How close should cross balance be?
05-12-2011, 08:34 PM
#1
Safety Car
Thread Starter
How close should cross balance be?
I just had my car cross balanced (no weight added, just suspension adjustments), and the two diagonals came within 50 lbs of each other. Does this sound about right? I thought that it would be closer?
Thanks,
Charley
Thanks,
Charley
05-12-2011, 09:06 PM
#2
Tech Contributor
Charlie,
The answer to your question sort of depends upon WHY you had the corner weights done, and were you (or your weight distribution) in the car during the process, and even what was your fuel level at the time.
For example, a great setup shop might sacrifice a few pounds in "wedge", in order to make the front corners more equal if they are working on a road racing car. Similarly, they could very reasonably make the same sacrifice for having the rear weights very close on a drag car. Perhaps they were "factoring in" your weight and position, if you were not actually in the car; so that when you ARE in the driver seat, that wedge comes closer to 50%. You might well ask the setup individual his/her reasoning for "stopping" short of 50/50.
Corner weights, and suspension setup, in general, is nothing more than a series of very learned compromises. When we think about it, 50 pounds is one and one-half percent of the weight of your car.
Ed LoPresti
The answer to your question sort of depends upon WHY you had the corner weights done, and were you (or your weight distribution) in the car during the process, and even what was your fuel level at the time.
For example, a great setup shop might sacrifice a few pounds in "wedge", in order to make the front corners more equal if they are working on a road racing car. Similarly, they could very reasonably make the same sacrifice for having the rear weights very close on a drag car. Perhaps they were "factoring in" your weight and position, if you were not actually in the car; so that when you ARE in the driver seat, that wedge comes closer to 50%. You might well ask the setup individual his/her reasoning for "stopping" short of 50/50.
Corner weights, and suspension setup, in general, is nothing more than a series of very learned compromises. When we think about it, 50 pounds is one and one-half percent of the weight of your car.
Ed LoPresti
Last edited by RacePro Engineering; 05-12-2011 at 09:19 PM. Reason: Elaboration.
05-12-2011, 09:32 PM
#3
Safety Car
Thread Starter
Charlie,
The answer to your question sort of depends upon WHY you had the corner weights done, and were you (or your weight distribution) in the car during the process, and even what was your fuel level at the time.
For example, a great setup shop might sacrifice a few pounds in "wedge", in order to make the front corners more equal if they are working on a road racing car. Similarly, they could very reasonably make the same sacrifice for having the rear weights very close on a drag car. Perhaps they were "factoring in" your weight and position, if you were not actually in the car; so that when you ARE in the driver seat, that wedge comes closer to 50%. You might well ask the setup individual his/her reasoning for "stopping" short of 50/50.
Corner weights, and suspension setup, in general, is nothing more than a series of very learned compromises. When we think about it, 50 pounds is one and one-half percent of the weight of your car.
Ed LoPresti
The answer to your question sort of depends upon WHY you had the corner weights done, and were you (or your weight distribution) in the car during the process, and even what was your fuel level at the time.
For example, a great setup shop might sacrifice a few pounds in "wedge", in order to make the front corners more equal if they are working on a road racing car. Similarly, they could very reasonably make the same sacrifice for having the rear weights very close on a drag car. Perhaps they were "factoring in" your weight and position, if you were not actually in the car; so that when you ARE in the driver seat, that wedge comes closer to 50%. You might well ask the setup individual his/her reasoning for "stopping" short of 50/50.
Corner weights, and suspension setup, in general, is nothing more than a series of very learned compromises. When we think about it, 50 pounds is one and one-half percent of the weight of your car.
Ed LoPresti
Thanks for the help,
Charley
05-12-2011, 10:09 PM
#4
Tech Contributor
Charley,
First of all, I am sorry for mis-spelling your name!
You, and your alignment shop, all sound like they know exactly what they are doing, aside from the notion of ADDING weight.
If you want to post up your car, with any suspension mods, and the final weight results, we can quickly tell if any improvement could easily be made.
Ed
First of all, I am sorry for mis-spelling your name!
You, and your alignment shop, all sound like they know exactly what they are doing, aside from the notion of ADDING weight.
If you want to post up your car, with any suspension mods, and the final weight results, we can quickly tell if any improvement could easily be made.
Ed
05-12-2011, 10:43 PM
#5
Drifting
Charley:
The cross weights on my C6 Z06 is less than 20 lbs, whether scaled for my co-driver or myself.
Left front is approx 25 lbs heavier than the right front. Left rear is approx 25 lbs heavier than the right rear.
Driver in car; low fuel load.
The cross weights on my C6 Z06 is less than 20 lbs, whether scaled for my co-driver or myself.
Left front is approx 25 lbs heavier than the right front. Left rear is approx 25 lbs heavier than the right rear.
Driver in car; low fuel load.
05-13-2011, 03:17 AM
#6
I'm racing in T1 with min weight at 3180 with driver. I don't know as much as Ed and would like to hear more about why one would sacrifice wedge for more equal weights between front and rear. Anyway, on my level setup platform in my garage on my scales this was my result about 2 months ago when I set my car up. A perfect 50/50 cross. It is not hard to achieve at all.
05-13-2011, 09:42 AM
#8
Safety Car
Thread Starter
Charley,
First of all, I am sorry for misspelling your name!
You, and your alignment shop, all sound like they know exactly what they are doing, aside from the notion of ADDING weight.
If you want to post up your car, with any suspension mods, and the final weight results, we can quickly tell if any improvement could easily be made.
Ed
First of all, I am sorry for misspelling your name!
You, and your alignment shop, all sound like they know exactly what they are doing, aside from the notion of ADDING weight.
If you want to post up your car, with any suspension mods, and the final weight results, we can quickly tell if any improvement could easily be made.
Ed
The shop has a good reputation...but, I find that the more I learn...The more I realize I don't know.
Here are my numbers with a 220 lb driver:
LF = 931, RF= 853
LR = 876, RR = 842
Total weight was 3502 with driver and half tank of gas. (which seems high also)
For alignment he set it to:
Caster = max 4.5 on 10 degree swing (I don't know what this means)
Camber: Frnt = -1.5, Rear = -1.125
Toe in: Frnt = 1/16 in, Rear = 1/8 in
Thank again for the help,
Charley
05-13-2011, 12:01 PM
#10
Safety Car
The half tank is a tough one. I did the same thing, twice, when I got mine corner balanced and then I was finally informed that "half tank" in a Corvette (C6 in my case) means only one of the tanks is full (drivers side?)... FWIW, my C6 Z51 with driver (near 200# at the time) and half tank was something like 3410#.
05-13-2011, 02:29 PM
#11
Tech Contributor
Charley,
Thanks for the numbers. I see the delta between L wedge and R wedge is actually only 44 pounds, and you are sitting at 49.4% with driver and fuel. Without physically moving (or RE-moving) weight around in the car, that is as good as you are going to get.
For road racing, a slight improvement could be had by lowering your ride height on the LF, or the RR, or some on both. That would more closely equalize the weight on your two front corners. Unfortunately, it would also create more of a disparity between your rear corners.
In the simplest of terms - when we do a "caster swing", we move through an arc described by turning your front wheels from left to right. Your 4.5 degrees was the maximum amount that your front tires are "pointed" ahead of your axles, during a 10 degree swing from center. Positive Caster provides your steering with a self-centering quality that is helpful in road racing.
And for BillyBob, and anyone else interested, the road racer can benefit from equalized front weights because of better stability under hard braking, plus more consistant turn-in between left and right turns. The drag racer cares little about those things, but would love to have a completely balanced weight transfer to his rear tires, and similarly weighted rear corners will help that.
Ed
Thanks for the numbers. I see the delta between L wedge and R wedge is actually only 44 pounds, and you are sitting at 49.4% with driver and fuel. Without physically moving (or RE-moving) weight around in the car, that is as good as you are going to get.
For road racing, a slight improvement could be had by lowering your ride height on the LF, or the RR, or some on both. That would more closely equalize the weight on your two front corners. Unfortunately, it would also create more of a disparity between your rear corners.
In the simplest of terms - when we do a "caster swing", we move through an arc described by turning your front wheels from left to right. Your 4.5 degrees was the maximum amount that your front tires are "pointed" ahead of your axles, during a 10 degree swing from center. Positive Caster provides your steering with a self-centering quality that is helpful in road racing.
And for BillyBob, and anyone else interested, the road racer can benefit from equalized front weights because of better stability under hard braking, plus more consistant turn-in between left and right turns. The drag racer cares little about those things, but would love to have a completely balanced weight transfer to his rear tires, and similarly weighted rear corners will help that.
Ed
Last edited by RacePro Engineering; 05-13-2011 at 02:39 PM. Reason: Caster
05-13-2011, 03:08 PM
#12
Burning Brakes
Thanks for the help...and don't worry about the misspelling, It happens so much I don't even notice it any more.
The shop has a good reputation...but, I find that the more I learn...The more I realize I don't know.
Here are my numbers with a 220 lb driver:
LF = 931, RF= 853
LR = 876, RR = 842
Total weight was 3502 with driver and half tank of gas. (which seems high also)
For alignment he set it to:
Caster = max 4.5 on 10 degree swing (I don't know what this means)
Camber: Frnt = -1.5, Rear = -1.125
Toe in: Frnt = 1/16 in, Rear = 1/8 in
Thank again for the help,
Charley
The shop has a good reputation...but, I find that the more I learn...The more I realize I don't know.
Here are my numbers with a 220 lb driver:
LF = 931, RF= 853
LR = 876, RR = 842
Total weight was 3502 with driver and half tank of gas. (which seems high also)
For alignment he set it to:
Caster = max 4.5 on 10 degree swing (I don't know what this means)
Camber: Frnt = -1.5, Rear = -1.125
Toe in: Frnt = 1/16 in, Rear = 1/8 in
Thank again for the help,
Charley
05-13-2011, 04:02 PM
#13
Race Director
I try and get a leaf-spring car withing 20-25lbs. If you go further, you just overshoot and end up cycling back and forth. Just to much "stiction" in the spring perches. With coils, you can get really close.
If you have a car that is really bad weight distribution (one side, or one end really heavy), you should also look at front/rear ratios on each side. Sometimes you want to split the difference between getting the cross weights even and getting the f/r ratios even.
If you have a car that is really bad weight distribution (one side, or one end really heavy), you should also look at front/rear ratios on each side. Sometimes you want to split the difference between getting the cross weights even and getting the f/r ratios even.
05-13-2011, 04:38 PM
#14
Le Mans Master
In the simplest of terms - when we do a "caster swing", we move through an arc described by turning your front wheels from left to right. Your 4.5 degrees was the maximum amount that your front tires are "pointed" ahead of your axles, during a 10 degree swing from center. Positive Caster provides your steering with a self-centering quality that is helpful in road racing.
I have about 6.5 degrees front caster, the max it would go, and I really like the "self-centering" of the steering wheel when I get too ambitious and get too much over-steer for whatever reason. I get really quick corrections with little drama. I sometimes even toss the wheel in snap over-steers and then grab it again when needed.
It really helps with lightning quick counter-steering as shown at the 4:10 mark of this video where I botch it a bit.
http://vimeo.com/23239361
Oli
