OE PPV & Pedders 2956/2957 chassis spring comparison

[Navy Lifer]

Here's info for comparison of uninstalled springs, with photo: (note - black springs are OE)

PPV springs.JPG (43.04 KiB) Viewed 25222 times

Front
OE PPV PN 92246827 (linear)
wire diameter - 0.600" (15.24mm)
free length - ~13.5"
5 turns

Pedders PN 2956 (progressive wound)
wire diameter - 0.560" (14.22mm) - 6.7% smaller than OE
free length - ~13.375"
5.75 turns

Rear
OE PPV PN 92256816 (linear)
wire diameter - 0.630" (16mm)
free length - ~13.25"
7.6 turns, including pigtail

Pedders PN 2957 (progressive wound)
wire diameter - 0.590" (15mm) - 6.25% smaller than OE
free length - ~13.25"
8.5 turns, including pigtail

Some observations:
1. Pedders lists these springs in the AU catalog for both Commodore/G8 & WM Holden as "zero drop" - I don't pretend to understand what that means, exactly, but this is what I got when I asked the seller: Pedders speak for Zero Drop means that the springs are at the bottom of the stock tolerance. Typically the stock tolerance for springs is about +-7mm, so our stock height springs are typically about 7mm lower than stock. "Stock" in this case does not mean PPV, of course--it's referring to VE & WM civilian spec cars, which ride a bit lower than PPV.

2. Not being an "engineer" with the smarts to do any actual calculations, here's what I do see: Pedders springs are smaller wire diameter than OE PPV springs = lower rate. Pedders springs have more coil turns, which translates to "softer", although the progressive winding design means the coils that are closely spaced, when installed & loaded, will close up into a solid "stack", and the actual working section of the spring is fewer turns, which, for a given wire size, translates to being stiffer--it becomes a shorter linear spring (less working wire length in free coil for same or similar wire diameter = stiffer/higher rate). The working height of the spring at load will be shorter, thus lowering the car. This is much more noticeable on the Pedders rear spring, although the Pedders front spring also has a slightly closer (progressive) spacing of the first couple of turns at the top.

3. The attached photo shows all springs upside down, just for ease of taking the picture. Left side is front springs, right side is rear.

4. Pedders offers several spring combinations - 2956/2957 is a "middle ground" choice. Pedders info shows 646mm (2956) vs 640mm (2954) front, a mere 1/4" difference, and 650mm (2957) vs 620mm (2955) rear, which is a more substantial difference--over an inch. I was not able to figure out what these numbers represent (the mm measurements provided) so the real point is that a 2954/2955 spring package drops the rear of the car substantially over their 2957 rear spring. Here is a picture of a WM on the Pedders AU website http://www.pedders.com.au/gallery/holde" onclick="window.open(this.href);return false; ... rice-sedan that shows 2954/2955 springs, and to me it's too low, but that's a matter of my own preferences, and just how much suspension travel remains at that height. It looks good, I admit, but I'm not sure what the ride would be like--especially with the 20" wheels and quite short-sidewall tires.

5. There are other spring sources, so I'm not suggesting this as an ideal or most preferred--each will have their own preference, taking into account several factors that all can be justified in each case.

Would be good to compare G8 OE springs with these spring combinations to get some idea what they would do vs Pedders - OE is less expensive. too. Later, I'll try to compare G8 & PPV with new SS springs--G8 GT & GXP use the same springs, FWIW--difference in the suspension package (FE2 vs FE3) is that FE3 (GXP) uses gas-charged struts & shocks (as does PPV) and a larger rear sway bar than FE2 (GT).

I'm not sure when I'm going to install these springs--hopefully soon! Will report with pictures and before & after trim measurements when done.

[gregc]

Install them ASAP so we can compare drops.

[Navy Lifer]

Still in Texas, and with time on my hands yesterday, I drove out to Center Point TX, literally out in the "middle of nowhere" (you can look it up). I was searching for Pedders USA....and I found it. In fact, even though it was well after normal business hours, there was (of course) plenty of daylight, and someone was at the location--owner of Pedders USA, Pete Basica. http://www.peddersusa.com/" onclick="window.open(this.href);return false;

While he was there doing other non-business related things, he took the time to help me in my pursuit of information about the Pedders springs I have (but STILL have not installed). He really thought it was great to learn that a few of these cars were actually in the hands of "normal" owners, and I gave him a brief rundown on what has happened in our community, how I got my car, etc.

He even crawled under the back of the car to look at the rear sway bar, saying the car actually BEGS for a larger rear bar (he says 24mm vs OE 16mm is a good thing)--he is curious to see the new parts from VF chassis to see how the bar configuration changes and whether any of the improvements will back-fit to VE/WM applications, so he is holding off on a final recommendation for bar upgrade.

He also explained (from his perspective as an aftermarket supplier) the benefit to using a couple of their bushing kits to markedly improve the worst behaviors this basic chassis (VE/WM) exhibits in production form. I have no personal stake in this, but if it works as described, it is something I will likely do at some point: http://www.peddersusa.com/product/G8-St ... fault.aspx" onclick="window.open(this.href);return false;

Short story long....I will be shipping the two (front/rear pair) OE springs I have to Pedders USA for evaluation/comparison with the 2956/2957 set I've got waiting to install. This will allow a valid match-up between the two spring combinations, to establish difference in wheel rates, what ride height change is likely to result, etc. More to follow, as soon as I get the springs to Pedders.

[Navy Lifer]

Springs (OE PPV) are at Pedders, waiting testing.

I haven't confirmed this with Pedders (for accuracy), but I did some "calculating", based on the info provided in the Pedders website regarding springs, and came up with this:

Front drop with Pedders 2956 spring on PPV - 1.3"

Rear drop with Pedders 2957 spring on PPV - 0.7"

Here's how I came up with these numbers:
Note that Pedders uses a standard methodology for measurement of car height changes that eliminates tire size (sidewall height) variability--instead of measuring from fender edge to ground, the distance from fender edge to lowest edge/lip of wheel is the measurement point. Think about it and it makes sense--completely factors out variations in tire choice between vehicles--invariably someone will say "I used that spring and didn't get the same results"--when trying to make sense of what spring "X" will do if installed in place of what was on the vehicle.

Per Web data:
2956 front on G8 with 19" wheel = 646mm, and with 18" wheel = 633mm (allowing 13mm for wheel radius difference)

The front drop compared to stock PPV springs (using 18" wheel), measured @ 664mm (stock PPV) vs 633mm, which yields a 31mm drop, or 1.3"

2957 rear on G8 with 19" wheel = 650mm, and with 18" wheel = 637mm

The rear drop compared to stock PPV springs (using 18" wheel), measured @ 654mm (stock PPV) vs 637mm, yielding a 17mm drop, or 0.67"

I guess my real question is whether the G8 measurements translate in a meaningful way, and whether the PPV's current stance/ride height is high enough now that the lowering by 1.3" in front is or is not a problem with regard to strut travel. I suspect "stock" G8 front springs do provide a lower ride height than what we see with the PPV springs, which begs the question of whether I'd be "happier" with OE-spec G8 springs instead of the 2956/2957 springs.

Spring rate differences and what the car (and I) will like best remains a bit of an unknown. Hope to know more when Pete @ Pedders checks out the PPV springs.

[Navy Lifer]

While at ISSCA Nationals, the Hendrick Performance PPV was on display. Pictures later, but here are the essentials:

1. LS7 engine - no dry sump

2. Baer front/rear brake package with drilled/slotted rotors and 6-piston Baer monoblock calipers (inside stock steel 18" wheels)

3. Pedders coil-over suspension conversion with adjustable struts/shocks, strut tower brace

If there were other changes, I'm not aware of them.

Body height measurements of Hendrick car:
NOTE: as explained previously, these measurements are taken from the lowest point of the rim (NOT tire or ground) to the edge/top of the body wheel arch

Front - 24.75" = 629mm (vs 633mm calculated with Pedders 2956 springs & 18" wheel)

Rear - 25.125" = 638mm (vs 637mm calculated with Pedders 2957 springs & 18" wheel)

So....if my earlier calculations are correct, and the 2956/2957 springs do result in the numbers I came up with on a stock PPV, the result is going to be VERY close to the stance of the Hendrick car, which I thought looked quite good, even with the stock (9C1) wheels--and much better than the current stock spring stance.

Please realize that this does nothing to address what spring rate changes are, how ride is affected, if bump stops are compromised in any way, etc. More investigation needed to get those answers.

Tom C. or Barry K. may have pictures of the Hendrick car they can post before I get the chance to, so it's possible for everyone to see what I'm saying about the change in stance and it's affect on appearance.

[nick brown]

do all ppv's have springs because it seems like mines just have struts.

[Navy Lifer]

Nick, yes, they all do have springs--the MacPherson strut* is made to rotate at the top--where the spring, which surrounds the strut, rests on a bearing & isolator, precisely located on the body, to provide the intended knuckle inclination angle (caster).

Unlike a more conventional front suspension with upper & lower control arms, the strut serves as the suspension locator for the knuckle, which is bolted to it, and in combination with the lower control arm and radius rod, acts to determine caster & camber settings for the front suspension.

When the wheel is turned, the entire knuckle, strut & spring rotates as an assembly, but the shaft for the working piston of the strut (functions as damper or shock absorber) is secured at the top and does not rotate.

*Wiki - http://en.wikipedia.org/wiki/MacPherson_strut" onclick="window.open(this.href);return false;

[nick brown]

thanks bill

[Navy Lifer]

photo in first post fixed!

[GTObert]

I hear Pedders USA is not in business anymore. Have you heard anything about this?