I took the car to have it aligned today,(or actually dropped it off last night and they kept it inside overnight). I took with me and had previously discussed with the alignment guy who said he had 'done a lot of old corvettes', the printed out alignment threads with excellent contributions by Duke, John Z and others. I made it clear I wanted the car set to these specs. The shop caters to high performance wheels tires and has been there forever. Got my P4000's there.

I got my 'results sheet' when I picked up the car today just before they closed at Noon. How close to these numbers is it realistic to have these guys get these settings?

Dukes #'s Front caster 2.0 without P/S
The guy got 1.8 on the left and 1.6 on the right as his result.

Dukes #'s camber 0 degrees front (with poly sway bar bushings)
The shop set it at 0.3 left, and 0.4 right

on the rear toe, which Duke suggests at 1/32"
the sheet says left .04" , right -.24" TOTAL TOE 0.29"
(I think 1/32" would be about .03")

The guy made the comment, "If it was my car I'd drive it that way, it'll be just fine. It would be too much work to get it to those numbers, you'd have to replace bushings, etc"
(EVERYTHING in my suspension is NEW)

I didn't confront him, he seemed like a nice guy. I think he got the readings to where his computer said 'within specs' it's printed on the sheet - 'within specs' and let it go.

I tried to be clear with about what I expected, with being an A-Hole.
But, how close can these guys get these specs to what we expect?

I guess I need to try another alignment shop, and I suppose I'll explain what happened at the first one when I do. I'll be SUPER CLEAR I expect these settings EXACTLY.

Today, they charged me $95.00 for a 4 wheel alignment.

Your Comments?

 

It all has to do with the experience and effort put into the job by the technician. I also use Dukes specs for my stock PS radial tire 66 Coupe. The first shop I used was an "old line" alignment shop. The guys did a terrible job and said that’s the closest they could come to the specs. I was very unsatisfied with the result and took it to a second shop. That technician used a Hunter set up and really took an interest in doing a good job. He even checked the front wheel bearing adjustments and all suspension parts to insure we were working with a solid base of fixed points. The result he achieved was dead on perfect specs.

 

It sounds like the guy set it up on the machine, read the numbers, pronounced it "okay", and charged you $95. If so, I think you got hosed.

The front numbers are not bad, but the camber could be brought closer to zero by adding shims to the front upper control arm studs with more on the rear studs to increase caster. The zero camber, 2.0 deg. caster is probably easily achieveable.

The RR toe is definitely WAY OUT - about NEGATIVE one-quarter inch. By swapping shims from the inside to the outside, one should be able to get is closer to .03". I would leave the LR alone. Your actual total toe is .20" TOE-OUT with .04" toe-in on the left and 24" TOE-OUT on the right. I bet the car has different right/left dynamic response with a tendency to oversteer when turning hard left.

It's reasonable for a shop to charge a "basic fee" to set up the equipment and read the numbers. If any adjustments are required from there, it's reasonable to charge for adjusting. The front is easy to adjust as long as you have a selection of proper shims, but the rear toe can be a bear, especially if the car has the captured shims that require the trailing arm, bolt to be removed.

You also want to make sure the shop has a proper selection of shims. They might for the front, but likely not for the rear. You can buy "shim kits" from the various Corvette suppliers for both front and rear. Rear toe can usually be adjusted by swapping shims inside to outside and vice versa, but you might need a couple of thin shims to make sure the stack is full. The last shim (a thick one) should require some light tapping to seat.

You did not state the measured rear camber.

A competent alignment tech should be able to achieve very close to the recommended numbers, but it will take some work, which no one seems to want to do nowadays.

I've spent a lot of time over the years dialing in the alignment on my cars (I do all my own alignment in my garage with an inclinometer and tape measure) and doing other chassis "blueprinting" tasks such as minimizing wheel bearing clearance, and I can tell you that attention to this kind of detail can make a difference between a wonderfully precise handling car and a canterkerous pig!

Duke

 

Duke, "(I do all my own alignment in my garage with an inclinometer and tape measure)", do you have a good DIY guide written down, web site or book that you could share?? I hate for you to have to spell it out from scratch. Thanks

 

No, I picked up the procedure from an old Herb Adams catalog, but I can briefly summarize it here.

First you need a "surface plate". Most home garages, especially on newer homes, will suffice, and you can use the inclinometer to measure. If it's no more than a quarter degree off flat then it should be okay.

Lay the inclinometer against the wheel flange to measure camber, directly with the wheels staight ahead.

Front caster is the arithmetic difference between the camber readings with the steering turned to left and right extremes.

Say the LF measures negative one at extreme right lock and positive one at extreme left lock. The caster is 1 - (-1) = +2.

It's best to set front camber first. To achieve zero camber, most cars will require shims to be added. Assuming your initial caster measurement is in the ballpark, add an equal amount on the front and rear studs to achieve zero camber or up to negative one (performance setting). Then remeasure caster. To increase caster, move shims from the front to rear stud. Once proper caster is established, recheck camber, but it should not change much.

It helps to be able to visualize what you are doing, geometrically. By adding shims to both studs you are moving the upper ball joint inboard. By moving shims from the front stud to rear stud you are moving the upper ball joint to the rear.

Toe can be set with a tape measure. Mark a convenient measuring point on the rear face of both tire treads with chalk - as high as possible without the tape interfering with anything. Take a measurement, then roll the car forward until the chalk marks are as high as possible on the front side without interfereing with anything. Take the measurement and subtract from the first. "Eyeballing" down the side of the car will give you a clue on the front whether it is equal on each side with the steering wheel straight. I usually have to tweak one tie rod to get the steering wheel dead straight after test driving.

Rear toe is the trickiest to measure and adjust. Since the toe must be distributed equally side to side, you need to measure from vehicle centerline, which can be determined by measureing the centerline across the frame at several points, then laying a string with plumb bobs to get the string to the correct height to use as a measuring reference.

You should always take multiple measurements of everything and look for consistency. If the readings are consistent, they are probably accurate, and after each adjustment you should roll the car back and forth several times and bounce it up and downto settle the suspension.

Duke

 

Duke, I appreciate your comments, and agree that the guy did the basics, then said - 'hey looks fine to me.' EVEN though I had it all in black and white for him.

He SEEMED like he was willing to cooperate though before, darn it!

FYI, the rear camber was 0.8" left and -0.9 right. They also measured the rear thrust angle at -.20, which he said was "very good". ???

I believe I will look for another shop, take the results sheet from this one as well as the expected specifications, and try again for better results.

 

One degree positive on one side and one degree negative on the other side? And that's "OK"? Good grief! It takes less than a minute per side to set rear camber on a rack. Check with your local NCRS chapter or Corvette Club and find out which alignment shop they trust that KNOWS Corvettes.

 

Ditto what John said - good grief, Charlie Brown!

Also, you want the thrust angle as close to zero as possible. The fact that you have nearly a quarter inch of toe-out on one side and a slight amount of toe in on the other yields a signficant thrust angle, which will make the car squirrely.

If the toe settings on each rear wheel are exactly equal the thust angle will be zero, which is the target, and it would not accept more than 0.05.

The "touring" setting for rear camber is negative 0.5 deg.; "performance setting is negative 1.0 degree.

Your front alignment settings are actually within the OE range, but the rear is way off!

Duke

 

That alignment is horrible. You will have a slight pull to the right and it will wear the outer edge off the rf tire. You need more caster on the rf to comensate for road crown. Since you need more caster and less camber all it needs is more shims. Not bushings. This is pure lazy on the part of the guy doing the alignment. Now with the toe-out on the rr wheel the car will try to drive left. I've seen a lot of lazy mechanics due this to compensate for a pull to the right. It will also scrub the tread off the rear tires. His comment that it'll be just fine means either his is lazy and lying or he is not smart enough to do a proper alignment. Here is another little trick. If the specs aren't correct they can have someone lean on the car or a tire to change the specs and then someone hits the print button. I have been doing alignments for thirty years and seen just about every trick ever pulled. Other than setting the rear toe-in, an alignment on a C2 or C3 is far easier than a '90s S10 Blazer. $90 is not a bad price for an alignment but in this case you got taken.

Mike

 

That advise is obsolete with today's paved roads, but it was applicable in the 1920s when most roads were dirt and highly crowned for drainage.

You want to set caster and camber as close to equal on both sides as possible. On a modern low crown road, such as an interstate higway, the car should just barely drift to the right, hands off the wheel, with no cross wind, which is what you want.

You do not want it to drift left as this will cause the car to drift into the oncoming lane on a two-lane road.

Duke

 

Appreciate the input. It's hard for those of us that don't 'speak the language' to walk in and talk to a guy who does this all day every day, and tell him he's wrong.

The information recieved here is powerful, and hopefully will enable me - and others - to get what we want when dealing with these guys, and not be at their mercy.

Dammit, I'm taking this printed thread with me to the next shop and having the alignment guy sign it in blood!!

 

Duke,
Here in Dallas roads are still built with high crowns. Some 4 lane have the crown in the center of the lanes. Possibly one of the reasons why there are so many wrecks involving cars crossing over into oncoming traffic. I agree that you should have a slight drift to the right and caster and camber should be equal side to side. But that's hard to explain to a lady driving an SUV with a cell phone in one hand and lipstick in the other. And a shop manager yelling because she says it's still pulling.
Concerning 65nassau I feel he did not recieve what he paid for. You gave him the specs and that is how it should have been aligned. If it was done as requested and he didn't like having the slight drift then adding more caster to the rf would help. Leaving the rr toed out is unacceptable. If the guy doing the alignment didn't want to do it right he shouldn't have taken the job. Or the money.

Mike

 

I always used the method that Duke describes to set caster, but with a minor difference to compensate for sometimes uneven lock-to-lock #'s - all it takes is a protractor so you can get the angle -

Caster = 1.4 x camber change for +/- 20 degree steer.

From 'center', crank front wheels 20 deg. one way, measure camber, crank it back 40 degrees (for 20 deg. the 'other way'), measure camber again, then just do the math.

FYI...for setting 'toe', we get our best results when using a set of cheap 'toe plates' with two tape measures, like the 'roundy-round' racers use all the time. They're just two rectangular metal plates, about the width of the tires' diameter, and 8-10" tall. Some have reliefs cut in the lower edge, so avoid error from the 'tire bulge'. There is a small slot on the front and back edge of each plate, which holds the tape measure tape on each side. Just read the tapes...if the measurement is bigger at the front, that's the toe-out. Bigger at the rear - toe-in.

Roadrace a lot, and do a whole bunch of endurance racing (ran a 12 hour race last Saturday, noon to midnight), and we've gotten our best tire life when we've use toe plates, rather than string systems or 'tire marking bars' or computerized, helium-cooled, nuclear-powered alignment machines.

Example: http://www.quickcar.net/chassis/ch_tp.html

...but we've made our own. Cheap, fast, accurate.

 

Determining caster by the arithmetic difference in camber with the wheels at extreme right and left lock is only an approximation (but a fairly close one), not an exact value. As long as it's equal side to side results should be okay, and turning the wheels to the locks assures consistency without the need to measure wheel angles, so it quickens the process.

In my case, with all my cars, I crank in as much caster as the adjustment will allow (I like lots of self aligning torque and on center feel) plus greater caster provides a better negative camber gain to help maintain the outside tire vertical to the ground as the body rolls.

My '88 Mercedes has about 10.5 degrees caster and my '91 MR2 has six, but they both have power steering. With manual steering the practical limit is about 2 degrees or the steering kickback will be enough to damned near break your arms. Been there, done that when I swapped the upper control arms side to side on my Cosworth Vega to increase caster from about one degree to six. The test drive was real short!

Duke

 

I didn't realize that


I can absolutely imagine that, that's the one reason I may consider going to power assist at some time.