keep my shocks pretty tight for carrying loads and pulling a loaded trailer. Preload is 3 in the front and 5 in the back, too tight for riding unloaded and too lazy to jack up the machine to adjust shocks back and forth all the time. I went out again for about a 10 mile ride yesterday and concluded that I love the change. My first concerns were more of a getting used to it I think and having the stabilizer at minimum. Headed out again today in a few minutes.

I probably would not recommend a person blindly making this change without measuring the caster before and after. At least until there is additional feed back. You need know where you are and can keep the caster substantially positive. Everything I've read seems to point to a caster between 3 and 4-1/2 degrees as being a sweet spot. Go too far and it would handle like an old king quad that had only 1.6 degrees very twitchy at speed and dangerous in my opinion.
 

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Wyo,

I like your thinking on a smaller size shim and working up to a quicker turning castor. I'm sure there is some give in the rubber bushings, but as long as they are not worn out, I think the shim will still have a meaningful impact.

I get the living on a budget -- in the long run those that do will be happier. My major atv spendage for the year was my wife's tires.

I need to let her get a feel for them, and get her preload tuned for best handling before I change anything else on her. We got in a small ride today; a little rocky loop near my house. First one of the year, so now I'm really wanting more.

The ride and your comments about bump steer got me thinking. When I come close to bottoming the front end, it often feels like it wants to duck under and jerk in the direction of least resistance. I assume this is bump steer. It happened once on our short ride today. No big deal, but....

I need to do some research and see if I can get the castor/stability/bump steer issue understood better.
As I understand it now, more castor = more resistance to turning= more straight line stability. As the wheel travels up, castor combines with camber, giving the wheel a longer lever on the bars, which is bump steer.

Might be that my machine is the one to experiment on first. I just replaced the entire bushing set on front and rear last fall, so I'm at a good place to start.

Mike
 

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Discussion Starter · #14 ·
<div class='quotetop'>QUOTE </div>
The ride and your comments about bump steer got me thinking. When I come close to bottoming the front end, it often feels like it wants to duck under and jerk in the direction of least resistance. I assume this is bump steer. It happened once on our short ride today. No big deal, but....
I need to do some research and see if I can get the castor/stability/bump steer issue understood better. As I understand it now, more castor = more resistance to turning= more straight line stability. As the wheel travels up, castor combines with camber, giving the wheel a longer lever on the bars, which is bump steer.[/b]
Way I understand it also. We have a trail 21 miles connecting 2 towns that is a converted rail road bed. With many years worth of ATV traffic on it. It has developed into a series of holes about 8-12 ft long 5ft wide and up 18-24" deep in many areas. One hole right after the other. Moguls (skiing term) is what I call them. When in the bottom of one hole with suspension collapsed as you're coming out of the hole and suspension unloading at the same time, you never really know which way your atv was going to dart or steer on it's own. The back end of the ATV would kick off side to side as you try to correct your line coming out of the hole and land at an angle to your direction or travel. As you say direction of least resistance. The tendency of the atv of doing this is substantially reduced after I made these changes. I'm riding this trail at speeds nearing 50-55 MPH where 30-35 mph was a scary ride trying to keep it under control when completely stock.

I didn't know Jack *****t about any of this stuff myself either, still not sure I fully understand what I think I know now. Spent about 3 days googling and reading various topics I found on the internet. The machinist level idea came from watching some videos on setting caster and camber on a custom hot rod website, and the plumb bob template was from a mini cooper owners forum. These along with forums like Nyroc for the king quad and a few Kawasaki brute forums gave me the idea on how to adjust caster on the cats.

http://www.flickr.com/photos/johnbullas/3247828773/page1/
 

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Discussion Starter · #15 ·
Shimmed the top A-arm on the 650H1 today. Originally it was about 5 degrees positive caster. I shimmed it forwards a total movement of about 0.195". There is one 0.045" shim in front and five shims in the rear. (four 0.045" and one 0.060") See the pictures. This reduced steering effort by 20 lbs according to the old bath scale. Before the mod it took between 60-65 lbs of pressure pressing on one bar end only. I now takes 40-45 lbs of pressure. I'm holding the scale with the end of the bar centered on the back if it. Then pushing on the front center to see how much pressure it takes to turn the tires with my weight on the ATV. Checking this on the garage floor, semi-smooth concrete without moving or rolling. Caster is now about 3 degrees positive. A reduction of 2-1/4 degrees. I decided to go a little further just to see what it handles like. If it is too twitchy I'll just take 1 or 2 shims from the back and place them on the front instead.
 

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would shimming the front of the lower a arm cause the same effect as shimming the rear of the upper, if so then you might get away with shimming both a arms instead of trying to cut your bushings

oh and this would be a good one to pin
 

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Discussion Starter · #17 ·
<div class='quotetop'>QUOTE </div>
would shimming the front of the lower a arm cause the same effect as shimming the rear of the upper, if so then you might get away with shimming both a arms instead of trying to cut your bushings[/b]
Yes I think it would be. The idea is to rotate the steering ball joints so they are more straight up and down instead of tilted back.
 

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I did some research on bump steer the other day. I got info off some race car sites, but it should still be pertinent to quads. Bump steer is defined as changes in toe caused by suspension and steering geometery. There are some issues with toe and steering stability that I need to re-read to understand, but I think what is going on with our quads is we are getting bump steer at the end of suspension travel which is caused by the tie rods actually changing the toe. Probably big toe out, but I'm not sure.

Anyway, what I get out of this, is not only does more positive camber help steering effort, but shimming the top a-arm to achieve it is changing the steering geometery in a manner that reduces bump steer.

I am guessing that shimming the lower a-arm will not make the same changes to steering geometery, even though it will change castor and reduce steering effort.

It seems to me that checking toe would be necessary after making a change to caster.

I am still working on understanding this stuff, but I visualize the toe changing out-in-out (or vice-versa) as the suspension travels through its full stroke. This is caused by the relationship between suspension and steering parts. There is an optimum way to put all this stuff together so bump steer doesn't occur or is minimized, but it is not always possible due to how the vehicle is designed. I'm still scratching my head here.

Mike
 

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<div class='quotetop'>QUOTE (miket @ Mar 27 2009, 01:10 PM) <{POST_SNAPBACK}></div>
I did some research on bump steer the other day. I got info off some race car sites, but it should still be pertinent to quads. Bump steer is defined as changes in toe caused by suspension and steering geometery. There are some issues with toe and steering stability that I need to re-read to understand, but I think what is going on with our quads is we are getting bump steer at the end of suspension travel which is caused by the tie rods actually changing the toe. Probably big toe out, but I'm not sure.

Anyway, what I get out of this, is not only does more positive camber help steering effort, but shimming the top a-arm to achieve it is changing the steering geometery in a manner that reduces bump steer.

I am guessing that shimming the lower a-arm will not make the same changes to steering geometery, even though it will change castor and reduce steering effort.

It seems to me that checking toe would be necessary after making a change to caster.

I am still working on understanding this stuff, but I visualize the toe changing out-in-out (or vice-versa) as the suspension travels through its full stroke. This is caused by the relationship between suspension and steering parts. There is an optimum way to put all this stuff together so bump steer doesn't occur or is minimized, but it is not always possible due to how the vehicle is designed. I'm still scratching my head here.

Mike[/b]
Easy way to check for bump-steer... Support the belly of the quad at the front between the arms high enough so almost all the weight is off the front wheels to ensure the front suspension is fully extended.

Remove a shock from one side. Move the wheel up off the ground while the other side is still touching. If you have bump steer in any significant amounts, you can visually see the wheel turn slightly left/right as you lift and lower the wheel to simulate the suspension in the fully compressed and fully extended position.

Interesting thing... Out on the trails, one side can be compressed by a bump turning that wheel slightly one way, and instead of a bump on the other side it can be dropping into a hole, extending the suspension. In that short moment of time, instead of going toe-in or out, the front wheels will actually both point to the left or right by a slight amount in that small moment of time. This causes more 'correction activity' for the rider, make it more difficult to control and more fatiguing.
 

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We have a small 110cc Chinese Quad for my son. As with many Chinese bikes the parts are not always readily available. The inferior rubber bushings went in a short time and I could not find a similar rubber bushing. I tried a stock oil based bronze bushing available at Princess Auto in the quad and with a little work it popped it. The bushing seems to be holding up well despite my son's best effort to destroy the quad, which in most cases he has succeeded. With my MIG welder nearby I have been able to weld it back together SO FAR. Anyway back to the bronzlite bushings idea my concern was the lack of flex in the bronzlite versus the rubber urethane stock bushing. The small quad has a poor suspension from the factory and I am not sure if it made any difference to the suspension other that tightening the loose parts. Given that quads flex over terrain and the original rubber bushing flex and absorb vibrations. I wonder what is the long term outcome of bronzlite over rubber urethane stock bushings?

Happy ATVing
MrJ
 
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