Corner weight balance questions
10-14-2013, 02:26 AM
#1
Burning Brakes
Thread Starter
Corner weight balance questions
Ok im trying to settle my coil-over setup.Everything is installed and adjust at max high on all 4 corner.Im having a hell a lot of trouble to have the correct measure(not weight balance) to have it level and have the correct .200" chassis rake.Of course all my test are done with driving weight inside.
Im beginning to think about having a complete corner weight balance since i want a good balance car.
I did call a guy that do all this in my area.He told me that he would play with the height of one of my corner.
-So is it just has simple has that... he put it on the scale then drop one of my corner to achieve the correct weigth ???
-Also i know that the corvette got a .200" body rake.Will the car keep its oem rake or its just not necessary after the weight balance ???
Trying to learn here
Thanks
Eric
Im beginning to think about having a complete corner weight balance since i want a good balance car.
I did call a guy that do all this in my area.He told me that he would play with the height of one of my corner.
-So is it just has simple has that... he put it on the scale then drop one of my corner to achieve the correct weigth ???
-Also i know that the corvette got a .200" body rake.Will the car keep its oem rake or its just not necessary after the weight balance ???
Trying to learn here
Thanks
Eric
10-14-2013, 10:26 AM
#2
Drifting
I think factory rake is between 3/4" and 1-1/8" if memory serves.
When adjusting height/weight balance I believe you disconnect at least one side of both sway bars then start small adjustments, one wheel at a time. Remember adjusting the right rear will affect the front left's weight as well. Then keep in mind as you play with right height your alignment specs will change.
I've started to read up since I'd like my car corner balanced before next year on track. So, anybody with a lot more knowledge than me... I'm all ears as well.
When adjusting height/weight balance I believe you disconnect at least one side of both sway bars then start small adjustments, one wheel at a time. Remember adjusting the right rear will affect the front left's weight as well. Then keep in mind as you play with right height your alignment specs will change.
I've started to read up since I'd like my car corner balanced before next year on track. So, anybody with a lot more knowledge than me... I'm all ears as well.
10-14-2013, 12:53 PM
#3
Melting Slicks
Member Since: Sep 2003
Location: If you don't weigh in you don't wrestle Road America
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The correct order of doing things is as follows:
Set ride height, then set your corner weights, then align the car.
As said before you want to make those adjustments with the sway bars disconnected. After you're done make sure you zero the sway bars with adjustable end links.
To get the best possible results you want to do the set-up the way the car will be run at the track, which means driver weight added to the drivers seat (if you instruct most of the time or tend to run with passengers then add weight in the passengers seat as well), fuel load - if you TT or autocross then you would probably only run around 1/4 tank or so try to get your fuel load around there. If you fill up at the beginning of the day and run all day I would aim for setting the car up with around 1/2 tank, this way the heights won't change as drastically as setting the car up with a full tank or empty.
(I've measured this and the difference between a full tank and an empty tank is about 1/8" in the rear ride height - so if you scale it at 1/2 tank you will only fluctuate by 1/16" either way instead of the full 1/8").
Another consideration is wheels and tires, you want to make sure that you have the correct size wheels and tires on the car for these measurements (whatever you run at the track) - you also want to have your hot tire pressures set as well. That should get you pretty close.
If this guy says he only makes changes to one corner of the car then he's not doing the process correctly, you want to make small adjustments to each corner to get the corner weights correct so you don't mess with the ride heights as much.
Set ride height, then set your corner weights, then align the car.
As said before you want to make those adjustments with the sway bars disconnected. After you're done make sure you zero the sway bars with adjustable end links.
To get the best possible results you want to do the set-up the way the car will be run at the track, which means driver weight added to the drivers seat (if you instruct most of the time or tend to run with passengers then add weight in the passengers seat as well), fuel load - if you TT or autocross then you would probably only run around 1/4 tank or so try to get your fuel load around there. If you fill up at the beginning of the day and run all day I would aim for setting the car up with around 1/2 tank, this way the heights won't change as drastically as setting the car up with a full tank or empty.
(I've measured this and the difference between a full tank and an empty tank is about 1/8" in the rear ride height - so if you scale it at 1/2 tank you will only fluctuate by 1/16" either way instead of the full 1/8").
Another consideration is wheels and tires, you want to make sure that you have the correct size wheels and tires on the car for these measurements (whatever you run at the track) - you also want to have your hot tire pressures set as well. That should get you pretty close.
If this guy says he only makes changes to one corner of the car then he's not doing the process correctly, you want to make small adjustments to each corner to get the corner weights correct so you don't mess with the ride heights as much.
10-14-2013, 01:45 PM
#4
Safety Car
Here's an article I wrote on this topic last year. It gives you all the basics. I'm not sure about this one corner guy. You usually end up chasing your tail around the car. Every time you move one thing another three things change. Sometimes you can do this in a few hours. Sometime you spend all day getting in right.
Remember you not only want the correct weights on each corner but you want the wheels properly aligned as well.
Richard Newton
Remember you not only want the correct weights on each corner but you want the wheels properly aligned as well.
Richard Newton
10-14-2013, 03:47 PM
#5
Instructor
Ok im trying to settle my coil-over setup.Everything is installed and adjust at max high on all 4 corner.Im having a hell a lot of trouble to have the correct measure(not weight balance) to have it level and have the correct .200" chassis rake.Of course all my test are done with driving weight inside.
Im beginning to think about having a complete corner weight balance since i want a good balance car.
I did call a guy that do all this in my area.He told me that he would play with the height of one of my corner.
-So is it just has simple has that... he put it on the scale then drop one of my corner to achieve the correct weigth ???
-Also i know that the corvette got a .200" body rake.Will the car keep its oem rake or its just not necessary after the weight balance ???
Trying to learn here
Thanks
Eric
Im beginning to think about having a complete corner weight balance since i want a good balance car.
I did call a guy that do all this in my area.He told me that he would play with the height of one of my corner.
-So is it just has simple has that... he put it on the scale then drop one of my corner to achieve the correct weigth ???
-Also i know that the corvette got a .200" body rake.Will the car keep its oem rake or its just not necessary after the weight balance ???
Trying to learn here
Thanks
Eric
Do you measure from the ground to the subframe in the front and the ground to the subframe in the rear and it is the difference between these two numbers??
Why is that important?
What happens if it is wrong?
Just wondering...
Jim M.
10-14-2013, 05:45 PM
#6
Race Director
So if you took a laser on that line to the front & back sub frames it would be more probably over a 1/2" but I never tried it.
Anyone Know?
That's just me.
Last edited by froggy47; 10-14-2013 at 05:48 PM.
10-14-2013, 06:54 PM
#7
Instructor
The fsm has specified the points to measure from (on the sub frames) and taking off from there everyone does it their own way. I like 1/4 inch difference from the front tie down spot to the rear tie down spot.
So if you took a laser on that line to the front & back sub frames it would be more probably over a 1/2" but I never tried it.
Anyone Know?
That's just me.
So if you took a laser on that line to the front & back sub frames it would be more probably over a 1/2" but I never tried it.
Anyone Know?
That's just me.
If somehow the rake angle that you want is wrong on your car, what do you feel?
What does the rake really do?
Thanks again Jim M.
10-14-2013, 06:55 PM
#8
Melting Slicks
Member Since: Sep 2003
Location: If you don't weigh in you don't wrestle Road America
Posts: 3,031
Likes: 0
Received 73 Likes
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Jim,
There are 3 typical ways to measure for rake - or at least that's all I know of.
The first is probably the least accurate way but it's also the easiest - just measure from the ground to the front wheel well and from the ground to the rear wheel well. With stock wheels and tires you are shooting for the rear to be between 7/8" and 1 1/4" higher than the front.
The second would be the be to use the tie down points like stated above - either to the fiberglass rocker panel or to the frame rail itself. Sometimes it's hard to find a flat spot at the tie down points because the cars have been jacked up there and it typically dents in. So I usually try to find an area that hasn't bent at all. If you measure from those locations you want the rear to be 1/4" to 1/2" higher than the front. (again with stock wheels and tires)
The last way is probably the hardest way to measure without an alignment rack or a drive on lift. That is to use the GM J-tool that measures from the bottom of the ball joint to the front side of the front lower control arm mounting bolt. The tool has a magnet that sticks onto the lower ball joint and a ruler that hangs off of the LCA mount bolt - there is a bubble level on it that tells you when the tool is level and ready to take your measurement. Here you are looking for the front to be 2 1/2" to 2 5/8" higher than the rear, but really since you are measuring ball joint to cradle you really are more concerned with the individual corner numbers. The front is between 1" & 1 3/4" and the rear is between 4 1/4" and 3 1/4".
Another nice thing about using this last method is that you don't have to worry about the wheel and tire package messing with your set-up.
Those are the measurements that I have taken in the past so I don't have a number from the cradles to the ground.
I don't think it's so much a matter of importance but more to know that you are in the ball park. Otherwise why are we doing all this work to get the car "set-up"? If you were too far off on the rake (lets say you have the back end jacked way up and you are running 1.5" higher in the rear than the front - measured at the frame rails). So you would be 1" higher in the rear than "typical" I would guess that the car would turn in really well but be fairly loose under braking, mid corner and exit. The opposite would be true if you had the front end jacked up and the back end slammed.
There are 3 typical ways to measure for rake - or at least that's all I know of.
The first is probably the least accurate way but it's also the easiest - just measure from the ground to the front wheel well and from the ground to the rear wheel well. With stock wheels and tires you are shooting for the rear to be between 7/8" and 1 1/4" higher than the front.
The second would be the be to use the tie down points like stated above - either to the fiberglass rocker panel or to the frame rail itself. Sometimes it's hard to find a flat spot at the tie down points because the cars have been jacked up there and it typically dents in. So I usually try to find an area that hasn't bent at all. If you measure from those locations you want the rear to be 1/4" to 1/2" higher than the front. (again with stock wheels and tires)
The last way is probably the hardest way to measure without an alignment rack or a drive on lift. That is to use the GM J-tool that measures from the bottom of the ball joint to the front side of the front lower control arm mounting bolt. The tool has a magnet that sticks onto the lower ball joint and a ruler that hangs off of the LCA mount bolt - there is a bubble level on it that tells you when the tool is level and ready to take your measurement. Here you are looking for the front to be 2 1/2" to 2 5/8" higher than the rear, but really since you are measuring ball joint to cradle you really are more concerned with the individual corner numbers. The front is between 1" & 1 3/4" and the rear is between 4 1/4" and 3 1/4".
Another nice thing about using this last method is that you don't have to worry about the wheel and tire package messing with your set-up.
Those are the measurements that I have taken in the past so I don't have a number from the cradles to the ground.
I don't think it's so much a matter of importance but more to know that you are in the ball park. Otherwise why are we doing all this work to get the car "set-up"? If you were too far off on the rake (lets say you have the back end jacked way up and you are running 1.5" higher in the rear than the front - measured at the frame rails). So you would be 1" higher in the rear than "typical" I would guess that the car would turn in really well but be fairly loose under braking, mid corner and exit. The opposite would be true if you had the front end jacked up and the back end slammed.
Last edited by 96CollectorSport; 10-14-2013 at 07:01 PM.
10-14-2013, 07:07 PM
#9
Race Director
You are putting more/less weight on the tires front vs rear and you are affecting aero at high speeds.
So if it was way off the car would feel light in the steering (say over 120 mph) in a straight line & also would change the oversteer/understeer balance at most speeds in cornering. Backwards rake = more understeer.
If the suspension is really soft you'd get dive under brakes (if it was raked backwards) but might launch better as you start with more weight on the rear.
So if it was way off the car would feel light in the steering (say over 120 mph) in a straight line & also would change the oversteer/understeer balance at most speeds in cornering. Backwards rake = more understeer.
If the suspension is really soft you'd get dive under brakes (if it was raked backwards) but might launch better as you start with more weight on the rear.
10-14-2013, 08:56 PM
#10
Instructor
Jim,
There are 3 typical ways to measure for rake - or at least that's all I know of.
The first is probably the least accurate way but it's also the easiest - just measure from the ground to the front wheel well and from the ground to the rear wheel well. With stock wheels and tires you are shooting for the rear to be between 7/8" and 1 1/4" higher than the front.
The second would be the be to use the tie down points like stated above - either to the fiberglass rocker panel or to the frame rail itself. Sometimes it's hard to find a flat spot at the tie down points because the cars have been jacked up there and it typically dents in. So I usually try to find an area that hasn't bent at all. If you measure from those locations you want the rear to be 1/4" to 1/2" higher than the front. (again with stock wheels and tires)
The last way is probably the hardest way to measure without an alignment rack or a drive on lift. That is to use the GM J-tool that measures from the bottom of the ball joint to the front side of the front lower control arm mounting bolt. The tool has a magnet that sticks onto the lower ball joint and a ruler that hangs off of the LCA mount bolt - there is a bubble level on it that tells you when the tool is level and ready to take your measurement. Here you are looking for the front to be 2 1/2" to 2 5/8" higher than the rear, but really since you are measuring ball joint to cradle you really are more concerned with the individual corner numbers. The front is between 1" & 1 3/4" and the rear is between 4 1/4" and 3 1/4".
Another nice thing about using this last method is that you don't have to worry about the wheel and tire package messing with your set-up.
Those are the measurements that I have taken in the past so I don't have a number from the cradles to the ground.
I don't think it's so much a matter of importance but more to know that you are in the ball park. Otherwise why are we doing all this work to get the car "set-up"? If you were too far off on the rake (lets say you have the back end jacked way up and you are running 1.5" higher in the rear than the front - measured at the frame rails). So you would be 1" higher in the rear than "typical" I would guess that the car would turn in really well but be fairly loose under braking, mid corner and exit. The opposite would be true if you had the front end jacked up and the back end slammed.
There are 3 typical ways to measure for rake - or at least that's all I know of.
The first is probably the least accurate way but it's also the easiest - just measure from the ground to the front wheel well and from the ground to the rear wheel well. With stock wheels and tires you are shooting for the rear to be between 7/8" and 1 1/4" higher than the front.
The second would be the be to use the tie down points like stated above - either to the fiberglass rocker panel or to the frame rail itself. Sometimes it's hard to find a flat spot at the tie down points because the cars have been jacked up there and it typically dents in. So I usually try to find an area that hasn't bent at all. If you measure from those locations you want the rear to be 1/4" to 1/2" higher than the front. (again with stock wheels and tires)
The last way is probably the hardest way to measure without an alignment rack or a drive on lift. That is to use the GM J-tool that measures from the bottom of the ball joint to the front side of the front lower control arm mounting bolt. The tool has a magnet that sticks onto the lower ball joint and a ruler that hangs off of the LCA mount bolt - there is a bubble level on it that tells you when the tool is level and ready to take your measurement. Here you are looking for the front to be 2 1/2" to 2 5/8" higher than the rear, but really since you are measuring ball joint to cradle you really are more concerned with the individual corner numbers. The front is between 1" & 1 3/4" and the rear is between 4 1/4" and 3 1/4".
Another nice thing about using this last method is that you don't have to worry about the wheel and tire package messing with your set-up.
Those are the measurements that I have taken in the past so I don't have a number from the cradles to the ground.
I don't think it's so much a matter of importance but more to know that you are in the ball park. Otherwise why are we doing all this work to get the car "set-up"? If you were too far off on the rake (lets say you have the back end jacked way up and you are running 1.5" higher in the rear than the front - measured at the frame rails). So you would be 1" higher in the rear than "typical" I would guess that the car would turn in really well but be fairly loose under braking, mid corner and exit. The opposite would be true if you had the front end jacked up and the back end slammed.
10-14-2013, 09:10 PM
#12
Race Director
Maybe you are bottoming out on the rear shocks, that'll bring her around.
Take a measure off the rocker panels all around and post.
10-14-2013, 09:16 PM
#13
just at front of door rocker panel to floor = 4"
Rear of rocker at front of rear wheel = 4.3/8"
The car is totally level to within 1/8" from wheel to wheel (VCT tile pads)
Thats without me in it obviously
Rear of rocker at front of rear wheel = 4.3/8"
The car is totally level to within 1/8" from wheel to wheel (VCT tile pads)
Thats without me in it obviously
10-14-2013, 09:22 PM
#14
Instructor
Darn computer....
Joel,
If I understand, the original numbers came from the J-tool at the ball joint and these numbers established the ride height. Correct??
Then the difference in these ride heights front to back gave you the rake that everyone is using.
Sound right???
I know this is established info for the Corvette.
I was wondering why.
I now see that it is used for leveling the lower "A" arms, front and rear.
It just so happens to have a rake when the "A" arms are level on a stock car.
The rake, in my opinion, is not near as important as the "A" arms level which, of course, changes with tire height.
I think some believe rake has something to do with aero, which it does not. The car is too "dirty" on the bottom to be affected by that small a change.
If I am wrong in my opinion, someone help me out.
I was asking if someone had experinced a difference in handling when the rake was changed.
Thanks Jim M.
Joel,
If I understand, the original numbers came from the J-tool at the ball joint and these numbers established the ride height. Correct??
Then the difference in these ride heights front to back gave you the rake that everyone is using.
Sound right???
I know this is established info for the Corvette.
I was wondering why.
I now see that it is used for leveling the lower "A" arms, front and rear.
It just so happens to have a rake when the "A" arms are level on a stock car.
The rake, in my opinion, is not near as important as the "A" arms level which, of course, changes with tire height.
I think some believe rake has something to do with aero, which it does not. The car is too "dirty" on the bottom to be affected by that small a change.
If I am wrong in my opinion, someone help me out.
I was asking if someone had experinced a difference in handling when the rake was changed.
Thanks Jim M.