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too much caster ??? UPDATE-FIXED ! #2924862
05/20/21 01:59 PM
05/20/21 01:59 PM
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moparx Offline OP
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what are the symptoms of having too much caster, other than "jacking up" the front wheels turning lock-to-lock while standing still ?
handling symptoms ? road feel ?
can reasonable camber cause issues with too much caster ?
also, how much cross caster is allowable in "normal" circumstances ?
would an X frame chassis flex too much using excessive caster ?
yes, i'm still chasing some issues on a brand "C" for those that remember other questions i have posted in the past.
TIA as always for the wisdom of those way smarter than me, and the opinions thereof. bow
beer

Last edited by moparx; 06/22/21 12:51 PM.
Re: too much caster ??? [Re: moparx] #2924864
05/20/21 02:03 PM
05/20/21 02:03 PM
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What is the car set at now?

Re: too much caster ??? [Re: NITROUSN] #2924881
05/20/21 02:53 PM
05/20/21 02:53 PM
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moparx Offline OP
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caster : left-5.90, right-5.46
camber : left : -1.71, right: -1.24
toe : -1/8"
beer

Re: too much caster ??? [Re: moparx] #2924882
05/20/21 02:55 PM
05/20/21 02:55 PM
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I wonder if "too much" exists, or if one could ever achieve "too much". It seems to me, most like more caster, and settle for whatever they get additional. Only downside at my pay grade I can think of, is the greater steering effort needed with greater caster, and the possible inclination to want "snap back" with extreme caster, if that is possible. It is a question I have never seen raised before. up


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Re: too much caster ??? [Re: jcc] #2924915
05/20/21 03:52 PM
05/20/21 03:52 PM
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moparx Offline OP
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this problem has existed after converting from manual to a 500 series power box using a GM "type 2" pump.
the assist is fine [way better than the "armstrong" box was] however, going down the road, it seems you always have to correct it.
at a minute correction, it seems the box wants to "keep correcting", then you input a minor correction the opposite way, and the box keeps correcting, rinse and repeat.
the pump is over driven now, [this setup is somewhat of a kit application. it came with the bracketry to fit the pump to the engine, but no pulley] but i can't find out what the original ratio was for the pump. it was a four cylinder pontiac application.
i got a flow valve restrictor to try, so we shall see how that goes.
beer

Re: too much caster ??? [Re: moparx] #2925003
05/20/21 08:35 PM
05/20/21 08:35 PM
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Is that the 58 Chevrolet. If so I think there is to much positive caster and to much negative camber. Personally I think you should have 2.5 to 3.5 positive caster, .5 Positive Camber and set the toe a little more 3/16 to 1/4 inch.

Re: too much caster ??? [Re: moparx] #2925027
05/20/21 09:59 PM
05/20/21 09:59 PM
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Originally Posted by moparx
caster : left-5.90, right-5.46
camber : left : -1.71, right: -1.24
toe : -1/8"
beer
my money is on the toe... go out.......

Re: too much caster ??? [Re: NITROUSN] #2925158
05/21/21 12:03 PM
05/21/21 12:03 PM
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Originally Posted by NITROUSN
Is that the 58 Chevrolet. If so I think there is to much positive caster and to much negative camber. Personally I think you should have 2.5 to 3.5 positive caster, .5 Positive Camber and set the toe a little more 3/16 to 1/4 inch.



i'm beginning to think you are right about where this should be set to. and yes, this is the 58 impala.
the flow restrictor helped some, and i have advocated more toe in to my buddy for quite a while.
ek, having less toe in would make it worse, i think.

for those that don't recall, this car came with air bags and [factory] manual steering originally, and that bag setup was a hack install.
the car was not fun to drive, so the first thing done was to install the 500 power box. that was an improvement, but the bag system was constantly acting up. so the next thing done was to replace the front bags with the factory coil springs and new tube control arms, along with all the bushings, tierod ends, etc. the rear bags were also replaced with springs, and while the springs were out, the lower control arms were boxed and all the rear bushings were replaced.
when he took the car in to get aligned, i told him to try to get around 4 positive caster and around -3/4 camber, with 1/8" toe in.
the shop doing the work has been around for almost 70 years, and is considered to be the best in the area. why they ended up with so much negative camber, i can't answer.
also, having 14" tires doesn't help any, even if they are new. [in my opinion]
the problem was there before the tires were replaced, so i'm confident it isn't tire related.
i'll get this thing straightened out eventually, but in all the years i have been playing with cars, this thing is "driving" me nutz ! biggrin
beer

Re: too much caster ??? [Re: moparx] #2925173
05/21/21 12:47 PM
05/21/21 12:47 PM
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It would be interesting to see what the factory PS alignment setting recommendation was.
But I would think it should have more neg caster on the right, and equal camber.
FWIW, and it's a different steering setup, my Duster drag car (Jack Arnew-modified) runs about 7 deg caster and goes straight as a string.
But you wouldn't want to stick your hand between the steering wheel spokes when the steering unwinds...

Re: too much caster ??? [Re: topside] #2925180
05/21/21 12:59 PM
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Moparx, that is a lot of negative camber for a street car. If the tires are narrow, it might be workable, but narrow tires aren't my wheelhouse. On a road course, it would be almost overkill, but would have great "turn-in" until the tires likely wore out. I would dial that camber number back first and see what improvement it makes. No way your posted caster numbers are overkill IMO.


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Re: too much caster ??? [Re: topside] #2925187
05/21/21 01:03 PM
05/21/21 01:03 PM
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Originally Posted by topside
It would be interesting to see what the factory PS alignment setting recommendation was.
But I would think it should have more neg caster on the right, and equal camber.
FWIW, and it's a different steering setup, my Duster drag car (Jack Arnew-modified) runs about 7 deg caster and goes straight as a string.
But you wouldn't want to stick your hand between the steering wheel spokes when the steering unwinds...


This should be factory specs. Caster-Zero, Camber +1/2 deg. Toe-In Inch 1/32-3/32

Re: too much caster ??? [Re: moparx] #2925190
05/21/21 01:07 PM
05/21/21 01:07 PM
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Originally Posted by moparx
Originally Posted by NITROUSN
Is that the 58 Chevrolet. If so I think there is to much positive caster and to much negative camber. Personally I think you should have 2.5 to 3.5 positive caster, .5 Positive Camber and set the toe a little more 3/16 to 1/4 inch.



i'm beginning to think you are right about where this should be set to. and yes, this is the 58 impala.
the flow restrictor helped some, and i have advocated more toe in to my buddy for quite a while.
ek, having less toe in would make it worse, i think.

for those that don't recall, this car came with air bags and [factory] manual steering originally, and that bag setup was a hack install.
the car was not fun to drive, so the first thing done was to install the 500 power box. that was an improvement, but the bag system was constantly acting up. so the next thing done was to replace the front bags with the factory coil springs and new tube control arms, along with all the bushings, tierod ends, etc. the rear bags were also replaced with springs, and while the springs were out, the lower control arms were boxed and all the rear bushings were replaced.
when he took the car in to get aligned, i told him to try to get around 4 positive caster and around -3/4 camber, with 1/8" toe in.
the shop doing the work has been around for almost 70 years, and is considered to be the best in the area. why they ended up with so much negative camber, i can't answer.
also, having 14" tires doesn't help any, even if they are new. [in my opinion]
the problem was there before the tires were replaced, so i'm confident it isn't tire related.
i'll get this thing straightened out eventually, but in all the years i have been playing with cars, this thing is "driving" me nutz ! biggrin
beer



If you really want your friend to make this car better get it aligned to the specs I posted. Another thing is mis-matched incompatible parts such as pitman, idler and center link. If all is ok then get it aligned.

Re: too much caster ??? [Re: NITROUSN] #2925201
05/21/21 01:31 PM
05/21/21 01:31 PM
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moparx Offline OP
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from what i have seen over the years, most "old" cars used positive camber because of the bias ply tires ?
i agree that the camber needs dialed back as well, maybe to a -3/4 or so.
and yes, i firmly believe the caster on this setup [now] is, or should be, good.
for the last couple of months, my knees and hips have been giving me tons of problems, so i haven't been crawling under this thing much.
i need to get under it again and just lay there looking, maybe seeing something i may have missed.
i do remember when the power box was installed, the crank pulley added to run the pump kissed the factory sway bay, so it was removed.
i have often wondered if spacing it slightly down and slightly forward to clear the pulley, and reinstalling it, would change anything.

so far this spring, there have been other projects coming and going before jumping back to this one.
a new front driveshaft section was built [the old shaft section ahead of the carrier bearing was too short and the joints were clocked off quite a bit] and a change to 3.08 gears from 3.36's were done first before getting back into the steering issue.
a couple of things i have discovered this year for sure. the older i get, the "dummer" i am, and fridays come lots "quicker" these days ! laugh2
beer

Re: too much caster ??? [Re: moparx] #2925204
05/21/21 01:35 PM
05/21/21 01:35 PM
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and yes, i'll get the car re-aligned. this time, i'll go with him so it's to your specs !
beer

Re: too much caster ??? [Re: moparx] #2925209
05/21/21 01:47 PM
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Originally Posted by moparx
and yes, i'll get the car re-aligned. this time, i'll go with him so it's to your specs !
beer


You need to do it. Right now you have way to much caster, way to much negative camber and the toe needs to be in not out. Once you hit those numbers you can then deal with other possibilities.If you can not align it to those specs I suspect there is an incapability in the parts and with geometry being off that is most likely the issue. If that car was to come to me that is what I would have it aligned to. If the customer wants to debate the reasoning he can go and argue with someone else. I could be rich if I could fix stupid.

Re: too much caster ??? [Re: NITROUSN] #2925276
05/21/21 05:02 PM
05/21/21 05:02 PM
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Why too much caster for OP?
I believe the goalposts on caster settings have moved since 1958, when cars were often manually steered, and steering effort was a concern.


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Re: too much caster ??? [Re: jcc] #2925324
05/21/21 09:08 PM
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Excessive caster may be a possibility. You have 2 numbers that dictate steering centering, kingpin angle and caster. One or the other is going to be what determines centering, generally they are far enough apart that it's clear which one is the dominant factor.

You might have them close enough that the physics is confused and it's not clear which one is doing the centering.

My understanding though is that when this happens, you get a shimmy or death wobble.

Do your alignment printouts list kingpin angle? Note it might be called SAI. Or if included angle is listed we can calculate it.

Edit, have you tried driving it with the belt off the pump?

Last edited by ruderunner; 05/22/21 07:03 AM.

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Re: too much caster ??? [Re: ruderunner] #2925399
05/22/21 07:55 AM
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Kingpin angle is not normally an adjustable setting as i understand it. If that is the case, why does matter if its at its OEM number?
I also am uncertain how it plays much of a part by itself in "centering".
care to explain?


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Re: too much caster ??? [Re: jcc] #2925502
05/22/21 12:58 PM
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kingpin/steering axis inclination is the imaginary line formed by the tilt inward of the upper ball joint [or kingpin] from true vertical compared to the spindle's horizontal line. this is controlled by the way the spindle is made, so it is a segment that can't be changed.
it's purpose is to place the vehicle load on the road contact patch of the tire, providing better tracking and easier steering.
this only works for OEM applications, using the parts designed for the vehicle in question.
any mix and match of control arms, spindles, and wheel offsets throws this spec out the window.
a guy can math out the original setup then do the same after the parts used to see how far off or close you come to OEM, but it is hardly, if ever, done.
beer

Re: too much caster ??? [Re: moparx] #2925584
05/22/21 05:06 PM
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Correct, kingpin is a manufactured number not adjustable. It does affect centering, think of a crooked gate hinge, the gate will stay at the low point. It's just opposite in a car as the weight of the vehicle is pushing down.

Most SLA cars rely on caster for centering , strut front ends tend to favor kingpin angle. One or the other is needed for centering, if they are too close stability can be compromised.

I guess one way to think of kingpin angle is caster rotated 90 degrees. Not front to back but side to side.


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