Castor??
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Caster
My ailignment shop guys are idiots. They could not get the caster in spec on the drivers side and so it pulls ever so slightly to that side. It did not pull at all before the alignment and my tires never wore uneven... I did just replace all of the control arm bushings with poly. I would like to experiment a little with the caster and I have searched the threads and have read conflicting posts on which shims to add or remove that will add or subtract caster and how that affects camber, Thanks!
Last edited by 81pilot; Aug 11, 2011 at 08:55 PM.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Increasing the number of rear shims in relation to the front increases caster. If static camber is already correct, generally speaking you'll need to split the difference to increase caster by adding about half as much shim at the rear while removing that approximate amount at the front. However, the ratio isn't linear as the CA shaft rotates further from parallel with the chassis, and you want the upper ball joint's distance from chassis CL as seen from above to remain constant to maintain a given static camber. If caster is already correct, pretty much add or subtract the same amount of shim front and rear to adjust camber. Hope that helps.
Oh, and to what specs? Not just any may suit your driving preferences, and some allow for quite a bit of tolerance.
TSW
Oh, and to what specs? Not just any may suit your driving preferences, and some allow for quite a bit of tolerance.
TSW
Last edited by TheSkunkWorks; Aug 7, 2011 at 04:47 PM.
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Increasing the number of rear shims in relation to the front increases caster. If static camber is already correct, generally speaking you'll need to split the difference to increase caster by adding about half as much shim at the rear while removing that approximate amount at the front. However, the ratio isn't linear as the CA shaft rotates further from parallel with the chassis, and you want the upper ball joint's distance from chassis CL as seen from above to remain constant to maintain a given static camber. If caster is already correct, pretty much add or subtract the same amount of shim front and rear to adjust camber. Hope that helps.
Oh, and to what specs? Not just any may suit your driving preferences, and some allow for quite a bit of tolerance.
TSW
Oh, and to what specs? Not just any may suit your driving preferences, and some allow for quite a bit of tolerance.
TSW
It had great straightline stability and turned very quickly. I assume that is oversteer, whatever it is called I really liked it. Now it does not turn as quick and has a slight left pull. So I would add a shim at the rear and add half that amount at the front of the control arm shaft to increase caster and keep the camber or do I just move a shim from the front to the back?
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
For fine adjustments, I'd start by moving a shim of half the total adjustment desired from the front to the rear to increase caster without significantly affecting camber.
FWIW, what you describe is turn-in responsiveness. Oversteer is when the tail is trying to come around.
FWIW, what you describe is turn-in responsiveness. Oversteer is when the tail is trying to come around.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 71
From: Oxford MA-----You just lost the game!!!!
My ailignment shop guys are idiots. They could not get the castor in spec on the drivers side and so it pulls ever so slightly to that side. It did not pull at all before the alignment and my tires never wore uneven... I did just replace all of the control arm bushings with poly. I would like to experiment a little with the castor and I have searched the threads and have read conflicting posts on which shims to add or remove that will add or subtract castor and how that affects camber, Thanks!
I'm just messin' with ya, buddy!! Front suspension and steering geometry is alot more complicated than the rear suspension is. If you are not confidant that you have a pretty good idea of what you are doing, my advice would be to take it to another shop with a good reputation. At least to get it to a known good baseline to work your experiments from.
Scott
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
What a buncha knuckleheads!!! They probably can't even spell caster correctly!!! Ohhhh........wait..........ummmm........ never mind.
I'm just messin' with ya, buddy!! Front suspension and steering geometry is alot more complicated than the rear suspension is. If you are not confidant that you have a pretty good idea of what you are doing, my advice would be to take it to another shop with a good reputation. At least to get it to a known good baseline to work your experiments from.
Scott
I'm just messin' with ya, buddy!! Front suspension and steering geometry is alot more complicated than the rear suspension is. If you are not confidant that you have a pretty good idea of what you are doing, my advice would be to take it to another shop with a good reputation. At least to get it to a known good baseline to work your experiments from.
Scott
If I want to retain the static Camber, I must keep the relative front/rear distance the same, which would mean if I add a shim front or back I must remove the same size shim on the opposite end. To adjust Camber you move it in or out equally after the caster is set. Toe is easy. Got it, just had to read a tad more.
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
7 Bolt-On Upgrades From Extreme Online Store to Level Up Your C6 Corvette
Pouria Savadkouei
How Likely Are These Five 2027 Corvette Rumors to Be True?
Brett Foote
9 Best Corvettes You Can Buy for Half Price (& 1 You Should NEVER Buy!)
Joe Kucinski
8 Very Best Corvettes of Amelia Island 2026
Joe Kucinski
Top 10 WORST Corvette Engineering Failures of All Time!
Joe Kucinski
10 Records the C8 Corvette Generation Has SMASHED (& 1 Glaring Failure)
Joe Kucinski
7 Wildest Corvette Concepts Ever Made
Brett Foote
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 71
From: Oxford MA-----You just lost the game!!!!
Nah. I learn things quickly. I fully understand the geometry now, and will buy the proper tool to do it myself from now on.....and I realize I spelled Caster wrong, maybe it was all those tramatic instances with Castor oil as a child!
If I want to retain the static Camber, I must keep the relative front/rear distance the same, which would mean if I add a shim front or back I must remove the same size shim on the opposite end. To adjust Camber you move it in or out equally after the caster is set. Toe is easy. Got it, just had to read a tad more.
If I want to retain the static Camber, I must keep the relative front/rear distance the same, which would mean if I add a shim front or back I must remove the same size shim on the opposite end. To adjust Camber you move it in or out equally after the caster is set. Toe is easy. Got it, just had to read a tad more.
Well, OK then, carry on! Let us know how it works out, will ya?
Scott
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
I sure will. I didn't intend to sound arrogant. I just really enjoy the satisfaction of learning new things and using that knowledge especially on a car. Suspension is one thing I have always had shops do. I always did my engine and tranny work. So I might as well do this as well. Thanks for the help to everyone.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 71
From: Oxford MA-----You just lost the game!!!!
I sure will. I didn't intend to sound arrogant. I just really enjoy the satisfaction of learning new things and using that knowledge especially on a car. Suspension is one thing I have always had shops do. I always did my engine and tranny work. So I might as well do this as well. Thanks for the help to everyone.
Scott
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 71
From: Oxford MA-----You just lost the game!!!!
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
I wish I could correct the spelling of Caster in the title (mods help please) so this thread maybe can help someone........I did learn something through my research. I was getting confused with various different sights, some saying add at the front to increase Caster and some saying add at the back....then I figured out why. On some vehicles the upper arm is mounted outside of the frame, on ours they are mounted on the inside of the frame. Where they are mounted determines the shims addition or subtraction to change the axis.....a good thing to know when surfing for various opinions..... To increase Caster on our C3's you must add shims to the rear of the upper arm....I think my alignment guy had settings crossed, or was thinking you always do it the other way. I have no shims on the rear and he said it needed more caster and had no room to remove any since there were none, when all along he should have added them, I will test this when I get home....Thanks All!
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Update
My ailignment shop guys are idiots. They could not get the caster in spec on the drivers side and so it pulls ever so slightly to that side. It did not pull at all before the alignment and my tires never wore uneven... I did just replace all of the control arm bushings with poly. I would like to experiment a little with the caster and I have searched the threads and have read conflicting posts on which shims to add or remove that will add or subtract caster and how that affects camber, Thanks!
I complained with a well worded letter to the effect that the tech did NOT know what he was doing and why he was wrong with facts when he told me that to add caster you need to remove rear shims on the upper arm, and I had none to remove aso my frame was bent and I needed offset shafts and then bring it back. But ours(c3's) require adding shims on the rear to increase caster (due to the upper shaft mounting inboard of the frame. ....which is exactly what I did and it tracks dead straight.(removed one from the front and added to the back to keep Camber close) The shop manager called and was a good guy and is giving me all my money back on the crappy alignment. From now on IF...I ever have someone else do an alignment it will be the only good alignment shop in town and NOT the tire shop. I will still buy tires from them but never recommend them for actual service. So they did the right thing, I have no ill feelings except for the tech that acted like a jerk when he told me about it. I think I know more about alignments than he does now....
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Measuring caster
With the suspension settled on level ground, turn the left front wheel to the left 20*, then level and zero the gauge. Next turn it 20* the opposite direction, level the gauge and read your caster angle. Repeat for the right front, first turning it to the right.
Any difference is cross-caster, which IMCO is undesirable in a sportscar. As this is one of those places where "garbage-in-garbage-out" axiom applies, the more accurate is your work the more accurate will be your results.
FYI, a set of 8 commercial grade vinyl floor tiles and some grease can make for a decent set of poor-man's turntables.
Any difference is cross-caster, which IMCO is undesirable in a sportscar. As this is one of those places where "garbage-in-garbage-out" axiom applies, the more accurate is your work the more accurate will be your results.
FYI, a set of 8 commercial grade vinyl floor tiles and some grease can make for a decent set of poor-man's turntables.
TSW