sjaroslo

I have finally gotten to the point where my car can move under its own power, after having been torn apart since January of this year for a total suspension rebuild. Today was alignment day at my local tire shop.

I brought in JohnZ's article on alignment from Corvette Enthusiast Magazine (Vol 9, Issue 7, July 2006) as my target specifications. I wanted to post what the shop performed and then ask some questions.

Left Front
Camber -.1
Caster 1.2
Toe 1/16"

Right Front
Camber .6
Caster .9
Toe 1/16"

Cross camber -.7
Cross caster .2
Total toe 5/32"

Left Rear
Camber -.5
Toe 1/32

Right Rear
Camber -.4
Toe 1/32"

Total toe 3/32"
Thrust Angle 0

There were 2 issues: #1, they ran out of stud on the right front wheel (rear stud), so he felt that they were OK as far as being in spec but they were unable to meet John's recommendations (the car has been pretty severely t-boned on this side in the past and I suspect the frame repair was not done properly). Issue #2 was, the owner states when I picked it up, "I was able to get the caster real close to the 1.5 degrees since you don't have power steering" -- which of course I DO have power steeering.... John's article recommends more like 3 to 4 degrees with power steering....

So, for those of you who have read this far and have an opinion, do you think that these specs are reasonable, and do you think that the 1.5 degrees on the front caster is OK to live with, even for a power steering car? Given that they ran out of stud with the settings they attained, if I took it back to get the camber dialed up would that exacerbate or ameliorate that situation?

Trying to apply my fuzzy logic to the situation, I am thinking that increasing the camber would require the removal of shims from the rear stud of the right hand (passenger's) side of the vehicle, which would be a good thing in my situation.

They charged me $100, for those of you who track that kind of thing......... Thanks for your opinions!

66since71

I am a bad one to ask about alignment specs, as I like autocross (aggressive handling) setups with lots of camber and odd toe settings. To get all of that camber, though, I used an offset upper A-arm shaft from Moog that was a crash repair part. It will fix just the problem you have (not enough stud for the shims). I got it so long ago, that I'd be surprised if your local auto parts outlet will have it. BUT, I noticed that Vette Brakes has it available. I'll post their PN as an edit to this post.. (check back later if its not here).

This is the edit: I found the box that the offset shafts came in (I keep all of the stock parts I pulled from the car over the years..restoration?) The Moog part number is (was?) K-6104. The instruction sheet in the box is dated 1984. Vette Brakes and Products has the shaft as part of two front suspension kits, part numbers 41751 and 41753. These are expensive kits, but VBP may sell just the shafts, if you call. I'd try Moog locally first! End of edit..

Another edit... It is a current Moog part number. Found on Amazon for $36.77/ea! end of edit

By the way, I would not recommend trying longer studs. This just increases the bending moment on the stud (it may be more prone to break). Note that road racers used the offset shaft and/or offset bushings, not longer studs.

Harry

kellsdad

A comment on your caster settings - My understanding is that larger caster angles help the steering center more easily at speed and make the steering more stable. The downside is that it takes more force to turn the wheels at very low speed such as when parking. Power steering solves the low speed problem. Us manual steering guys run lower caster angles for low speed maneuvering at the expense of a little high speed stability. ... I suggest you drive the car with the current settings and see if its comfortable. If its not, then change it. ... I had an excellent four wheel alignment after I rebuilt my car, but it drifted just a little on the majority of the roads on which I drive. I tinkered with the shims until it felt right to me.

Lee H

After a suspension R&R this spring I took my 65 vert to the alignment shop with John's spec. The tech said no problem and got it right on. $65 dollars.

JohnZ

To go more negative on camber at the right front (to match the left front camber setting) would require more shims on each stud (not removing shims), and that's where they ran out of stud. In order to do that you'd require an offset upper control arm shaft on that side.

If you're on radials, the front toe (5/32" total) should be zero to 1/16" total; 5/32" would be correct for bias-ply tires.

Looks like they did an excellent job at the rear.

66since71

I jumped right to the solution in my first post.. sorry.

I think more caster is better, if you have power steering (I agree with kellsdad). I am also sure, that for a street car JohnZ has made some good recommendations.

Both my Original Owners Manual and the factory service manual for 1966 do not distinguish between power steering and conventional steering.. They simply list: 1 +/- 0.5 degrees. So the shop that did the alignment may be right that it is set up to factory spec.

To get more caster, you have to move the upper ball joint rearward. You do that by adding (not removing) shims to the rear most stud. If you have run out of stud, and are still not close to your target, you are probably right about the frame being bent. Thats expensive to fix, so I recommended just changing out the upper A-arm shaft to get more effective adjustment range. The shaft is probably the equivalent of getting 1/4' to 3/8" additional shims in. VBP suggests that a setting above 2.75 degrees caster will require the shaft or a special A-arm. So the frame may not be that badly bent.

Finally $100 for a complete front and rear alignment seems pretty fair to me..

Harry

sjaroslo

Thank you all for your replies.

Harry, I don't understand how one would want to move the upper ball joint rearward to increase caster; it seems to be it would be the opposite, you want to move the upper ball joint in front of the lower, therefore, on the passenger side, that would be done by removing shims from the rear bolt, allowing the crossbar to move outboard at the rear, pivoting it on the front bolt and moving the balljoint forward. Having the upper ball joint in front of the lower would create positive caster, and would encourage the wheel to point strait ahead.

JohnZ, did you have an opinion on the caster? Since I have power steering, should I ask them to set it to the 3to-4 degree setting? Thanks.

GTR1999

I just got back my 72 and here is whatI got for comparision.

LF camber -.1 RF camber .3

LF caster 2.8* RF caster 2.9*

LF toe .13 RF Toe .13

Steer ahead 0* What is this spec? Th toe seems to be out but the car steers straight.

Rear

LR camber .1 RR .1

LR Toe .11 RR Toe .13

This was done on a hunter machine and I guess it has color coded windows - green - good Red NG?

What do you think, this is one of the few things I have to farm out. I was looking for toe to be 1/8" instead of 1/4"

What signs should I be aware of if out of spec?

I have not driven the car myself yet.
Thanks,
Gary

Joys

Sjaroslo, I'm afraid you have it backwards. Think of the way a bicycle has the front fork(leaning forward) This gives a positive caster angle and aids steering return/straight ahead stability. Negative caster will make your car not very pleasant to drive!

sjaroslo

Joys, I see what you are saying about the bicycle, but whenever I think of caster I always think of the front wheels on a shopping cart. The axle of the wheel (the lower point) is well behind the attachment to the cart (the upper point) while moving forward. Whether you push the cart forward or back, the wheel will always pivot to have the upper connection "leaning in" to the direction of travel, and have the lower point trailing. So to me, "increasing the caster" is akin to making the assembly more like a caster wheel--the lower point is behind the upper point, therefore, I want the upper ball joint to pivot forward, therefore I want to remove shims from the rear bolt.....

I've certainly been accused of having fuzzy logic in the past, and it seems likely that I'm suffering it again in this case, but I'm just not seeing your scenario.....

66since71

Grocery cart is a good example! The wheel turns around a vertical shaft. That shaft is always in front of the wheel, in the direction of travel.. Namely it's axis intersects the ground at a point in front of the point where the wheel contacts the ground. On your car, adding caster means getting that point on the ground further in front of the wheel. A line through the two ball joints is the same as the shaft. In the case of C-1's, they actually have a shaft (the kingpin).

Hope this hasn't made it even more fuzzy??

Harry

JohnZ

Caster angle is the side view angle of a line that intersects the upper and lower ball joints. You always want it positive (so the line intersects the ground forward of the tire contact patch), which improves tracking and steering returnability. Moving the upper ball joint rearward increases positive caster, moving it forward makes it less positive.

sjaroslo

It is official--I'm a dumbass.

Thanks everybody. From now on, I'm going to be the smartest man on the face of the Earth. I will apply my keen intellect and power of reasoning to every situation that I am faced with. Upon arriving at the only logical conclusion, I will commence to do the exact opposite thing as I think that I should.

I will never be wrong again.