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How Much Caster?

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#1
bmarshall1

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On my 99- about 3.4 degrees of front camber is what I think I'll be shooting for, no rake, about (1) 'Frank Finger'  of ride height, mid-pack driver on Bilsteins.  Give me an idea of what caster setting I want. Thanks!

 

Also since I'm here.  Is there a proper sequence such as rear cams first, set caster, then mover to front cams or something of that nature.  It seems I get caster set, then camber is off, then I set camber, and caster is off.  I read the set-up guide V2 but it really only states to set max caster with rear cam and go from there.



#2
Jim Drago

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On my 99- about 3.4 degrees of front camber is what I think I'll be shooting for, no rake, about (1) 'Frank Finger'  of ride height, mid-pack driver on Bilsteins.  Give me an idea of what caster setting I want. Thanks!

 

Also since I'm here.  Is there a proper sequence such as rear cams first, set caster, then mover to front cams or something of that nature.  It seems I get caster set, then camber is off, then I set camber, and caster is off.  I read the set-up guide V2 but it really only states to set max caster with rear cam and go from there.

 

I typically run +6 on dominant side and 5.5 on the other side. ( I don't subscribe to max caster) 

 

I typically start with caster adjusters at 12 o' clock ( dead center)  Set approximate ride height, then I set camber, then I set toe.  You will need to go back then and check camber and heights and caster again, sometimes 3-4 times bc as you said each can effect the other. You want all close and make very small adjustments as you get close to desired numbers


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#3
bmarshall1

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Thanks Jim - I assume the dominant side is the outside tire in a corner?

 

So, if I have this straight (and this may help other newbs)  The REAR cam (attachment point) is the 'caster' cam as it adjusts the caster by .401 degree per graduation and camber by only 3/10 degree per adjustment graduation (.03) - (per the shop manual).  It was a little difficult for me as the Shop Manual deals in positive and negative, so twist the cam to 'positive' which to me means more, but it means less negative (we're used to saying "We need more camber"); I think I have my chart correct.

 

 

                                    FRONT CAM      (CONTROL ARM ATTACHMENT POINT)  .401/.408 degree per graduation hashmark

         left                                                             right

CASTER    +.401 deg.   MOVE ARM IN    +.401   CASTER (more)

CAMBER   -.408 deg.                                 -.408   CAMBER (less)

 

CASTER    -.401 deg.   MOVE ARM OUT  -.401   CASTER  (less)

CAMBER   +.408 deg.                                  +.408   CAMBER (more)

 

 

                                    REAR CAM caster cam (CONTROL ARM ATTACHMENT POINT)  .401/.03 degree per graduation hashmark

 

CASTER    -.401 deg.    MOVE ARM IN    -.401    CASTER   (less)

CAMBER   - .03 deg.                                  - .03     CAMBER (less)

 

CASTER   +.401 deg.  MOVE ARM OUT   +.401   CASTER   (more)

CAMBER  + .03 deg.                                   +  .03   CAMBER  (more)



#4
bmarshall1

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Jim - help me understand the relationship of more caster on the dominate side.  When I think of a lot of caster, I think of a Harley Chopper - turn the wheel (handlebars) and the wheel turns but also literally flops over, dramatically increasing camber.  Whereas if the wheel is has 0 caster the camber upon turning does not change.  So - by having more caster on the dominate wheel (say LF tire on a right hand turn), I am increasing the camber while turning on the left side only more as compared to the right side, correct?

 

Doe the camber increase on the non dominate tire in the same situation?



#5
Jim Daniels - FIG

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Stock car stuff.  Always turn left.....

 

So, higher right side caster increases the wheelbase on the right. Less caster on the left decreases wheelbase on that side.  This allows less scrub at the apes etc.... in the dominant turns.  Caster was and is always a secret with my setups. 

 

When I run circle stuff the car wants to turn left when you take your hand off the wheel.  SM does not need that much, well except at Lime Rock, but you get the idea. 

 

Ackerman needs to be factored in as well of course. 

 

JD


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Tom Sager

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Stock car stuff.  Always turn left.....

 

So, higher right side caster increases the wheelbase on the right. Less caster on the left decreases wheelbase on that side.  This allows less scrub at the apes etc.... in the dominant turns.  Caster was and is always a secret with my setups. 

 

When I run circle stuff the car wants to turn left when you take your hand off the wheel.  SM does not need that much, well except at Lime Rock, but you get the idea. 

 

Ackerman needs to be factored in as well of course. 

 

JD

Hi Mr. Jim.

 

Ah yes, Ackerman or lack of it if you're driving an NA. Last time I checked an NA at racing ride height when cornering and wheel turned loses ackerman as you turn the wheel.  It's still fun standing on this soapbox. 


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#7
Jim Daniels - FIG

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Now that would depend on many many manipulations that still meet stock specifications.

That's before we even talk about actual toe settings at static ride heights.

I wrote a guide once upon a time. I did not say it's what I actually use....... JK

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#8
bmarshall1

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Stock car stuff.  Always turn left.....

 

So, higher right side caster increases the wheelbase on the right. Less caster on the left decreases wheelbase on that side.  This allows less scrub at the apes etc.... in the dominant turns.  Caster was and is always a secret with my setups. 

 

When I run circle stuff the car wants to turn left when you take your hand off the wheel.  SM does not need that much, well except at Lime Rock, but you get the idea. 

 

Ackerman needs to be factored in as well of course. 

 

JD

Hi Jim - long time no see, you were my 'pit crew' many years ago at Summit Point when getting licensed.  We had Sun, Rain, and Snow all in the same weekend (April if I recall).  Thanks for the explanation on caster, it all makes a more sense.

 

Other than wanting to turn, I assume unequal caster will also help the car stay planted and maximize grip in the corners?



#9
Jim Daniels - FIG

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Hi Jim - long time no see, you were my 'pit crew' many years ago at Summit Point when getting licensed.  We had Sun, Rain, and Snow all in the same weekend (April if I recall).  Thanks for the explanation on caster, it all makes a more sense.

 

Other than wanting to turn, I assume unequal caster will also help the car stay planted and maximize grip in the corners?

 

Howdy, yes more grip for sure.  But, don't have a split more than 2 degrees, can get a caster shake under braking. 

 

I won the 2006 MX5 cup race at Lime Rock.  I had never been to the track, sim practice only.  Also, I had a function with my kids and missed all practice sessions.  I put the car on the pole in a single 20 min session and won the race.  My secret, asymmetrical setup, camber and caster etc.... Total guess with no testing but it was good enough...... 


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