Weighed the car (00 ITR) at Roebling yesterday. Car had full interior and 3/4 tank of gas. Forgot to take out the spare & jack...opps!

Car Empty: 2546 lbs

LF: 827 RF: 782
LR: 460 RR: 477

Car w/driver: 2732 lbs

LF: 893 RF: 807
LR: 532 RR: 500

Ok, I have a set of APEXi N1 coilovers. I assume I want Right to Left as equal as possible with me in the car. What would I do to accomplish that?

 

sleeves on coilover moved up/down as appropriate

 

I know that fool.

Will raising the driver side literally just shift the weight to the right? That is what I'm not sure of. Will this effect camber on that one side? Don't want to mess with anything before I know all the facts.

I also will not have access to re-weighing the car for now. Should I even mess with it then.

 

No, to obtain left-right or front-rear balance, you must physically shift weight (battery, etc).

Adjusting coilovers is good for adjusting cross weights (LF+RR=RF+LR).

http://grassrootsmotorsports.com/cornerweight.html

 

Or here http://www.ground-control.com/gctalk4.htm

Your trying to get (LF + RR) = (RF + LR)


[Modified by StageOne, 2:43 PM 5/13/2002]

 

Think about it like this: if you could shift weight laterally or longitudinally using preload then with enough preload you could support the whole car with just the wheels on one side or one end of the car. I've only seen stuff like that in cartoons and Mad magazine.

Scott, who likes cartoons...their fiction you know....

 

*scratching head*

 

Actually, to use your example.... if I had enough suspension travel to raise the left side of my car up, oh... 4 feet... then yes, all of the weight would eventually be supported by the right side. Right before the car flipped over on it's side.

 

Number one: You obviously know nothing about good cartooning. Was you too busy laffing?

Number two: You've got a point about the reality, but within the range of useful values for the purpose of this conversation no material lateral or longitudinal displacement of the CG will occur.

Scott, who likes having someone get too technical on my ***.....

 

The cross weights are more improtant than the left to right static weight. (take evrything with you in the car). You are 54 lbs off in the corner weights with you in the car (LF+RR vs. LR+RF). I would say move the battery from the right front and put in the right rear to start. Then re-weigh (this time with the "race" weight, no spare, tools and roughly race fuel load) and re-check it. should be much closer.

The left right weights can be adjusted with the coil overs, but do this last, as this is for finite adjustments. It also helps to have a set of scales on hand all day so you can "check" what a particular adjustment will do without having to wait to re-weight it the following day/week/month event...you get the idea.

Corner weighting IS the biggest pain in the ***, until you get it close...Then it's fun...
(edit)--Remember to put weight in the driver's seat to simulate you being in it whenever you are taking measurements. You will be drinking beer that day, all day so YOUR weight will vary)

Jeff


[Modified by jasyatz, 1:30 PM 5/13/2002]

 

[QUOTE]
Number two: You've got a point about the reality, but within the range of useful values for the purpose of this conversation no material lateral or longitudinal displacement of the CG will occur.
QUOTE]

Of course you're right...
It's very misleading to see countless references say that you CANNOT shift [any is implied] weight by adjusting height. It just messes with people's heads because it contradicts what many people know to be true.

 

OK to really answer your question -

What you can do with adjustable coilovers is change the height of one corner of the car independently of the others.

Pretend your car was a go-cart without springs. If you could adjust the height of one wheel enough the car would rest on only 3 wheels and the corner weights would change.

The same thing happens in sprung cars to a lesser degree. By adjusting one wheel up or down we can make the car put more weight on a diagonal.

To make the car handle the best in both right and left corners what you want to do is make it so the Left Front plus Right Rear weight equals the Right Front plus Left Rear weight. Or as other have written:

LF + RR = RF + LR

Now in your case:

LF + RR = 1393
and
RF + LR = 1339

So you have a cross weight of 54 pounds

What you want to do is to:
Raise the perch height on the RF or LR
OR
Lower the perch height on the LF or RR
OR
Do a little bit of each

How do you know which to do?
First you need to accurately check ride heights and determine if one side of the car is high than the other. This will make your decisions easier. But it is not an exact science.

All this should be done with the driver's weight including helmet in the car and with the fuel level at the level you will compete at.

Also don't forget about windshield washer fluid. Some resevoirs are on one side of the car at the very corner of the car and hold 1 ghallon of fluid (8 pounds!) Whether this is full or empty can actually make a substantial differnece in corner weights since it is outside the wheelbase on many cars.

Good luck,
Alan

 

crank away on the fronts'

to add weight raise the frame rail height of the car in that corner
shoot for these weights

which means screw down on the the LF
LF Original

top
|
|
---
|
|

LF New

top
|
|
|
---
|


Desired Corner weights
868 844
485 463

you can't alter weights left and right.. but you can change weight front to rear with the coilovers


when you do adjustments.. do them small.. and do the opposite adjustment in the right if you adjust the left
for ex screw down 2 turns LF screw up 2 turns RF


[Modified by Crazydave, 11:39 PM 5/13/2002]


[Modified by Crazydave, 11:41 PM 5/13/2002]

 

Thanks for the help Alan.

Is 54 lbs a BIG difference?

Since this is my daily driver still, should I really adjust the car for X amount of gas in tank? Will this cause ill-effected handling during the other 99% of the time I drive my car?

Would air pressure change the cross-weight after set-up?

 

air pressure is a fine tuning for cross weights... but is more effective with bias ply tires because b/p tires grow more with more air compared to radials.

for finding which tire to use...
fill them all to the same psi and measure the circum. of the tire.

then decide which tire you want where..
bigger tires = higher frame rail height in that corner which means more weight
then set the tires to starting psi and measure away.



[Modified by Crazydave, 11:50 PM 5/13/2002]

 

OK....Here are my numbers.

I did a quick check today with a slight adjustment.

Before
LF 806 RF 786
LR496 RR401

After
LF 823 RF 765
LR 474 RR 425

My crossweights are better 50.12% and 49.75% but just looking at the numbers it now looks like I have less traction on on my RF?
Since the front wheels are the steering, braking and accelerating wouldn't it be more important for them to have equal numbers?
Is there anyway to get them equal left to the right besides physically placing ballast?
Would raising both the RF and the RR increase the R side weight to kind of balance things out but since raising a corner also raises the opposite if you did it to both wheels on the right side what would happen?
What is a reasonable cross weight %?


Modified by PaulB at 6:00 AM 3/8/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PaulB &raquo;</TD></TR><TR><TD CLASS="quote">OK....Here are my numbers.

I did a quick check today with a slight adjustment.

Before
LF 806 RF 786
LR496 RR401

After
LF 823 RF 765
LR 474 RR 425

My crossweights are better 50.12% and 49.75% but just looking at the numbers it now looks like I have less traction on on my RF?
Since the front wheels are the steering, braking and accelerating wouldn't it be more important for them to have equal numbers?
Is there anyway to get them equal left to the right besides physically placing ballast?
Would raising both the RF and the RL increase the R side weight to kind of balance things out but since raising a corner also raises the opposite if you did it to both wheels on the right side what would happen?
What is a reasonable cross weight %?</TD></TR></TABLE>

Damn, Paul, you dusted off this thread didn't you!

Was the sway bar disconnected this time? I was thinking about the numbers you got over the weekend and I think they look better now. You aren't going to be able to get a FR/FL balance without moving weight or screwing up the rear. It's better to focus on the cross weights (which in your case is only 11 lbs "after," 75 lbs "before"). It's just too bad you don't have something like an accusump that you could put on the passenger floor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PaulB &raquo;</TD></TR><TR><TD CLASS="quote">OK.... Since the front wheels are the steering, braking and accelerating wouldn't it be more important for them to have equal numbers? ...</TD></TR></TABLE>

Some would agree with you on that. If you do that AND you end up biasing the crossweights 1-2% in favor of the dominant direction of a race track, one gets two little bonuses.

K

 

Dusted off this thread? I don't understand the new lingo......
Check your PM.

The rear bar is w/o any preload.....I can unbolt it w/o any tension while the wheels are on the ground. So I hope I'm OK.

Now that brings up another question....the rear swaybar has adjustable Heim joint ends.
If the Heim joint links on my rear swaybar are adjusted longer or shorter the same amount on both ends is that the same a stiffening or softening the sway bar? It seems like both of the heim joints extended to there full length on both ends-say 5 inches would be different than one shortened to a 1/2 inch?
Could someone explain???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PaulB &raquo;</TD></TR><TR><TD CLASS="quote">Dusted off this thread? I don't understand the new lingo......
</TD></TR></TABLE>


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RStoR &raquo;</TD></TR><TR><TD CLASS="quote"> 2:07 PM 5/13/2002 </TD></TR></TABLE>

PS: Way to use Search

 

if the LF/RR has a higher total then the RF/LR, which direction of turn does that favor?