Corner balancing question

JamesShort · **Posted:** Thu Apr 14, 2011 11:26 am

How does corner balancing work. I understand it can't change F/R ratios or L/R ratios, but just the cross weights, but how does raising one corners ride height increase the load on that corner and the cross corner and, in turn, reduce the load on the adjacent corners?

Is it purely small changes in the lateral/longitudinal/vertical location of the CoG such that the static force/moment analysis is such?

Cash Davidson · **Posted:** Thu Apr 14, 2011 11:35 am

Think of it as legs on a coffee table. As you lengthen the left-front or right-rear, you reduce load on the other two corners - until you need a book of matches to keep it from wobbling.

For best handling balance, you shoot for equal cross weights: LF+RR = RF+LR.

It can be a tedious process that isn't helped with the consumption of beer - ask me how I know.

JamesShort · **Posted:** Thu Apr 14, 2011 11:49 am

I've seen that analogy a few times and it makes sense, but unlike a 4 legged chair, the adjacent corners to the one you are raising the height of a car have suspension that can extend such that you don't need those matches

.

Just trying to grasp the basic physics of it and it's eluding me

.

Cash Davidson · **Posted:** Thu Apr 14, 2011 12:02 pm

Right, but since the length of the spring is a function of the load on the spring, the load must have decreased if the spring lengthened to allow the tire to stay on the ground. Make sense?

JamesShort · **Posted:** Thu Apr 14, 2011 12:13 pm

Ahhh...duh

.

So when you raise the ride height of a coilover (forgive me, I've never had fancy suspension on a car....just busted koni's

) you are simply raising the height of the lower perch relative to the lower attachment point. If there was just a 500lb bag on top of this corner, the spring would remain equally compressed but it would be a bit higher from the ground. However on a 4 contact patch car, each corner being suspended, when you raise that ride height the adjacent corners need to extend a bit to 'keep up' and in doing so, the spring is no longer the same compressed height anymore so the F=-kx is such that there is less load on those to corners. Then the corner you raised and the opposite corner have to take up the load lost on the other 2 corners. Bout right?

Cash Davidson · **Posted:** Thu Apr 14, 2011 12:24 pm

Very good, grasshopper! I think you have it.

The hard part is trying to guess how much a height change will impact the loads. When you change one corner, ALL the other corner loads change.

Combine this with trying to set a specific or consistent ride height and you find yourself going around and around - add beer and it is a near futile effort.

JamesShort · **Posted:** Thu Apr 14, 2011 12:39 pm

Not to mention changes to camber/toe that ride height affects and needing adjustable sway bar endlinks so the sway bar is not preloading and killing your expensive corner balance

.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Just to add a bit more to the equation...

While corner balancing the car. You need to set ride height to work with your suspension geometry. You could corner balance and still have poor handling. I can lower my car too low and be balanced but the suspension is not operating within its proper range it was designed for. You want to know the optimum angles of the control arms etc too. Also the rake of the car is important for some. I need to maintain a rake of 1/2" - 3/4" higher in the rear to keep the car settled at high speed. For AX you might not care, for track you would.

It goes beyond simply staying off the bump stops. Though that would be bad.

Also on setting ride height with coil-overs. Depending on the design of the coil-over is an issue. Some have the body adjustment independent of the shock length/travel, some don't. So the more you lower the more you limit shock travel.

If you can corner weight and get ride height optimum it makes for a very well balanced car that should be as close to neutral handling as is possible for that car.

Jason Tower · **Joined:** Wed Jun 11, 2008 3:31 pm **Posts:** 1173

this is the recipe i use when dialing in adjustable suspension:

1. disconnect front and rear swaybars if they have adjustable endlinks (only one side needs to be disconnected)
2. ballast the driver seat with your body weight and fill gas tank halfway. if you sometimes carry a passenger put about 100# in the passenger seat to give a reasonable compromise.
3. adjust the spring perches to set ride height/rake where you want it making sure left and right sides are similar. it helps to verify that camber/toe are reasonably close to desired final values.
4. using scales adjust the perches to get your cross weight 50/50, making changes such that it minimizes ride height changes. you can change the cross weight by adjusting any of the four corners. for example if the LF/RR weight is too high lower their perches a tad and raise the RF/LR perches an equal amount, that will keep ride height/rake/side-to-side more or less unchanged.
5. recheck ride height, tweak slightly if necessary. if you were careful in step 4 it should require minimal adjustment.
6. if you made changes in step 5 recheck corner weight, it should require only minor adjustments at this point
7. set camber
8. set toe
9. hook up sway bars if necessary, adjusting the endlink lengths so there is no preload

remember to bounce the car several times to "settle" it back to normal height every time it's jacked up, and it should be rolled back and forth a bit as well, especially when setting camber/toe.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Jason Tower wrote:

this is the recipe i use when dialing in adjustable suspension:

1. disconnect front and rear swaybars if they have adjustable endlinks (only one side needs to be disconnected)
2. ballast the driver seat with your body weight and fill gas tank halfway. if you sometimes carry a passenger put about 100# in the passenger seat to give a reasonable compromise.
3. adjust the spring perches to set ride height/rake where you want it making sure left and right sides are similar. it helps to verify that camber/toe are reasonably close to desired final values.
4. using scales adjust the perches to get your cross weight 50/50, making changes such that it minimizes ride height changes. you can change the cross weight by adjusting any of the four corners. for example if the LF/RR weight is too high lower their perches a tad and raise the RF/LR perches an equal amount, that will keep ride height/rake/side-to-side more or less unchanged.
5. recheck ride height, tweak slightly if necessary. if you were careful in step 4 it should require minimal adjustment.
6. if you made changes in step 5 recheck corner weight, it should require only minor adjustments at this point
7. set camber
8. set toe
9. hook up sway bars if necessary, adjusting the endlink lengths so there is no preload

remember to bounce the car several times to "settle" it back to normal height every time it's jacked up, and it should be rolled back and forth a bit as well, especially when setting camber/toe.

Or you can do it like the lemons car with ebay coilovers.

1. Drop car onto scales
2. Observe 52% crossweight and ride height "about right"
3. "Shit yeah!" Crack open a beer.

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Corner balancing question

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