Thought I'd pass on a bit of information to all the new C7 owners in No. California. We have at least two alignment shops in our area who are, in my opinion, qualified to do the special rear caster alignments on the C7's. And they both have the required special tool to do the job correctly.

1) Gary at the Alignment Shop in Fairfield (707) 399-7275, and

2) Mark at Motorsport Image in Roseville (916) 784-2323 (yes, Mark is still doing alignments).

Give either of them a call to book an appointment.

Ernie

 

Is this needed when you lower a C7 via the bolts?

 

Conceptually, lowering will slightly alter the alignment. I don't think most folks worry too much about those slight changes in alignment, though. New factory deliveries, however, are frequently out of alignment enough to affect both handling and tire wear. As an example, on my 2015 C7, front caster, front toe, and rear caster were all outside of factory specifications when checked at 4200 miles. The settings that were within factory specs were not optimum settings, nor symmetrical side to side, and essentially every one of them was changed slightly. I think it's prudent to have the alignment checked early on, then periodically thereafter.

Ernie

 

C7s need the rear caster aligned? I know these beasts are new from the ground up. Do they have rear wheel steering?

 

Changing the rear caster is going to affect the rear bump-steer since it changes the height of the toe link. Perhaps GM's rear caster specification is designed to minimize the bump-steer, but that's got to be an average across the manufacturing and assembly tolerance of all the parts involved. To really set it correctly, I'd want to check the bump-steer as I adjusted the caster to get bump-steer as close to zero as I could. I noticed that GM changed the rear hub carriers and the way the toe-link attaches to the hub carrier on the C7. On the C7, the toe link now attaches with some kind of horizontal joint instead of the vertical ball joint used on the C5/C6 hub carriers. Side note... I don't know if anybody actually does it, but since the C5/C6 rear hub carriers are the same as the fronts (left for right, right for left), in theory you can modify and install Baer's front bump-steer kit to allow you to adjust the rear bump-steer independently of camber, caster, and toe.

I wonder if the "special tool" is a bracket that attaches either an angle gauge or mirror (for a laser setup) directly to the hub carrier to provide a direct reading of the caster. Normally caster is derived mathematically by measuring the change in camber across a known sweep (i.e. by steering the wheels through an exact amount of steering angle, like +/- 15 degrees), but obviously you can't do that in the rear.

Bill

 

No rear wheel steering, but the new C7s do require setting rear caster to 0.00 degrees +/-0.8 degrees. Since you can't swing the rear wheels thru an arc as done with front caster adjustment, a different method must be used. An adapter bracket is placed in pre-drilled holes in the spindle, then an angle gauge (zeroed to the alignment platform) is attached to the adapter. Caster angle is read directly on the gauge readout (exactly as stated by Bill, above). All rear adjustments are made via eccentric adjusters, even the toe setting -- 3 eccentrics per side.

Ernie

 

Wow, that does sound like specialized equipment is needed.