ideal caster degree

[72ratnova]

what is the ideal caster degree. i see Detroit Speed is adjustable, global west is 6 degrees and others i see is 4 degrees. does is matter?

[JRouche]

Great question. Cause really, caster is one of those settings that has alot of latitude. Not like toe adjustments, small changes make for some big handling issues. Camber, same thing, ya kinda want to run straight up, but more to a lil neg, say like .5 degrees, too far over and you will be eating tires and lose strait line traction.

So we like to have our street driven cars with the tire fairly straight up and down, a lil camber to tilt the tire in, but not much. We hope for some decent camber gain so when the car rolls into a turn we still have the tire contact patch square to the road surface.

Thats where caster comes into play. Straight line positive caster settings can make the car track straight and not wander all over the road. So we dial in some positive caster.

And if you go by the factory specs its a minor positive caster setting. Why so small?? Well, they need to be driven by everyone. Too much caster makes the car a bear to turn in the turns. So they prescribe just enough to get a straight line tracking and cut it off (pos caster) before it becomes a problem.

What is nice about some major caster is it helps the poorly designed suspensions, yeah, the early GM cars for one. They have a poor camber gain, if any. Thats why you see all the tall ball joints, spindles and mods. Trying to get a better camber curve.

Well when you toss the spindle way back on top, major positive caster, you get some camber gain on bump in a turn. And thats where it counts. No camber gain on bump in the straights, that can cause issues. But on a fast turn, the positive caster brings the top of the tire in. And its the outside tire that gains. And it just happens to be the tire taking most of the turning load. So as that wheel is turned in with a positive caster the top of the tire gets pulled in giving you some camber gain. And really, its only alot at full turn which you wont be taking a fast turn with that much wheel angle. But its a lil bit more than if you were to have say 1* of caster VS 6* of caster.

Its a trade off. Too much caster?? Whats the number?? Depends on the car. 6* of static caster on one car will make it VERY heavy and feel like a pig. It will feel heavy and slow at the front even though its a light car. Not good. On another car that is heavy and has power steering it may not be noticed that much.

Like everything on a car, or any system where sub systems have to work together, too much of a good thing can be bad for the whole system.

It sucks to be sure. It would be nice to pump each individual component up to the maximum of its positive value. But in the real world those subsystems have to interact with other subsystems. And when they do too much of a good thing it will interact with the other adjustments and make it not fun to drive.

I say keep within the 4 to 5 degrees of pos caster. If you have power steering go for 5-6 degrees.

My car? Manual rack and pinion steering and 5.5 degrees of caster at ride height.

But total caster isnt linear for camber gain. On my car the caster induced camber gain doesnt happen till the wheel is way over past 10* of steering input. Thats way too far for any speed turns. So the camber gain prolly wont see any benefit on the track or road. Keep that in mind. Major caster wont be seen for camber gain till the steering wheel is cranked over. And on any fast turns you may not even get into the benefits of the camber gain with a major pos caster. So you will be losing trying to gain.

So dont toss out any handling (road feel and steering sensitivity) for a possible camber gain with an extreme caster setting. The auto manufactures went all through this already. And they gave us the best of both worlds in their eyes..... Dont go overboard... Too much is too lil sometimes... JR