Diminishing caster return
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Joined: May 2015
Posts: 209
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From: Richmond Hill, GA
Diminishing caster return
Where is the generally accepted point of diminishing returns on caster at? Planning to roll at 6-6.5 degrees, but it isnt something I've seen discussed much here or elsewhere since not many people are able to adjust their suspension that far. Input welcome. Car has electric PS, steering effort is a non issue.
Last edited by Dietcoke; May 24, 2020 at 06:03 AM.
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I usually like at least 4.5 usually around 5.5 and never more than 6.5 or 7. The more caster you have the more caster jacking. You are jacking the car up on one front corner and down on the other. A little of this can be a good thing as it puts weight on the inside front tire. But too much and you start to have a pretty radical change in corner weights and it feels weird in my experience.
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I'm guessing a lighter Exo with low offset wheels will have generally lower steering effort than a heavier Miata with higher offset wheels. Given that assumption, these are what worked for me on track
Depowered rack and 245's , about 3.5°
Manual rack and 225's, 4.5~5.5°
ELBJ's increase effective caster so I run closer to 3° with depowered rack.
Caster creates weight jacking when you turn the wheel. This is how go karts turn. Ever notice when car is on lift how LF tire swings lower when you steer left? That changes cross weight, increasing LF/RR cross which makes the car easier to turn left. That's "wedge". Stock cars have lots of wedge.
Astute road racers will tune wedge in for each track to optimize for say, prevalent right turns on a clockwise course. Anyway, If your car is generally tight on turn in but neutral mid turn and off, more caster helps to get it rotated in. No real downside other than increased steering effort.
OTOH, if your car is too loose on entry but maintains the good balance through the rest of the turn, more caster is not a good idea.
Caster is just one part of the total recipe for handling balance. So there is no definitive number or direction to go, just an adjustment that works with all your other settings and hardware.
Depowered rack and 245's , about 3.5°
Manual rack and 225's, 4.5~5.5°
ELBJ's increase effective caster so I run closer to 3° with depowered rack.
Caster creates weight jacking when you turn the wheel. This is how go karts turn. Ever notice when car is on lift how LF tire swings lower when you steer left? That changes cross weight, increasing LF/RR cross which makes the car easier to turn left. That's "wedge". Stock cars have lots of wedge.
Astute road racers will tune wedge in for each track to optimize for say, prevalent right turns on a clockwise course. Anyway, If your car is generally tight on turn in but neutral mid turn and off, more caster helps to get it rotated in. No real downside other than increased steering effort.
OTOH, if your car is too loose on entry but maintains the good balance through the rest of the turn, more caster is not a good idea.
Caster is just one part of the total recipe for handling balance. So there is no definitive number or direction to go, just an adjustment that works with all your other settings and hardware.
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Thread Starter
Junior Member
Joined: May 2015
Posts: 209
Total Cats: -171
From: Richmond Hill, GA
I'm guessing a lighter Exo with low offset wheels will have generally lower steering effort than a heavier Miata with higher offset wheels. Given that assumption, these are what worked for me on track
Depowered rack and 245's , about 3.5°
Manual rack and 225's, 4.5~5.5°
ELBJ's increase effective caster so I run closer to 3° with depowered rack.
Caster creates weight jacking when you turn the wheel. This is how go karts turn. Ever notice when car is on lift how LF tire swings lower when you steer left? That changes cross weight, increasing LF/RR cross which makes the car easier to turn left. That's "wedge". Stock cars have lots of wedge.
Astute road racers will tune wedge in for each track to optimize for say, prevalent right turns on a clockwise course. Anyway, If your car is generally tight on turn in but neutral mid turn and off, more caster helps to get it rotated in. No real downside other than increased steering effort.
OTOH, if your car is too loose on entry but maintains the good balance through the rest of the turn, more caster is not a good idea.
Caster is just one part of the total recipe for handling balance. So there is no definitive number or direction to go, just an adjustment that works with all your other settings and hardware.
Depowered rack and 245's , about 3.5°
Manual rack and 225's, 4.5~5.5°
ELBJ's increase effective caster so I run closer to 3° with depowered rack.
Caster creates weight jacking when you turn the wheel. This is how go karts turn. Ever notice when car is on lift how LF tire swings lower when you steer left? That changes cross weight, increasing LF/RR cross which makes the car easier to turn left. That's "wedge". Stock cars have lots of wedge.
Astute road racers will tune wedge in for each track to optimize for say, prevalent right turns on a clockwise course. Anyway, If your car is generally tight on turn in but neutral mid turn and off, more caster helps to get it rotated in. No real downside other than increased steering effort.
OTOH, if your car is too loose on entry but maintains the good balance through the rest of the turn, more caster is not a good idea.
Caster is just one part of the total recipe for handling balance. So there is no definitive number or direction to go, just an adjustment that works with all your other settings and hardware.
Anyway, thanks for the reply. Will start at 5 degrees and then do a session at 4 and one at 6 and see how it feels.
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