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optimum caster

 
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10sec.et
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Joined: 29 Mar 2006
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Location: Houston,Texas
347040.52 points


1969 Oldsmobile Cutlass

PostPosted: Mon Sep 10, 2007 11:13 pm    Post subject: optimum caster Reply with quote

im just curious what caster setting would be best for a street/strip car assuming that there were no physical limitations to prevent one from achieving the "preferred" setting.

i have been told that the more positive caster you can get, the better. i modified the Cutlass years ago and can adjust the caster/camber anywhere i want it. i currently have 10 degrees positive caster. it drives very well (doesnt feel like a barge anymore) but im wondering how this will affect it on the track.

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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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Knarley Darley
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PostPosted: Mon Sep 10, 2007 11:26 pm    Post subject: Reply with quote

I have mine at 8 degrees, and would not recommend any less than 4 on a drag car. Just think of a motorcycle fork the way it rakes forward so if you let go of the bars it would try to track strait or straiten out automatically if it were turned and you let go of the bars. Your upper balljoint should be behind the lower one. If the upper is in front of the lower you are going to crash!LOL 10 degrees is fine except it may feel a little funky when you back up. Most street alignments are at 1/2 degree positive.
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af2
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1933 Willys Coupe

PostPosted: Tue Sep 11, 2007 10:05 am    Post subject: Reply with quote

When I built the front axle for the Willys I put 10* in it. It is very stable at 133 mph. A bitch to turn in a drive way though. Laughing
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squeeezer
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1991 Chevrolet Camaro

PostPosted: Tue Sep 11, 2007 5:43 pm    Post subject: Reply with quote

straight line only vehicle i would take caster8-10 deg positive

if i want a handling car take away a little caster for some negative camber
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af2
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1933 Willys Coupe

PostPosted: Tue Sep 11, 2007 8:02 pm    Post subject: Reply with quote

squeeezer wrote:
straight line only vehicle i would take caster8-10 deg positive

if i want a handling car take away a little caster for some negative camber


Or have both! 10* positive caster and 1* negative camber as my setup is.
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10sec.et
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Joined: 29 Mar 2006
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Location: Houston,Texas
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1969 Oldsmobile Cutlass

PostPosted: Tue Sep 11, 2007 9:14 pm    Post subject: Reply with quote

ok, so i should leave it alone before i f@#k something up Laughing .
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It seems we can look at our magical Balls and come up with a fix?

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clay
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Location: South Carolina
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1972 Chevrolet Nova

PostPosted: Wed Sep 12, 2007 11:10 am    Post subject: Reply with quote

Something Tiremine ran across on the caster subject a while back that is interesting. The caster specs on the older cars I deal with are usually something like -1/2 to +1. This was for two reasons from what he found. One to have light steering and the second is bias ply tires. The theory was that at speed, a bias ply tire actually deforms and this moves the contact patch rearward and has the effect of adding positive caster. Once you install modern radial or steel belted tires that stay rounder, all of a sudden there isn't enough positive caster to give a decent feel at speed. I have +4 in my Nova which was a huge inprovement but I stopped there because of a limitation - I'm sort of balancing between caster and camber. I have about -2 camber now and the more positive caster I put in, the worse camber will get. So I guess I really didn't answer your question, but maybe I provided some information . Clay
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10sec.et
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Joined: 29 Mar 2006
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Location: Houston,Texas
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1969 Oldsmobile Cutlass

PostPosted: Wed Sep 12, 2007 11:19 am    Post subject: Reply with quote

clay wrote:
Something Tiremine ran across on the caster subject a while back that is interesting. The caster specs on the older cars I deal with are usually something like -1/2 to +1. This was for two reasons from what he found. One to have light steering and the second is bias ply tires. The theory was that at speed, a bias ply tire actually deforms and this moves the contact patch rearward and has the effect of adding positive caster. Once you install modern radial or steel belted tires that stay rounder, all of a sudden there isn't enough positive caster to give a decent feel at speed. I have +4 in my Nova which was a huge inprovement but I stopped there because of a limitation - I'm sort of balancing between caster and camber. I have about -2 camber now and the more positive caster I put in, the worse camber will get. So I guess I really didn't answer your question, but maybe I provided some information . Clay



good info. i always wondered why the caster settings were so low and the cars (with new tires) drove like shyte.

actually, my question was primarily directed to those (like yourself) who have to live with "as good as it gets" and i was curious what your settings would be if the limitations were removed.

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clay
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1972 Chevrolet Nova

PostPosted: Wed Sep 12, 2007 12:08 pm    Post subject: Reply with quote

If I had power steering and all limitations were removed, I don't see a problem with +8 to +10 on caster. However with manual steering, I definately noticed an increase in steering effort as af2 mentioned so once again, it's a balancing act. To me, caster is strictly a drivability adjustment. I know it's more than that and one thing that would be interesting to investigate is how increased caster affects other front geometry like ackerman, bump steer, etc. Clay
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squeeezer
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Location: new richmond WI
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1991 Chevrolet Camaro

PostPosted: Thu Sep 13, 2007 12:32 am    Post subject: Reply with quote

well at least caster doesnt wear out your tires

bmw's use alot of positive caster(they use 2 pivot points @ lower ball joint though)they are about -10 deg
thats alot good for high high speeds/stability
camber will wear the shit out of your tires 2 deg negative is way too much (wear the insides outa em)
bmw's also have about -.5 deg camber(cornering)
those are the easy ones to play with

wheather you have a drag car roundy round car or daily comuter
its the tow i wouldnt know how to deviate from the factory specs(deflection at speeds)
i could only guess and test
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