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If you added more shims then yes you changed camber. in theory, if you move shims from front to back or vice-versa, but do not add or remove the total amount of shims then camber is supposed to stay the same. All of the alignments I've completed this very seldom is the case. You have most likely changed your toe adjustment and will probably get some bad tire wear because of it.
Caster is the angle to which the steering pivot axis (a line drawn through the upper and lower ball joints) is tilted forward or rearward from vertical, as viewed from the side.
If the pivot axis is tilted backward (that is, the top pivot is positioned farther rearward than the bottom pivot), then the caster is positive; if it's tilted forward, then the caster is negative.
This is adjusted by either adding shims to the front or rear mounting point of the upper control arm pivot shaft. If you add to the front and remove from the rear you tilt the pivot axis to the rear or you add positive caster.
CAMBER
Camber is the angle of the wheel relative to vertical (a line that passes through the center of the spindle), as viewed from the front or the rear of the car.
If the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber.
So by adding or removing an equal number of shims on both the front and rear mounting points of the upper control arm pivot shaft you can adjust camber.
By adding shims you are adding more negative camber. By taking away shims you are adding positive camber.
After your caster/camber adjustment you want your toe set in 1/16-1/8 inch.
I increased the shims to give myself more positive caster, and my alignment guy said I changed the camber and toe in.
Is this true for a 1971 cutlass?
It could be. The adjustment provisions on the A-body front suspension require inserting or removing shims between the upper A-arm shaft and the frame mount. Changing shims equally on both bolts changes chamber and MAY change toe. Changing shims unequally changes caster and MAY change toe and camber due to the geometry of the front suspension. You need an alignment machine to check.
Think about it looking down on the suspension from the top. The upper control arm is a triangle with the ball joint at the peak and the two shim packs in the lower corners. Removing a shim from one pack and inserting it in the other causes this triangle to rotate in the top view. This is what moves the upper ball joint backward to increase caster. Unfortunately, the upper ball joint moves in an arc when you change the shims like this, so depending on where you are in that arc, you may have also changed camber by moving the ball joint closer to the center of the car. Also, since you are moving the upper ball joint but not the lower one, you are changing the angle of the steering knuckle, which may change toe as well.
If you changed your caster I would be willing to bet camber and toe are off at least a little and likely enough to cause tire wear. I know the car chassis is much different than a 4 wheeler chassis but with my experience in 4 wheeler motocross and freestyle, Just a little caster movement will greatly affect toe and have at least some effect on camber. When I set up a race quad I have to get everything in the ballpark and then start with caster then move to camber with checking caster after the camber to be sure it didn't move. Toe is always last. Again, This is much smaller scale than a car chassis and the geometry will not be the same but the affects should still be the same.
If you changed your caster I would be willing to bet camber and toe are off at least a little and likely enough to cause tire wear. I know the car chassis is much different than a 4 wheeler chassis but with my experience in 4 wheeler motocross and freestyle, Just a little caster movement will greatly affect toe and have at least some effect on camber. When I set up a race quad I have to get everything in the ballpark and then start with caster then move to camber with checking caster after the camber to be sure it didn't move. Toe is always last. Again, This is much smaller scale than a car chassis and the geometry will not be the same but the affects should still be the same.
Keep in mind that the ability of one adjustment to affect another is primarily dependent on the design of the suspension. What works on one vehicle may or may not apply to another with a different suspension design and adjustment process. You are correct that toe should always be adjusted last, since it is most affected by other adjustments. For suspension designs that move the upper control arm pivot shaft, caster and camber need to be adjusted at the same time, and it is an iterative process to get them both correct.
Allrighty then, I was hoping for a different outcome.
Here's the deal.....my car wanders and tracks the highs and lows in the pavement.
Any easy fixes out there?
I heard changing the power steering box is one of the fixes?
any others?
If you have wide tires, the tendency is higher. What are you running for air pressure? Also when was the last time you rotated your tires? If your running 2 different sizes your can just swap from left to right? What settings are your camber, caster, and toe set at now?
Allrighty then, I was hoping for a different outcome.
Here's the deal.....my car wanders and tracks the highs and lows in the pavement.
Any easy fixes out there?
I heard changing the power steering box is one of the fixes?
any others?
Back up. What "different outcome"? You STILL can increase the caster. You just can't do it without performing a complete front end alignment. Changing the caster will require also readjusting the camber and toe back to spec. That's not a big deal, you just need the equipment to measure it. The problem may be that alignment shops will be reluctant to adjust to non-stock specs, since they have waaaay too many lawyers.
You need to find a privately owned alignment shop that will take the time to address your issues and give you a proper alignment. Find a shop that specializes in trucks.
You need to find a privately owned alignment shop that will take the time to address your issues and give you a proper alignment. Find a shop that specializes in trucks.
Thanks, I will look there next time as I was not happy with my alignment this year.
Back in the day and maybe today when you went in for 4 new tires and the front end align it seems they never actually put a wrench on your car in many cases because the measurements fell within thir specs so you need a good garage that will get it on the money
The problem is that the newer machines are all computerized and the old cars are not in the data base. The techs do not know how to set ours up. To compound the problem, when you change the dynamics of the suspension combined with not original stock tires and wheel offsets, none of the original specs work. However there is a general rule of thumb to set one of our old cars up if you can find an alignment shop that is capable and patient enough to do it.
Ask around at car shows for a reference from people who are happy. Do not assume a Sears, Goodyear, or any chain store to be able to align your car.
Longacre makes tools to set caster and camber. Toe in can be set with two straight boards, blocks to sit them on, and a tape measure. Caster and camber are set first, check afterwards until you get both where you want them. Set toe in last.
Last edited by Run to Rund; August 25th, 2013 at 06:47 AM.
Anyone know what stock caster is? I just bought some tubular uppers for my 66 Cutlass and they are supposed to give me +4.
What does it matter what the stock settings are? The reason people buy tubular control arms is to get more positive caster. If you google performance front end alignment specs, you'll see there are proven settings that work well for most cars based on what the usage is.
just an FYI,
The more positive caster the more stable at speed in a strait line. The less caster angle the faster and easier it will turn, (darty or choppy). Just don't misunderstand and think less caster is better for turning and road handling.
Last edited by jensenracing77; January 31st, 2017 at 05:05 AM.
what does it matter what the stock settings are? The reason people buy tubular control arms is to get more positive caster. If you google performance front end alignment specs, you'll see there are proven settings that work well for most cars based on what the usage is.
That will move a significant amount of weight to the back side of the spindle. Assuming you have driven the car much in the past, you will notice a big difference.
That will move a significant amount of weight to the back side of the spindle.
No, not really. The wheel load, by definition, is centered under the wheel bearings no matter what the caster setting is. The increased stability is from the fact that the tire contact patch is further behind the spindle pivot axis (called the kingpin axis). This provides a longer lever arm (labeled "Mechanical Trail" in the drawing) and thus a higher "correcting" force that keeps the tires pointed straight ahead.
No, not really. The wheel load, by definition, is centered under the wheel bearings no matter what the caster setting is. The increased stability is from the fact that the tire contact patch is further behind the spindle pivot axis (called the kingpin axis). This provides a longer lever arm (labeled "Mechanical Trail" in the drawing) and thus a higher "correcting" force that keeps the tires pointed straight ahead.
We always called everything by weight transfer in chassis setups. The top ball joint moved to the back side of the vertical center line adds weight to the back side of that center line. Yes it is also the contact patch that is behind the ball joint center line. Both together makes the wheel not want to "lay down" as it turns and makes it want to return to center.
Last edited by jensenracing77; January 31st, 2017 at 11:50 AM.
We always called everything by weight transfer in chassis setups. The top ball joint moved to the back side of the center line adds weight to the back side of the center line. Yes it is also the contact patch that is behind the center line. Both together makes the wheel not want to "lay down" as it turns and makes it want to return to center.
I'm not sure what you are calling the "center line". If you mean the vertical line through the spindle, it is impossible for the contact patch to be anywhere other than directly below it. If you mean the spindle pivot axis then I agree with you.
I'm not sure what you are calling the "center line". If you mean the vertical line through the spindle, it is impossible for the contact patch to be anywhere other than directly below it. If you mean the spindle pivot axis then I agree with you.
Fixed it. I was talking about two different center lines and did not differentiate between the two.
The top ball joint moved to the back side of the vertical center line adds weight to the back side of that center line.
Sorry, but I still disagree.
First, since the wheel is on a bearing, the load MUST be directly below the spindle. If the load were "behind" this line, it would cause the tire to spin. Draw the free body diagram.
Second, with a suspension system that has the spring on the lower control arm, the upper ball joint doesn't carry any vertical load; the upper control arm just pivots.
If you are saying that changing caster changes front/rear weight distribution, that effect is nearly negligible. Yes, increasing caster moves the spindle rearward by a small but non-zero amount, but do the trig. Assume the caster was zero before and is now 4 degrees. With a tire diameter of about 27", that meas that the spindle and wheel centerline move rearward by sin(4)*13.5 = about 0.94". This means that you've actually increased weight on the front wheels, since the contact patch moves rearward relative to the weight of the engine.
Last edited by joe_padavano; January 31st, 2017 at 01:07 PM.
Reason: "Camber" was supposed to be "caster"
The weight under the tires are not going to change
If you move the front tires rearward relative to the CG, a higher percentage of the weight is on the front wheels. The difference is not large, but it is not zero either. This is simple physics.
Anyone know what stock caster is? I just bought some tubular uppers for my 66 Cutlass and they are supposed to give me +4.
The arms do not "give" you anything. The allow you to adjust for more caster and/or camber. When you lower a car, the camber usually goes negative. The extended arms are designed to compensate for running out of adjustment space for the fixed frame attachment points where the suspension arms mount. You can achieve the same results with an offset pivot shaft.
Usually, changing camber does not affect caster, if you move the front and rear pivots the same amount. If you change caster with the same but opposite motion of the pivot points, you should not change the camber. There may be some suspensions that do not follow these rules, but a properly designed system will make adjustment straight forward. I do my own alignments, and being in tolerance does not make it drive comfortably. Since most roads have a crown, and we drive on the right, a slight amount of additional negative camber on the right front will make the car drive straight on almost all roads. About 1/4 of a degree is sufficient to compensate for the crown. On an absolutely flat road, the car will wander to the left a little.
In racing, having a little negative camber will allow the tires to work better, but if you are not "at speed" it will drive strangely, and get uneven tire wear. This must be balanced with the rear camber, which is set with more negative camber than the front. Often the rear camber is set by the rear axle at "0" degrees. If that is so, a slight amount of positive camber (about .8 deg.) on the front will allow the car to have over steer (tight), which is easier for most people to drive with, because the front will tend to slip out from under the car before the rear comes around from under steer (loose).
Caster is for feedback from the steering, and directional stability. The more you have the stronger the feedback. You need some positive camber to make the car want to go straight naturally. It should be the same on both sides, unless you are only turning one way. For example, circle track racing.
Toe just makes the tires wear evenly. A tiny little bit of toe in will make the car want to stay on a given line. Toe out will make the car tend to wander. A little toe in will also take up the slack, and compensate for the compliance of bushings and worn tierod ends. Along with toe, you have Ackerman built into the steering. On race cars, where you are always driving at a slip angle in turns (both tires scrubbing), Ackerman effect may not be designed into the steering. Ackerman allows the tires to follow separate arcs without scrubbing the tires. Anti-Ackerman is another term for not having Ackerman designed into the steering. One or both tires will scrub going around a turn.
The arms do not "give" you anything. The allow you to adjust for more caster and/or camber.
Actually, you can now buy aftermarket upper control arms that have the ball joint relocated rearward from the original location. The amount of adjustment is still governed by the shims, but instead of, say, an adjustment range of -1 to +3 degrees with the stock arms, these aftermarket arms give you a range more like +2 to +6 degrees, so effectively, they do "give" you more caster adjustment. Note that I made those numbers up for illustration - I'm not sure of the exact numbers.
'70 Cutlass Conv't. I want to increase caster but retain OE arms. Moog makes an offset upper control arm shaft that allows for more camber than stock. See > https://www.moog-suspension-parts.com/moog-k5250
Since caster and camber are inter-dependent in the shim adjustments, would this offset shaft help to allow for more caster (as well as camber)? I'm not seeking more camber, of course. Want to retain stock camber setting. Has anyone installed this offset shaft in an A-body?
Thanks.
Last edited by Toms cutlass; August 27th, 2018 at 09:28 PM.
The camber and caster can be independently adjusted. Adding or subtracting equal size shims to/from all stacks adjusts only the camber. Adding to or subtracting equal size shims from front and rear stacks will adjust caster. If you add or subtract from only one stack it will adjust both camber and caster.
If you move 1/16 inch shim from the back to the front, you can increase your caster without changing your camber. The rest of your alignment should stay about the same. I would check the toe after any changes, but it may not need any adjustment. All shim adjusted Chevy front suspension works the same.
See my prior post in this thread from January 31, 2017.
Last edited by Fred Kiehl; August 27th, 2018 at 10:06 PM.
'70 Cutlass Conv't. I want to increase caster but retain OE arms. Moog makes an offset upper control arm shaft that allows for more camber than stock. See > https://www.moog-suspension-parts.com/moog-k5250
Since caster and camber are inter-dependent in the shim adjustments, would this offset shaft help to allow for more caster (as well as camber)? I'm not seeking more camber, of course. Want to retain stock camber setting. Has anyone installed this offset shaft in an A-body?
Thanks.
When you add a bunch of positive caster, you'll also gain negative camber along with it. Think about it from a top view - as you put shims in the back of the upper control arm, the center of the cross shaft also moves in, which therefore drags the camber negative. "Twisting" the cross shaft from a top view around it's midpoint influences caster, while movement inboard/outboard of the midpoint of the cross shaft influences camber. If you use the offset cross shaft to push the bushings back outboard, it will restore a reasonable camber number while allowing the caster gain.
Originally Posted by Fred Kiehl
Since most roads have a crown, and we drive on the right, a slight amount of additional negative camber on the right front will make the car drive straight on almost all roads. About 1/4 of a degree is sufficient to compensate for the crown. On an absolutely flat road, the car will wander to the left a little.
You typically want to account for road crown with cross-caster, not cross-camber, because caster is a non-wear adjustment.
When you add a bunch of positive caster, you'll also gain negative camber along with it. Think about it from a top view - as you put shims in the back of the upper control arm, the center of the cross shaft also moves in, which therefore drags the camber negative. "Twisting" the cross shaft from a top view around it's midpoint influences caster, while movement inboard/outboard of the midpoint of the cross shaft influences camber. If you use the offset cross shaft to push the bushings back outboard, it will restore a reasonable camber number while allowing the caster gain.
You typically want to account for road crown with cross-caster, not cross-camber, because caster is a non-wear adjustment.
You do not just add shims to the back. You remove equal amounts from the front, and the center of the cross shaft stays in the same place, so the camber does not change.
Caster is the preferred way to account for road crown, but camber will also do the same, and the amount of "wear" is negligible. The camber will still be in spec for the suspension.
August 23rd, 2013, 05:48 AM
Does caster change camber on a 71' cutlass
