Corner Balance Question
#1
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Corner Balance Question
While at the track two weeks ago I was able to put my car on a set of scales for the first time. The weights are with me in the car (195 pounds) and 5/8 a tank of fuel.
Here are the weights from the drivers seat perspective:
978 906
824 827
SO.....My initial thoughts are this isn't too bad for having never been on scales.
My handling is good, but a friend of mine who is a past IMSA driver and has both driven and ridden in the car says that in his opinion the rear of the car could use a little more ride height (and spring).
My question.........I can easily raise the rear....but while I am doing that I would like to get the cross weights a little closer if possible. I've done some reading on this issue and understand the general principle, but would really like some real world advice on our cars since I will not have the scales available to me again until August.
Thanks as always for your suggestions,
Ken
The current springs are the progressive Eibach, I have adjustable shocks and the ride height is currently at the factory minimum spec both front and rear.
Here are the weights from the drivers seat perspective:
978 906
824 827
SO.....My initial thoughts are this isn't too bad for having never been on scales.
My handling is good, but a friend of mine who is a past IMSA driver and has both driven and ridden in the car says that in his opinion the rear of the car could use a little more ride height (and spring).
My question.........I can easily raise the rear....but while I am doing that I would like to get the cross weights a little closer if possible. I've done some reading on this issue and understand the general principle, but would really like some real world advice on our cars since I will not have the scales available to me again until August.
Thanks as always for your suggestions,
Ken
The current springs are the progressive Eibach, I have adjustable shocks and the ride height is currently at the factory minimum spec both front and rear.
#3
Drifting
The only way to get the cross weights better is to move weight from the left front to right front really. You could lower the front left a bit and add a little height to the opposite diagonal, but I'm sure you already know that.
#4
Chronic Tool Dropper
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In this case you would very carefully increase the left rear load, perhaps 20 lbs on the spring. That will carry just a bit more of the driver's weight on the rear, and balance the front side-to-side some by cross-loading the right front.
The fenderline of the 928 makes it look like the rear is low when in fact the car is level at the measuring points. Make sure your efforts to raise the rear are for real suspension reasons and not to improve the "appearance".
The fenderline of the 928 makes it look like the rear is low when in fact the car is level at the measuring points. Make sure your efforts to raise the rear are for real suspension reasons and not to improve the "appearance".
#5
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Which numbers are the front and which are the rear?
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Here are the weights from the drivers seat perspective
Regards,
Ken
#6
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Dr Bob,
So lets say in theory that I decide to raise the rear by 2 full turns on the right and 2.5 turns on the left. So how much weight would you guess I would get with the extra half turn ?
Ken
So lets say in theory that I decide to raise the rear by 2 full turns on the right and 2.5 turns on the left. So how much weight would you guess I would get with the extra half turn ?
Ken
#7
Burning Brakes
this is kinda confusing. If the current weight bias is towards the front, raising the rear would load the front more. If you were trying to corner balance (equalize the f/r weight, wouldn't you want to raise the front/lower the rear?
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#8
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John,
It is confusing...but I really am not as concerned about the front - rear weight balance as I am about the corner to corner weight and getting the rear raised in order to help corner turn in.
Ken
It is confusing...but I really am not as concerned about the front - rear weight balance as I am about the corner to corner weight and getting the rear raised in order to help corner turn in.
Ken
#9
Burning Brakes
ok re: front/rear balance.
But I am very interested in your friend's comment about raising the rear. Does that mean that our cars should have a bias towards the front?
But I am very interested in your friend's comment about raising the rear. Does that mean that our cars should have a bias towards the front?
#11
Chronic Tool Dropper
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The cars do have a bias towards the front. The L-R bias changes with fuel tank load as well as the driver's weight. Attempting to "load" one end of the car by raising both sides the same amount will generally have a very small effect on the total F-R distribution. What you do have control over is the uneven wieght on the LF vs RF, and the LR vs RR. Ultimately the actual center of gravity of the car will determine the differences.
Ken--
A half-turn difference might be a good place to start. You'll want to verify on the scales again of course. It's just as easy to overshoot on these adjustments.
Remember that you'll want to go drive the car some between adjustments, don't raise the car at all on the suspension before getting a reading, and all weight readings are taken with at least one droplink on each swaybar disconnected. If you end up lifting the car to make an adjustment, especially the front, you are committed to a 75-100 mile settling drive before you can get another valid set of weights. If you are doing this at home, it is absolutely critical that the scales are perfectly level and at the same height. Put ramps between the pads at the same height so the car can roll smoothly onto the pads.
And honestly, I'd be very very happy with the original numbers you posted, especially for a street car. The balance will be off by a lot more than that as sson as you roll onto pavement with the slightest uneven surface. It isn't worth messing with the current adjustments for a street-driven car with rubber suspension bushings.
Ken--
A half-turn difference might be a good place to start. You'll want to verify on the scales again of course. It's just as easy to overshoot on these adjustments.
Remember that you'll want to go drive the car some between adjustments, don't raise the car at all on the suspension before getting a reading, and all weight readings are taken with at least one droplink on each swaybar disconnected. If you end up lifting the car to make an adjustment, especially the front, you are committed to a 75-100 mile settling drive before you can get another valid set of weights. If you are doing this at home, it is absolutely critical that the scales are perfectly level and at the same height. Put ramps between the pads at the same height so the car can roll smoothly onto the pads.
And honestly, I'd be very very happy with the original numbers you posted, especially for a street car. The balance will be off by a lot more than that as sson as you roll onto pavement with the slightest uneven surface. It isn't worth messing with the current adjustments for a street-driven car with rubber suspension bushings.
#12
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What width front and rear track tires/rims?
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Remember that you'll want to go drive the car some between adjustments, don't raise the car at all on the suspension before getting a reading, and all weight readings are taken with at least one droplink on each swaybar disconnected.
I think that I will make a small change before going to the track and then I can always reverse my count if it doesn't have the desired effect. Right now I am fighting the car on corner entry (push). Mid corner off where I can breathe the throttle, rotate the car and squeeze on the power I'm good to go...
You can see it a little bit of the push in the video linked below in my signature.
I'm down to a 1:45 at Mid Ohio and I think there is another second or two in the car and about that much in me.
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And honestly, I'd be very very happy with the original numbers you posted, especially for a street car. The balance will be off by a lot more than that as sson as you roll onto pavement with the slightest uneven surface. It isn't worth messing with the current adjustments for a street-driven car with rubber suspension bushings.
Ken
#13
Owns the Streets
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Ever thought about running a front splitter?
Does that 'big' rear wing give the rear of the car more downforce?
Do you get enough track time to run without the rear wings just as a test.
Not sure if you'll lose much rear traction. Car seems to claw its way out of the corner.
Does that 'big' rear wing give the rear of the car more downforce?
Do you get enough track time to run without the rear wings just as a test.
Not sure if you'll lose much rear traction. Car seems to claw its way out of the corner.
#14
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Actually I have some plans that I have put together for a front splitter....I'd like to build it before I go to Putnam Park outside of Indianapolis the weekend of July 13-14th. I want to start with about a 50 mm lip and then have at least two cut outs (venturis) back from the leading edge with a maximum of 17 degree incline to allow the air that wants to stall at the edge of the splitter to get away.
The rear wing does function, I could tell some difference when I installed it. I would like to build a couple of different height "wicker-bills" to add to it and be able to change those at the track.
The car is pretty balanced and I lowered it in the rear initially to improve the way the car felt under very heavy braking...more of a squat right now than an on the nose "wallow". I'm at about 140MPH at the end of the back straight every lap at MidOhio. You can see the 6000-6200 RPM upshift from 4th to 5th at the kink and then a good long 10PSI boost pull in 5th. Entry into the esses is probably under 50 MPH.....so lots of quick heavy braking.
Ken
The rear wing does function, I could tell some difference when I installed it. I would like to build a couple of different height "wicker-bills" to add to it and be able to change those at the track.
The car is pretty balanced and I lowered it in the rear initially to improve the way the car felt under very heavy braking...more of a squat right now than an on the nose "wallow". I'm at about 140MPH at the end of the back straight every lap at MidOhio. You can see the 6000-6200 RPM upshift from 4th to 5th at the kink and then a good long 10PSI boost pull in 5th. Entry into the esses is probably under 50 MPH.....so lots of quick heavy braking.
Ken
#15
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Lightened up the photo to try and show the 2 sharks with splitters.
The struts stabilize the splitters and are used to pull up the splitter during loading and unloading off the trailers. Picture a few years old. Not sure who's got the green racer now. Was raining so they're on factory wheels with rain tires.