A Guide To Setting Up Your Front Suspension

Blaner

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Mar 26, 2008
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So, you’ve got your hands on a set of extra HP fully adjustable A-arms for your Blaster and im sure you are very excited and keen to bolt them all up and go churn some mud, many may do just this without considering - or if you got that far, without understanding what the “fully adjustable” part of your new bits actually means, I will do my best to explain some basic suspension dynamics and how you may adjust them in order to achieve optimal settings and use out your front end.

If you are reading this and thinking “Mmm, better get cracking and setup my stock Blaster!” I regret to tell you that the stock blaster front end is not “fully” adjustable and only has two avenues of adjustment, whereas a set of ASR, Houser etc with Elka etc shock can provide you with up to six different dynamics to set.

These six settings are: Caster, Camber, Toe, Shock Spring Tension, Shock Compression and Shock Rebound. Of these. I will attempt to deal with setting your caster, camber and toe.

I will be using a set of what looks to be +2 Full Flight A-arms for a YFZ450 with YFZ450 shocks.

Lets start with a brief rundown of what these three terms mean:

CASTER:

Caster is the amount of angle that the spindle has in relation to the vertical centre line of the wheel.

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If the upper ball joint is further forward than the lower ball joint, it is said to have negative caster. If the upper ball joint is further to the back than the lower ball joint, it is said to have positive caster. The greater the amount of positive caster, the more stable the ATV will be at speed. The less positive caster it has, the easier it will steer and the quicker it will turn. As the spindle is laid back, the tire has to lie over more when the front tires are turned- (much like a Mercedes Benz when they are parked with the wheels at full lock…ever noticed?) This adds stability. If there is not much angle, the wheel will turn more easily, making it quicker and easier to turn.

Now Blaaster was kind enough to suggest that the stock Blaster caster is set at 9 degrees, this is not adjustable on a stock Blaster as this measurement is built into the frame by way of A-arm mounting positions.

Lonestar Racing suggests these settings for Caster:

Motocross: 5 -7 degree
Cross Country: 5 – 7 degree
Sand Duning: 3 – 5 degree
Desert Racing: 6 – 8 degree
Recreational: 5 – 7 degree

Perhaps Yamaha set the Blaster caster at 9 degrees to make it more stable and controllable for beginner riders as it was an entry level bike… this makes sense when you consider how heavy your steering gets when you add front spacers or flip your front rims.

CAMBER:

Camber is the amount of degrees that the tire and wheel is tilted in or out at the top in relation to the bottom of the tire.

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A tire that is tilted in at the top and out at the bottom is said to have negative camber. The further it angles out at the bottom the greater the amount of negative camber.

For positive camber, the top of the tire is further out than the bottom. The reason for having camber in your front end is because your suspension is forced over in a corner and in doing so, the suspension flexes. With everything in motion, all this force wants to flex the tire more upright, or reducing the amount of negative camber.

A tires greatest traction is achieved when more of the tread is in contact with the ground. As the bike enters a corner, the forces tend to bend everything over, adding positive camber. To make sure that the tires greatest amount of tread is in full contact when it is most needed, we set up the front suspension with a negative camber.

Again on a stock blaster your camber is not adjustable!

Lonestar Racing recommends the following camber settings:

Motocross: 1 -3 degree
Cross Country: 1 – 3 degree
Sand Duning: 2 – 4 degree
Desert Racing: 2 – 4 degree
Recreational: 1 – 3 degree

TOE:

The toe of an ATV measures the relation of the leading edge of the front tires to the back of the tires. Toe-out refers to the fact that the front of the tires point out. Toe-in refers to the fact that the front of the tires point in.

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Mostly, the recommend setting of your toe-in is ¼ of an inch.

Now you are able to set your Toe on your stock Blaster!

Now that we have established what is what, we need to learn how to set all of this up accurately and symmetrically.

Before you start, you need to check a few things and make your sure you have all the tools you will need. To start with find yourself a garage or level paved surface, then find a spirit level (bubble level) about 1m long and check the levelness of your chosen surface, you may notice a slight gradient in the case of a garage, this is to allow for water to run out the door and not into the corners, bear this slight angle in mind, although it shouldn’t play a huge role.

Next, make sure all your tire pressures are equal, set your tires just a little above what you normally ride with them at. It is important to remember that while you may need a stand or a jack to get the wheels off and make adjustments, it is vital to replace them and let the bike stand on its wheels when checking the measurements

Other tools you will need include all your necessary spanners, a shorter 500mm spirit level and ideally an angle finder (contractors protractor) or a clinometer, I was lucky enough to have a Brunton geological compass on hand which incidently is able to measure angles by using a small bubble level and a clinometer built in to it. You will also need a steel ruler, a tape measure and a few other goodies like a notebook, pen and a permanent marker.

Your first port of call when setting up is your caster, followed by the camber and lastly, the toe.

SETTING CASTER:

My A-arms utilize heim joints on the upper A-arms which allow for the adjustment of the top A-arm and setting of the caster, some others do not use this system and instead employ a shim system, regardless of which, the measuring of the caster is exactly the same for both, since I have heim joints, I will be explaining this method.

When you get your top A-arms the first step is to screw in the heim joints all the way, once you have them all in, line them up by ignoring half a turn or so in order to get both joints located on the same axis so a bolt can pass through them. Get a permanent marker and make a mark on the top side of the arm and on the heim joint so you know which way is up and so you can count the turns.

here you can see my upper heim joints:

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In order to get your top ball joint behind the back one, you sort of need to twist the arm by turning out only one of the joints, to push the ball joint back, you need to turn the back heim joint OUT, start with 3 complete (360*) turns and leave the front heim at 0 turns, It is handy to have a notebook on hand and keep track of these turns!

Adjusting the heim joints requires you to remove the arm each time and turn the joints, this is a mission but its part of the deal…

Ok so once you have set them as mentioned, assemble the arm, put the wheels back on and let the bike stand on the ground, you may at this point want to simulate rider sag by measuring how much suspension travel you have when you are on the bike and use ratchet tie downs to compress the suspension to the measurement, I for one didn’t find this too necessary because the caster does not change through suspension travel, what is important however is frame angle, if the back is lower than the front, it pushes the bottom ball joint further forward and pulls the top ball joint backwards thus giving more caster than when level, and vice versa for the front end, however in reality, with riding, generally, both front and back will compress at a similar time such as hitting a ditch etc, and although this is very simplified, including suspension travel dynamics will make things VERY complex, for example, do the left and right front suspensions move exactly the same in real life conditions? Not likely and so to keep it simple, I ignored suspension travel, it is important to have the tires on in order to get the basic frame angle right, if you put the front on a stand and lift it up, you are simulating back end compression and thus measuring and setting it up like this will give you false readings.

Ok, so you have 3 turns on the back upper heim joint and 0 on the front, now turn the wheel you are working on the extreme outer limit of its turn and grab your 1m level, position it against the bottom ball joint thread and against the top ball joint thread. If the top of the straight edge leans towards the rear of your quad, you have positive caster. This is what you want. Rest the angle finder on the edge of the straight edge. This will tell you the exact caster setting. You may need to adjust the Heim Joints by turning one in or out more than the other to get the appropriate setting. In my case I used my compass as so…

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Do this for each wheel and make sure they are both the same, I had an issue with the front leg of the upper A-arm hitting my spring and so can only achieve 3.5 degrees of caster before I hit the spring.

Once you have a degree measured and set, you can double check this using god old trigonometry! To do this, measure the distance between the thread of the ball joints, mine turned out to be 190mm, then place your level against the bottom thread and lean it away from the top thread until the level is perfectly level, then measure with a ruler the distance between the edge of the upper ball joint thread and the edge of the level. Mine turned out at 12mm.

Once you have these two measurements, you can do a simple trig calculation to work out the angle, I am looking for angle theta and so use sine-1 = Opposite/hypotenuse to work out the angle of caster, in my case my calculations matched my measurements. sine-1 = 12/190 = 3.6 degrees

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SETTING CAMBER:

It is important to note that you shouldn’t set your camber until you have set your caster, this is because with the heim joints, screwing the joints in or out directly affects your camber as well as your caster and so it is best to set your caster and then fix up the camber afterwards using the threaded ball joints.

Setting the camber is a much easier process. Rest the straight edge of the level against the outside of your front tire (making sure both wheels are pointing straight and you are touching the same part of the tire, top and bottom). The top of the level should lean inward for negative camber. Now put the angle finder against the straight edge and note the reading. If you need more or less camber than you want or need, you are going to have to remove one of the ball joints in order to adjust it. First remove the split pin and castle nut off of the ball joint, then “smack” the side of the spindle right where the ball joint goes through the spindle to jar the ball joint loose. It will take some pressure to remove it, and it helps if you lift up on the arm itself as your hitting the spindle. For more negative camber, turn the upper ball joint into the a-arm (clockwise). Reassemble and recheck, I got mine in at 3 degrees which looks purposeful :)

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SETTING TOE:

There are a number of ways to set your toe, what you want is the front edge of the wheels pointing in a little more than the back edge. It is also vital that your front wheels are in line with your back axle, and thus you must use the back as a baseline to set up the front.

To do this, find two heavy objects, I used a set of axle stands, then get some fishing line, position the stands in front of the bike one in line with the left wheel and one in line with the right wheel about 2m ahead of the bike, then tie the line onto one stand and run it around the back tires, make sure the line catches half way up the back wheels, then run it up the other side of the bike and tie it onto the other axle stand.

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Find your measuring tape and check the distance between the lines just in front of your back tires by running the tape measure under the swingarm, note that reading and then measure between the lines right up at the axle stands, move the stands until you have the same measurement, (line must be square) to make sure your stands are centralized, make sure the lines touch the sidewall of the back tires ever so slightly, if you have a gap on one side, you are probably out of line!

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Now position the front wheels roughly in line by eye, then jump on the bike and centralize the steering bars, grab your ratchet tie downs and anchor the bars in the middle so they do not move.

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Now grab your ruler and measure on each front wheel between the sidewall and the nylon in the front and back of the tire (ahead and behind the centre point of the wheel) you must now turn the tie rods which ever way necessary in order to attain a 3mm difference between the front and back of the tire (toe in) do this to both sides and your toe will be 6mm which is the target.

You may also measure between the two wheels in the front and at the back in order to get the 6mm toe in, which ever method you prefer!

Tighten up the tie rod nuts carefully, remember that each rod has one normal thread and one reverse thread, tighten carefully as not to upset your toe value!

Once you have done this, you are basically done! Stand back and do a visual check, does anything look weird? If so, measure it! Tighten up all castle nuts and ball joint jamb nuts and a-arms nuts, you should be good to go!

Do some test drives and experimentation to work out which is the best caster for you, remember different riding styles and terrains demand different caster settings!

Enjoy
 
The caster on one of my front wheels is off. How can I adjust this on a stock suspension?

Thanks

Caster in not adjustable on the stock setup. What makes you think its off? did you measure it?

Unequal caster is not a good thing, you loose a lot of stability and control at speeds, Inspect oyur A-arms for any bends. Also check your frame carefully.
 
Caster in not adjustable on the stock setup. What makes you think its off? did you measure it?

It is off a considerable amount. I can tell just by looking at it. When you look down at the front of the ATV, the right side wheel sits out further than the left. Is there a specific part of the A-arms that would be most susceptible to getting bent?
 
Caster in not adjustable on the stock setup. What makes you think its off? did you measure it?

It is off a considerable amount. I can tell just by looking at it. When you look down at the front of the ATV, the right side wheel sits out further than the left. Is there a specific part of the A-arms that would be most susceptible to getting bent?

it is typically a bent spindle that thows that off on blasters
 
ya very likely the spindle is bent. It can happen when you roll. Your caster is most likely to be damaged in that event however.

What you can do is this:

Get a steel ruler, put a stand under the front of the bik so the wheels are off the ground. then, select a point on the frame that is accessible with the ruler but is symmetrical on both sides, such as the frame tubes that bend and run vertially down just behind the bumper. This point must be the same on both sides, or you could use the steering stem nut or something that is central to both a-arms sets, left and right.

Then measure from this set point to selected parts on each a arm, Ideally the center of the ball joint bolt will work best. Do this for the upper and lower joint, your measurements should be the same both left and right.

You can also visually inspect the a arms, a point where they may bend is at their ends where they spread taper towards the ball joint. Compare each one carefully.

Best method is to get a stell bar and something you can measure inclination with. Android has a nice Clinometer app you can use on your phone for this. Follow my instructions in the main post to see what your caster is and how much it is out, your target should be 9*
 
Are you talking caster or camber.

Caster is the angle the wheel sits over the vertical in the forward plane.

Camber is the amount the the top of the wheels tip inwards toward each other.
 
Bending of the A Arms in the places circled in red on the pic above will effect camber mainly, however, it depends on the bend, it also effect caster.

Im my opinion, caster problems are either frame or spindle related. But nothing accident derived is ever a text book case.
 
Here are some pictures of my front end.

Horizontal pic- The spindle on the right (looking at the quad) looks pretty much vertical- like it always has. The spindle on the left however is angled. Where the spindle connects to the lower A-arm sits further forward that where the spindle attaches to the upper A-arm.


I noticed the caster was off when I had put my wheel back on the quad after I had it off. I had to replace a front brake cable and figured I should inspect the brake at that time. I tried to loosen the nut that is on the spindle with the wheel off. Could this have bent something?

I have not had time to taken the front end apart yet, but that is my next project.
 

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Looking at that, I can see the gap between the shock spring and upper arm on the right hand kicker side (left in pic) is much smaller than the gap on the other side. I also see the bottom ball joint sticks out further than it should. This will give that wheel MORE CASTER. This would make it VERY heavy to steer.

The A-arm itself looks fine. the front upper arm mounts look fine. get some more pics of the rear upper a-arm mount and some closer pics of the spindle. I cant see whats bent, but you are right, something is very wrong.

I doubt you would have the necessary force to bend the spindle by hand, unless you used excessive leverage on the nut.

Im not sure if this will help, but check it out to get familiar with how things look. Basically, symmetry is the ultimate goal. both sides MUST be exactly the same.

http://www.blasterforum.com/suspens...-450-complete-front-suspension-blaster-36120/
 
I found a kink in the lower frame rail. I think this may be my issue. I have another picture but I can't attach it, I think it is too big even after I made it smaller. You can see the difference in the A-arm angle. I have the quad standing up on its wheelie bar on a level surface.
 

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I found a kink in the lower frame rail. I think this may be my issue. I have another picture but I can't attach it, I think it is too big even after I made it smaller.

uhhhh.... yeah... that's a tweaked frame. time to find a new one if you want it to go straight. lol