Setting caster without turn plates

Technical and Repair Discussions
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Posts: 740
Joined: Mon Dec 05, 2011 10:03 am
Location: Greenwich, Connecticut
Chassis:
860
PostPosted: Mon Feb 13, 2017 2:25 pm
breton wrote:Make the steering a lot stiffer! If you have scales, take a look at what happens when you turn the wheel lock-to-lock. There will be significantly more weight transfer corner-to-corner (e.g. as you turn the steering wheel right, the left front and right rear will gain weight and the opposite corners will lose weight). Also note the increase in camber on the left front. The car will tend to turn in better due to more favorable camber and initial outside front loading, but may also exhibit mid-corner understeer. This will more dramatic on slow speed corners than high speed, though the increased caster can also be helpful at higher speeds due to stronger self-centering so the car won't feel like it's "hunting" back and forth on the straight (especially if you run toe-out at the front).

I get a bit freaked out when driving someone else's car with low caster as it feels noticeably more "darty" in a straight line (and feels like it has power steering, both in terms of effort and lack of feel). It is easier to feel the limit of the tires with more caster, as the heavier steering effort will change more dramatically when you've reached or exceeded the limits of the tire, giving you more feedback at the limits of the tires.

Downside, high caster angles can be more tiring to drive with the extra effort required, especially with high-downforce tracks and long, high speed corners.


To quote my chassis set-up guru and late friend Joe Stimola when I asked him how much caster is too much? His answer, "as much as you can stand." He explained that's because of advantageous dynamic corner weight jacking (see Bob Breton's post above) when correcting a slide. That's always served me well. I'm running about 5.5 degrees positive caster with no noticeable extra effort.

Now, where that can show up as extra effort is on tighter banked corners like Turn One at New Hampshire where you need beaucoup "top right hand" to force it around.
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