[george kujanski]

So I need my memory refreshed......on an "A" body....

If I want to add positive caster without messing up anything else, removing a shim from the front bolt and adding it to the rear bolt does the trick, right?

Also, any idea what the relationship of the shim thickness and the change in caster is, if the above is true?

George

[Skip Fix]

Generally yes all cars trucks the further in the rear of the control arm goes the more positive caster you get. Limiting factor to get a lot of positive caster is bolt length or hitting steering shaft with the back of the control arm

My Firebird shop manual actually has a whole page chart of how many shims to add/subtract front and rear to get from one setting measured to where you want it. I'll tak a look and see what it is.

[JLMounce]

Your method will add possitve caster, yes. Whether it effects other angles, that's hard to say.

Depending on how the car is currently aligned, that may or not may not be possible. There's just not much adjustment with stock components. It becomes easier however as you dial in static negative camber. This, due to extra stacking of shims, that then allow you to remove shims or add them.

I wouldn't know where to start on the relationship of shim thickness to angle changes. I know that it's not a 1:1 ratio.

Given the changes you are trying to make, I'd opt to have a full alignment done. Either by a shop you trust or by yourself. Speedway makes an economy camber/caster gauge that doesn't break the bank at under $50.00.

https://www.speedwaymotors.com/Speed...iABEgJBP_D_BwE

As I mentioned before, I'm not certain about your method not changing the camber angle. If you are looking at the upper control arm top down, based on where the alignment measurements are occurring, the ball joint is moving in an arc and is fixed to the spindle. This means that as you add positive caster, you're moving the ball joint along that arc, about the center of the upper control arm pickup points. Since the spindle doesn't stretch, moving in this arc will pull the arms closer together. Since the lower control arm is not pivoting around the arc, this will also tend to move the spindle inboard, creating additional negative camber.

That's actually how caster works in the first place and why on this type of suspension setup, you want more.

This action on the spindle will also have some effect on the toe setting as the spindle relationship to the steering components has now statically changed.

Now is the maybe degree or so of extra caster angle you're adding going to make that big of a difference? I don't know, but I wouldn't think so. But another reason to do the whole alignment when doing this.

[Skip Fix]

As Jason said one change actually tweaks all the settings. Toe in camber and caster.

I've tried some of the less expensive front end gauges ended up best was a Longacre that has dual "bubbles. The a less expensive($100) ebay adjustable wheel attachment as the Longacre has a magnetic base-an does not work on aluminum wheels.

[Geoff]

George,
You are correct. But it also changes toe in & camber. I played around with my 66 with the shim trick [ one shim ] & didn't notice any difference driving the car. Not until I bought aftermarket upper arms that were adjustable & I was able to set caster at 4* did I notice two things: better straight line stability & some steering return on corners [ power steering; probably more noticeable with man steering ].
I used SPC adjustable upper arms, as they were the only adj arms I could find that had rubber bushes, something that I think GM got right...

[Skip Fix]

Here is the shop manual chart.

[Keith Seymore]

Originally Posted by Skip Fix

As Jason said one change actually tweaks all the settings. Toe in camber and caster.

I've tried some of the less expensive front end gauges ended up best was a Longacre that has dual "bubbles. The a less expensive($100) ebay adjustable wheel attachment as the Longacre has a magnetic base-an does not work on aluminum wheels.

Off topic but here goes: for use with aluminum wheels, could you use 3M double sided tape (or hot glue) to stick to the wheel?

I have some work to do to my truck, which does have aluminum wheels.

K

[george kujanski]

Thanks all for the responses.

First, I'm not against getting a proper alignment done, this is more of an experiment to see if more caster would be beneficial. If so, that would be my target when I take it to an alignment shop.

The existing alignment was done REALLY long ago so I don't even know what it is, therefore it needs to be done anyway. Assuming it is at OEM specs, (that's what a shop would normally do, right), just shotgunning it towards a target number was my thought, hence the idea of knowing what shim sizes would need to move.

I'll use the chart to try some adjustments, but a question: for better handling on an otherwise stock setup, what would be some good target numbers for caster, camber, toe?

Thanks again.

george

[Skip Fix]

Keith the wheel attachment works great and is adjustable and get tight on the wheel. Really makes it easy and repeatable. I had bought one of those Quick Trick Aligment kits that has a bracket to attach to the wheel but does not really grip it well. Also uses a level on the bracket to measure for camber and cater sweep. Since the bracket just hangs there is way too much freeplay to be repeatable. It is good for measuring toe in/out. You can put the tires on double plastic bags for a cheap turntable but you can get cheap ones on E bay also.

Did the aligment on the Camaro IA and at 120 straight as an arrow.

[Schurkey]

Originally Posted by george kujanski

T for better handling on an otherwise stock setup, what would be some good target numbers for caster, camber, toe?

MY philosophy with a stock- or near-stock suspension in good condition, is to shoot for negative camber, minimum toe, and all the positive caster I can get while keeping the camber negative.

HOW MUCH negative camber is up for discussion. So far as I'm concerned, the most-negative camber according to OEM spec is the most-positive I'd want.

In other words, if the OEM spec for camber is +2 to -1/4, I would want to be at -1/4 to -1/2, maybe as much as -1 depending on the suspension geometry and intended use. I don't get too worried about tire wear at 1/2 degree, I have some concern at 1 degree or more. If you're driving a grocery-getter, you look for maximum tire life. If you're looking for cornering power, some tire life gets sacrificed.

Remember, the engineers and lawyers DELIBERATELY sabotaged the handling of these cars when they were designed. They would build-in boatloads of understeer in order to absolutely prevent oversteer. Part of that was spring rates, sway-bar and tire sizing, but some of that was adding too damn much positive camber. There's also the issue of dynamic camber change--tall and soft springs coupled to too-short steering knuckles leads to lots of body roll. Lots of body roll leads to positive-going camber change on the outside, load-bearing wheel, only some of which is removed as the outside suspension compresses on the turn.

Camber is a tire-wearing angle. It will also cause "pull". Caster is not a tire wearing angle, but also causes "pull"--but it takes twice the caster to pull as much as camber. Used to be, cars were intentionally aligned to pull slightly left. Roads were "crowned", so the roadway itself made the car drift to the right. Highway engineers are taking the crown out of the roadway in favor of humps and dips. I don't approve, but no-one asked my permission. Given a choice, I like to have a vehicle that will drift VERY SLIGHTLY to the right on typical roadways. Driver falls asleep, he hits the ditch instead of oncoming traffic.

IN GENERAL, a 1/4 degree difference in camber L/R, or a 1/2 degree difference in caster l/R was used for road-crown compensation. I'm not sure that much difference is needed any more as roads have less crown.

The trick is to get the camber where you want it, while maximizing positive caster. Positive caster makes for strong self-centering of the steering, and also increased steering effort--but these cars had way too much steering assist to begin with, so extra effort is a non-issue.

Then a minimal amount of toe especially with wide tires. Too much toe wears tires really fast, and makes for wildly unpredictable handling--twitchy, darty, won't-go-straight. With rear-wheel drive, toe-in partially compensates for worn steering joints and loose wheel bearings. If the suspension/steering is still "tight",--and it better be--you don't need a lot of toe.

[george kujanski]

Thanks Shurkey.

George

[Holeshot71]

They make offset cross shafts for the upper control arms that some refer to as "camber savers". These will help get some positive camber back for sagging frame issues but will also allow more adjustment for positive caster. Helps when you're trying to get some positive caster with stock control arms.

[LATECH]

I installed upper conrol arms that have the offset caster built in.Worth every penny.

Also I opted to run the howe upper ball joints with the .5 inch longer stud to curb the camber jumping so far postive when suspension is compressed.
( Raises the pivot point for the upper control arm / upper ball joint )

The car drives completly different.Thank God, cause it sure drove like crap before.

4 degrees caster, .5 degree negative camber, 1/8 inch toe in.

[Schurkey]

Originally Posted by LATECH

I installed upper conrol arms that have the offset caster built in.Worth every penny.

I have not done this, but I sure like the idea. I will likely drill some holes and perhaps weld some material to the upper control arm mounting point on my Nova--to perform the "Guldstrand Modification" improving caster and raising roll-center. Cheaper than aftermarket control arms, more labor-intensive, though.

Originally Posted by LATECH

Also I opted to run the howe upper ball joints with the .5 inch longer stud to curb the camber jumping so far postive when suspension is compressed.
( Raises the pivot point for the upper control arm / upper ball joint )

The car drives completly different.Thank God, cause it sure drove like crap before.

4 degrees caster, .5 degree negative camber, 1/8 inch toe in.

There's multiple things that can be done to increase cornering power. The big issue with "American" cars is excess overall weight, excess weight HIGH AND FORWARD, poor suspension geometry, and older cars came with too little tire. Narrow 14 and 15 inch tires were a friggin' joke, and one that took way too long to correct.

The suspension geometry has imaginary angles through the joints and tire contact patch, which intersect at the so-called "roll center". When drawn in a "front view", you find that the roll center of the vehicle can be UNDERGROUND due to poor choices for locating the various pivot points.

The roll center interacts with the height of the center of gravity. The greater the distance between them, the longer the imaginary "lever arm" that makes the vehicle lean in corners. Leaning in corners does nothing good for those suspension angles you tell the alignment guy you want. Leaning in corners is EXCELLENT for telling Doofus Drivers that they're about to lose control of the vehicle, and "slow the hell down, you idiot." GM, Ford, Chrysler, and all the others DELIBERATELY trade away cornering power in order to provide "excessive" warning to the driver regarding his "aggressive driving.".

Shortening that lever arm is CRUCIAL for good handling. You can shorten the arm by lowering the center of gravity--remove weight above the CG: scrap the iron intake manifold and exhaust manifolds for an aftermarket aluminum intake and headers; or installing "tall ball joints" on the LOWERS or shorter springs to lower the whole car.

Conversely, you can RAISE THE ROLL CENTER by dicking with the angles the control arms operate at--"Tall spindle" disc brake conversion, "Tall upper ball joints" or doing the "Guldstand Modification" to the upper control arm mounting bracket, as popular on the old F-body. Anything you do to shorten the distance between C.G. and roll center is like adding a stiffer sway bar--without any of the drawbacks to a stiff sway bar such as added weight, bulk, and the partial loss of independent action between left and right suspension.

When the C.G. is lowered, and the roll center raised appropriately, you don't need super-stiff springs for handling. A reasonably-soft spring makes for good "ride", while the suspension geometry--not too-stiff springs and sway bars--keeps weight split among all four tires instead of under-loading the inside and over-loading the outside tires. SOME lean in corners provides necessary feedback for the driver.

https://www.pro-touring.com/threads/...-Mod-Templates

[389]

George, call Mark at SC&C.

You can get maybe 2 degrees positive caster max. What ever the factory recommends in negative you can take it to positive but that's the max. Do not pile shims under that back bolt like an idiot!! You will screw up the suspension plot. Think of a door with two hinges with two inches of shims under one of the hinges. Hows it going to swing? Its the same with your upper control arm except your caster will be changing as the suspension cycles.. Those things have enough bumpsteer!

I would take it to a shop with a Hunter Hawk eye rack.
Tell them.
Caster positive driver side +1.5 passenger side +2
Camber negative .75 to 1 degree.
Toe in 1/32 both sides..

Call Mark..

Polona Semper Fi Brother!!

[389]

Gilstrand Mod YUCK!!!!!

I got to get the F out of here !!!!

[Geoff]

Don't see how adding or subtracting shims will cause the caster to change as the 'suspension cycles'. Shims, placement & number, will change the static caster angle, but the angle stays the same as the wheel moves up & down.

[rjpaige3]

Originally Posted by Geoff

Don't see how adding or subtracting shims will cause the caster to change as the 'suspension cycles'. Shims, placement & number, will change the static caster angle, but the angle stays the same as the wheel moves up & down.

If both the upper and lower A-arm pivot points were parallel to each other in top view, and if the arms were parallel to each other in side view, and were of equal length, you'd be right. But that isn't the case. This is also why camber changes through the suspension sweep, and why bumpsteer becomes a thing.

[389]

I really shouldn't post after having a week from hell and then getting half crocked.. Sorry for the rude remarks, we all come on here to have fun..

[weevilkenevil]

I am at this point right now with my 65 gto. Car has been down to a bare frame and is now being built back up. I currently have the front suspension mocked up with no springs in it so i can run the travel up and down to do measurements. I can say without joking that i was stunned at how bad the geometry is stock. you do not need any measuring equipment to see whats happening. With the brakes and springs removed ,lifting the axle stub up and down through its full travel the positive camber gain and bump steer are clearly visible with the naked eye. My lower control arms were in bad condition so i purchased a ebay kit consisting of new tubular upper and lower arms, upper arm has the ball joint moved rearward, supplied spindle and ball joints were stock lengths. uppon fitment measured caster was around 4 degrees but camber gain on compression remained the same and bump steer was now MUCH worse. Moving the top balljoint rearward had raised the outer steering tie rod end and the axle twisted back and forth a huge amount when running the suspension up and down. mods to get camber gain under control was tall upper and lower balljoints, this fixed camber issues with the stub axle now tipping to negative camber on suspension compression instead of positive but made bump steer EVEN WORSE! ,as again the inner tie rod had been raised by the taller lower balljoint. the addition of one of those rose joint equipped adjustable outer tie rod "bump steer kits" was not able to fix the bump steer issue even with the tie rod in its fully lowered position. So the tall lower ball joint was removed and with the bump steer kit on its max lowest setting bump steer improved but was still visible. so i looked at he available spindles and could see that there was a couple that had the lower steering arm mount holes in a visibly lower spot than stock so i purchased speedway motors tall 2 inch drop spindle and fitted it.with the tall top balljoint swapped back to stock. now i have approx 4 degrees positive caster . negative camber gain on suspension compression, and with the bump steer kit on the lowest setting no visible bump steer, i then fitted some laser pointers to the front and rear of the spindle and projected onto graph paper on the floor and was able to confirm that i could get no visible and almost no measureable bumpsteer through full travel . but i didnt like the open tie rod on the bump steer kit so i purchased the half inch taller outer tie rod ends for firebirds and some longer adjuster sleeves. So currently i have tubular global west copy upper and lower "A" arms, standard height upper and lower ball joints , speedway motors tall 2 inch drop spindle, proforged 1/2 inch taller firebird tie rod ends and longer adjuster sleeves. 4 degree caster ,negative camber gain ,barely measureable bumpsteer. hope its going to ride ok but time will tell.