After getting my ride height right on front (cut 1/2 coil), and Bairs rebuilding my driveline, I had a four wheel alignment today. Hill City in Greensburg PA did my first alignment after restoration, and they take on classic cars, so I gave them another shot. They were willing to use my specs, which I chose from a number of sources on this forum, VBP, etc, . I watched them do it over two hour period.

They use Visual Liner Pro 32 modern computerized equipment, and what was blatantly obvious right away is how sensitive the equipment is. Even when they were just wrenching on an adjustment of any kind, the numbers on the screen bounced all over a wide range, and I could not even see any perceptible movement of the car. My takeaway from that is that maybe I have a misconception of reality. I tend to be a perfectionist, but I could see the reality is these small differences in numbers we shoot for are not even realistic. The do it yourself guys with your strings and bubble levels are hardly getting as close to accurate as this modern equipment. I am wondering if I need to recalibrate my thinking on this.

Maybe I was getting a line of bullshit, but when I questioned why we could not get caster closer to matching, he told me there was not a thin enough shim to close that gap! I was targeting 2.00 degrees, due to my manual steering, and I ended up with 2.75 on left, 2.48 on right. He basically said you cannot get it closer than that? I want to know what you all think about that statement.

As for rear toe, we got 1/16 on left, 3/32 on right, and again, he said he could not get it closer if he tried. What I do know is when he first moved the left from 0.00 to 1/16, he moved the thinnest shim there is from one side to the other. So had he moved the right side with same thickness, I would still not be matched perfectly. Total toe is 5/32, which is only 1/32 more than my target 1/8 total toe. When you think about a 1/32 difference,......its hard to really think of this as a problem.

My main question to you all for input is about the reality of these numbers. Is it ridiculous to expect to get numbers exactly what you shoot for? My final numbers were:

Front Caster Target was 2.00 Positive, ended up at 2.74 Pos / 2.45 Pos
Front Camber Target was 0.25 negative, ended up at Neg 0.26 / Neg 0.28
Front Toe Target was 1/8 inch total, ended up right on at 1/16 / 1/16

Rear Camber Target was 0.50 negative, ended up at Neg 0.49 / Neg 0.58
Rear Toe Target was 1/8 inch total, ended up 1/16 / 3/32 for total of 5/32 inch total

I also asked him if he put the car back on the rack after I drove it a few miles, would it be the same numbers, and he said no, it would be different, but close. I drove the car home, because I had to get to work, but it felt good. I need to hit the twisties hard before I finalize a conclusion.

 

I don't get it. The alignment guy gave you just what you wanted except he did you a favor. You asked for 2.00 positive caster and he gave you more. With 2.00 it's like driving a shopping cart on the street and even old GM specs were more than that. Take the extra caster and more if you can. Alignment shims are not made thin enough for what you are asking and with rubber or aftermarket bushings it isn't repeatable anyway. He did just what you asked on the rest.

 

why in the heck are you running .25 neg camber? and 1/8 toe????


and the problem with more positive caster is that it makes it harder to turn on manual steering racks... sure its great at highway speeds, but parking lots... not so much

 

Just buy moving shims for caster and camber its IMPOSSIBLE to be perfect on both sides. You need adjustable upper control arms. Caster settings within .2 degrees side to side is very expectable setting. so .3 is not bad. Take the car to in a month from now and have them only measure the alignment and compare. This should not cost more than 30-35 dollars.
Camber settings within .1 degrees side to side is also a very good alignment. Your front toe is more than I like, usually 1/16" total toe, but 1/8" total is the max.
Front camber @ .25 is good for performance driving and aggressive alignment, but will provide less tire life. Weekend street driving you could target for 0 degrees.

Rear camber is also a very good setting.

I DIY my alignments before every track event and except .1 camber side to side. .2 caster side to side. But more important is to get the rear thrust angle < 0.01 degrees.

What is the final rear thrust angle on the print out ?

Also moving shims doesn't allow for a prefect side to side match. I have adjustable front control arms from SPC to get a better match, but due to suspension parts / bushings (rubber vs poly) the alignment varies each time I measure.

The best test to the alignment is how long do the tires last, then how does it drive. Most corvette people that DIY go only by how it drives since they only drive < 3000 miles a year, tire age is more of a issue than tire wear.
In my case since I drive at the track tire wear is obvious before tire age.

Your alignment looks good to me.

 

Your reassessment of reality as far as the alignment goes is pretty accurate. The rubber bushings that are used to isolate us from noise, harshness, and vibration, prevent the alignment from being/staying perfect. Those bushings distort while driving down the road which causes slight changes in the alignment.... which in the end, doesn't really matter. The alignment settings have a "range" of tolerance. As long as the alignment settings are within that range, tire wear and handling should be normal. Whenever I do alignments on older cars, I sometimes have to compromise some of the settings. If you have stock front upper control arms, you can replace the bushing shaft with an offset one that will help you get closer to your desired settings.... if you haven't already installed them. If I was doing the alignment, I would try to get the passenger side caster higher than the driver side if possible to help counter the effects of road crown. I usually tried to have at least a 1/2 degree split.... higher on the right.

 

I think what you may not know, or did not catch in my first post, is that I have MANUAL steering, i.e. no power steering. On manual cars, GM set caster at 1.0 degrees on manual steering cars, mostly to reduce steering effort. I understand the "more is better" concept. After Bairs did my driveline work, they had their alignment vendor set my car at 1.0 degree, an it was much lighter steering effort, but I did not like the feel.

My only question about this more is better idea is , at what speed does the increased caster become relevant? 30mph? 50 mph? 100mph?

 

Thanks Cagotzmann for the response, see my highlight comments below to your statements:

Just buy moving shims for caster and camber its IMPOSSIBLE to be perfect on both sides. Camber settings within .1 degrees side to side is also a very good alignment.

THANK YOU for that statement, as I was hoping someone like you, who races your Vette, and therefore understands alignment well, would validate what the guy told me, and make me feel better about the numbers.

Your front toe is more than I like, usually 1/16" total toe, but 1/8" total is the max. I actually went in to the shop wanting 1/16 total toe on the front, and had it written on my paperwork, and he and I missed it at the end. Maybe I could turn my adjustable tie rods equally, by a small amount to bring it back to 1/16. Any recommendations on how much of a turn on each will get it back to 1/16 total?

Front camber @ .25 is good for performance driving and aggressive alignment, but will provide less tire life. Weekend street driving you could target for 0 degrees. My original alignment after restoration was 0.00. When Baer's did my driveline, their alignment guy put me at a POSITIVE camber on the front, which is apparently factory recommendations. Again, I used the spreadsheet I found on the forum, with VBP, Guldstrand, Greenwood, Herb Adams, Van Steel to come up with my numbers. Many spec'd Advanced Street or Sport at even more than .25 negative, so I thought it was a good compromise number.

Rear camber is also a very good setting. Bairs alignment guy had my rear at 1.0 negative, and I just did not like the look of that much negative, cause you can see it. And it made sense to me that would definitely wear tires.

I DIY my alignments before every track event and except .1 camber side to side. .2 caster side to side. But more important is to get the rear thrust angle < 0.01 degrees. What is the final rear thrust angle on the print out ? The Thrust Angle on the final printout is -0.04. What will be the noticeable driving result of this number?

Also moving shims doesn't allow for a prefect side to side match. I have adjustable front control arms from SPC to get a better match, but due to suspension parts / bushings (rubber vs poly) the alignment varies each time I measure. Again, comforting for me to know that I was not being fooled and that there is a reality to how close these numbers need to be.

The best test to the alignment is how long do the tires last, then how does it drive. Most corvette people that DIY go only by how it drives since they only drive < 3000 miles a year, tire age is more of a issue than tire wear. In my case since I drive at the track tire wear is obvious before tire age. Your alignment looks good to me.

I drive about 6000 miles a year. And what I wanted was a slightly sportier or advanced alignment. I am not racing, but my understanding is the factory alignment numbers GM put in the books do not properly address radial tires, 255/60/R15 all the way around, composite spring, Bilstein shocks, car is lowered, and just the plain desire for the car to handle a little better than factory. That was my goal. I admit I am a complete amateur at this subject and I am just trying to learn as I go along.

 

I spent a lot of time researching this forum and others on what numbers I wanted to target, given what I use the car for, and how my particular car is built. I openly admit I really don't know much about this subject, and I am not going to race the car. I do love the Pennsylvania twisties, and want the car to handle as well as it can given the limitations.

I can tell you the from my original alignment done three years ago, compared to Bairs vendor alignment done two months ago, there was a noticeable difference in how the car handled, and I did not like it. Their alignment vendor mandated FACTORY numbers. They aligned the front caster at 1.0 degree, and I think that was the most noticeable difference from the original 3.0 degree plus caster I had originally. The steering was much lighter in the center (remember I have factory manual steering), but the road feedback also seemed to be less and I sensed some amount of wandering in the road ruts. It just felt less stable and loose. I liked the firmer effort it took to drive the car with the higher caster numbers. So I chose a compromise target of 2.0 degrees (which is also the number one of the experienced racing posters on this forum recommended for manual steering). I ended up with slightly higher, and I think that is okay. I have no problem with the amount of steering effort the factory manual steering provides, and actually prefer it.

I need to get the car out on the twisties and see how it feels. I am hopeful that I will like it.

 

I sometimes complain about the alignment guys that are satisfied with simply "getting it in the green" rather than on the nominal, but then I think about how much more sensitive, and accurate, the alignment systems are today, compared to 30-40 years ago. Today, they're "splitting hairs" using lasers, and in the past, they used lights and prisms, hanging on the wheel, and projecting a bean toward a printed scale on the wall in front of the car. And with Corvettes, in the 60s through the 80s, they did the front end first, then had to drive the car off the rack, and drive it on backward, to align the rear end....and hope the mechanic remembered that on the rear, "toe-in" was read as "toe-out"....

 

The way these cars flex, I consider any "precision" alignment as money wasted. Push the car in any direction and camber and toe are a crap shoot. Close enough to the DIY numbers I want and adjust till the car drives straight ahead is good enough. How much does an alignment cost anyway?

 

1/8" of a turn would be the most I would turn. (mark the current position before changing) I use tape around the sleeve and use a marker for top, bottom, front,back (90 degrees) and then turn 1/8". Make sure you get the direction correct to toe-out each wheel.

During acceleration the rear of the car may push left or right depending on where the rear is pointing. Its only 0.04 which is not a lot and unless you often WOT you may not notice a difference.

 

Just for clarification, a 1/4 turn would be 90 degrees, 1/2 turn would be 180 degrees. 1/8 turn would be half way between 1/4 turn. In your statement about, you said 1/8", but I think you mean 1/8 turn. Am I correct in what you are saying?

As for thrust angle, I don't do WOT, so hopefully I will be fine.

 

Yes 45 degree turn = 1/8 turn.

 

Thrust angle is also critical for stable braking, as well as acceleration. Also, a dedicated road race or autocross alignment may be great on the track, but terrifying on the street. Rear toe in helps stabilize the car in a straight line, rear toe out can help a car corner, but too much toe out can make the car feel unstable in a straight line.... keeping in mind these are generalizations. Each car can feel a little different with close to the same settings. Also remember tire technology has advanced massively since these cars came off the assembly line. Mix in different suspension upgrades with changes in geometry and or bushing materials, etc. and the stock alignment settings become a baseline... unless you have an unmodified/restored to original car of course.

 

If I were you, I'd leave it alone. You could see how sensitive the adjustments were when on the machine. You are going to do better than that in your garage? NOT.

Sounds like he did a super job, considering what you were asking. Run it and see how it feels before you want to change anything. And, if you decide to change something....take it back to the same dude that did the work the last time.

 

I've paid anywhere from $150 to $200 for alignments at an excellent shop in my area of Texas.

The $200 charge was after total suspension changes on the front and rear of the car. It took over four hours but darn well worth it. I had a 30mph headwind on the way home. I was driving 80 mph and the car stayed in the lane and never drifted. The alignment and the Borgeson setup really made my car fun to drive.

Craig

 

PM me this shop - I am in the middle of a total rear end suspension refurb and will need a good shop to dial the alignment in....

 

PM sent

 

THAT statement above... says it all. I have commented on threads about alignments with basically the same comment and that is reality. Wasting time to get perfect numbers is pointless due to they will change.

As long as you are happy in how your car handles for you is all that matters. If it needs to be 'dialed in' more to your liking...then you and only you will know that.

DUB

 

​​​​​​Definitely agree and here's why.

​​​​​My 72 vette has the full VBP suspension kit front & rear. After the kit was installed, I took the car to our local alignment expert. He'd done excellent work for many years on our other family cars. He spent 4 hours sorting the alignment out and got the 72 vette very close to the VBP suggested specs. Ran into exactly the same thing that the shim was too thick to get a "perfect" alignment. That clearly bothered him that it was of like a 1/16 of an inch etc. Basically, the same as the OP mentioned.


He said the car drove correctly to him, so I should to go drive. Easily the best alignment the 72 had ever had. The car drove correctly. I was happy to pay for the alignment because the 72 drove the best it ever had. That was six years ago. 12,000 miles later the tires had the best wear pattern we've see on this car over the last 35 years.

I would not worry about being slightly off published spec with a C3 when the car drives and handles correctly. Keeping the tires correctly inflated will have more effect than a slight variance like my car had.