After screwing with the rear spring (changed to a VanSteel low arch 360) and the front spring (cut 1/2 turn off each) I did a rough (very rough) rear camber set. Now I want to do a little better setting while I have some time (it seems)

I made us a set of cheap rails to clamp to the rim so I can measure toe etc but I would like to verify the thrust and I can't get a decent reading to the side of the frame without removing the rocker moldings and I was trying to avoid taking more stuff apart.
Is there any other KNOWN symmetrical location on the frame I can check to or am I stuck removing the rockers?

Also, can anyone confirm my calculation
Trailing arm length (wheel center to pivot pin) = 17 3/8"
A 0.1" shim would equal 0.33 degrees on the wheel?
(0.1 shim would be about 0.160" change in toe on a 28" tall tire)

Thanks
M

 

You are close - small angles are equivalent to radians. That times 57.3 (approx) converts to degrees.

So (0.1/17.375) * 57.3 = 0.329....

 

Thanks
Now to find something to check to see if my toe is centered even remotely close
M

 

Use the front axle points, since that is the what drives the front wheels. Now Also check how good all the axle points are. There should be equal distance front vs rear wheels. (Wheel base)

Here is my DIY alignment method. This shows you how I setup rear thrust and check the axle points. (Wheel base measurements)
https://www.corvetteforum.com/forums...nt-method.html

 

For a lot less than a full alignment, I suggest you get an alignment check with a printout. Now you know what you are working with and have a baseline.

 

Thanks
I been referencing that post often with this and the only thing I'm trying to avoid right now is using the front spindle for a reference since I'm not sure where it is on either side (all front everything has been replaced and initial alignment is unknown, pulls a little to the right and floats more than I'd like (roads around here are terribly rutted) so I was trying to get some point from anything else to start with.
I thought about it yesterday and I think I'm going to see if I can get a starting reference off the lower balljoint somehow as that should be a fixed point on both sides

Got the rear camber set last night and did a quick toe check and it's at about 3/32 (total) measured from the front of the tire to the rear (28" tire) with unknown thrust
Then I noticed that Vansteel is saying 1/8 per side (.265 total) and VBP is 1/8 (+1/32 -0) total, greenwood 0-1/4 total... so eventually I'll try for a little over 1/8 total I guess...
I'm measuring at the wheel front/rear but one of the videos I watch where the guy flipped the rotor (I'm on the rim) he's measuring 1/8 across the rotor, that's got to be 1/4" on the wheel, per side.... TO me toe was always measured at the front and rear of the actual tire...

It's supposed to rain today so this will be a good day to roll around the floor with tapes and straight edges
M

 

That's my plan, but I want to get a few things closer and then take it in for checking so I can see how my measurements work out, putting in time more than most I think
M

 

I guess its 6 of one and half a dozen of the other. I replaced my ta bushings, did a camber and toe alignment in my garage with the Longacre alignment kit and then went to the alignment shop for a full alignment. When I got home I checked the shop's settings with my alignment kit. My kit was darn close to the sophisticated laser alignment at the shop. As for all the alignment specs out there, just choose the one that suits your. Don't get hung up over a +/- 1/64" total toe difference between different sources for alignment specs.

 

I was just surprised when one was double the other
M

 

If you use the center of the front spindle it doesn't matter what the front toe is set to. Center doesn't change. If you use the edge of a wheel then it wont work.

Also because of the distance you are measuring a 1 mm difference over 98" (wheel base) is only 0.023 degrees even a 3mm difference is only 0.069 degrees.

 

I suppose the difference would be pretty minimal
I was just thinking if the camber is different side to side it would toss that measurement, also my centercap / spinners but I guess I can check that from the outer rim and see that they are the same easy enough
My floor is level at the pads left to right but slopes away about 3/4 degree towards the door (rear of the car)

Right now with the laser and a tape it seems the passenger is toed in more that the passenger (4-7/16 minus on the passenger and 4-29/32 on the drivers) which is totally possible and I think in theory I should be able to use my measured toe and some trig to verify it that is possible
Care to share your excel sheet

M

 

The Sheet I have is setup for my measure bar and setup so it may not work for you, but I don't use it anymore since I have pre calculated a difference from 1 - 12 mm. So for my DIY toe settings I adjust for 0-4 mm difference which is 0 to 1/16" toe in.

Make you own chart

eg. If the front bar to rear bar difference is 2780 then for 1mm difference = inverse tan for 1/2780 = 0.02060999 degrees total toe.

1mm= 0.02060999 degrees
2mm= 0.0412199 degrees
3mm= 0.0618299 degrees etc.

Then use a online calculator to convert degrees to toe inches.

https://robrobinette.com/ConvertToeDegreesToInches.htm

So for a 27" dia wheel

1mm = 0.019424457533470052" or 0.62158/32"
2mm = 1.24/32" etc.

1mm=

 

Already done (excel) not as complete as yours but enough for what I'm doing (I think)
Thanks again for the post
M

 

OK, finally back to this
Close and yet all over the place

Just want to verify something for anyone who knows, when checking caster and turning the wheels from 20deg left to 20deg right, does the level go "through" zero.
I didn't zero on the turn either way (zero on straight ahead) and was surprised to see that it went from minus when turning the one way to positive turning the other way, Total angle movement works out, just curious
M

 

Usually I leave the level at 0 for a actual 0 degree angle. So if camber is -1.0 with the wheel straight (using left wheel) turning the wheel 20 degrees right and angle should read more negative camber eg( - 2.8 degrees), and when you turn the wheel left it may read + .5 where the total degree change is 3.3 degree's. So for 20 degree wheel change the multiplier is 1.5 for caster ~ = 3.3 * 1.5 = 4.95 degrees

On both my 78 & 2010 corvette the actual camber angle goes from - camber to positive camber.

 

These posts are some of the best content on this site.

 

Thanks for verifying the caster measurement change through zero
Right now mine is set so I get -1.8 to +.85 so total 2.65 * 1.5 = 4 deg on the drivers. I could add a little more on there but can't seem to get much more than 3.7 (started with just over 1) on the passenger so I'm going to take a little out of the drivers to get them close to each other then see if I can do any more once I take it for a drive. VBP was suggesting only 2.75 at one point anyway so I imagine I'll be lots happy with 3.5

Then I've got to see where my camber ended up. Was at 0 on drivers but .5+ on passenger, I'm going to try for 0 to -1/2
Front toe is a bit much at 1/4" but actually drives fairly decent at speed so I'll back a little out and see what the other changes do and go from there

Back toe total was good but the thrust is towards the drivers side too much so I'm planning on moving 1/16 shim from the drivers inner to outer and the passenger outer to inner to hopefully leave the total about the same but move it closer to center. The machine says 1/4 degree out and my rough calculation was .1 shim = .33 deg so the 1/16" shim should be close to .25 ish....
I'll do that last anyway
I'm some glad I moved the alt to the passenger side, makes getting at the drivers side shims a lot easier... of course the passenger side is now slightly harder....

Anyway, another rainy day tomorrow so maybe I'll get another chance to play around
M

 

So I adjusted the rear toe today and I'm not sure what went wrong.. or if it did
Toe was .1875 when I measured it, .160 on the machine
Thrust was .484" difference from one side to the other (laser to spindle) which calc to .28 degree, machine said .24 degree so actually pretty close
BUT
I just realized that the difference I measured should be cut in half when calculating the angle (I think) so I would have only measured .14 deg which is not really all that close anymore (I know, tape measures and all)

Going by the machine, the toe on the drivers side was -.04 (actually toed out I guess) and the passenger side was .20 in (total .16)
So I moved 1/8 + 1/32 from the driver inside to the outside and on the passenger I moved 1/8 from the outside to the inside thinking that the driver side was off more than the passengers type of thing

Went for a drive around (hot and humid today, thunderstorm warning in effect)
Checked the rear toe
Measures .25 total (a little less maybe)
But now I'm 7/8" different (7/16 thrust) on the spindles towards the passenger side...
Guess I took WAY too much of a bite

so I'm going to ***-U-ME that a 1/8 + 1/32 change on one side + a 1/8 change on the other side made a total change of about .242 one way to .4375 the other = .680 (to keep it simple) swing. then I need to come back a hair less than 2/3rds (.643)
so instead of moving the 1/8 shims over I should have only moved 1/32 shim over and then another 1/32 on the drivers side

Back up on the quickjack...
M

(On the plus side, the front seems good)

 

1/8 shim change is like .8" change at the front spindle... what was I thinking
M

 

Did you take the time to remeasure the alignment to see if you can replicate what the machine measured. This would have been a good time to refine your measurement technique. You should also be able to repeat the same measurement 3 times.

So what measurement did you get at each front spindle. For my 2010 corvette I get 135mm and 134mm. (distance from the laser line to the front wheel center hub) laser mounted on each rear wheel.