Corner weights

[xxxturbo6]

Today I Scaled the car using TOLEDO mechanical scales from my local Round track shop. They said these are the most accurate so I went ahead and got some numbers. 3/4 Tank of Gas!

I'm wanting to get the percentage between the front & rear, Can someone tell me the formula to achive this correctly?

(Just the car by it's self)

LF = 997 lb
RF = 956 lb
......................Total = 3,389 lbs
LR = 695 lb
RR = 741 lb



(With Driver/ Me)

LF = 1085 lb
RF = 986 lb
.....................Total = 3,632 lb (Car with Driver "me")
LR = 788 lb
RR = 773 lb



Scot W.

[LateNight72]

1953 + 1436 = 3389

1953 / 3389 = .57627 = 57.6% Front Bias
1436 / 3389 = .42372 = 42.4% Rear Bias

I seriously doubt that's what you're looking for though.. :dunno:

[xxxturbo6]

1953 + 1436 = 3389

1953 / 3389 = .57627 = 57.6% Front Bias
1436 / 3389 = .42372 = 42.4% Rear Bias

I seriously doubt that's what you're looking for though.. :dunno: Todd,

That's good to know too but i'm not sure that is what i'm looking for, hell it might be!! LOL. I think what i'm looking for is " The percentage difference Between the front and rear weights". Like Steve Rupp did with Bad Penny, he had came up with 52% difference but not sure how he came up with that number.

Maybe Steve or Dave pozzi will chime in with how Steve got that number and their personal thoughts on my numbers..


Scot W.

[Bill Howell]

He got the number the same way as above Scot. 52% is a good number. 57% is not, though most of our cars are similar. You want to be as close to 50/50 as possible. I think the charger is 56/44.


Looking at the top set of number with car by itself, it is a bit strange that the LF and RR are heavy. Battery must be LF and spare tire RR?

[Bad Bird]

You want to be as close to 50/50 as possible.

Yes, no, maybe?

It's a little more contentious than that IMO. A lot of well setup front or front-mid rear wheel drive cars have greater than 50/50, you often see stuff like 45/55. More weight over the back - 1) Allows fuel loads to be accounted for and 2) Allows the rear wheels to provide more traction.

[Bill Howell]

Yes, no, maybe?

It's a little more contentious than that IMO. A lot of well setup front or front-mid rear wheel drive cars have greater than 50/50, you often see stuff like 45/55. More weight over the back - 1) Allows fuel loads to be accounted for and 2) Allows the rear wheels to provide more traction.

While I agree with you, that is probably not going to happen with many of our cars here. I am not sure I know of any protouring cars, street driven, real cars that are 45/55. I of course could be wrong, wouldn't be the first time. That is why I used 50/50 as a reference for Scot.

[6'9"Witha69]

For a front engine rear drive car, 50/50 is about as close as you can get.

[cheapthrillz]

While I agree with you, that is probably not going to happen with many of our cars here. I am not sure I know of any protouring cars, street driven, real cars that are 45/55. I of course could be wrong, wouldn't be the first time. That is why I used 50/50 as a reference for Scot.

Yea, I would say Tony's corvair is probably somewhere in that ballpark.

It's more than just 52/48 or 56/44. The distance between the center of these two "masses" is also important, if not more important.

[Bill Howell]

Yea, I would say Tony's corvair is probably somewhere in that ballpark.

It's more than just 52/48 or 56/44. The distance between the center of these two "masses" is also important, if not more important.

LOL, you ever looked at a 72 charger? Then you KNOW how screwed I am here....haha I got about three feet in from of the front tires and the same out back.

[xxxturbo6]

He got the number the same way as above Scot. 52% is a good number. 57% is not, though most of our cars are similar. You want to be as close to 50/50 as possible. I think the charger is 56/44.


Looking at the top set of number with car by itself, it is a bit strange that the LF and RR are heavy. Battery must be LF and spare tire RR? Thanks Bill, Now I have somewhere to start this process.. Thanks for jumping in with your thoughts!



Scot W.

[xxxturbo6]

Yea, I would say Tony's corvair is probably somewhere in that ballpark.

It's more than just 52/48 or 56/44. The distance between the center of these two "masses" is also important, if not more important. So would you like the measurment between those two masses?

Here are a few more numbers on our GNS test car:

Wheel base: 2746mm - 108.1in

Track
Front: 1486mm - 58.5in
rear: 1466mm - 57.7in

Length: 5095mm - 200.6in

Width: 1819mm - 71.6in

Height: 1387mm - 54.6in

Length/wheel base: 1.86



Drag Coefficient: 0.410




GNS

[xxxturbo6]

Looking at the top set of number with car by itself, it is a bit strange that the LF and RR are heavy. Battery must be LF and spare tire RR? I agree Bill! This has been really strange to me as well. Opposite! The battery is on the RT front and the spare is on the RR (Both passengeer side) "BUT" the spare was left out so the whole trunk was empty!!!


Please keep up with the thoughts on these numbers as they are as much a wonder to me as well as everyone else. I just want some advice from the pro's on what they mean and what to do to change them for a better performance stand point!

This is my first go around with these things and I want to do things right the first time. ANY input is good input!!!! LOL


Scot W.
GNS Performance

[ArtosDracon]

My guess for your side to side imbalance is your swaybars. If you can, disconnect the end-links on your swaybars and re-weigh it.

[cheapthrillz]

LOL, you ever looked at a 72 charger? Then you KNOW how screwed I am here....haha I got about three feet in from of the front tires and the same out back.

Don't get me started on boats again lol. At least your seats are comfortable!

[xxxturbo6]

Still looking for an answer on how to get a % difference between the front and the rear.

Example: (52% more in front vs the rear)



Scot W.

[cheapthrillz]

1953 + 1436 = 3389

1953 / 3389 = .57627 = 57.6% Front Bias
1436 / 3389 = .42372 = 42.4% Rear Bias

I seriously doubt that's what you're looking for though.. :dunno:

This is the only thing I can figure you're looking for....

57.6% of the weight of your car sets on the front tires.

?????????

[xxxturbo6]

This is the only thing I can figure you're looking for....

57.6% of the weight of your car sets on the front tires.

?????????Okay, That's all I wanted to know.. I wasn't sure if that was how the other guy's got their number or not, no one really mentioned it. So judging by this formula below (with driver) my number is now 57% ?

Front: 2,071 / 3,632 = .5700 = 57%
Rear : 1,561 / 3,632 = .4300 = 43%

Okay, looks like we need to loose some weight up front and possibly transfer it to the lighter corner in the rear??? lol


Scot W.

[Bill Howell]

Just streach the steering column, put some extentions on the pedals and drive sitting in the trunk, that should do it for you...haha

Seriously, while 50/50 would be a dream, don't count on ever getting there in a street car, just get as much as you can off the frontend. If you get 53/47 that would be huge.

[Van B]

Okay, That's all I wanted to know.. I wasn't sure if that was how the other guy's got their number or not, no one really mentioned it. So judging by this formula below (with driver) my number is now 57% ?

Front: 2,071 / 3,632 = .5700 = 57%
Rear : 1,561 / 3,632 = .4300 = 43%

Okay, looks like we need to loose some weight up front and possibly transfer it to the lighter corner in the rear??? lol


Scot W.

This is why the first thing most guys do is move the battery to right rear trunk area.

[David Pozzi]

Todd,

That's good to know too but i'm not sure that is what i'm looking for, hell it might be!! LOL. I think what i'm looking for is " The percentage difference Between the front and rear weights". Like Steve Rupp did with Bad Penny, he had came up with 52% difference but not sure how he came up with that number.

Maybe Steve or Dave pozzi will chime in with how Steve got that number and their personal thoughts on my numbers..


Scot W.

Steve's number of 52% is just the front weight in percent. At least between Steve and I, we talk about front percentage when comparing weight percentages car to car and leave off the rear percent. The general goal with our cars is to try and reach 50% front weight, but usually we only get to 53% to 51% at best. Stock for early Camaros is 56% to 58%.

Your left front and right rear are heavier than they should be. IF the scales were perfectly level with each other, then you should try and lower any adjustment on those corners until they even up more. The left side usually is heavier than the right, - without driver. I disconnect front and rear anti roll bars when scaling, then connect them on the scales and shim them so they don't jack weight from one corner to the other. Raising a spring perch on the LF corner will increase weight on the LF and RR corners.

Your left and right side weights add up to almost even, so by adjusting the heavy corners you should be able to balance them pretty close without driver.

I like to do basic scaling without driver, just because the driver weight can vary depending on who it is. And I don't want to mess with placing 180 to 200 lbs of weight in the car every time I do a corner balance, and usually I don't have a spare person around the exact weight of the driver that can sit in the car. If the driver is around I'll sit him in the car for a weight when done.

Here is an online calculator that should help, I haven't used it but it should work. http://www.opuscorvair.com/cornerweightcalculator.html
When trying to even up cross weight you want to get close to 50%.
David

[cheapthrillz]

David,

Is it EVER advantageous to add any ballast weight to the rear of the car to get closer to 50/50? I know it wouldn't be the case with Scot because he would have to add about 500 lbs, but would that EVER work?

I'm just hypothesizing.... lol

[David Pozzi]

I don't believe in adding rear weight to get a car closer to a 50-50 weight percentage. I do like to run with an almost full tank of gas when I autocross. Especially with cars that are having some wheel spin issues. The extra weight can help you get a little better rear traction, but adding a lot of rear weight is just making the car heavier and that isn't worth it.

[406 Q-ship]

I don't believe in adding rear weight to get a car closer to a 50-50 weight percentage. I do like to run with an almost full tank of gas when I autocross. Especially with cars that are having some wheel spin issues. The extra weight can help you get a little better rear traction, but adding a lot of rear weight is just making the car heavier and that isn't worth it.

I always wanted to get my cars closer to 52/48 with the fuel tank at 1/2 full (see I am an optimist). Of course I am lucky if I get 55/45 with a full tank.....now I am not feeling so optimistic.

[xxxturbo6]

This is why the first thing most guys do is move the battery to right rear trunk area. Yes but in my case it looks like it would have to go on the drivers side because my pass side rear is way heavy already and there isn't a thing in the trunk!!


Scot W.

[xxxturbo6]

Steve's number of 52% is just the front weight in percent. At least between Steve and I, we talk about front percentage when comparing weight percentages car to car and leave off the rear percent. The general goal with our cars is to try and reach 50% front weight, but usually we only get to 53% to 51% at best. Stock for early Camaros is 56% to 58%.

Your left front and right rear are heavier than they should be. IF the scales were perfectly level with each other, then you should try and lower any adjustment on those corners until they even up more. The left side usually is heavier than the right, - without driver. I disconnect front and rear anti roll bars when scaling, then connect them on the scales and shim them so they don't jack weight from one corner to the other. Raising a spring perch on the LF corner will increase weight on the LF and RR corners.

Your left and right side weights add up to almost even, so by adjusting the heavy corners you should be able to balance them pretty close without driver.

I like to do basic scaling without driver, just because the driver weight can vary depending on who it is. And I don't want to mess with placing 180 to 200 lbs of weight in the car every time I do a corner balance, and usually I don't have a spare person around the exact weight of the driver that can sit in the car. If the driver is around I'll sit him in the car for a weight when done.

Here is an online calculator that should help, I haven't used it but it should work. http://www.opuscorvair.com/cornerweightcalculator.html
When trying to even up cross weight you want to get close to 50%.
David Thanks for the reply David,

I used a set of those Taylor mechanical scales, zeroed them out and jacked the car up in the middle and then sat the car down on the scales front, then rear. I never thought about the scales being exactly level to each other while in the shop. I will check this as well next time!

I also had a guy offer to loan me his digital pad scales so I will most likely take him up on it and do as you recomend by disconecting the sway bars and see if it measures any different than the first time. The passenger Rear is what is really confusing to me because there is No spare or anything in the trunk and 3/4 tank of gas.

I will do that and report back.

Scot W.

[David Pozzi]

You only need to disconnect one end link on each bar, then as they are connected check that you didn't jack any weight the wrong way. Washers can be installed to correct end link length up front. If you can't shim the end links on the rear, then shim the mounts.

[MrQuick]

LOL, I just saw your sig David. LOL


ahhh forgot what I was going to add. sorry.

[malibu43]

hi guys,sorry to get involve in this topic but its a very interesting to me.
I do race my 80 malibu as a road course,and am planning to weight it the next week,but something got me really confussed.
For logic the front end of the car will be more heavy then the rear right?
How do i increase the rear weight ? if my car have the stock suspension? i mean no coil over,i veheard something about the shims,but i dont know how they works,and how to fit them?.
Anybody can help me? and teach me?
thanks

[wmhjr]

I also had a guy offer to loan me his digital pad scales so I will most likely take him up on it

The digital scales are real nice. That's what I borrowed to weigh my ride. You first set the scales up and calibrate them and then lower the car onto them. They do all the math. FWIW I was extremely surprised that my car was so close to 50/50 (actually, 25/25/25/25) as I expected it to be much more biased to the front. It's heavier than I'd like (3700) but 50.6 front, 49.4 rear, just about exactly equal left to right. Weighed it twice before I was convinced.

[exwestracer]

Today I Scaled the car using TOLEDO mechanical scales from my local Round track shop. They said these are the most accurate so I went ahead and got some numbers. 3/4 Tank of Gas!

I'm wanting to get the percentage between the front & rear, Can someone tell me the formula to achive this correctly?


(With Driver/ Me)

LF = 1085 lb
RF = 986 lb
.....................Total = 3,632 lb (Car with Driver "me")
LR = 788 lb
RR = 773 lb



Scot W.

IMO, looking at the car with driver is the most accurate measure, as that is how the car will be used. I agree the first step would be to disconnect the bars and re-check the weights. Check ride height (on a level surface) at the side frame corners and see if the car is sitting level. A few fractions of an inch would account for your weight readings. Also, were the tire pressures set correctly?

Having said that, 15lb of split across the rear with a 1500+ lb. axle weight is nothing to spend any money trying to correct. Driver weight seems to be distributed logically. Unless you have coliovers or jack bolts in there, there's not a lot you can do to alter the cross weights, short of moving components around, as others have mentioned.

[exwestracer]

hi guys,sorry to get involve in this topic but its a very interesting to me.
I do race my 80 malibu as a road course,and am planning to weight it the next week,but something got me really confussed.
For logic the front end of the car will be more heavy then the rear right?
How do i increase the rear weight ? if my car have the stock suspension? i mean no coil over,i veheard something about the shims,but i dont know how they works,and how to fit them?.
Anybody can help me? and teach me?
thanks

The only way to alter the overall F/R weight distribution (at a fixed ride height) is to move components from the front of the car to the rear. Shimming springs will add or subtract weight from a given corner, but the total axle weight will not change.

Be careful about moving things around to get more rear weight, though... The closer to the rear bumper you get with the battery or whatever, the bigger effect it will have on weight bias, but that weight will also become a pendulum during cornering, which can have a drastic effect on handling balance.

[xxxturbo6]

IMO, looking at the car with driver is the most accurate measure, as that is how the car will be used. I agree the first step would be to disconnect the bars and re-check the weights. Check ride height (on a level surface) at the side frame corners and see if the car is sitting level. A few fractions of an inch would account for your weight readings. Also, were the tire pressures set correctly?

Having said that, 15lb of split across the rear with a 1500+ lb. axle weight is nothing to spend any money trying to correct. Driver weight seems to be distributed logically. Unless you have coliovers or jack bolts in there, there's not a lot you can do to alter the cross weights, short of moving components around, as others have mentioned. I agree, Next is to re-scale the car and do what Dave recomends by removing One link F&R and see if it's different from the first measure.

Thanks to everyone for all the help and quideance on this subject, Please keep the tricks and tips coming, looks like it's helping others as well..

Scot W.