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?

hm... thinking...

several years ago, this came up with the C4 springs. I don't have the suspension link with me.

The person you really need to talk to is Gary at HardbarUSA.

Well, if you know the wheel rate of a leaf spring setup, and the spring angle of the coilover setup, shouldn't you be able to set them equal to each other and solve for the coilover spring rate?

I'm using this as a reference: wheel rate calculation

Tom is correct, the motion ratios (shock travel/wheel travel) need to be equated. The leaf spring forces are reacted on the lower a-arm in the middle of the web(s) and the coil overs have both the ratio of lever ration and the angle of the coil-overs as well. This is not necessarily linear, and in the case of the C5 and C6 the rear motion ratios for a coil overs are not only not linear/constant but have a falling rate that makes a linear spring a bad idea. The rear shock is at a severe angle and that angle gets less with bump travel. This means that a linear spring that is appropriate at ride height is too soft at full bump and vice-versa. That is why we use a dual rate setup on our Hardbar/Penske coil over package and also use a very significant bump "rubber" (really a polyurethane foam) that makes it a triple rate to compensate for this non-linear motion ratio.

Where did you get those spring rate numbers? The Hyperco and VBP rates are advertised, but I am especially curious about the OE numbers.

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.

I should post up some of the springs and wheel rates from the C4 specs book.

Sounds like a good idea...

Here's the spring rates

http://www.corvetteactioncenter.com/tech/c4/susp_chart.html

FYI,
1 N/mm = 5.7 lbs/in.

Hummm,
One Fig Newtonmeter = 5.7lbs. or 5.7 inches to your waistline?