I'm getting an autocross alignment and was going for -1.5 camber front and -1.25 rear. The alignment guy says the stock eccentrics are only good for +- 1.00 is that true? Do I need to buy something else to get the amount I want?

And why does VBP reccomend less caster for autocross/racing than street?

Thanks!!

 

Castor angle is measured from the vertical.

More castor angle results in more straight line stability - good for normal road and highway driving.

Less castor angle results in easier/quicker steering and subsequently less straight line stability.

You if you need more castor adjustment than the eccentrics provide on the lower control arm then you can shim the upper either fore or aft were it meets the frame. If you shim, that needs to be done first, then dial it in with the eccentrics. by adding shims to the front half of the upper control arm you will increase castor angle. Conversely if you shim the rear portion of the upper control arm you will decrease castor angle.



To help you understand the effects of changing castor angle think of pushing a wheelbarrow. Pushing one in the normal position with the legs just barely off the ground it is very stable to go straight but takes more effort to make a turn. Now if you tip the wheelbarrow up so that your arms are straight out in front of you, you have dramatically decreased the castor angle in the vertical direction and it becomes unstable going straight but changes direction more easily.

If you are looking for another autocross trick, try toeing the front out rather than in. This is called ackerman angle. This again will be detrimental to straight line stability but causes the front wheels to follow a much better track for cornering if the intent is pure autocross.


Hope this helps,

Chuck.

 

Chuck has it right... running less castor will make the car more tossable and provide quicker turn-in, but it can make the car unstable at speed and prone to wander. Typically C5/C6s like more castor than conventional wistom would suggest. Most try to get it up north of 6 near 7 degrees. Less than 6 and most will complain of sloppy handling on track.

As far as camber... you should have no problems getting 1.5 and 1 out of the car, but more than that you'll need a camber kit from Gary Hoffman @ Hardbar. In some cars there are washers/shims under the upper A-arms, you can remove these and get more camber easily.

Also, if your car is street driven keep toe angles set at zero. Typically a track car likes some toe-out up front and toe-in in the rear. This will provide better turn in and the slight toe-in rear will allow the tires to straighten out when the car squats under power and provide better traction.