gedupont

I've read many of the forum postings where the recommendation is to add Z51 swaybars to the F55 suspension package to increase handling performance. Has anyone also added the Z51 springs?

LTC Z06

Shocks or as they should be called, dampers, are designed to dampen the spring and the anti-sway bar which is a torsion spring, but because it is not always in play it does not over whelm the damper. Z51 springs may be too much for the F55 dampers.

cadguymark

one thing you have to remember is that the damping rate is contolled by a computer program which uses input from several different sensors. To do it right, Changing any of the suspension components should also mean changing the programming. GM did allot of work to get it the way it is, what chance do you have of improving on it? If you want to tinker with things don't get F55, at least if the point of the tinkering is to improve. that said, it's your money and by the way if you do it and find dramatic improvement, let me know, because mine is going to have F55.

torch2000vert

Z-07 freak

... Say what?

Another Yellow

Suspensions are designed as a package by the engineers after careful testing. I'm always amused by those who think they will get improvements by changing part of the package.

LTC Z06

What part did you not understand?

Z-07 freak

Why would the springs from a Z51 be too much for F55 shocks? Or what do you mean by too much?

Follow-up question; IYO, how much better are the F55 shocks over the FX3 shocks?

shopdog

The job of a shock is to dampen the motions of the spring. Too much dampening, and the car will ride like a farm wagon. Too little rebound dampening and it'll ride like a pogo stick. Too little jounce dampening and it'll dive on whoops. The F55 shocks have enough jounce dampening on the sport setting to handle the higher rate Z51 springs, but the amount of rebound dampening available is questionable. That's tuned to the spring rate at the factory, and the tour/sport setting doesn't really affect it much. So the high rate Z51 springs may be too much for the F55 shocks to properly damp in rebound.

On to your second question, the Sachs shocks used in the non-F55 cars aren't very good at all. They have too much jounce dampening, and not enough rebound dampening. Swapping in a set of Bilsteins is an eye opening illustration of the difference proper shock valving can make.

Tom400CFI

Really?? So you don't see a benefit of changing just the shocks?? That is after all, only "part of the package".

Depending on what the goal of the OP is, any part could be changed to get some "imporvement".

Black04Vert

Those engineers changed the sways on the F55 Corvette for 2007 without making any other suspension changes. Does this mean the engineers screwed up and all previous suspensions were designed incorrectly? Of course not.

Black04Vert

I disagree. Adjustable shocks behave the way you describe, F55 shocks do not.

There is no factory rebound or jounce settings on the F55 shocks. The amount of damping is set in real time by varying the amount of current through the shocks. By applying max current, the F55 shocks are stiffer than Z51 shocks, by turning off the current, the F55 shocks provide little to no damping. "Tour" or "sport" settings do not map to a static damping setting, they change the algorithm used to adjust the shocks in real time.

LTC Z06

Do you have numbers? The F55 is very good. I've driven a C5 with the magna shocks, hotchkis bars, full poly suspension bushings, and MPS comp tires around the Nurburgring and it handled the 'Ring very similar to my Z06. If I had the F55 and wasn't going to do track days, I would add Z06 or Hotchkis bars and call it a day. You'll have a very nice handling car that absorbs bumps like no other.

jschindler

Someone posted a couple of weeks ago that he actually measured his 07 bars and they are not any bigger.

However, if they did change the bars, don't you think they might have reprogrammed the shocks to work with them?

Z-07 freak

What are the spring rates for a C6 FE3/Z51?

Miaugi

The short answer is NO! Why don't you let us know how it turns out?

shopdog

The settings actually change parameters used by the algorithm, but for our purposes here that's just a semantic difference. With the current off, the rheological fluid still has a minimum viscosity that's in fact similar to the fluid used in more mundane shocks. So they still provide damping even with the current off.

Ordinary shock valving forms a very simple analog computer. The valving is the algorithm made metal, and controls the response of the shock. The sizes of the jounce and rebound orifices, together with the fixed viscosity of the fluid, determine how the shock will behave.

MR shocks add the ability to dynamically change the viscosity of the fluid flowing through fixed size passages. This provides more dynamic control. But the orifices are still fixed, and the magnetic field can only change the viscosity of the fluid so much.

Adjustable shocks let you change the valving, in essence changing the algorithm the shock uses. But in all cases, there are limits to how much damping you can produce within the parameters of a given shock design.

The MR shocks used in the F55 package have limited ability to control rebound because the rebound orifices are fairly large and the magnetics saturate at 4 amps. They can't damp as much in rebound as even the Sachs Z51 shocks, much less a good shock like the Bilstein.

They do better in jounce because those orifices are sized to give damping control of high pressure transients. Rebound is a lower pressure transient, so the required rebound orifice size in order for the magnetics to have any functional control is larger. But the MR shocks used in the Corvette have rebound fluid passages that are actually too large to handle the rebound transient produced by the higher rate Z51 springs. Even with the magnetics saturated, they flow too much for proper control of a spring with that high a rate. They work fine controlling rebound of the lower rate F55 springs, of course. That's what they were designed to do.

cadguymark

they may have changed the program, how the system responds to the sensor inputs, or maybe they didn't. One thing for sure, if they swapped to Z51 bars they would sell more F55, but not because it is actually better, but that people would think it was better

I would hope that how the F55 supension responds was tailored to the components used, if that is true, then swapping suspension components may actually decrease performance. My theory is if you are the type of person to do mods involving suspension get base or Z51, if you are going to buy F55 leave it alone

LTC Z06

Read my post # 13. This C5 had over 200 laps on the 'Ring (A 12 mile course!), plus every other track in Europe, the owner is a semi-pro who owns a team that runs in the 24 hours of Nurburgring; and is very fast. His car and MR dampers handled the larger anti-roll bars very well and the MR dampers handled his driving and many thousands of race track miles and high speed auto-bahn driving. He does know better than to change the springs though.

crabman

Im with majz06 on this one. I think the F55 upgraded from the inadaquate stock sways may well be the best road combo available. Better ride and give up next to nothing in cornering. For those of us that can admit we dont have the skills of Mario, well, we probably would be giving up nothing at all in the handling department. I would not change the springs, for most owners this will at best reduce ride quality with no real world gain in performance.