todinlaw

In my continuing series of questions regarding alignment and track set up. My current Caster setting is 7.80 degrees left and 7.92 right. the max setting I think is 8.83 degrees. I am told that the more caster you run it may make it more difficult to turn the wheel but caster gives you more Negative camber with the wheel turned and less with the wheel straight. With all of our discussions on track settings and camber and toe settings we have not talked about Caster, so are you track junkies adjusting Caster out to the outer range and if so what?

Also I have been trying to use the table that someone sent me to convert the manuals discussion of toe from degrees to inches, so what is the conversion of
front +6' and Rear +13' if anyone has that handy.

Brian S

More caster is great at high speed, but you lose turn-in which you can regain by using 0 toe or toe-out. More caster also lets the car straighten out easier out of the corner as well.

I use 8.2

todinlaw

Thanks Brian, my current caster is 7.8 left and 7.92 right. can you explain what yo mean by "you lose turn-in", i thought that at turn in increased caster enhances the amount of camber you get, but that it makes it a bit more difficult to turn the wheel?

C.J. Ichiban

if you're using caster to lengthen the wheelbase, it will make the car more stable and therefore harder to rotate on entry and exit, so you either have to run different toe settings or increased camber on the front wheels to get some of the turn-in back. My car is set up to shorten the wheelbase in the rear so that it's easier to rotate using the gas pedal.

Brian S

Unfortunately I don't know the physics behind why this is the case, I just know from trying various alignments that when I use around 7 degrees the car will dart to the corner while barely touching the wheel, the car will naturally feel drawn toward corner entry at low speed but it will push when I'm on power exiting a corner or in a high speed bank. When I get around 9 degrees the car tends to wash a bit on corner entry with what I feel is the same speed but exits the corner much better and seems to carry more speed around fast high g corners, I believe because the high caster does not have to fight the camber as much and frees up the car at higher speed.

slingshot

Caster is the agnle of the steering axis, fore to aft.
Picture your car's steering axis as a unicylce. With your unicycle straight up and down (zero caster) you'll have maximum steering response, since your steering input produces 100% response in changing the wheel's direction.
If you manage to defy physics, and tilt your unicycle's seat backwards as you ride (pretty lousy analogy now that I think about it, but too late), you will have increased caster. Now you'll find that your steering input will cause camber to increase and will yield much less change in steering angle, thereby dulling your turn-in.
One way to counteract this loss of turn-in is, as stated above, to make toe as neutral as possible.