From complete scratch C5 full suspension measurements and calculations
 

From complete scratch C5 full suspension calculations:
All measurements taken and rechecked. String used to center up bolt holes to give a clear measuring point. Measurements are accurate to 0.1 in

Front Lower Control Arm:
Total length of arm from chassis bolt holes to steering knuckle ball joint 15.75 in
Length to leaf spring pad 10 in
Length to sway bar link 10 in
Length to damper mount 12.75 in


Rear Lower Control Arm

Total length of arm from chassis bolt holes to steering knuckle ball joint 17.65 in
Length to leaf spring mount 11.1 in
Length to sway bar link 7.8 in
Length to damper mount 14.6 in









Ride Height Calcs:

Stock wheels on, 275/40r17 / 295/40r18

Front right fender lip 26 and 7/8 in above ground
Bottom of hub is 10 and 3/4 in off ground

Front left fender is 27 and 1/8 in

Rear right fender is 28 and 3/4 in
Bottom of hub is 11 and 5/8 in off ground

Rear left fender is 28 and 1/2 in







Angulation of Dampers while car is at normal ride height:
Dampers are tilted in towards the chassis at the top. With bump (wheel moving up into the wheel well) the angulation will increase. The rear dampers are also leaning towards the tail of the car, and lean more as they are compressed.

Front damper measured 64 degrees
Rear measured 52 degrees, and drops with bump. 49 degrees with a good bit of bump





C5 sway bar dimensions and lengths:

A Bar width
B Arm length (from center of bushing to link hole)
C Arm perpendicular distance (from center of bar measured 90 deg back to mountinghole, without regards to lateral width)
D Arm lateral width (measured in parallel to bar to mounting hole)

2002 Factory Z06 sway bars (measured while off car)

Front:
Outer Diameter 1.18 in
Inner Diameter (supposedly) 0.177 in
A 32 in
B 12 in
C 8 in
D 8 in

Rear:
Outer Diameter 0.94 in
Inner Diameter (supposedly) 0.138 in
A 25.5 in
B 11.25 in
C 5.2 in
D 9.2 in


GM T1 sway bars (Measured while installed on car)

Front:
Outer Diameter 1.5 in
Inner Diameter (supposedly) 0.25 in
A 32 in
B 12 in
C 8 in
D 8 in

Rear:
Outer Diameter 1.07 in
Inner Diameter (supposedly) 0.25 in
A 25.5 in
B 12 in
C 4.75 in
D 9.5 in

Why not weigh everything too so then you can do all the empirical calculations for springrates wheel rates and chassis frequencies etc?

I plan on doing that when I take the leaf springs off. I'm going to directly weigh a front and rear corner with a scale.

Rate calculations coming up next. Wheel rates at leaf pad / mount, damper / coilover mount, and sway link connector. I will have a simple coefficient that you can multiply your leaf spring, coil spring or sway bar rate with to yield your wheel rate.

L8d

Angle of dampers in relation to chassis (they are tilted in at the top)
Front damper measured 64 degrees

Rear measured 52 degrees, and drops with bump

49 degrees with a good bit of bump. Will use 51 deg as a middle ground estimate.


OK so new wheel rate "multiplier calculator numbers" with measured angles on my car:

WheelRate = SpringRate * MotionRatio^2 * sin(SpringAngle)

Front:
WheelRate = SpringRate * MotionRatio^2 * sin(SpringAngle)
WheelRate = SpringRate * 12.75in / 15.75in * sin(64)
WheelRate = SpringRate * 0.655 * 0.899
WheelRate = SpringRate * 0.589

Rear:
WheelRate = SpringRate * MotionRatio^2 * sin(SpringAngle)
WheelRate = SpringRate * 14.6in / 17.65in * sin(51)
WheelRate = SpringRate * 0.684 * 0.777
WheelRate = SpringRate * 0.531

So Final Multiplier Calculator Numbers to calculate wheel rate from coil spring rate for the C5 corvette:

F 0.589
R 0.531

So if you run 1000 lb/in coil spring up front, the wheel rate is 589 lb/in

If you run 1000 lb/in coil springs in the rear, the wheel rate is 531 lb/in

Just multiply one of the numbers above by the coil spring rate to get your rate at the wheel.

More information to come regarding ride frequencies, and estimated (not measured) sway bar rates for stock 2002 C5 Z06 sway bars and old style (non adjustable) GM T1 sway bars.

Front stock Z06 leaf wheel rate 108 (as per another website)
Rear stock Z06 leaf wheel rate 151

Corner weight average no passengers of my 02 Z06 (with extra safety equipment and cooling equipment)

868 lbs front 741 lbs rear
Add 200 lb driver est:

902 lbs front
807 lbs rear
est that unsprung weight is 85 lbs front, 80 rear

Great ride frequency calculator!
https://www.racingaspirations.com/ap...cy-calculator/


OK! Wheel rates per spring, and ride frequencies

Front:

Coil Spring Rate (lb/in) Wheel rate (lb/in) Ride Frequency based on above weights (Hz (cycles or bounces per second))

200 lb/in 118 lb/in 1.19 hz
250 147 1.33
300 177 1.46
350 206 1.57
400 236 1.68
450 265 1.78
500 295 1.88
550 324 1.97
600 353 2.06
650 383 2.14
700 412 2.22
750 442 2.30
800 471 2.38
850 501 2.45
900 530 2.52
950 560 2.59
1000 589 2.66


Rear:

200 106 1.20
250 133 1.34
300 159 1.46
350 186 1.58
400 212 1.69
450 239 1.79
500 266 1.89
550 292 1.98
600 319 2.07
650 345 2.16
700 372 2.24
750 398 2.32
800 425 2.39
850 451 2.47
900 478 2.54
950 504 2.61
1000 531 2.68

OK! So you want a higher ride frequency in the rear of the car by 10-15%. This is because your front wheel hits an apex gator before your rear wheel does, and you want them to settle at the same time, rather than oscillate / undulate around.

I'll post examples of good spring rate choices next!

This is very interesting info. I actually want to do a similar exercise (not this deep, but get accurate geometry measurements) for n older Maserati project car. Care to give a quick explanation of how you’re accomplishing this accurately? I started the process a few months ago with string and a ruler, but gave up over fear of inaccurate measurements influencing incorrect modifications.

Tape measure, string, an assistant, great light, and multiple measurements. It is pretty accurate

Any chance you have also calculated the roll center for the car sitting at stock ride height? all this information is literally what i was about to spend my saturday doing so im super glad i found this thread. Just need roll center and i can start figuring out what i need for springs and shock valving on the car

Sorry man, I have not. I do not have that software. It would be nice to calculate degrees roll per G however!

If you like the thread, like it or get a mod to sticky it or something.

L8d

I was just looking for this on a C6 because I need to increase my rates for aero loading.
Great info for the C5s here

Level8Drummer...question for you about measurements you've taken, I see you have the front lower but do you happen to have the front upper as well? I'm trying to build a custom front frame to mount a C5/C6 front suspension to it but unfortunately I lost my engineer that was working with me due to the pandemic (he's fine, just an older gentleman that has stayed home when the pandemic in our area got worse, plus I'm a PT & around covid patients sometimes so he doesn't want to take chances which I don't blame him). My engineering skills severely lack in that area, but I can weld up the frame but I need measurements of the front & lower UCA's basically in relation to each other. Do you happen to have the measurements for the front UCA as well? Feel free to send me a PM instead of posting in the thread, but I would really appreciate any help you could give me because I've searched all over for those measurements but I can't find them anywhere from anyone and I'm stuck right now. I know Performance Trends' Suspension Analyzer has canned suspension numbers from a C5 but I don't know how accurate they are. Like I said, any help you can provide me with is greatly appreciated.

The numbers you have listed as "Inner Diameter" are actually wall thickness, to find actual inner diameter multiply your wall thickness x2 and subtract from the outer diameter.

You can verify the wall thickness of the factory style bars by measuring the thickness of the ends of the sway bars where the bar is crimped together it's basically wall thickness x2.

Good info, thanks for sharing I was going to go through all this when I was gonna ditch the mono. What kind of aero are you planning?

https://docs.google.com/spreadsheets...it?usp=sharing

Man I wish I could help, I haven't taken those measurements!

L8d

Thank you for that correction! Will recheck, redo math, and repost sometime when I get a chance!

L8d

Software
 

4-5 years ago I had the Roll Center Plus software from Performance Trends.
Performance Trends
It doesn't do everything their more expensive program does but for $150 it works really, really well. I had done a set of measurements for the car I was working on and saved them. From then on I would start w/ that set but then do an immediate 'save as' and name the new file differently usually just by date. There were a couple of times I had something apart and could get a more accurate measurement. So I went to my stock measurements set and updated it. Depending if I was still using one of the other files or not, I would mod it also. I didn't see any real significant changes from these updates because they were usually under 1/8 inch. It is really nice to be able to plug in a possible change to a pivot point for instance, and then use the program to see how it would affect roll center. It lets you roll or dive or roll and dive the car by any dimension you want, and see how it moves the RC and also how it would affect camber change curves. It becomes obvious real quickly why we end up using static negative camber. It isn't possible to get say 3 deg of camber gain to make up for 3 deg of roll w/o having a high RC that also moves a lot. At the time I was working on a solid axle car but I always thought this would be a great way to work at getting similar camber change curves for front and rear of a car w/ IRS.
BTW early on I gave up on trying to find the car centerline. For LCA inner pickups for instance it's usually easy to measure the distance from one to the other. The car center is then 1/2 of that dimension from either pickup. The UCAs are a little more difficult but I did them similar. Depending on access I could use either a carpenter's square or a plumb bob to mark the UCA inner pickups on the floor and measure their distance apart.

So how do sway bars play into wheel rates? My first assumption is that wheel rate from spring and wheel rates from sway bars are combined for "total wheel rate"?

OP you mentioned that you want the rear wheel frequency 15-20% higher due to hitting a bump by the front wheel first. I assume this means the front wheels take longer to settle than the rear but they end up settling at the same time due to the delay hitting the bump?

I don't road race...I autocross and street drive but I'm running:
550 front coilovers (324 wheel rate and 1.97 Hz)
600 rear coilovers (319 wheel rate and 2.07 Hz)
C6ZR1 front bar
C5Z stock rear bar

Yes but only in roll. In straight line accel or braking the bars do nothing. This is why one needs some experimentation/see what the fast guys are running. For instance; It's easy to install huge bars and the car will corner much flatter. But if it has already used up most of the front suspension travel while braking there can be a problem on corner entry. And the handling could vary depending if the corner follows a straight, so there was heavy braking involved, or it it's more of a series of S curves w/ little braking.

Did you ever settle on rates?

Shock damping also plays a big roll in the rear settling faster. Otherwise no one would run such high front rates (ie Danny).