Barbara_S

I had the alignment done yesterday on my C4 ZR1 -

I asked for
Front 1/8" toe out total -1.5 deg camber each side
Read 1/8 - 3/16" toe in total -2 deg camber each side
(I didnt' ask for caster because I sort of thought these were enough to try getting right)

I got degrees - he did not have a way to input inches.
Toe front said .20 deg and .19 deg
Toe Rear said -.03 deg and -0.14 deg

Pulling the control arm shims from the right side got -1.8 camber , pulling the left side got -.9 degrees camber. Cross camber is .9 degrees

What should I do now? Put shims back in to get rid of the cross camber issue and then have less than needed camber?

My assumption is I need to go to a body shop and straighten something before I can get the camber right. I am wondering if anyone here thinks there's more to getting camber correct on one of these cars and a more experienced race alignment guy would be a better idea than a body shop or are shims really it, and I have a frame or knuckle that is not right.

Also, the toe just doesn't feel toe'd. enough. The car is too nice and easy to drive.

help

c4cruiser

There are offset control arm shafts available that will allow you to get more negative camber. Not being able to match high camber values from one side to the other is pretty common on C4's even if they have never been wrecked. My 87 is the same way.

It looks like the specs you asked for are close to the Vette Brakes "Autocross Baseline" values. You should also include 4-5 degrees of positive caster in the front. Caster is not included in the rear alignment specs.

A shop with a good computer-controlled alignment rack that is properly adjusted and a tech that has experience with it should easily get the specs set up the way you want. Toe can be measured in inches and a final printout of the completed alignment will show that measurement.

If you are going to drive the car on the street, the toe value is going to make the car a real handful on roads with ruts from heavy traffic. Expect increased tire wear due to the toe and camber settings.

AUTO_X_AL

I have heard of some C4's only getting less than a degree total on the drivers side. I dont think that is uncommon at all. I am not sure what class(s) you want to run and you may want to look at the rule book for whatever group you are racing with before you modify a part to compensate for the cross camber diffrences.

Slalom4me

If you measure or estimate your tire diameter and use trig
you can convert from toe degrees to toe inches. DavidFarmer
and ghoffman reminded me of this a few years ago.

- Alignment: Inches to Degrees, Thrust Angle

I don't need to run the numbers to know that the shop has
short-changed you with the rear toe settings because the left
rear has a small amount of toe-OUT and the right has a lot of
toe-OUT. I predict snap-oversteer when braking hard and
especially when turning in to the left.

The front has been set for toe-IN instead of toe-OUT.

It is not uncommon to be able to achieve only minimal neg camber
on one side at the front - this is not (automatically) a sign
of frame issues.

As for how to proceed about the camber. Often courses are
counter-clockwise - resulting in more left turns than right. Thus
the right front wheel does more of the work. It is near your
desired camber, you could just accept that the left is not
optimimal.

Alternatively, more camber can be achieved changing to offset
lower control arm (LCA) bushings such as those sold by VB&P.
A modest increase is also possible by grinding the backs of the
concave spacers on the bolts for the upper control arm bolts.

Edit: Change evaluation of effects of rear toe in recognition that
the values after alignment are negative and thus reflect toe-OUT.
I had initially overlooked the negative sign.

.

Slalom4me

From a recent thread - Oversteer! Wasn't expecting that!
Edit: Change from 1/32" (0.3125") to 1/32" (0.03125")

Barbara_S

I also have a R&D camber brace installed in the front - and although the answers here are useful, the guy who did the alignment is going to try again and thought the camber brace may be adding to the problem.He's focusing there, but I'll be more specific with caster too and ask to even out the toe.

I'm not running in any SCCA class events with this car , just local car clubs so I can do anything to it and it's purpose is only autocrossing this years so drivability isn't important.

thank you.

barbara

90Z51

When you installe dthe camber brace, did you have to spread the frame tabs to mount it? That's the only way I could see that giving you problems, it would have added positive camber. When I installed my camber brace it pulled the tabs inwards, I went from -1.3 camber on both sides to -1.44 camber.

Slalom4me

This is fine, as long as he is earning his education on HIS nickle, not yours.

If you search the archives here you will find many instances of posts
from other members describing similar experiences with left/right adj.

I have a camber brace, too. I chose not to use it to pull the frame
ears together for additional camber.

.

TommyBoy72

Here is the rough conversion:

Toe front 3/8" AND 3/8" = 3/4" total toe out
Toe Rear -1/16" and -1/4" = 5/16" total toe in

Personally I would not be happy just on toe settings alone. The front toe will chew up some tires. You need to know what your thrust angle is, it could potentially be pretty ugly.

AUTO_X_AL

If you get the fat washers behind the upper control arms cut it will increase you negative camber a good bit. 1.5 on each side would be easilly attained. Maybe even close to 2*. Definatly get the toe even.

Slalom4me

TommyBoy72, like you, I initially overlooked that the shop has reversed
the toe direction Barbara_S requested. Positive toe is toe-in at the
front. Negative toe is toe-out at the rear.

Therefore, I believe the inch approximations on a 26" tire are

Toe front 3/32" (0.2066º) and 3/32" (0.2066º) = 3/16" total toe-IN
Toe Rear -1/64" (-0.0345º) and -1/16" (-0.1377º) = -5/64" total toe-OUT

An example of determining angle for 1/32" toe with a 26" tire using
AJDesign's on-line trig calculatorMy vote is that Thrust Angle here is not a big deal, adjust the
rear toe settings and the TA will be resolved.

.

Slalom4me

I don't know about the ZR-1, but the later design front suspension on the
non-ZR-1 cars do not have spacers that are as thick as the ones on
the early design cars.

.

Slalom4me

Here is a photo from 'From The Bottom Up' by Andy Bolig in Corvette Fever
Although the article is about an '85, the spacers between the control arm shaft
and the frame ears have been updated to the newer thinner versions.



From an old thread about the '84-'87 cars

.

Slalom4me

To clairify. The newer non-ZR-1 cars already have the thin spacer.
Perhaps the ZR-1 does, too.

The part number might be useful to someone who wants to modify
a spare set of washers for a new car. If you are willing to work without
a net, then proceed to grind the existing thin washer.

.

TommyBoy72

Wow you are right. Sheesh and I just corrected another post with that inverted too! Maybe thats what threw me off.

Thanks for the math formula. I usually did .03 degrees = 1/16". It was a general rule for Hunter alignment racks. I haven't done much with strings so I didn't know the math for larger diameter. That will definitely come in handy.

Slalom4me

Barbara_S, I wonder whether there is a chance that the tech thought
you had reversed the fr/rr numbers? Or perhaps the tech reversed
them on the sheet you received displaying the 'After' numbers?

The numbers you GOT were:
The numbers you ASKED FOR were (inch approximations on a 26" tire):
While this is not a perfect fr/rr reversal of the numbers you requested
(because of the left rear variance, which can happen in the course of
an alignment), it sure looks like a possibility.

Edit: To remove the neg sign
-3/16" total toe-IN should read 3/16" total toe-IN

.

Slalom4me

As mentioned above, DavidFarmer and ghoffman get the credit for reminding
me about the trig calculations. In the thread on this referenced above,
DavidFarmer points out that "Sin/Cos conversion aren't linear, so you
can only scale the above numbers within a small range."

I had to edit two posts in this thread myself.

Hopefully, we leave it in a condition that helps Barbara_S and others
understand and achieve what they wish to regarding alignments.

.

Barbara_S

I had it written down so that I would not make a mistake in the request - Front toe out, rear toe in basically from the vbandP settings and review of what I did on my 88. The guys doing it appear to be new to doing a special customer request and I'm not literite enough to educate them. They did my tire mounts, front and rear spring install plus shocks, camber brace and then corner weight ,cross weight and height adjustments last week which all turned out OK, but the type of alignment request was new to them and I had no idea whether it was right or wrong as it was being done, but it didn't feel like I had hoped afterwards which is why I came here.

And wow - good thing I did - I can give them a second try with some of the info from this thread and if it doesn't work - I have another source to go to but Evolution school is next week up here and I was hoping to go with a car that was ready.

Thanks again!

Slalom4me

Oops

I see that in cutting & pasting to create the 'you ASK FOR' reply
I left a neg sign that should be removed.

-3/16" total toe-IN should read 3/16" total toe-IN

I made a correction in my post. The error persists in Barbara_S'
quote of the post.

Regrets,
Ken R.

.

96GS#007

FWIW, even the later ones can be machined. I had mine machined .120"