i am scaling a 95 civic hatch and wondering what you guys are able to achieve for weight distribution or if you have recommendations.

95 civic with a Kseries engine.

 

The cross weights should be equal (LF+RR=RF+LR) with the driver in position and the intended fuel load in the car.

Ignore left-to-right and front-to-rear distributions when cornerweighting because there is nothing you can do about those unless you physically move weight around in the car.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Targa250R &raquo;</TD></TR><TR><TD CLASS="quote">The cross weights should be equal (LF+RR=RF+LR) with the driver in position and the intended fuel load in the car.

.</TD></TR></TABLE>

ive got a 141 pound difference when doing that formula..

dont know if i need to get it corner weighted or not

LF-747 RF-728
LR-467 RR-387

that comes out to 48.6 cross weight?

 

raise the rr a touch

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ZUL8R &raquo;</TD></TR><TR><TD CLASS="quote">

ive got a 141 pound difference when doing that formula..

dont know if i need to get it corner weighted or not

LF-747 RF-728
LR-467 RR-387

that comes out to 48.6 cross weight? </TD></TR></TABLE>

Cross weight is (RF + LR) / Total, or 1195 lbs. (51.3%) in your car. You added the LF and RR.

To achieve the ideal 50% cross weight, without shifting ballast or anything, your weights should look like this:

LF-769 RF-706
LR-445 RR-409

I used this website to calculate the ideal cross weights...
http://robrobinette.com/corner_weight_calc.htm

I agree with beanbag. It looks like you need to raise the RR a tiny bit.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ThoseDarnKids &raquo;</TD></TR><TR><TD CLASS="quote">

To achieve the ideal 50% cross weight, without shifting ballast or anything, your weights should look like this:

</TD></TR></TABLE>

I don't mean to thread jack but I see this as still on the subject.

how can you add/remove weight to a corner of the car without shifting ballast?

if you adjust the heights at different corners soo... fr:4", FL:3.5", RR:3.75", RL:4"
and you achieve perfect corner weight, is the perfect balance going to cause any other issues when handling with uneven heights on the 4 corners? would it be better to just use ballast with even height?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by unrealwrc &raquo;</TD></TR><TR><TD CLASS="quote">if you adjust the heights at different corners soo... fr:4", FL:3.5", RR:3.75", RL:4"
and you achieve perfect corner weight, is the perfect balance going to cause any other issues when handling with uneven heights on the 4 corners?</TD></TR></TABLE>
The only real issue it can cause is uneven camber left-to-right. If you have a camber adjuster kit already it won't matter, but if you don't have one, it opens up a whole new can of worms.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">would it be better to just use ballast with even height?</TD></TR></TABLE>
No.

That's only theoretically possible anyway; I doubt anyone could ever get it to work out well in reality.

 

It's possible to have even height AND correct cross weight

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beanbag &raquo;</TD></TR><TR><TD CLASS="quote">It's possible to have even height AND correct cross weight</TD></TR></TABLE>

okie, i'll bite.... how? (as i prepare to cornerweight my car today for the 20th time, in my 9th year setting up the same chassis....)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rodney &raquo;</TD></TR><TR><TD CLASS="quote">

okie, i'll bite.... how? (as i prepare to cornerweight my car today for the 20th time....)</TD></TR></TABLE>

First, assume you get the cross weights correct, but now the car is all crooked.

You can adjust left-right tilt by raising both springs on the same side. This does not affect cross weight.

You can adjust front-back tilt by raising both springs on the front or both springs on the rear. This does not affect cross weight.

You can adjust diagonal tilt by a linear combination of the above two operations. This does not affect cross weight.

Note that I didn't say to change the spring perch heights by the same amount. You have to figure in motion ratio and etc.

Ideally, you use the power of math to get it all done in one shot

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beanbag &raquo;</TD></TR><TR><TD CLASS="quote">

First, assume you get the cross weights correct, but now the car is all crooked....</TD></TR></TABLE>

great theory. you will end up with all the same crooked heights, but with a taller/shorter car. i'll stick with my personal method, the one that wins races, thanks.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beanbag &raquo;</TD></TR><TR><TD CLASS="quote">It's possible to have even height AND correct cross weight

[...]

Ideally, you use the power of math to get it all done in one shot</TD></TR></TABLE>
Eh, yeah . . . let us know how that works out for you

 

I run a DC2 with near perfect diagonal weights (1103 and 1098) with driver and fuel onboard and the ride height is within 5mm (1/5'') from lowest to highest. Most of that is the rake we have built in

I can't give you any magical theories on how to achieve this other than to just keep playing with it. Took us half a day on a proper ramp/scales to get it this good.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rodney &raquo;</TD></TR><TR><TD CLASS="quote">

you will end up with all the same crooked heights, but with a taller/shorter car. </TD></TR></TABLE>

I don't understand this statement here. Can you please clarify? Corner balancing is a science, not an art. Can you give an example where you can't have both even height and correct corner balance? (Assuming your chassis isn't bent)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Irish Racer &raquo;</TD></TR><TR><TD CLASS="quote">

I can't give you any magical theories on how to achieve this other than to just keep playing with it. Took us half a day on a proper ramp/scales to get it this good.</TD></TR></TABLE>

I'm kind of curious whether you made any calculations for how much you needed to raise or lower a corner after each weighing, or whether you just used trial and error. I would have thought it would take no more than 2-3 iterations.

 

Thinking about it a little bit more, corner balancing and leveling is a 4x4 matrix diagonalization problem, where you convert operations on each of the 4 spring perches to the new basis vectors of left-right tilt, front-back tilt, overall height, and cross weight. Most of these conversions are trivially easy, except for the last one, which take into account spring rate, chassis bendiness, etc.
Solving this matrix problem means being able to do corner weighting and balancing in "one shot".

To clarify somewhat, the cross weight "eigen-operation", if you want to call it that, is the tweaking of spring perches that only affects cross weight but doest not affect tilt or overall height. It consists of raising the front right and rear left corners, and lowering the two other corners, but not by the same amounts, coz this is where spring rates and etc come into play.
But even this one can be calculated, or better yet, measured, where by "measured", I mean, you do an approximate calculation of what the operation should be, and then measure its projection onto the other modes, e.g. tilt. So now you've made it a "two shot" procedure, but oh well.

It seems to me the reason why corner balancing takes so long is because people don't realize this and rather do a kind of haphazard tweaking of the spring perches, where each operation affects all of the modes. For example, if you just raise and lower one perch at a time, you affect all four of the modes, namely two tilts, overall height, and cross weight.

 

for some people doing math is out of the question... college FTMFW. As for creating an equation a person would have to have a very good understanding about the subjectmatter and have already done extra work to create the excel/ equation to pre-populate the answers with a simple press of the enter button(in order to simplify future cross weightings and other cars). BUT since not many people cross balance their car often let alone others, reformatting the equation for multiple cars can just be 2 much of an issue.

There can be ALLOT of variables that the equation can overlook and the guess and check method substitues them with time. plus being able to have the equation tell you the specifics on lowering the car at each corner is a ton of work. I might look into creating a dos/matlab program with this. looks like it could be a fun experiment, although i will need to find a scale to check the findings.

 

i still do not see how you can CW, and maintain same heights at all corners at the same time using just the adj spring perch. cutting/welding parts, sure.... but not just adjusting the perches.
i have done easily 50 cornerweightings in the past few years, and on average it takes me a good 2 hours or more. i have developed quite a system doing this, and cars handle phenominally afterword (well, after an alignment....).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rodney &raquo;</TD></TR><TR><TD CLASS="quote">i still do not see how you can CW, and maintain same heights at all corners at the same time using just the adj spring perch. cutting/welding parts, sure.... but not just adjusting the perches.
i have done easily 50 cornerweightings in the past few years, and on average it takes me a good 2 hours or more. i have developed quite a system doing this, and cars handle phenominally afterword (well, after an alignment....).
</TD></TR></TABLE>

It's called (by me) the "eigen operation" for cross weights.
Assuming you have a car that starts off level, but the cross weights are off:
First you raise both the fr and rl corners. You increased the weight on this diagonal. The entire car raises up a little bit, but doesn't tilt.
Then you lower both the fl and and rr corners. You took weight off this diagonal, and added more weight to the original diagonal. The entire car lowers down a little bit, but doesn't tilt.

Net result: more weight on fr-rl diagonal, car at same height, no tilting.

 

Hello BeanBag,

No how, no way! Pull out your 4 leg coffee table and try your drivel out, just won't happen. Theory is interesting but unless you can proof it it is meaningless.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beanbag &raquo;</TD></TR><TR><TD CLASS="quote">

I'm kind of curious whether you made any calculations for how much you needed to raise or lower a corner after each weighing, or whether you just used trial and error. I would have thought it would take no more than 2-3 iterations.</TD></TR></TABLE>

Just good old fashioned trial and error!

I'm sure you know but don't forget to disconnect antiroll bars before doing corner weights!

 

I just came to the realization that some of you may be thinking of "even height" to mean that the spring perches are all set at the same height. What I mean by even height is that the four corners of the car (as defined by the jacking points, for example) are even. Of course the spring perches will be uneven. I mean, duh.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beanbag &raquo;</TD></TR><TR><TD CLASS="quote">I just came to the realization that some of you may be thinking.... I mean, duh.</TD></TR></TABLE>

you have no idea what i am thinking. and you are still wrong. short of modifying a suspension piece or ballasting, there is no way you can get all 4 jacking point heights the same, and keep an even crossweight. on one end you can get the same height, but the opposite end will allways be uneven. do you even have scales? or are you just using "math"?

in fact, one of my racer buddies has a shop in your neck of the woods. sias tuning. he has a set of scales, so stop over there and i want to see pics of you working your magic on his m3. i will be patiently awaiting the results....

 

Did you see my statement earlier where I issued the disclaimer that "unless your chassis is bent"? Obviously you can never get even heights if the 4 jacking points are not coplanar. Ballasting is a way to get a bent, but flexy, chassis flexed back into shape via different forces on the chassis.

Here's some questions for you:

In the course of your 2 hour corner balancing procedure, how many times do you end up putting the car on the scales, and how many adjustments do you make? (Counting a tweak of each spring perch as an adjustment)

To what degree of evenness in height and cross weight do you aim for before you consider yourself "done"?

In any case, the point of busting out "math" is to show that there is a systematic procedure to get cross weighting and leveling done in a minimal number of steps. See my post at 12:18 PM 8/28/2008


Modified by beanbag at 12:03 PM 8/30/2008