View Full Version : Bump Steer,Camber,Toe -in & Out,Caster

11-21-2007, 09:03 PM
Understanding handling and these compenets

11-21-2007, 09:04 PM
What is Bump Steer?

This is when the travel of the suspension changes the tow of the tire from it's set position. The best way to tell you what it feels like is if you've ever ridden an ATV with the wrong toe in setting down the road. It wants to dart from one side of the road to the other without any warning. Just imagine this happening to you while racing and you are fatigued! Talk about a disaster waiting to happen.

How do you know if you have bump steer for sure and how much?

Take off your shocks and measure there overall length from eye to eye. Then measure there shaft length. Subtract the shaft length from the eye to eye measurement. Then align your handlebars so they are straight. Put a jack under your frame and raise it until the measurements from where the shock mounts to the frame to where the shock mounts to the A-arms is equal to your eye to eye measurement. Now take a tow in measurement and write it down. Lower the jack until the shock mount to shock mount locations equals the eye to eye minus shaft length. Measure your toe in again. If it is the same amount of tow in before you lower the quad then you have hardly any bump steer. But if they are different, then you have some bump steer!

Ok, Now that you know you have Bump Steer. How do you eliminate or at least improve it?

The easiest way to accomplish this is by raising or lowering the tie rod ends. This will be a trial and error procedure. I would recommend raising or lowering them at least 1/8" at a time so you can tell much easier which way you need to move them. If bump steer gets worse, then go the other way. The easiest way I have found is to put a washer under the tie rod ends to raise them. In some extreme cases though you may have to cut the tie rod end mounting plate off of your steering stem and relocate it higher or lower on the stem.

11-21-2007, 09:05 PM
What is Camber ?
Camber is the angle of the wheel relative to vertical, as viewed from the front or the rear of the car. If the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber . The cornering force that a tire can develop is highly dependent on its angle relative to the road surface, and so wheel camber has a major effect on the road holding of a car. It's interesting to note that a tire develops its maximum cornering force at a small negative camber angle, typically around neg. 1/2 degree. This fact is due to the contribution of camber thrust, which is an additional lateral force generated by elastic deformation as the tread rubber pulls through the tire/road interface (the contact patch).

11-21-2007, 09:06 PM
What is Toe -in / Toe -out
When a pair of wheels is set so that their leading edges are pointed slightly towards each other, the wheel pair is said to have toe-in. If the leading edges point away from each other, the pair is said to have toe-out. The amount of toe can be expressed in degrees as the angle to which the wheels are out of parallel, or more commonly, as the difference between the track widths as measured at the leading and trailing edges of the tires or wheels. Toe settings affect three major areas of performance: tire wear, straight-line stability and corner entry handling characteristics.

11-21-2007, 09:09 PM
What is Caster ?
Caster is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. If the pivot axis is tilted backward (that is, the top pivot is positioned farther rearward than the bottom pivot), then the caster is positive; if it's tilted forward, then the caster is negative.
Caster ,is the move the a-arm at the point of the chassis front to rear,think of a shopping cart.

This gives you your roll through the corner,the more caster,the more roll and thus the more braking required.
Less caster,and cart will not roll freely.thus requiring less breaking. Greg

11-21-2007, 09:25 PM
Caster is not as important to us (ATV) as with our quarter midget cars,we need roll through in the corner OFF - POWER,but the other three are really important.
I wanted to share my knowledge of these suspension componets and handling characteristics with you all . Maybe this will help you all in the whoops ,or just keeping it straight with less fatigue .
Bringing a little something from the road to the dirt.Greg

11-22-2007, 08:07 AM
You can adjust caster on any quad that uses heim joints on the a-arms (Typhoon). You just move the front of the a-arm forward or backwards by screwing the heim joints in or out. To move the bottom a-arm forward just unscrew the bottom rear heims. You have to reset camber and toe when you get done. I just put some positive caster and negative camber in my kid's Typhoon and it really helped keep it straight through the bumps and made it less twitchy.

11-22-2007, 08:24 AM
You are absolutely right Brian
I did not realize you could move the a-arms forward or backwards at the frame mount . My bad ,
I understand now,adjust one and it moves it back or forward.

11-22-2007, 04:39 PM
Yea, I wish all of them had heims on the a-arms. The only bad thing is when you fool with one adjustment it throws something else out. It takes a little trial and error but when it's dialed in it is so much better.

11-22-2007, 05:05 PM
I could see what else it would effect making that adjustment..
I can see the tires being pulled in when the front heims are lenghtened
In this application you cannot just move the a-arm assembly back or forward and remain neutral in toe and camber.