C5 Corvette Sway Bar Sizes & Leaf + Coilover Spring Rate Research Notes
Submitted by shredjesse on Mon, 11/07/2022 - 11:54
While researching coilovers and then subsequently researching why the QA1 coilovers understeered and drove like shit, I took a lot of notes on sway bar diameters along with spring rates. A lot of informaiton I took from other folks and from various forum posts. Here's my collated information from researching these things.
Swaybars
Make | Front | Rear | Notes |
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 | |
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 | 22.0mm | |
C6 Z51 | 31 mm-front | 25.4 mm (1")-rear | |
C6 Z06 | 31mm front | 28.8mm rear | |
C5 Hotchkis | 31.75 mm-front | 25.4 mm-rear | 4mm/4mm thickness |
C5 Progress Swaybars | 35mm - Front | 25mm rear | 6.35/3.96 sidewall 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 - Pfatty | 35mm - front | 28.5mm rear | |
C5 T1 (GM Racing) | 38.4mm front | 27.5mm-rear | 6.35/6.34mm thickness |
C6 T1 (GM Racing) | 38.4mm front | 27.5mm rear | 6mm/?? Thickness |
Spec Corvette | 38.4mm front | 27.5mm rear | Exact same as C5 T1 supposedly |
AFE Control Sway bars (BLUE) | 35mm | 29mm | Rear adjustable: 465/540/625 lbs |
AFE Control Sway bars Johnny O'Connel(Yellow) | 35mm | 29mm | Chromoly -- 3 way adjustable rears no rates mentioned |
Springs Rates
Make | Front | Rear | Notes |
Leaf Springs (NOTE: higher numbers to coils, but effective rate lower) | |||
C5 Z06 | 526# | 714# | Leaf Spring |
C6 Z06 | 531# | 728# | Leaf Spring |
C6 Z51 | 526# | 645# | Leaf Spring |
T1 C6 | 420# | 657# | Leaf Spring (?) |
T1 C5 | 582# | 793# | Leaf Spring (?) |
Hyperco HPS (Street) | 565# | 764# | 12405HPS / 12406HPS Leaf springs |
Hyperco HPT (Track/Solo | 625# | 850# | 12407HPT / 12408HPT |
VBP Sport | 990# | 650# | |
VBP Extreme | 1050# | 855# | Roughly equivelant to 404/446 lb coilover springs |
COILOVERS | |||
Spec Corvette Penske Shocks | 550# | 550# | Have yet to see a person say they wouldn't prefer stiffer springs in the rear when they discuss their spec corvette rates. |
QA1 Proma Stars | 550# | 550# | Understeered with Progress sway bars |
QA1 proma stars (as I have them) | 550# | 650# | VERY balanced. Had to get custom springs from Eibach. |
Feal 441 Coilovers | 1000# | 560# | Converted from KG/MM to LB/IN |
Aldan America (Default) | 550# | 550# | |
Aldan American (Extra springs) | 550# | 650# | Ships with extra springs for rear |
BC Coilovers | 391# | 559# | Convert from KG/MM to LB/IN |
Silvers Neomax (Stock) | 672# | 447# | 12/8 - Stock car spring rates, "soft" per website. Converted from KG/MM to LB/IN Available in double adjustable. Available in lightweight aluminum bodies to save 5# per kit |
Silvers Neomax (All around) | 672# | 559# | 12/10 normal install for modified performance cars - Standard Convert from KG/MM to LB/IN. Available in lightweight aluminum bodies to save 5# per kit |
LG G2 | 700# | 700# | Per forum post, as provided by LG |
LG G2 | 650# | 550# | Per forum post, as provided by LG |
LG G2 | 650# | 600# | Per user from corvette track enthusiasts facebook group who streets/tracks LG coilovers. |
Viking Crusader Coilovers | 500# | 700# | Suggested track day spring rates with occasional street use. |
Fortune Auto (default) | 896# | 672# | Converted from metric. Per user feedback this oversteers with C6 Z06 swaybars. Rates can be customized, default values just listed here. |
Pfadt Feather Light / Pfadt Black Series | 460# | 600# | The Black Johnny O'Connell Series system does have its own "special tested aggressive valve code" per manufactuer. 28 clicks of single adjustment. |
General Notes On My Findings
- Article from grassroots motorsporst researching and testing coil vs leaf effective spring rates. (TLDR: Not a direct comparison between the two)
- Ultra informative post on measured rate vs stated rate of leaf springs versus coilover springs (TLDR: Extreme leafsprings about Match 500lb coilover springs)
- Differentiation in spring rates on front versus rear is due to leverage ratios. If you look at the rear control arms with a coilover in them versus the front, the front is morevertical, the rear is less vertical. Thus the rear of a C5 corvette will compress the rear coilovers more for the same amount of suspension travel, thus requiring a higher spring rate to help balance the car.
- Spec Corvette runs balanced spring rates and compenstes for it with huge sway bars supposedly. Reviewing sway bar sizing, that very much appears to be the case!
- Per conversation with a fellow who ran spec corvette for two years, he too wanted to run higher rear spring rates but instead was able to get the handling he wanted stiffening the spec corvette rear sway bars, which are already pretty thick per my findings above.
- I spoke with the gentleman who helped develop QA1's coilovers, and he ran 550/650 spring rates per his testing, and is what he recommended QA1 runs, Not sure why QA1 didn't follow that and instead went with 550 squared.
- QA1 does have a 700lb spring available they can send. Eibach of course makes 600lb and 650lb springs.