dizwiz24

I figure you guys would know more about this than anyone else on the forum...

Does a c4 alignment shim 'kit' exist? The factory donut spacers have a special indentation in them that centers them against the control arm.

Heres what I am trying to do:

I have a C4 vette and want to increase negative camber and add positive caster.

The factory service manual says take an equal amount of shims, off front and rear bolts on each side to increase negative camber.

It says add more shims to the front bolt (or take shims off the rear bolt) to increase positive caster - for that side.

I see where I can yank some shims and prob give myself an extra -.5 negative camber. (Im currently at -.3).

Steve85

I haven't messed with the caster, but I took out all but one of the shims of rearward bolts and then an equal number out of the front and ended up with about -1.3 degrees. Essentially all shims to maxmize neg camber and maintain caster were removed. I think the front bolts have 3-4 shims.

I remember reading Richard Newton's site and I think he said that removing all shims does get you to about -1.5 or so. So, I feel pretty confident my measurement is accurate.

Aardwolf

Go to offset lower bushings or adjustable upper control arms. I can't get enough camber out of mine with all the shims removed. I'm going to use offset bushings and machine those conical spacers to move the arm closer to the frame ear.

dizwiz24

I recently took an alignment class - for my job, and the guy teaching the class kept stressing 'caster is faster' and gave examples of german cars and their handling reputation. Then he pointed out how they were running higher caster than their american counterparts.

I could see his point, because caster makes it so that both tires are cambered the corrected way when you are turning.

jaa1992

I have the same problem. Best I can get is 0 (thats right zero) camber on the front. Offset busings are part of the winter refresh.

Aardwolf

Me too. Did you find a good price on them somewhere? I haven't looked into it much but I'll need to source them soon. I'll be adding zerks in as well.

Kubs

I must have been pretty lucky. On my lowered '90 with all the shims out I was able to -2.0* of chamber. I left one shim in the front bolt and that gave me between 5-6* caster.

This alignment works well with Kumho V710s and their rounded shoulders, but on Hoosiers I round the outer edges in the front and they are about 15-20* F hotter than the inner. I am making my own adjustable control arms to get about -2.5* chamber.

MSR

You're looking to maximize grip, yes? There's a lot you can do to help with that, but it's true you won't find truly world-class grip levels without more negative camber up front. Here's my setup and observations, if it helps:

I have offset lower arm bushings on my '96. I intended to machine the spacers on the upper arm as well, but got enough camber with just the bushings. However, I started out with over -1 as a max, at stock ride height, before adding the bushings.

I originally had a lot of caster when I first installed the bushings, at the slight expense of some camber. I believed this would help very slow, tight radius autocross corners, where the late C4 seemed to give up a lot on the early C4. When I took out all the shims to max camber at the expense of caster, the car went faster, and seemed to grip better even in the tight stuff.

In its current state, I don't ever have front grip issues that aren't obviously track/corner-specific. It's very comforting to finally have that, I now basically drive the rearend. Note that I use a camber brace. The only reason for this is that my particular frame seemed spread apart pretty far, and I got an extra 0.3 degrees per side from the tightening the upper mounts onto the camber brace. (I don't know what happens dynamically, I haven't spent any effort into measuring that, but I do perceive more grip.) Net result is very close to -3 degrees at about a 1" drop from stock ride height. I also keep the car taller than most C4s I see, I have to in order to keep the car off its bumpstops in most corner/bump situations where I race or track.

Additional work was to correct bumpsteer to 0 within -1" to +2" from ride height, 1/16" total toe out, and fresh upper control arm bushings (just oem rubber). I maintain rubber bushings on the anti-swaybars, as I kept having issues with urethane as the lubricant wore off. I use a relatively small front bar compared to most, but I still don't experience very much roll at all. The front is an 1115# spring with a 26mm tubular anti-swaybar, balanced with a 550# rear spring with a 20mm rear bar (from an early C4). I tried quite a few bar combinations, going through an oem 30mm solid front, the Addco 1.25" tubular front, oem 26mm, 24mm, and 22mm rears in addition to what's on the car now. The car was just as fast with the 1.25"/24mm combination, if less tolerant of overly aggressive driving. It would probably be faster if I could smooth myself out and take advantage of the bigger bars. I didn't stick with it because the urethane kept binding up and causing weird issues. It would handle fine for a while, then degrade, after relubricating it. I actually stumbled onto the current combination because I didn't have rubber bushings for the 1.25" bar, and on a whim just decided to try the small bar combination.

I've also been through many different shock combinations, but found shock tuning to be of little value in terms of consistent front grip and balance. They sure did make a huge difference in transitions, and in the apparent responsiveness of the car, though. Having tried multiple custom valvings offered for the Bilsteins, I feel the Koni Sports are as good as anything short of a true competition shock. (I think a forum member is partly to thank for that, as he helped Koni setup the final valving via testing in autocross. The valving still works well even with my spring rates, even though they were tuned with a Z07 or Z51 car.)

hope that helps...

-michael

Aardwolf

I know how you feel about the grease going away. Mine started binding and wouldn't rotate. I've been adding zerks to everything.

Slalom4me

This inquiry is for a '93 C4, correct?

If one does exist, then it just consists of a selection of conventional
horseshoe-shaped alignment shims. There is nothing special about
shims used for the C4.

If by 'kit', you mean a pre-packaged assortment that when installed
will produce a given Caster/Camber combination - then no, a vendor
can't pkg an Alignment In A Box. This is due to mfg variance and
in-service chassis tweaking (curbs, tow trucks & ect.) that lead
to differences from vehicle to vehicle.

It is likely that you are referring to the 'Upper Control Arm Washers'

• the thick one is called 'Position #1' (p/n #10268931 - qty 2)
• the thin one is called 'Position #2' (p/n #10268932 - qty 6)

Yes, this tips the top of the wheel in toward the center line of
the vehicle.

Yes, either action has the effect of tipping the top of the wheel rearward.

Imagine a line passing through the center of the upper and lower ball
joints. If they are directly over top of each other, a line through
them intersects ground level at the center of the tire, which describes
0º caster. If the upper ball joint is positioned toward rearward, then
a line passing through the lower ball joint will slope forward and
intersect ground level ahead of the center of the tire, which describes
positive caster.

0.5º change in camber isn't much of a change. If it is available,
then take it, but a consideration is that it may not be possible to get
the same degree of increase on both sides of the suspension. Several
C4 owners have found that there is less adjustment range on the pass
side for increasing camber.

Except for special circumstances, my vote is that both sides should
have the same Caster/Camber settings. Where one side permits greater
adjustment than the other, this means choosing the lowest common value.

Be aware that when at the limits of adjustment, it can be tedious
to achieve optimal C/C settings. Chasing camber affects caster,
chasing caster affects camber.

To increase the range of adjustment, some gain is possible by
machining (grinding) the Upper Control Arm Washers.

If allowed, offset lower control arm bushings add further gain (it
is important to install the bushings so they are offset in the proper
direction.)

If allowed, aftermarket adjustable upper control arms go even further.



.

rfn026

Ok - I've just caught up with this thread. I run about -2.0 degrees of camber and about 6-degrees of caster. It wasn't easy to get there.

I used the offset lower control arm bushings (VBP) and had the upper donuts machined to virtually nothing. The Corvette Challenge spring (from Corvette Central) lowered the front of the car which also gave me more negative camber.

The result is that I now need shims to get to -2.0. Without any shims I could probably be at -3.0 - which would be way too much.

I'm a big fan of keeping things equal side to side. That's because I'm not that good. The really fast guys have different left and right sides. Sebring is basically all right hand turns. so you need to get the car turning right. At least that's what the pros do. I'm not a pro so I make both sides the same.

Richard Newton
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Slalom4me

'Way too much' for what: daily driving, Solo II events, Road America,
Daytona's banking ?

Within a range, alignment settings are situational. -3º front camber
might be found to be reasonable for a C4 in certain circumstances.
The OP has not stated what his intended usage is, nor what other
changes from OEM have already been made or are contemplated.

Consider the Milliken MX-1, as discussed a while ago in 'He's got more camber than you do'.



.

MSR

Yes, I'm curious about how you determined this. Did you use a tire pyrometer, skidpad testing, lap times... All of the above? What tire? What spring/bar combination do you have on your car?

Thanks.

-michael

Aardwolf

Any idea how much extra the offset lower bushings give?

I can get 1.1° on the passenger side and 1.4° on the driver. 5° caster. I would like to get 2.0°!

Sidney004

On my 94, the offset bushings were worth 1 degree of neg camber. Well worth the effort.

Aardwolf

Thank you. Did you get them from VBP? It looks like they have them for $110, which seems like a lot.

rfn026

First, I do take tire temps - several times a day. If you don't do this you're just wasting your time. Learn how to take temps and then try to learn what it means. It's sort of a black art - but essential.

I've got a column coming out in Vintage Motorsport magazine next month on various tire tools. You need to build a tire data base.

I'm not a huge fan of the VBP bushings but there is no alternative. I would much rather have Delrin bushings but they would make the VBP price seem stupid cheap.

My car is strictly a track car. it's almost undriveable on the street. Keep that in mind here. If my Corvette was a street car I would stay with whatever was original.

btw - If you're going to the Mid-America Funfest I'm going to do a couple of suspension and track day seminars. Love to see some of you.

Richard Newton

lbs90ZR

The VBP offsets added about 1 degree to mine also. With no shims and the spacers ground down as far as possible, it's at about -2.3 camber. Passenger side needs shims to match. I'm pretty happy with the front grip and the tire wear, I still have to flip the tires to get it done. I might have to put those adjustable upper contol arms on the list.

Sidney004

Yes, VBP. I think they are the only game in town for these bushings.

MSR

Interesting, Richard. So what tires do you use that work with -2 degrees on your setup? Tons of factors affect this, of course, track surface, total vehicle weight, bushing compliance (what upper arm bushings do you use?), roll stiffness, etc, so I shouldn't be surprised that two "working" configs would be so different. Also, is yours early or late front suspension?

Thanks.

-michael