Looking for more caster
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Joined: Mar 2005
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From: Vancouver
jfo,
Low castor by itself is not a problem. As Red-MX5 mentioned, the root cause of castor not able to reach values before damage is the main concern.
Kind of off-topic but regarding effect of castor, it doesn't change steering ratio so changing castor will NOT "slow down" steering to Nascar-style. Like Teamking said, castor increases steering effort and therefore increases steering and road "feel". Also, castor does much more than just that. As Teamking and Twohoos mentioned, castor is like dynamic camber, the bigger the steering angle, the more -ve camber on the outside front wheel.
There's also a less-known effect of castor. Due to the nature of front suspension geometry, castor creates weight-jacking. Say in a left turn, the right front tire gets more -ve camber while the left front gets more +ve camber from the castor. This means that the right front gets lifted up the pavement while the left front gets pushed down. This is like changing corner-weights by shifting weights from right front and left rear to left front and right rear. And that means the right front tire at this point can take more cornering load than the right rear which means reducing the likelihood of understeer.
Low castor by itself is not a problem. As Red-MX5 mentioned, the root cause of castor not able to reach values before damage is the main concern.
Kind of off-topic but regarding effect of castor, it doesn't change steering ratio so changing castor will NOT "slow down" steering to Nascar-style. Like Teamking said, castor increases steering effort and therefore increases steering and road "feel". Also, castor does much more than just that. As Teamking and Twohoos mentioned, castor is like dynamic camber, the bigger the steering angle, the more -ve camber on the outside front wheel.
There's also a less-known effect of castor. Due to the nature of front suspension geometry, castor creates weight-jacking. Say in a left turn, the right front tire gets more -ve camber while the left front gets more +ve camber from the castor. This means that the right front gets lifted up the pavement while the left front gets pushed down. This is like changing corner-weights by shifting weights from right front and left rear to left front and right rear. And that means the right front tire at this point can take more cornering load than the right rear which means reducing the likelihood of understeer.
Thread Starter
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Joined: Aug 2002
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From: Lewisville, TX
I left my house this morning very despondent. After the tuning session I was a bit encouraged. After reading the suggestions/tips/help, I almost smiled. 
I called the body shop that had my car last year. They had the before and after specs for the alignment. Castor before alignment, but after wreck was 3.9. They were able to get both sides to about 5.9 afterwards.
I'm totally confused now, but am ordering another front lower control arm. Because the car has 62k miles and some of those were hard
, should I consider replacing both sides?
I called the body shop that had my car last year. They had the before and after specs for the alignment. Castor before alignment, but after wreck was 3.9. They were able to get both sides to about 5.9 afterwards.
I'm totally confused now, but am ordering another front lower control arm. Because the car has 62k miles and some of those were hard
, should I consider replacing both sides?
Joined: Jun 2003
Posts: 1,352
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From: allentown
I agree with above statements about castor gain and if there were enough adjustments the car could attain the max negative camber and the max positive castor it would be a good thing.
I think if you go for max castor you will not get max negative camber and if you go for max neg camber you don't get as much caster.
Max neg camber would be IMHO more important than caster so I would set that first and let the caster fall where it does.
Unless I am wrong about the toe neg/pos it looks to me like you have toe IN on the front and toe OUT on the rear which would be the opposite. I would have toe OUT on the front for more steering and toe IN on the rear for straight line stability. Correct? If you have toe IN on the front that would affect your turn in--making it slower or not as crisp.
Might as well replace both sides to keep everything even on life cycle unless the arms are horribly expensive.
That and............................forget about all the technical stuff and just drive the car harder.
I think if you go for max castor you will not get max negative camber and if you go for max neg camber you don't get as much caster.
Max neg camber would be IMHO more important than caster so I would set that first and let the caster fall where it does.
Unless I am wrong about the toe neg/pos it looks to me like you have toe IN on the front and toe OUT on the rear which would be the opposite. I would have toe OUT on the front for more steering and toe IN on the rear for straight line stability. Correct? If you have toe IN on the front that would affect your turn in--making it slower or not as crisp.
Might as well replace both sides to keep everything even on life cycle unless the arms are horribly expensive.
That and............................forget about all the technical stuff and just drive the car harder.
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Joined: Feb 2005
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From: MD
skip...
that ground to fender measurment probably isnt that good, I was checking out the numbers I had (I measured mine the same way) and I measured an inch lower on the front and over an inch in the rear.
that ground to fender measurment probably isnt that good, I was checking out the numbers I had (I measured mine the same way) and I measured an inch lower on the front and over an inch in the rear.
Thread Starter
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From: Lewisville, TX
Originally Posted by twohoos,Apr 7 2006, 01:31 PM
Yes, look for bent lower control arm (might not be visibly bent), and/or damaged bushing (see https://www.s2ki.com/forums/index.php?showtopic=165828 ).
Agree w/ teamking on caster. Think of it as "dynamic camber".
Agree w/ teamking on caster. Think of it as "dynamic camber".
I'll check those tonight when I get home from work. Richard, I'll check my manual for the places to measure. Do you track guys go outside oem specs for that as you do on alignment settings?
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Joined: Aug 2003
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From: Lusby, MD
Fore warning that I didn't read the "entire" thread but another tell tale sign sometimes of a problem can be tire wear. Do your front tires look the same in terms of wear? I agree a bent control arm is the first source to check out.
I also agree w/ jfo on the toe recommendation. Usually you want some toe out in the front, and toe in in the rear. The amount is usually driver dependent on what he/she likes. Keeping record of tire temps is also a good way to tell if your toe settings can be hurting or helping you. Toe in in the front if I'm not mistaken can cause the floating feeling you spoke of. Good luck Skip, I hope you get everything figured out.
Ryan B.
I also agree w/ jfo on the toe recommendation. Usually you want some toe out in the front, and toe in in the rear. The amount is usually driver dependent on what he/she likes. Keeping record of tire temps is also a good way to tell if your toe settings can be hurting or helping you. Toe in in the front if I'm not mistaken can cause the floating feeling you spoke of. Good luck Skip, I hope you get everything figured out.
Ryan B.
I read the first post and tried to give feedback?