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How do you make the AC handle better.

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  #1  
Old 06-25-2007, 04:23 AM
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Default How do you make the AC handle better.

A lot of people have written to me, and in person have asked me about the handling characteristics of the AC's. How to lessen the tippy feeling of the AC's and how to make it a fun 'buzz-around' machine. I will tell you there is no magic too it, some basic principles of geometry, physics and logic can have you running around having a great deal of fun and really enjoying your AC without having to put up with tippy, ill handling.

First of all lets start with tires. All tires 'roll-under' some roll more than others. 2 ply will roll more than 4 ply and 4 ply more than 6 ply etc. Why? because 6 ply have stiffer side walls than either 2 or 4 ply. The stiffer the sidewall the less roll-under. What does roll-under do - it causes oversteer (makes you feel like it is doing a nose dive over the outside wheel while turning) or (the sensation that the front is tucking under). If taken to extreme the machine will roll onto its side. In a nut shell 'roll-unders' can cause 'roll-overs' How do you stiffen sidewalls? Simply, add more air or add tubes or both. With that said.
On to profiles (sidewall height) - a low profile tire will always have less 'roll-under' than a tall profile tire. A 25 inch tire has a lower profile than a 26 inch tire and a 26 has a lower profile than a 27 inch etc. So in a nut shell again a 25 inch tire will always give you superior handling characteristics over a 26 inch and taller tires. A side note here, a 25 inch tire will also accelerate faster because it maintains a lower gear ratio. And also if your engine because of the gear ratio change may not be able to pull the full RPM range, you may find that the 25 inch tire will also run a faster top speed. It will certainly get to the limiter quicker and it will also put more power to the ground. (Same principle that you are putting more power to the ground in low-range than in high-range).

Now let's talk about springs and suspension. General rule - soft suspension grips and stiff suspension doesn't. (The physics behind this is that gravity is a constant downward pressure, when you soften a suspension you are making it heavier because gravity can act on it more, if you make your suspension stiffer then your are resisting gravity and making the load lighter - heavy is traction/grip) If you look at the setups on the AC you will see different physics and geometry on the front as apposed to the rear. You get most all the stability from the rear suspension. The rear suspension is attached to the lower A-arms and the springs/shocks are at a different angle as apposed to the front. The front suspension is by design made to move up and down and to compensate to an ever changing camber, it is not designed to stabilize the machine (to offer more stability the shock would have to have more angle, which would limit it's ability to compensate for the changing camber and also limit its ability to move up and down and to absorb weight transfer without compromising the camber). So by stiffening the front you are counter productive in making the machine stable and in fact making it more unstable, and if taken to extreme it would make your machine mushy in the rear like you had a flat tire back there and the rear would float and feel squirrely. Because the shocks on the rear are attached to the lower A-arms and have a sharper angle to the frame, by design it is there to stiffen the frame and to stop the machine from tipping. (this is why sway-bars are attached to the rear and not the front).
So what actually happens when you turn? Well to a degree you need to slow down, this causes some weight to be transferred from the rear to the front. and when you actually initiate a turn some of the weight from the inside is transferred to the outside. This puts a heavy load on the outside front wheel. Remember soft grips and stiff doesn't, if your springs are too stiff (which you may think would assist in handling the weight transfer and make the machine more stable - it doesn't) the machine will plow or want to go straight. Remember the rear does the stability not the front. If the front is soft it will absorb the weight transfer and grip, a stiffer rear will keep it from feeling tippy. (we actually do have some extra stiffness in the front by having appropriate air in the front tire to stop 'roll-under' - tires to some degree are like mini springs - but without the control of rebound or compression that a shock offers - all we can do is to remove some those properties by making the tire stiff). This way the shock can do its job in a controlled fashion, with minimal affect from the tires rebounding and compressing uncontrollably. The front and rear do just the opposite as well as the left and right. When we load the front we are unloading the rear and visa versa. When we load the left we are unloading the right and visa versa. What is loading and unloading - simply, transferring weight.

Ok now we go into a turn.
If the rear is too stiff or the front too soft we overload the front causing the rear to be excessively unloaded (light - loose) - results are the rear will prematurely slide and the front will oversteer and we may actually have to counter-steer (steer opposite of the turn) to keep the machine from spinning out or having a tuck and roll if the tires are too soft and 'roll-under'. This is called 'loose going in'.
If the front is too stiff and the rear too soft we have the opposite in that the front will understeer or plow because it is not being loaded enough (too light - too stiff) and if the tires are too soft and 'roll-under' we will get the feeling that we want to do a handstand on the handle bars and the inside rear tire may in fact want to leave the ground because the right rear is loaded to heavily and wants to go straight and the inside rear wants to get to the outside (or jump over the outside rear - because the outside rear is planted too firmly - it is soft and has grip and has not given up its weight). This is called 'tight going in'.

A good turn is to have the front soft, load the weight, grip and head into the turn. The rear needs to be stiff enough to resist gravity and give up its weight to the front but not so stiff as to go loose but only to follow the front to the apex (the point at which the turn basically is complete and we have negotiated the entrance) of the turn, at this point we are ready to hit the gas to unload the front and to load the rear again. On occasion this may cause the rear to break loose or loose traction and slid a bit. Once that is complete and the transfer of weight is almost done the rear will load to the point of hooking up (it has no enough weight to get traction), the front has unloaded and now rebounding and becoming light, we may even be able to loft the inside front tire off the ground. We are basically about out of the turn completely and headed straight again.

On to track width. A wider track will always offer better handling. Here is the simplistic physics and geometry behind that principle. A wide track offers stability from left and right weight transfers by decreasing the angle of tippiness. Instead of the weight wanting to go to the outside of the tire it is directed to the inside of the tire causing the suspension to squat rather than roll. Thus in effect simulating a lower center of gravity and not transferring as much weight. Thus confining the transfer of weight within the track width and lessening the transfer to the outside. You can get a wider track with offset wheels or the addition of wheel spacers.

The basics in a nut shell.
1)stop the roll-under from the front tires - low profile and stiff sidewalls.
2)soften the front suspension - to counter the stiffer tires and to more easily absorb the loading of weight without throwing it to the outside (tippy - tuck) or resisting to accept the transfer (plowing - too stiff)
3)stiffen the rear suspension - to enhance the unloading of weight and resist gravity and become light enough (give up some traction) to follow the front (without premature loose going in) and to be light enough with less traction to be able to slide if necessary (at the apex) in order to complete the turn and to get heavy again only when the gas is applied and to hook up.

Any comments, suggestions etc are welcomed contributions.

My question back to all who write to me or in person ask me about the handling is: Why would anyone that already has 12 inches of clearance (industry leader - when all others have 7-11, and basically are forced to make their machines handle worse to gain GC) and has a tippy machine (by nature), want to make the machine handle worse by putting taller tires for a meager ½ inch of clearance, that may be of benefit once or twice a year, in a special situation? And the taller the tire the worse the handling.
 
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Old 06-26-2007, 05:42 PM
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Default How do you make the AC handle better.

Thanks for the lesson. I've never understood the need for lift kits, clutch kits, and bigger tires either. I do have a question for you, is the AC TRV models with their 58 inch wheelbase more/less stable than a regular ATV?. I have a girlfriend I want to take trail riding with me since there are more ATV trails available than Prowler ones, but I want NO tip overs. Would a TRV be too cumbersome on an 'intermediate' rated trail?.

And do you have a clue as to why AC in their infinite wisdom and smarts, can't design, manufacture, and install an axle seal that doesn't leak?.

Leaky axle/ diff seals seems to be the biggest problem with AC products.

Thanks,
Hefty
 
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Old 06-26-2007, 05:52 PM
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Default How do you make the AC handle better.

my 27 inch itp 589's gain me ground clearance and because of the stiffer sidewalls as you noted make it alot more stable the the crappy stock 26's. heck i may go to 28's with my next machine cause it will still handle better with those then the stock 26's.and for my style of riding i prefer the shocks to be stiffer for more aggressive riding and if i soften the front suspension it will just make it dive in the corners. one thing i have heard alot of ppl do on the cats to cut down on the negative feedback on the handlebars is to move them forward as far as you can in more of an aggressive angle. this is supposed to really help i guess for hard steering.
 
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Old 06-26-2007, 06:01 PM
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Default How do you make the AC handle better.

<div class="FTQUOTE"><begin quote>Originally posted by: HeftyLefty

Thanks for the lesson. I've never understood the need for lift kits, clutch kits, and bigger tires either. I do have a question for you, is the AC TRV models with their 58 inch wheelbase more/less stable than a regular ATV?. I have a girlfriend I want to take trail riding with me since there are more ATV trails available than Prowler ones, but I want NO tip overs. Would a TRV be too cumbersome on an 'intermediate' rated trail?.



And do you have a clue as to why AC in their infinite wisdom and smarts, can't design, manufacture, and install an axle seal that doesn't leak?.



Leaky axle/ diff seals seems to be the biggest problem with AC products.



Thanks,

Hefty</end quote></div>

I have ridden with some TRV and they don't seem to be handicapped at all (Or should I say 1 out of a 100 situations - and sometimes the opposite is true where the extra wheelbase length is an advantage). The extra length gives a nice smooth ride too. As far as the tippy part - I don't know for sure as I have never ridden one. It would seem to be that the extra lenght would contribute to more stability somehow. I think that by design (1 rider vehicle, 2 rider vehicle) that AC would take into account the added weight and where it is located and made compensatory adjustments or mods for that, with respect as to how the suspension is set up. If I did not have my machine I probably would have a TRV.
If you feel that the TRV is too tippy for about $180 you can put wheel spacers on all 4 wheels and that will surely take care of it. I have wheel spacers on mine and for the last 800 miles I have not encountered a situation where the 50" width was a problem. Facts are they have helped in many situations allowing me to ride more off-camber situations, ride a little out of other peoples ruts. I have had it greater than 45 degrees and driven along and it did not tip over, and I have been loaded down pretty top heavy with extra gas cans etc too.
If I were you I would definately get the TRV - you will love it. People that have them love them and what I have seen, what they can do has impressed me.

About seals - mine have never leaked, I repacked my wheel bearing this spring and put new seals in and they don't leak either (they are made in china too - lol)...
 
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Old 06-26-2007, 06:39 PM
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Default How do you make the AC handle better.

<div class="FTQUOTE"><begin quote>Originally posted by: weez440

my 27 inch itp 589's gain me ground clearance and because of the stiffer sidewalls as you noted make it alot more stable the the crappy stock 26's. heck i may go to 28's with my next machine cause it will still handle better with those then the stock 26's.and for my style of riding i prefer the shocks to be stiffer for more aggressive riding and if i soften the front suspension it will just make it dive in the corners. one thing i have heard alot of ppl do on the cats to cut down on the negative feedback on the handlebars is to move them forward as far as you can in more of an aggressive angle. this is supposed to really help i guess for hard steering.</end quote></div>

Gee, and I was always under the impression that soft, long travel on suspension was better for agressive riding (like baja machines) and that stiff suspension would bounce you around like a 'pogo-stick'... lol... Just kidding with you, what ever works for you is fine with me. Well with no bumps to deal with and on relatively flat surface yes, you probably could stiffen the whole suspension up a tad. A well setup suspension would be one that upon entering a corner too fast would slide all 4 wheels equally but still attempt to negotate the turn (without plowing - 'tight', 360 - 'loose', or tipping over - 'balanced - left and right')

My handle bars are tipped forward a little (to get them higher) only because while riding agressively over rough terain I stand and use my legs as shock absorbers and let the machine bounce around only dealing with its own weight and not throwing me around and popping me 2 feet off the seat or up-rooting my teeth.
 
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Old 06-27-2007, 10:05 AM
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Default How do you make the AC handle better.

im not saying b/s or anything on what you've stated buck, but i just want to ask some questions to clear some things up. ive had the settings on soft in the front before, and the ac's have powerful brakes, once i grabbed em a bit, rather than being progressive, and the front squatted and the back end came up, luckily its just stood on its nose and didnt come over the top anymore. what im trying to get at is that b/c of the long travel and tendency to have the front end dip under either braking or cornering, is the reason i have them set to stiff, to limit that movement. id rather have my machine slide a bit in a corner than have my outside front wheel grip and that corner compress and the machine come up and over, which has happend to my father and almost a few times with me. now if any of my assumptions here are wrong, please let me know and correct me, im on these boards to learn about stuff not blab on thinking that i know all. just curious.
 
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Old 06-27-2007, 11:04 AM
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Default How do you make the AC handle better.

<div class="FTQUOTE"><begin quote>Originally posted by: AC4LIFE

im not saying b/s or anything on what you've stated buck, but i just want to ask some questions to clear some things up. ive had the settings on soft in the front before, and the ac's have powerful brakes, once i grabbed em a bit, rather than being progressive, and the front squatted and the back end came up, luckily its just stood on its nose and didnt come over the top anymore. what im trying to get at is that b/c of the long travel and tendency to have the front end dip under either braking or cornering, is the reason i have them set to stiff, to limit that movement. id rather have my machine slide a bit in a corner than have my outside front wheel grip and that corner compress and the machine come up and over, which has happend to my father and almost a few times with me. now if any of my assumptions here are wrong, please let me know and correct me, im on these boards to learn about stuff not blab on thinking that i know all. just curious.</end quote></div>

You are correct. Different machines may need a little different setting as well as with different riders (remember there is body english too). It is all about weight loading and unloading and your wheight plays into that too.

The major improvement is to stop the 'roll-under' with the front tires. Once that is accomplished then the rest is a matter of personal taste and how a person uses their own body weight with the machine. You seem to prefer that the front push a little - and that is fine. I on the other hand don't like it because when it stops pushing it will grab and there is a sudden snap to the turn.

If you like your front springs a little stiffer that is ok. But you may find that the rear may have to go up also for a good balance... i.e front on 1, rear on 2, then you adjust front to 2, you may have to put the rear on 3. See what I mean.

When you get everything done, a good balance is a machine that will enter a turn too fast and all 4 will slide. Not just the front and not just the rear. As a general rule most setups will have the rear stiffer than the front. What I meant with having soft suspension while setting up handling is that soft will grip and stiff will slide. If you have a machine that is gripping too much in the front then you make it a little more stiff to unload the weight and by the same principle if the rear is sliding too much while entering a turn then you soften it a bit. You can stiffen and soften with both the shock preloads and tire pressure.

All things are not equal. Your front springs from the factory may be a tad softer than mine. My rear springs from the factory may be softer than yours.....

I did the whole article so that people would know what to do if their machine was doing a certain thing. If you go into a turn and the machine wants to go straight or plows then you can either soften the front or stiffen the rear or both and you can accomplish this using both the preloads or tire pressure.

A lot of people thought that if it was tippy then if you stiffened the front that would take care of it - well to some degree it would but then your machine would push like crazy. The tippy is really controled from the rear, that is where you get the stability for the most part.

The article was done so that people when making changes would have some degree of knowing what was going on and not just keep making changes on a trial and error and getting frustrated.

The biggest thing is to stop the roll-under from the front tires. That could mean 6lbs, 8lbs 9lbs or air or putting tubes in the tires or getting a 6 ply tires etc etc. or any combination mentioned. But for good handling the 'roll-under' from the sidewalls of the tires is the first thing that must be adressed and eliminated. Then you can get on with the suspension... once the suspension is set then you may find that you can take a 1lb of air out.

The whole point is that the ill handling and the tippy feeling from the AC's can be addressed and the handling can be greatly improved (and you don't have to do trial and error - that if you know what is going on and what to do then you can make adjustments appropriate to improve the handling). Some people did not know where to start or what to do. Some people didn't know what was happening when it felt like you were doing a handstand on your handle bars or that it felt like you were going to do a nose dive over the outside front wheel. I made an attempt to let them know that when this particular thing was happening, here is why it was happening and here is what you can do to correct it.

So in your case where the front seems to be too soft then yes stiffen it but don't forget about the back too, If you stiffen the front and your handling goes away don't think that you have to set it back, you may only need to add more air to the rear tires or go up one preload setting to bring the handling back.

Whew - I get going and don't know enough to stop... hope this helps.
 
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Old 06-27-2007, 11:29 AM
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Default How do you make the AC handle better.

Here is a fun exercise that you can do to really understand grip and slide.

Take your machine and set the front preloads on the softest and your rear on the stiffest. Put 4 lbs of air in the front and 10 lbs in the rear. Then on asphault at 1 or 2 mph turn left then right. You will see that it turns pretty easy. It may steer hard but it will turn easy - there is a difference between steering and turning.

Then do the opposite. Put 10lbs in the front and the preloads on the stiffest and in the rear put the preloads on the softest with 4lbs of air. Then do the same turns left and right and you will see that the thing just does not want to turn.

Test both settings driving forward as well as backing up.

Slide = giving up traction (to any degree even ever so slight) and being light.
Grip = holding traction and being heavy.
 
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Old 06-27-2007, 04:40 PM
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Default How do you make the AC handle better.

thanks alot buck, u really cleared things up and i appreciate you being able to do so w/o sounding like an arrogant fool, which is what too many people on boards like this tend to be. ill play around with it some more to get it dialed in.

im a very active rider and am able to throw my weight around when i ride, i dont just sit and ride. anyway, when i got the 650 the first thing i noticed is how much heavier the steering seemed to feel than the 400, at first i thought it was just the tires, since the suspension and steering geometries should be almost the same right? well i swapped the tires off the 400 onto the 650, since the 650 has the diff lock and could prolly get away w/ crappier tires on it, and it still was heavy, but now your article sort of explained that.
 
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Old 06-27-2007, 06:18 PM
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Default How do you make the AC handle better.

<div class="FTQUOTE"><begin quote>Originally posted by: AC4LIFE

thanks alot buck, u really cleared things up and i appreciate you being able to do so w/o sounding like an arrogant fool, which is what too many people on boards like this tend to be. ill play around with it some more to get it dialed in.



im a very active rider and am able to throw my weight around when i ride, i dont just sit and ride. anyway, when i got the 650 the first thing i noticed is how much heavier the steering seemed to feel than the 400, at first i thought it was just the tires, since the suspension and steering geometries should be almost the same right? well i swapped the tires off the 400 onto the 650, since the 650 has the diff lock and could prolly get away w/ crappier tires on it, and it still was heavy, but now your article sort of explained that.</end quote></div>

I am glad that you feel that you have benefited. I do my testing in one area. I know how it handles there and when I make changes I can tell almost instantly what is going on. I don't know if you have a place handy for you to be able to do the same, but it helps me to compare settings and changes.

It actually is fun to play around with the settings to dial your machine in I am sure you will have fun doing it. It is also fun to know when you machine does a certain behavior that you know what adjustments to make to correct it, and not just blindly hit or miss, trial and error try to correct it.

The AC is no sport machine but you can have a sporty ride from it and you can take the tippy out and you can 'dirt-track' with it. Since you are active with your body weight you should have a ball.

If your budget can swing it (not really that expensive) but 1" spacers really make a tremendous difference.

Anyway enjoy and have some fun dialing your machine in. Keep me posted as to how you are coming along.
 


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