[C5kid]

Ok my buddy of mine has scales that he is letting me borrow. I am waiting on my coilovers from LG. So I unhooked the sway bar endlinks and put the scales under the car, here is what I came up with.

LF=833 RF=809

LR=724 RR=718

Total=3084

What so I shoot for when I install the coilovers? A perfect 50/50 balance from side to side and front to back? or alittle more up front or little more in the back.

 

[405HP_Z06]

:z:

 

[mgarfias]

According to my worksheet, you want this:
LF = 801.8 RF = 801.8
LR = 740.2 RR = 740.2

You don't appear to be in the car (unless you weigh like 20lbs), if your corner weight it without you in the car, you'll be biased to the left when you're done. Also how much fuel do you have in the car? Are you planning on having a passenger most of the time, or no?

I balanced mine assuming I'd have a passenger now and again, and put 75lbs in the passenger seat. Discovered I spent far more time alone in the car. Not surprisingly, my LR tire wore faster.

http://garfias.org/~mike/CrossWeight-Worksheet.xls

Use that to calc where you want to be.

 

[Subdriver]

A couple thoughts on corner balancing.

1) You can not change the front to rear and side to side weight by raising or lowering the corners. The front will be about 53%, rear 47% unless you physically move weight from the front to the rear. The left side will be about 51% and the right side about 49%. Again, you can not change this without moving weight in the car from left to right.

2) To properly corner weight a car, it is critical that the scales be perfectly level (e.g. all four at exactly the same level plane). You need a good laser level and shims or a true racing alignment setup to do this. I use 16x16 tiles from Home Depot to "level" my floor.

3) When corner weight, what you are actually trying to do is get the cross weights equal. LF + RR = RF + LR.

4) When you corner weight, you want it to be in the as driven condition (driver, fuel, passenger?)

Here are my actual corner weights with sways disconnect, driver in the car, and just over 1/2 tank from last week:

LF 905 RF 871
LR 816 RR 772

Front 52.8%
Rear 47.2%
Cross 50.1% (within 10 lbs which I felt was as close as I could reasonably measure)

Here is a good article on the topic:
http://www.grmotorsports.com/cornerweight.html

 

[DavePro]

Brad:
When corner weighting, shouldn't the shock absorbers also be disconnected?

 

[DJWorm]

Some say that some shocks do in fact impart a pre load.

It all depends on what a shock dyno says and what length the shock is at. If you lower a car and retain the OEM shocks they will have a preload at the lowered height, for example.

My car is lowered but I have shorter Penske DA shocks. If the shocks are adjustable and shortened for the apppropriate ride height then I recommend just setting the Compression (Bump) to the minimum setting as a base line.

You can disconnect them and note the Corner Weights and Cross Corner % and then reconnect them and recheck the data points to determine the effect, you may find it significant or not.

The other side of the theory is; as you will be running the car with the shocks connected, as opposed to a sway bar which could be disconnected or changed out for a stiffer bar or use adjustable end links with different preloads, set up with the shocks connected should be the static and dynamic base line.

 

[Subdriver]

Brad:
When corner weighting, shouldn't the shock absorbers also be disconnected?

Never heard that before. DJ's explanation makes sense. I always leave mine connected and it doesn't seem to negatively impact the handling I notice on the track. And I can notice if the corner weights are off. :cheers:

 

[DJWorm]

Another Suspension Set Up "Pearl" here concerning shocks & Corner weights since the question was asked:

You can quickly diagnose a faulty shock by checking the corner weights against your baseline corner weights.

All of a sudden on a run the car became "squirrely" as my left rear wheel (inside, unloaded) started hopping while in a left turn. This was confirmed by the corner worker(s).

Thinking that the rebound setting had moved, we checked the rebound setting first and it was right where it should be. Next, suspecting the shock had failed or malfunctioned, rather than rip the shock off the car and tear it apart at the track, we placed the car on the scale set up platform and found the left rear corner weight to be 150 #'s light from the baseline readings (and all the others, especially the riight front was heavier)...this confirmed that it was something with the left rear shock and we needed to look at it further. Our doubts were that these shocks have a great reliability history and very few actually fail catastrophically.

Upon examining the shock further we found a small crack in the fitting where the remote reservoir SS line connects to the shock. It had been loosing pressure and fluid. We replaced the fitting (on the car), refilled the shock fluid and repressureized the system/reservoir. All in about 20 minutes. We rechecked the corner weights and they were dead on base line.

We theorized that the fitting was stressed and damaged during street driving, possibly hitting a pot hole or rough pavement and the suspension was jounced into full deflexion.

So this illustrates how the baseline corner weights can not only be used to set up the car statically but be used to diagnose a dynamic suspension problem and isolate & confirm the corner it is coming from.

Thanks be to the SCCA for having the scale platform at the event. They had it there to grossly weigh cars for conformation to the class rules but had the corner weight function as well.