The found a failed Body Control Module (BCM) and replaced it under warranty. It was one of those "we can't reproduce it, come get the car" and when I showed up to get the car the battery was dead. Then they started digging. Finally somebody noticed the power to the mirror wasn't shutting off... they traced it back to a failed electronics module...

Well, put a brand new Yellow Top in the car on a suggestion from a friend. Stop issues persists and the battery was down again today when I went out just now to go for a ride. I guess the car is going to the dealership...

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You don't need to do that for track days, or HPDE, or even some time trials (see: NASA). You will need to do that if you're talking wheel-to-wheel racing.

For a nice, safe, first track day, find a local HPDE organization that provides novice drivers instructors. Put fresh brake fluid in, maybe a set of fresh pads, and go out, go what feels to be slow and gentle, and get an idea of what it's like. You don't need to bomb down the straights and fly through the corners to see what it's like.

Also, some organizations are willing to rent you a car, like a Spec Miata, to go out a use so you can try without any work on your car at all... just remember, nobody is turning Michael Schumacher times their first event.

Call Randy @ Doug Rippie Motorsports.

Do you want to do a track day or High Performance Driving Event? This is where you go out, drive the track, don't collect times, and don't race folks. That's where I'd recommend starting. There you don't need a cage. You can even do some time trials, against the clock, but not wheel to wheel without the safety equipment.

If you want to go wheel to wheel, you need a cage and a tonne of other safety gear. And a lot of money, a tow vehicle, a trailer, etc, etc.

Check out www.nasaproracing.com ...

Another good thought, but I actually carry the fob in my left pocket and phone in the right. Somebody elsewhere suggested my battery was having issues, which I couldn't really understand since hitting Stop means the alternator is running already for power, but I'm going to give it a shot. Since the battery had been drained twice there's a good chance it's junk anyway. I put a D34/78 Optima Yellow Top (in the '06) so we'll see if that makes all the issues go away...

Anybody else see this new feature on the Nissan 370Z? The car auto-blips the throttle for you on downshifts!

http://www.nissanusa.com/370z/?dcp=pp ... cc=0.208949595#/features/

When is a manual not a manual? When will we see manual-sequentials in street cars?

0 rake? 1/2" rake? that seems a huge difference, but you'll find people saying both. You'll find people saying cut the stock pieces to lower the car a little more, and others that run the car fairly high.

Where is your car? Where was it "stock"?

So many opinions on this subject... let's hear 'em!

My C6 Z51 showed up 5.0" to the jacking puck holes, front/rear and left/right. I'm actually running -higher- than that right now!

Ah, first coffee. The four post guys have no ceiling height requirements. City by-laws won't let me have a 12ft ceiling that most two-post lifts want...

I'm kind of wanting a four-post if I can swing it. But the minimum pad height on the bridge jacks is pretty high for sports cars (4.5"). I was mostly curious about the Pro-Park because they have a fairly cheap, manual bridge jack system with a minimum pad height of 3.5"...

We've always had two-post Bend-Pak or Rotary at the shops I've been at. Never an issue with them, not sure what's got me thinking four-post... maybe setting toe with the car happily on its wheels...

Anybody know anything about the Pro-Park lifts? I'm familiar with the Bend-Pak and Rotary Lift names, but the Pro-Park guys look to have a nice four-post with a manual, low-profile bridge jack.

It's a dream right now, but want to get some research out of the way, so who can brain dump some knowledge on lifts?

This is getting worse. Went out yesterday morning to start the car after the night before having the "stop doesn't stop" issue and found the car with a dead battery. Looks like my only choice is to strand the car with the dealership for some period of time. *sigh*

Lots and lots of data mining on the internet so take them with a grain of iSalt. You'll notice the C6 Base numbers have a note to the right with a VBP tag... VBP measured the stock springs on their rig and came up with those values which brought at least a little validity to the others.

Do all shocks have high- and low-speed bump and rebound circuits? Meaning, does a non-adjustable have all four circuits? or a single? or double? or do you really need to get in to triple and quad for the shock to actually carry all those features?

I ask because a non-adjustable, or single-adjustable will obviously have a bump and rebound. Couldn't they be built with high- and low- speed as well without adjusters? I'm starting to get the impression they're not typically?

I actually have Prepare & Tune to Win, but I don't really remembering them talking about how the shocks actually work, more about how to adjust them.

It's actually those books that made me wonder why everybody, especially Corvette folks, love to throw huge swaybars on the cars. At $1000 for the Pfadt Pfatty bars, you can put some much higher rate VBP springs on the car...

Just realized the formula you gave is probably OD^4 - ID. So an OD changed is much more drastic...

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Hm. I was wondering if it was the distance from the CG to the actual weight that could let the spring rates be lower if only controlling front<->rear weight transfer, and that's why we needed to add left<->right roll stiffness with swaybars on top of the springs.

Or is it simply that we can generate more cornering force than braking or acceleration forces? Is that statement even true or can we generate the same forces?

I am a little confused, somewhere over the years somebody told me that with a solid bar and a hollow bar of the same diameter the solid bar would be softer. I never understood that -- it sounds like you're saying that's not true? Also, if the formula says (OD-ID)^4 won't the material required to make an equally stiff hollow bar come to the same amount of material?

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Okay, RF will be loaded at some rate, controlled only by the RF bump damping, but the car is a platform on four wheels. If you can't "pivot" around the CG by extending the LF while you compress the RF what's going to happen?

Great pictures!

It would appear you're not talking about crazy handling characteristics there, but rather the fact that your car appears to have four nice solid contact patches and the Noble is showing daylight under both tires on the unloaded side?

Good point about the A-arm and the spring; I had completely skipped that in my head thinking only of the chassis and wheel and not of how it actually all fit together!

What would the "not enough bump damping" option be? Now we're joining another thread and I see why you're looking to combine them! So bump on the loaded side -combined- with rebound on the unloaded side is the roll control, not one or the other?

There seems to be a significant trade-off necessary with shocks in general; everybody wants maximum travel. But more rebound travel means less compression travel, and vice versa. They're both important. Too little compression travel and you end up with an infinite spring rate. Too little rebound travel and, well, what happens? Do you lift the wheel off the ground, or do you force the chassis to follow the wheel?

I had talked with a local shock builder at one point and he talked about running 0 droop and no rebound damping at all. I'm not sure I entirely comprehend how that would work. Seems like it may be okay for a race car, but for a dual-purpose or street car I can't wrap my head around it. I can kind of envision it helping weight transfer, but at the same time what exactly happens when you enter a dip?

No rebound damping. Doesn't that leave the spring uncontrolled to recoil after a compression? Very confusing...

With the soft springs do you choose big anti-roll bars?

What role is each suspension component supposed to have?

Aren't shocks simply there to control the springs? And springs to hold the car off the ground and provide roll resistance? Swaybars to add side-to-side roll resistance that can't [comfortably] be provided by the springs?

If springs are too soft aren't you putting the shocks outside of their comfort zone? Using them to try to control the roll and not just the roll rate?

I'm looking at this as an Optimal spring rate, and then a too stiff or too soft spring rate. It's all about compromise, right? Too stiff works only on smooth surfaces or with a crazy good driver. Too soft has a much bigger sweet spot for surfaces and drivers -- until you bottom out and go infinite on the spring rate.

All this is outside of the whole bump/rebound and what each is supposed to control. Or how a bleed, shim stack, or blow-off come together to control things that cause different shock shaft speeds, of course. :-)

I'm trying to understand the real compromise in valving; since you need to control a front/rear weight transfer, and a left/right weight transfer and those seem like they're very different things. Top that off since the two distinctly different roles of roll control (low-speed) and bumps (high-speed) ... I'm trying to come to grips with how the innards of a shock differentiate that.

• C5 Base Suspension: 23 mm-front / 19.1 mm-rear / 3.81mm/2.0mm thickness
  
• C5 Z51 (97-99): 25.4 mm-front / 21.7 mm-rear
  
• C5 Z51 (00-04): 28.6 mm-front / 23.6 mm-rear / 4.15mm/3mm thickness
  
• C5 Z06: 30.0 mm-front / 23.6 mm-rear / 4.5mm/3.5mm thickness
  
• C6 Base: ?? mm-front / 22.0 mm (7/8")-rear
  
• C6 Z51: 31 mm-front / 25.4 mm (1")-rear
  
• C6 Z06: 31 mm-front / 28.8 mm-rear
  
• C5 Hotchkis: 31.75 mm-front / 25.4 mm-rear / 4mm/4mm thickness
  
• C5/C6 Addco: 32 mm-front / 25.4 mm-rear
  
• C5/C6 Addco: 35 mm-front / 25.4 mm-rear
  
• C5 Pfadt (Adjustables): 32 mm-front / 26 mm-rear
  
• C5 Pfadt (Adjustables): 35 mm-front / 28.5 mm-rear (Pfatty)
  
• C5 T1 (GM Racing): 38.4 mm-front / 27.5 mm-rear / 6.35/6.35 thickness
  
• C6 T1 (GM Racing): 38.4 mm-front / 27.5 mm-rear / 6mm/?? thick
  

Hollow? Wall thickness? Solid? Why does it matter? How can something hollow be stiffer than something solid? Does arm geometry factor in?

What role does a swaybar really play? Soft springs, big bars? Big springs, soft bars? Moderate & moderate?

Why tie an independent suspension together with a big bar? Why not? Why would engineers not design a chassis that could work solely with springs? Why throw swaybars in to the equation? Would the spring rates required simply be too much? Couldn't truly progressive rate springs solve this?

Is a large part of this dilemma because the wheelbase is so much more than the track width?

We all talk in spring rates, but how do they relate?

• C5 Z06: 526# Front, 714# Rear
  
• C6 Z06: 531# Front, 782# Rear
  
• C6 Z51: 526# Front, 645# Rear
  
• T1 (C6): 582# Front, 850# Rear
  
• C6 Base: 420# Front, 657# Rear (VBP: 400-420 F / 600-620 R)
  
• T1 (C5): 582# Front, 793# Rear
  
• Pfadt Coil-overs: 425# Front, 575# Rear
  
• Hyperco HPS (Street): 565# Front (12405HPS), 765# Rear (12406HPS)
  
• Hyperco HPT (Track/Solo): 625# Front (12407HPT), 850# Rear (12408HPT)
  
• VBP Sport 990# Front, 650# Rear
  
• VBP Extreme 1050# Front, 855# Rear
  

What does all that mean? How do you equate a leaf rate with a coilover rate? The answer is "wheel rate," of course. But that doesn't help me understand what a 1200# front leaf is comparable to in a coilover. How does one calculate an equivalence?

Why do we use rebound to control the rate of weight transfer rather than bump?

Left hand turn, two options:

1. Slowing the extension of the left side shock with rebound to control the rate at which we load the right side tire.

2. Use bump on the right side shock to slow the compression of the right side shock?

Theory:

We use rebound to control roll rates, because we want to use bump simply to control, well, bumps. Also, controlling the rate of weight transfer is only part of the system, you still need to control forces applied to only a single wheel. If we used bump to control roll rate you'd have to run super stiff bump valving, but then if you hit a bump, it'd be very harsh, right?

Shock valving seems like a huge compromise when you first think about it; the bump/rebound system to control weight transfer is much much different than the valving you would want to control individual actions on a single wheel. How does a shock tell the difference in its two roles? High speed vs low speed? Single, double, triple, quad adjustable?

Anybody have a good book about shocks and valving? Bonus if it goes in to how the springs and swaybars come in to the system. The number of variables in the system seems huge and it feels an awful lot like the only way to put together something "right" is through a huge amount of testing on each individual platform. Throw in the option of limiting travel by limiting droop, or by limiting bump, and things get even more exciting.

Enough rambling, anybody want to share their theories? :-)

Had to replace the uprights because the LBJs had been run a little loose -- my bad when I installed the poly bushings and coilovers, I guess. But the wrench at the dealership tried to tell me it was so loose things had rubbed the rims... which was entirely false, the 11in wide front wheels rub the tie-rod at full lock.

It's all warranty all the time, including GMPP for this car. :-)

I have very little faith in the dealership these days, not to mention the price gouging on the parts. I'd prefer to walk in having some idea of what they should do or at least knowing whether this is a common problem they should know how to fix.

2006. No tune, no engine mods, not even an airfilter. Just suspension & brake mods.

Really started happening after the cars last trip to the dealership.

Anybody else having times when you hit the stop button, the dash goes dark, the O light lights, but the engine keeps running?

It's happened to me a few times now; caught me out once because the radio was louder than the motor... thankfully there was nothing in front of the car to hit.