YLOFEVR

There's always much talk about switching sway bars, but seldom any reference to changing the leaf springs with it. Isn't this also one of the things necessary to factor in when setting up a firmer suspension? For example, I have a '06 Z51 Coupe. I have a Z06 rear sway waiting in the wings to be installed, 'cause I'm installing Z06 brakes, and ZR1 wheels and Pilot PS2 19/20's. My intentions are to set it up for drag racing--no autocross or track. In this event, shouldn't leaf spring rates be considered as part of the package?

oscarav098

Interesting thread. My C6 has the Z51 package and I recently installed aftermarket wheel and tires. The rear wheels are 11" wide. I've noticed the steering turn-in is not as sharp as it used to be. I'm thinking this is caused by using non-run flat tires and/or the wider rear tires.

Would replacing the rear sway bar with a Z06 sway bar improve the steering turn-in?

All opinions are greatly appreciated.

2006c6keller

I basically agree with all that is said with minor variations of opinion.

In quick reference to the F55 with the Z51 sway bars. The base front spring rate is 420# to 526# on the Z51, the rears are slightly different, 12#'s. I have found out that in the F55/Z51 that you need to run in "Sport" mode in AGGRESSIVE TURNS because the front end will dive and oversteer and pivot almost on a dime, especially if your are braking in the turn. I think and Wayne O will probably agree that the F55 shocks and program was DEFINITELY set up for the base suspension and touring driving, even in "Sport", there was still a lacking until Z51 sway bars added.

I would like to see the ZR1 spring, shock, bar sizes to compare to base, etc. Wayne O, do you have any numbers on this? Thanks!

2006c6keller

Not trying to disagree, remember that the RACING TEAMS have been perfecting the balancing of the car over a period of time AND are now just trying to "fine tune" it to the racing conditions. NO DISRESPECT!

scrannel

Ok, so, not to be picky, but which version of the F55 were/are you running? I believe they recalibrated (to it's detriment) the system after '05 or '06 to give more "feel" in difference between Sport & Normal/Tour.

Thanks!

2006c6keller

As far as I know, the 2006 F55 versions and on were all the same (not familar with 2005, 2004 had three modes I believe) on the base models of C6 (NON ZR1), there have not been any downloads to my knowledge. I think this is the concensus on the CF.

GM only downloads by VIN # with a specific request for a problem, they look for dl's for your particular problem.

Wayne O, have you heard of any dl's for the F55, he has a contact with a design engineer on F55.

The biggest problem with the F55 "feel" is that it worked so well that many could not feel the "real" difference. One way to check is to put car in "tour" at 40 mph and turn steering wheel back and forth very quickly causing the car to roll back and forth quickly and the then go back and forth between the two ride modes and the fenders will stop rocking in "sport". Sport mode really helps in high cross winds.

There have been improvements in: steering, transmission and paddles, clutch packs??, suspension, and I can't think of any others at this moment. Anyone else, please chime in. Thanks!

Dif

I can only speak for my 09, but I notice a lot of difference.

When in Tour mode, it is noticably smooth/forgiving on rough rods and roll is noticable when pushed in a turn.

When in Sport mode, the ride and handling is stiffer and more stable.
I notice the steering stiffens a bit and more precise.
Also noticably "less" forgiving on rough roads and roll is "less" when pushed in a turn.
When the road is really rough, ... switching out of Sport into Tour mode makes a big difference in ride smoothness and in "some" cases, if the road is Very rough, better handling.

The longer I've owned the car, the more I tend to use Sport mode.
On smooth twisties just cruising along, or on the highway at highway speeds, it will be in Sport mode.
But if the roads get too rough, it's in Tour mode for best all around ride.

Some mention they can't feel much difference cruising on the highway, when switching between Tour and Sport.
But I notice right away switching to Sport mode makes the car more stable with improved handling.
My observation for what it's worth.

I'm happy with the Stock ride/handling for 90% of my driving.
But have a set of Z51 bars I want to try on this Spring.
Visually, when looking at the Stock bars, the Z51 bars are a lot bigger

All the posts have been positive and haven't seen anyone complain after putting Z51 bars on the F55 suspension.
My personal concern is how much stiffer they make the ride.
I'll see when I put them on

2006c6keller

What are you waiting for, put those Z51 sway bars on NOW. If you have room to crawl around on the garage floor, install them now. When you first drive with them, your'll say to yourself, "Why did I wait so long to install." After install, you will drive in "Tour" mode all of the time, EXCEPT when driving aggressive and then you will need "Sport" because of nose diving and oversteer in tight turns especially with braking. You will discover a whole new driving experience and now will have some condidence in your car when running with Z51's and Z06's on cruises. Now the enjoyable fun will begin.

NARIMAN

i still can't decide
so for every day i have 13 inch wide wheel and 345 invos on the rear
but i will be autocrossing on stock wheels with toyo r888 tires 305 wide

i how is z06 sway bar for every day basis? safe?

can't make up my mind

avizandum

IMHO, don't do the rear bar. Too much, especially on those tires. Softer is better to lay down the power.

Besides, doing the rear bar bumps you out of stock. Do the shocks and the front bar and you'll be happy.

Nightstalker Medic

I put Z06 sways front and rear on my 2007 F55. Lowered the car too.

Handles like a dream.

Pylons

part of the answer lies in what class you want to compete in

in stock (SCCA) classes, you can only change the front bar, not the rear

NARIMAN

do you mean keep stock rear sway? not even z 51?

NARIMAN

well i want to autocross in stock
i am planning to get r888 tires on stock wheels hope it keeps me in stock

Pylons

yes...the only way (in SCCA Super Stock) you could use a Z51 rear sway on a non-Z51 car is to change *everything* that is associated with the Z51 package (with the exception of things that are "free" in stock class anyway...like shocks and front sways). So to use the Z51 rear sway in SS, you have to have Z51 springs, Z51 brakes, etc.

Pylons

that would be fine...wheels must be oem diameter and width and within 1/4" of oem offset. Tires can be any DOT-approved tire that will fit on that wheel.

NARIMAN

thanks
so why yes for front sway bu No for rears?
is it worth it to put front sway only for me, would i feel the differents
or i should just forget about SS class and do whatever class for fun only

avizandum

It's just the rules... yes, you will feel the difference. A guy here in Detroit runs a stock '08 with Z06 front bar and Z06 shocks and I've ridden with him and the car handles very nicely, and he's very competitive.

I'd start with the simple mods that keep you in stock. The rear bar will make your car very tail happy. I wouldn't do it either way. Also, the R888s need heat to really stick which doesn't happen in AutoX. You might think about running on Bridgestone R-11s or Kumho XSs in street-tire class then tansitioning to Hoosier A6s when you're ready.

I stay in stock. To really make the car faster it's big bucks and it's plenty fast as-is. Do those mods and you'll have a car plenty capable... My .02.

Pylons

it was originally a safety thing and has just carried over...a front swaybar (or bigger bar) could keep a car of the 70's from flopping about all over the place with sticky tires on it (some cars didn't have a bar at all, i think)

Front only can help...I have the 35mm hollow addco bar on my Z51 car. Autox is largely transitional handling and a big front bar is very nice for transitional elements (also helps put the power down coming out of turns).

as for what class, it depends what your goal is...if you're autoxing to be competitive, stick with SS and prep to those rules

if you're just in it for some fun, so the mods you want to do and run where those mods put you.

NARIMAN

makes sense thanks