Janssen Motorsports A-arm Set-Up Guide

Camber

Camber is the amount of tilt measured between the top and bottom of a tire in reference to a vertical plane orientated in the same direction as the vehicles forward motion. The camber of the wheel is typically measured in degrees of tilt. A tire that is tilted in at the top and out at the bottom is said to have negative camber. The farther it angles out at the bottom the greater the amount of negative camber. To obtain positive camber, the top of the tire would be positioned farther out than the bottom.

The reason for having camber in your front end is as follows. As an ATV starts to initiate a turn at speed, the weight of the vehicle in motion (inertia) begins to compress the suspension and the quad starts to dive. The force generated at the contact area between the tire and the ground begins to flex the bottom of the tire under the machine. The flex of the tire as well as the change in attitude of the machine, tries to reduce the amount of negative camber.

A tires greatest traction is achieved when the maximum amount of tread is in contact with the ground. Maximum front tire traction is crucial when trying to turn the vehicle. Therefore, negative camber is added to the front tires to compensate for the cornering forces that act on the vehicle during a turn. The amount of compensation required depends on a number of factors such as the amount of suspension travel, the bike geometry and the type of terrain you plan to ride on. Below is a recommended starting point for your camber adjustment.

Motocross: 4.5 degrees
Cross Country: 4.5 degrees
Sand Dunning: 2 - 4 degrees
Desert Racing: 2 - 4 degrees
Recreational Riding: 1 - 3 degrees

Caster

If an imaginary line were to be drawn that passes thru the center of both the upper and lower heim joints, the angle that would be created between that imaginary line and a vertical plane constructed thru the spindle axle is referred to as Caster. If the upper heim joint is farther forward than the lower heim joint, it is said to have negative caster. If the upper heim joint is farther to the rear of the lower heim 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 the vehicle has, the easier it will steer and quicker it will turn. Below is the recommended starting point for your caster adjustment (not available on most Factory Pro arms excluding those manufactured for both Kawasaki and Suzuki)

Motocross: 4.5 degrees
Cross Country: 4.5 degrees
Sand Dunning: 3 - 4.5 degrees
Desert Racing: 6.5 degrees
Recreational: 3.5 -4.5 degrees

Toe

The toe-in or toe-out of an ATV refers to a measurement taken between the front tires. The first measurement is taken between the leading edge of the two front tires. The second measurement is taken between the trailing edge of the two front tires. The difference between these two measurements is the "toe" of the vehicle. If the measurement taken between the leading edges of the front tires is less than the measurement taken between the trailing edges, the vehicle is said to be toed in. If the measurements are reversed, the vehicle is said to be toed out. An ATV should never be toed out. If an ATV is toed out, it may dart unexpectedly from side to side. This darting effect is magnified in sandy or deep loamy conditions. 

How to set up your new Janssen front end

Before you start this procedure, a few things need to be done first. Make sure your work space floor is completely level. You will need a straight edge and an angle finder (available at your local hardware store). Do no attempt to set up your front end on a stand of any kind. Your quad must have the tires on, inflated to their appropriate operating pressure and in contact with the ground at the desired ride height.

Setting the Caster

This step does not apply to most Factory Pro arms excluding those manufactured for both Kawasaki and Suzuki. Prior to installing you're a-arms, thread the rod ends in all the way on the upper arms. Leave the front rod end alone and back the rearward rod end out (3) complete revolutions. This is a good starting point. Now install you're a-arms. Securely tighten all mounting hardware. Rest the straight edge against the side edge of the upper and lower heim joint threads (side towards the front of the bike). Be sure the straight edge is touching the same section of thread on both the upper and lower heim joints. If the top of the straight edge leans towards the rear of the 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. Adjust the rod ends in or out to obtain the desired caster setting.

Toe Adjustment

To set this adjustment, all you will need is a tape measure. Make sure the handlebars are straight, then make sure both tires are pointing straight forward. To do this, measure from the inside of one tire to a point on the chassis. Make a note of the distance. Repeat this measurement for the other front tire. The reference points on the frame need to be equal distance from the centerline of the vehicle. The measured distances needs to be the same to verify that the tie rod initial settings are equal. Adjust the tie rod ends as needed. Now you may start your toe adjustments. On the leading edge of the front tire about half way up, place one end of the tape measure on the center tread of the tire and take a measurement from the same point on the other tire. Record this measurement. Then repeat this measuring procedure for the rear of the front tire the same height from the ground as you did for the front measurement. Record this measurement. The front measurement needs to be at least 1/4 of an inch less than the rear measurement. Always make equal adjustments to both tie rods. More toe-in will decrease the speed and accuracy of your steering input but will increase stability upon deceleration.

Make sure to completely tighten all nuts and bolts on your new front end. It is recommended that you use Loctite 242 or equivalent on all fasteners.

If for any reason you are having trouble using this procedure, feel free to contact us at            (920) 766-3411       or e-mail us at janssenracing@aol.com

Please Note: These instructions only apply to our sets of a-arms that are adjustable.