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Discussion Starter · #1 · (Edited)
So we all know what castor/camber/toe is.

We know how all of them work and how it affects our car's handling, cornering grip, and tire temperatures.

My questions are as follows.

1) Castor is a calculated number right?
2) How do you calculate castor?
3) How can you calculate camber gain say.. per degree of steering input based off castor.
4) How can I calculate camber loss on the inside tire?

Reason why I'm asking is, assuming most of the corners at my local track requires 45deg of steering input. How much camber can I gain/lose with say 45deg of input.

Just wondering because maybe I can try to maximize castor and minimize my camber so I can brake later, harder and have better acceleration.

Example at what I'm trying to get at.
I require -2.5deg of camber to prevent rollover and have even tire temps.

I currently have -2.25 camber but if I turn my wheel with 1.5deg of castor, it becomes -2.5 camber.
However, if I lower camber to -2.0 and raise castor to 2.5deg, with the wheel turned I still get same -2.5 camber.
 

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K24 > K20
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So we all know what castor/camber/toe is.

We know how all of them work and how it affects our car's handling, cornering grip, and tire temperatures.

My questions are as follows.

1) Castor is a calculated number right?
2) How do you calculate castor?
3) How can you calculate camber gain say.. per degree of steering input based off castor.
4) How can I calculate camber loss on the inside tire?

Reason why I'm asking is, assuming most of the corners at my local track requires 45deg of steering input. How much camber can I gain/lose with say 45deg of input.

Just wondering because maybe I can try to maximize castor and minimize my camber so I can brake later, harder and have better acceleration.

Example at what I'm trying to get at.
I require -2.5deg of camber to prevent rollover and have even tire temps.

I currently have -2.25 camber but if I turn my wheel with 1.5deg of castor, it becomes -2.5 camber.
However, if I lower camber to -2.0 and raise castor to 2.5deg, with the wheel turned I still get same -2.5 camber.
ooo
 

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i thought castor is a measured angle (it is measured in "degrees", afterall)

this is just my theory, so it might be wrong:
- dynamic camber (ignoring the camber gain/lost from suspension motion) is affected by both castor and SAI.
- SAI negates the effect castor.
 

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Caster is the angle from the vertical of the steering axis (Think bicycle steering rake). Whatever your caster angle is, the outboard negative camber will equal the caster angle if the wheel could be turned 90 degrees (which it can't). I'm not sure if the geometry is linear, but you can probably approximate the outboard negative camber as a percent of caster angle, that is a 45 degree turn (half of a full 90 and probably at the limit of real steering) would give you camber equal to half of the caster. A 22.5 degree turn (90/4) would give you camber approximately 1/4 of caster angle. An 11.25 degree turn (90/8) would give you camber approximately 1/8 of the caster angle.
 

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Engineering
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i like where this thread is going too. could learn alot from this thread.
 

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The GREG
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Caster is the angle from the vertical of the steering axis (Think bicycle steering rake). Whatever your caster angle is, the outboard negative camber will equal the caster angle if the wheel could be turned 90 degrees (which it can't). I'm not sure if the geometry is linear, but you can probably approximate the outboard negative camber as a percent of caster angle, that is a 45 degree turn (half of a full 90 and probably at the limit of real steering) would give you camber equal to half of the caster. A 22.5 degree turn (90/4) would give you camber approximately 1/4 of caster angle. An 11.25 degree turn (90/8) would give you camber approximately 1/8 of the caster angle.
Are we certain the numbers aren't exponential? I haven't done these things in years.

EDIT...Bolded it there.
 

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Borrowed this from someone else but here's how you measure castor:
Caster (deg) = (180 / 3.1415) * [(camber1 - camber2) / (turnangle1 - turnangle2)]
Turn angles must be equal and opposite.

Suspension tuning is full of compromises
 

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Discussion Starter · #9 ·
Borrowed this from someone else but here's how you measure castor:
Caster (deg) = (180 / 3.1415) * [(camber1 - camber2) / (turnangle1 - turnangle2)]
Turn angles must be equal and opposite.

Suspension tuning is full of compromises
what numbers do you use for camber1 and camber2 and turnangle1 and turnangle2?
 

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Discussion Starter · #10 ·
Are we certain the numbers aren't exponential? I haven't done these things in years.

EDIT...Bolded it there.
I don't know anything, and I have nothing to back my reasoning. But I would guess it is exponential as well.

But of course like I said, I have nothing to back my reasoning.. just a hunch.
 

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in on this one:)
 

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Discussion Starter · #12 ·
Caster is the angle from the vertical of the steering axis (Think bicycle steering rake). Whatever your caster angle is, the outboard negative camber will equal the caster angle if the wheel could be turned 90 degrees (which it can't). I'm not sure if the geometry is linear, but you can probably approximate the outboard negative camber as a percent of caster angle, that is a 45 degree turn (half of a full 90 and probably at the limit of real steering) would give you camber equal to half of the caster. A 22.5 degree turn (90/4) would give you camber approximately 1/4 of caster angle. An 11.25 degree turn (90/8) would give you camber approximately 1/8 of the caster angle.
Is that based off anything or just your speculation?

I don't know anything about castor but it makes sense at least even if it was just speculation.
 

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Is that based off anything or just your speculation?

I don't know anything about castor but it makes sense at least even if it was just speculation.
Well the uncertainty is not what happens with the wheels straight or with the wheels turned 90 degrees, that much is definite. I was uncertain if the geometry changes between the two extremes, which is where the steering operates, was a linear progression, or more exponential. If you can imagine a bicycle wheel with a 10 degree rake in the steering column, it would have a caster of 10 degrees. If you lay the wheel over so its pointing sideways (90 degrees), the camber of the wheel will be in line exactly with the rake (slant) of the steering column. What happens in between is the question. I will think big thoughts and try to check the geometry in between.:run:
 

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what numbers do you use for camber1 and camber2 and turnangle1 and turnangle2?
camber 1 is the measurement of camber at turn angle 1 and camber 2 is the measurement of camber at turn angle 2. The turn angles must be equal and opposite, so turn the wheel +20 degrees (doesn't have to be 20), measure the camber, then turn the wheel to the -20 degree position (straight ahead obviously 0), and measure camber.

Edit: Like HighRev mentioned, SAI diminishes castor.. just take a look at Realtime's RSX (http://i304.photobucket.com/albums/nn199/18463/Car_Pics/RTR_RSX_front_strut2.jpg)
 

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Discussion Starter · #16 ·
camber 1 is the measurement of camber at turn angle 1 and camber 2 is the measurement of camber at turn angle 2. The turn angles must be equal and opposite, so turn the wheel +20 degrees (doesn't have to be 20), measure the camber, then turn the wheel to the -20 degree position (straight ahead obviously 0), and measure camber.

Edit: Like HighRev mentioned, SAI diminishes castor.. just take a look at Realtime's RSX (http://i304.photobucket.com/albums/nn199/18463/Car_Pics/RTR_RSX_front_strut2.jpg)
Cool.

Sounds like thats why alignment people have to do the sweep from left/right before the alignment is done? Or is that unreleated?

Also what is SAI?

Wish I had my previous alignment spec sheet.

I need to get my shock bracket cut off and welded like the Realtime Racing one so it sits over the balljoint. :p
 

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Cool.

Sounds like thats why alignment people have to do the sweep from left/right before the alignment is done? Or is that unreleated?

Also what is SAI?

Wish I had my previous alignment spec sheet.

I need to get my shock bracket cut off and welded like the Realtime Racing one so it sits over the balljoint. :p
SAI = Steering Axis Inclination. Dialing in more negative camber with plates increases SAI and so decreases the effectiveness of castor, bummer huh?
The stock offset is to allow wider wheels, your going to have to run some aggressive offset wheels in order to replicate what Realtime did.

Edit: look at the new civic, much better.. http://forums.clubrsx.com/showpost.php?p=20220291&postcount=8
 

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Discussion Starter · #18 ·
SAI = Steering Axis Inclination. Dialing in more negative camber with plates increases SAI and so decreases the effectiveness of castor, bummer huh?
The stock offset is to allow wider wheels, your going to have to run some aggressive offset wheels in order to replicate what Realtime did.

Edit: look at the new civic, much better.. http://forums.clubrsx.com/showpost.php?p=20220291&postcount=8
Aggressive offset wheels?

Like my 8 inch wide +30 offset wheels?

How is SAI measured? Why does dialing in camber using plates increase SAI?

Maybe I'll get more camber with slotted shock brackets like the N+.
 

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Engineering
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how about my offset and width :laughing:
never knew what realtime's suspension looked like, maybe i can do something like that....learning alot from this thread
 

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Aggressive offset wheels?

Like my 8 inch wide +30 offset wheels?

How is SAI measured? Why does dialing in camber using plates increase SAI?

Maybe I'll get more camber with slotted shock brackets like the N+.

30 may be enough, measure the gap between your inside wheel/tire and the RSD. I'm about .5" with 235 tires and 17in e45 wheels.

SAI is measured in degrees and is the measurement of the steering pivot line from the front of the vehicle. So basically the top pivot and the bottom ball joint.
 
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