Modshack

Those of you from the old C6 days know this was a desirable mod. The Base C7, not having a rear bar stock requires a few more hardware bits, but nothing expensive or tricky. The (Z51) mount points are on the car so this upgrade is very easy. While I'm not the first to do this, I contacted Gene gene@gmpartshouse.com at GM partshouse and requested he put together a kit for me. Gene's pretty much the parts expert here, and he quickly put the list together, I gave him the Go, and a week later I had the parts on my bench. Cost was around $275 + whatever shipping to you is.

Here are the parts:


2 Z51 bars, bushings (now Poly instead of the OEM soft rubber), Droplinks for the rear, 2 clamps, 4 bolts and 4 nuts.

First step is to mount the drop links to the rear bar. Note the Nuts are interference types, so you'll need an 8mm socket to keep the joint from spinning, and an 18mm wrench to tighten the nuts:



It is an easy job to mount the rear bar into position. Use the new clamps, and bushings. Lube before assembing. Attach the drop links to the Lower control arm and you're done. a 20 minute job

Existing mount points:



Bar and droplink positioning:



Clamps on, tighten these and droplinks and Done.



The front is a simple remove and replace but a little more awkward to work on. Remove the top drop link nut:



Remove the clamps and fish out the bar. Lube new bushings and reverse this operation.



This completes the swap.
Everyone likes stats so here they are.

Front stock bar 7.85 lbs, 26.2mm (hollow)
Z51 bar 7.95 lbs, 28mm (hollow)

Rear Z51 6.9 lbs, 26.5mm (hollow) + 2.2 for new hardware.
Rear stock None

Net increase in weight 9.2lbs

Driving impressions: I ordered a base car for a variety of reasons. I did this in 2008 as well and was very happy with how the car turned out with a minimal investment. The C7 does not disappoint. We know it handles great, but it wallows a bit, particularly in the rear on undulating turns. The Z51 bar ties everything together nicely. No body roll, tied down feeling in the rear, and a big increase in confidence when pushing the car. No change in overall ride quality, though a little stiffer when traversing uneven surfaces. It is uncanny as you can literally feel all 4 corners of the car working. This I mean in a good way!. Overall this will probably be the best $300 you can spend on your base car if you put any value on handling. Everyone knows how good the Z51 is. Build yourself a Z25.5 for a few bucks, while retaining the ride quality and comfort you currently enjoy. Gene is geared up on these. Shoot him an email to order.

Steve

ZPirate

Nice write up Steve. I'm certain a lot of the base C7 owners would enjoy this mod.

Modshack

Thanks John!...

Theta

I laughed really hard at the 25.5 line. Nice write up!

Vic T

You've got me considering this now, Modshack. Thanks for the detailed writeup. I wonder if you had thought about leaving the standard front sway bar in place (since it is matched to that front suspension) and just add the rear bar?
Did anyone advise you one way or the other and give good reasons why?
I really like the ride quality of my standard C7 so a little reluctant to mess with it, but since I will not track the car, would you still think it's an overall improvement?

Gene Culley

Thank you for your business and the awesome post!

Nyvetteguy007

Did this on my C6...Is on the list of mods to do to my C7

Modshack

I did not consider leaving the stock front bar on for several reasons. Bars are usually paired in appropriate sizes to achieve some neutral-ness in handling.
A bigger front bar will increase understeer.
A bigger rear bar will increase oversteer (or in most cases reduce understeer somewhat, same thing).
Ideally you meet in the middle somewhere with a balanced chassis.

Balance here is the key. Weight distribution front and rear, Tire slip characteristics, spring rate all come into play. Fine tuning can be done with tire pressures. Reduce the front pressures, increase understeer (tires plow), Increase rear pressures reduce oversteer (tire slip angle is reduced). As you can see it's a balancing act. The Z51 combo is pretty well engineered and achieves almost perfect balance. I'm sure the engineers spent a lot of time on this, so why second guess them? My decision comes from years of experience on numerous platforms, most of which I've added suspension parts to improve. Bars are easy and effective with immediate and noticeable results. Anti-roll bars are essentially torsion springs which increase overall spring rate when they are unevenly loaded (as in a turn). In Straight ahead driving they impose no additional springing so do not affect the ride in that mode. Overall, the package improves chassis control, therefore handling. The car is more tossable with a greater feeling of confidence and control. No wallowing or feeling of "Looseness" on undulating turns. If you just do the rear bar, I'd juggle tire pressures a bit (increase rear a few PSI), but overall I'd recommend both for best performance. adding the front is only a + $100 more..

killascrimp

[QUOTE=Modshack;1586736254]I did not consider leaving the stock front bar on for several reasons. Bars are usually paired in appropriate sizes to achieve some neutral-ness in handling.
A bigger front bar will increase understeer.
A bigger rear bar will increase oversteer (or in most cases reduce understeer somewhat, same thing).
Ideally you meet in the middle somewhere with a balanced chassis.

Balance here is the key. Weight distribution front and rear, Tire slip characteristics, spring rate all come into play. Fine tuning can be done with tire pressures. Reduce the front pressures, increase understeer (tires plow), Increase rear pressures reduce oversteer (tire slip angle is reduced). As you can see it's a balancing act. The Z51 combo is pretty well engineered and achieves almost perfect balance. I'm sure the engineers spent a lot of time on this, so why second guess them? My decision comes from years of experience on numerous platforms, most of which I've added suspension parts to improve. Bars are easy and effective with immediate and noticeable results. Anti-roll bars are essentially torsion springs which increase overall spring rate when they are unevenly loaded (as in a turn). In Straight ahead driving they impose no additional springing so do not affect the ride in that mode. Overall, the package improves chassis control, therefore handling. The car is more tossable with a greater feeling of confidence and control. No wallowing or feeling of "Looseness" on undulating turns. If you just do the rear bar, I'd juggle tire pressures a bit (increase rear a few PSI), but overall I'd recommend both for best performance. adding the front is only a + $100 more..[/QUOTE HAS anyone swapped the suspension for the larger bilstein shocks? that would a nice touch, it would be a Z3.0

Modshack

I don't think anyone has done that (yet). I added Bilsteins and bars to my C6 and it was really nice. The C7 has Bilsteins (35mm shaft) stock. The Z51 units are 45mm. When folks start adding coil-overs I'm sure some lightly used units will come on the market. Again, consider balance, as the stock shocks seem well paired to the spring rates. Increasing shock rates without increasing spring rates will impose some stiffness increases. Dunno how much til it's tried though..

kp

Good post, may do this down the road but so far rear sway-less it seems to be OK. Give me something to do I guess

Wonder if the springs are higher rate for the Z51, I would assume they are.

Modshack

I understand they are..

FYREANT

I sent an email over to Gene to order mine. Hoping he gets back to me soon!! :-)

Modshack

He's pretty good about that!...

Gene Culley

Thank you for all of the orders. We are getting them in steadily and will keep working on getting them as quickly as possible. Contact me to order your set today!

AFVETTE

I too did this mod to both my C5 and C6 and love it. Best bang for your buck.

Maybe I missed it what what are the torque specs on the various nuts/bolts?

And this will be the first accessory I order for my new C7, so Gene will get my first mod money.

Tom
USAF Retired

STINGREYES

Did this mod a week ago and after a few hundred miles on the. 2014 C7 BASE 2LT VERT A6
I agree with ModShacks assessment below, well said ModShack.

"The C7 does not disappoint. We know it handles great, but it wallows a bit, particularly in the rear on undulating turns. The Z51 bar ties everything together nicely. No body roll, tied down feeling in the rear, and a big increase in confidence when pushing the car. No change in overall ride quality, though a little stiffer when traversing uneven surfaces."

ncrowe

Gene is great - I ordered mine about a week ago, got them quickly. The front sway bar I got wasn't the right one (not Gene's fault - it had the wrong stickers on it from the factory - see pic with 2 different part numbers on the same bar), Gene is already ordering me a new one. Always be sure to measure your bars - 28 mm for front Z51

I can tell you with the rear bar on the car is definitely much tighter, but you can definitely feel the slop of the stock rubber bushings in the front when you have the rear bar and poly on the back - can't wait to get the front bar on!

I would recommend Gene to all

Vic T

OK guys, I have caved and sent an email to Gene to order the Z51 sway bars. Thanks for starting this discussion and providing an education, Modshack, and to Stingreyes and Ncrowe for pushing me over the edge.

FYREANT

I ordered from Gene as well, and my bars will be here in 2 days time. Im so excited!!