A Corvette Forum member asked me to provide some in site for the reason we added rear caster settings on the C7, so here goes……
If you recall the camber adjustment on the C6 was done by moving the rear lower control arm rear inboard attachment only. There was no adjustment on the front attachment. So, when the rear attachment is moved outboard to increase negative camber, the rear lower control arm ball joint also moves forward creating rear caster. This also put an undesirable preload on the real lower control arm inboard front bushing.
The further we moved the rear lower control arm rear attachment outboard and the rear lower ball joint forward to increase negative camber, also increased rear caster, and produced ride and roll curves that were undesirable. I no longer have access to these curves, but I do remember we wanted/needed to improve them for the C7. The toe change in ride and roll on the C6 when the rear negative camber/caster was increased produced some motions that were subjectively unfavorable.
So, for the C7, we made both inboard attachments on the rear lower control arms adjustable. This kept the ride and roll curves linear. However, there was a bi-product of adjusting both lower control arm inboard attachments which was a rear caster setting that needed to be monitored as we increased rear negative camber.
Therefore, the rear caster adjustment was never included to be some kind of tuning setting, but it was necessary to maintain 0 degrees as rear negative camber is increased.
When we were at the Nürburgring, several times I worked with our technicians doing alignments on C7’s. Maintaining 0 degrees caster in the rear was not that difficult when increasing rear negative camber. An extra set of hands helped but was not necessary. I believe there is a special tool that goes into holes in the rear knuckle, but all we used was a digital level. There are 2 machined surfaces on the inboard side of the knuckle that the level can be placed against. As we adjusted rear negative camber, we always ensured the rear caster was 0 degrees.
Because of the undesirable toe curves generated when the rear caster was not 0 degrees, we never deviated from that setting.
Finally, I know there are production tolerances on the alignment settings that are way more than I like. Decreasing them was a battle I continually lost. Also, I recently was been told dealers do not monitor rear caster when performing an alignment, I never knew that, but this is also unfortunate.
I’m not sure there is much more I can add, but I hope this helps.
Last year I purchased a C6 Grand Sport convertible. I bought the car in Texas and drove it back to Michigan. In the fall of 2018, Jim asked if he could upgrade my car to get my thoughts. The transformation is unbelievable! The pleasure of driving the car in either tour or sport can’t be understated. On my drive back from Texas I never put it in sport. Now I do almost all my driving in sport. If I just want a nice cruising car, tour is perfect. In both tour and sport, the car just glides over the bumps that used to beat me up bad. Also, I noticed how much better the steering is, which surprised me. Now I can’t imagine driving the car without the new programs. Read More Testimonials ->
After a total of 10 hours of seat time. In both tour and sport. Mix of freeway 55-90mph with hours rural backroad and small-town slow driving. I like this new cal so much. Both tour and sport absorb the bumps very very nicely and are still stable and composed. Everyone will notice a considerable difference. Read More Testimonials ->
Jim come to my house to put the calibration in my 2010 ZR1. When I bought the car, I had to drive it back from Texas to Michigan. 18 hours on the road was a bit of a headache. The car was a blast except for hitting potholes, railroad tracks, and impacts in general. Since the calibration, my car drives and handles 100x better. The impacts seem to be non-existent. Going over railroad tracks are a breeze and the sport mode is a true sport mode now. I’m amazed every time I take out my car. Love every bit of my new calibration. Read More Testimonials ->
The ride and handling for both modes is a dramatic improvement. As soon as I left Jim’s house in tour mode, I instantly felt a more “modern” feel to the car. Very comfortable now and yet more the handling is more responsive. I do not feel the hard rebound over larger bumps. It doesn’t pound my dash when I go over railroad tracks like it used to. I feel that there is more steering response at lower speeds and of course at high speeds.
When I put it into sport mode, I feel a good difference. Now I feel a nice transition between tour to sport. Before the upgrade, I never put it in sport unless I was showing my friends how harsh it was. I am driving it in sport mode more often now. The ride is so much better as well as the cornering. I want to say it feels like a new stab bars were installed. It’s that much more balanced through the corners. Read More Testimonials ->
Just wanted to let you know how happy I am with the driving improvement. Drove over 250 miles yesterday. I am no expert but would say the car feels much more stable, planted, kind of hard to describe but driving over rough pavement sections has a sense that the suspension is working much more refined. These are really nice cars and your program just adds to the experience. Read More Testimonials ->
On a regular basis, I’m on roads with rough, heavily-worn asphalt, pot holes, sections of cracked and broken-up pavement and fragmented road edges. For around-town driving, I have MR set in the “Tour” mode and with Jim’s MR cal the car gets over all those crappy road surfaces with a bit more comfortable ride. On roads which are in better condition, but with bumps and heaves, the ride seems more controlled.
When hammering my ZO6 through the twisties in the mountains near my home–State Route 33 from Oaji, California over to where joins with SR166 is a favorite of mine–I put MR in “Sport” mode. With the Mero-calibrated “Sport”, when driving over high-frequency, low-amplitude chatter bumps, ripples, cracked pavement and stuff like that, I don’t feel those disturbances quite as much. Also, Sport, with a Mero MR cal, seems more appropriately-damped in that kind of driving than did Sport with the stock MR cal. Lastly, the car’s response to steering input, especially in an autocross movement or an emergency evasive maneuver seems different. The best way I can describe this situation is that steering is more “crisp”–for lack of a better word.
In short, I was impressed with Jim Mero’s C6 MagnaRide calibration, not only because of the improvements discussed above, but because his stuff is for “real world” driving and not specific to track use. Read More Testimonials ->