Corner balance

[nsx2tall]

You might laugh at this:

With the spring change and the strut rebuild/re-valve I did for the race car, I figured the corner balance to be pretty important so I bought some scales (couldn't find any to borrow) and set aside a whole day to get it right. I get the scales out and test them, everything looks good. I disconnect the sway bars, inflate the tires to hot pressures, shim the scale pads to less than 1/30" out of level, set the the car on the scales and this is what I get for my first reading:

932 872
670 614
Cross weight LR,RF 49.94%, LF,RR 50.06%

My corner balance is off by less than 2 pounds. I could have skipped the $1000 scales and the $100 laser level and the 4 hour morning and been none the worse off than having done nothing. Hah!

-RJ

 

[Ponyboy]

Are those numbers with driver ballast included? If so, awesome!

 

[ediddynsx]

I was going to say the same thing.....who sat in the car that was your weight while you were doing all of this? Or did you have a giant sand bag in there.

 

[nsx2tall]

I was in the car at the time though the car was short about 120 lbs. of bodywork. I figured that the bodywork weights were essentially even side to side.

A couple of things I discovered after playing around a bit. First, a mere quarter turn of spring preload about .020" of ride height took 6 lbs. off the corner. Second, due to wheel caster even the slightest variation in the front wheel angles (steering) created large variations in cross weight. Just a few degrees of steering wheel angle altered the weights by more than 10 lbs. It adds another variable you'd need to check when taking measurements.

In my mind, once you are pretty close it is time to move on. There are just too many other variables that make a good static corner balance less meaningful. Minimize, measure, move on.

 

[Mac Attack]

Good general information to post, but keep in mind that weight sensitivity to your height adjustments highly depends on how stiff the vehicle is.

I have no idea how stiff your race WRX is (guessing it's probably as stiff of a structure as the NSX), but just saying it's something to keep in mind.

If folks on here can make claims through street driving that a Type R or STMPO front chassis bar greatly improved front NSX stiffness and response , then making car-to-car generalizations may not be the best.

I know it's a lot of time and I didn't make the same observations you did when doing my own corner balancing, but I thought the NSX was a little more sensitive to height adjustments than that.

I even left my sway bars (well, I don't have a rear one) connected since that is what the car will see on the road, and after 20 years, I'm positive the chassis has some tweak to it anyways.

But like you said, if you're somewhat cognizant and can measure corner heights accurately (and some folks don't understand you have to be on a perfectly flat surface), then chances are you won't be really screwed up on cross balance.

Dave

 

[nsx2tall]

My springs are 550 and 450 lb respectively and a full cage makes the chassis fairly stiff. But with those rates, I was already thinking that a quarter turn seemed too sensitive to be useful. If a half pound of air pressure in a tire could possibly yield more change to ride height than 20 thousandths of an inch, then it would provide a good point of handling comparison as a half pound of under-inflation wouldn't typically generate enough change to handling to notice (though some might argue otherwise, it is difficult to even have a half pound of accuracy in a hot tire). I would surmise then the corner balancing is relevant to the 10's of pounds but probably not relevant down to the single digit pounds level.