Ride height: Positive Rake vs. Negative Rake
Jun 10, 2007, 07:57 PM
#17
Corner balancing will not get you to 50/50 weight distribution.
The cross weights should be 50/50, but it will take a lot more then corner balancing to get to 50/50 front to rear.
I think you may know this already, but I just wanted to clear it up for anyone wondering what corner balancing really is. I hear all sorts of things all the time!
- Andrew
Last edited by GTWORX.com; Jun 10, 2007 at 10:16 PM.
Jun 11, 2007, 05:38 AM
#18
Corner balancing is a simple concept. The car weighs what it weighs. The proper way to do it is to get the total weight first. Then get the front, side, and rear weights. These weights are the exact weights of the car, and in reality cannot be changed without removing or moving parts of the car around. (Our cars are going to be roughly 60/40. I've changed the front/rear heights already a couple times and it had no effect on the front/rear weight ratio.)
So, to get what the most ideal weight distribution would be for each tire you would use a simple equation. Take the front weight and multiply by the percentage of each side to get the left and right tires weights, then do the same for the back.
For example, these are the weights of my car when I went in to get corner balanced:
Front (L/R): 1084 + 1007 = 2091 (61%)
Rear (L/R): 675 + 662 = 1337 (39%)
Left side (F/R): 1084 + 675 = 1759 (51%)
Right side (F/R): 1007 + 662 = 1669 (49%)
Total weight = 3428
Here is the way the car should have left (using the above equation):
Front (L/R): 1066 + 1025 = 2091 (61%)
Rear (L/R): 682 + 655 = 1337 (39%)
Left side (F/R): 1066 + 682 = 1748 (51%)
Right side (F/R): 1025 + 655 = 1680 (49%)
Total weight = 3428
This would make the car's corner balance at 49.7 (or 50 rounding up). Notice that the increase or decrease needed at each tire:
LF: - 18 RF: + 18
LR: + 7 RR: - 7
Also notice that the cross weights are both positive or negative. This is because lowering the height at one corner (decreasing the weight) will also decrease the weight at the opposite corner (thereby increasing weight on the other tires).
Now it is still possible to get a 50% cross weight, however per the equation these are merely the ideal numbers for that car. When I got corner weighted, the final equation was a bit different from the one I posted here, not to mention that the final numbers also added up with a two pound difference in total weight. So make sure when you get your car's corner balanced, the guy doing it actually knows the concepts behind it, and doesn't simply use a computerized weight scale to do the "work" for him.
So, to get what the most ideal weight distribution would be for each tire you would use a simple equation. Take the front weight and multiply by the percentage of each side to get the left and right tires weights, then do the same for the back.
For example, these are the weights of my car when I went in to get corner balanced:
Front (L/R): 1084 + 1007 = 2091 (61%)
Rear (L/R): 675 + 662 = 1337 (39%)
Left side (F/R): 1084 + 675 = 1759 (51%)
Right side (F/R): 1007 + 662 = 1669 (49%)
Total weight = 3428
Here is the way the car should have left (using the above equation):
Front (L/R): 1066 + 1025 = 2091 (61%)
Rear (L/R): 682 + 655 = 1337 (39%)
Left side (F/R): 1066 + 682 = 1748 (51%)
Right side (F/R): 1025 + 655 = 1680 (49%)
Total weight = 3428
This would make the car's corner balance at 49.7 (or 50 rounding up). Notice that the increase or decrease needed at each tire:
LF: - 18 RF: + 18
LR: + 7 RR: - 7
Also notice that the cross weights are both positive or negative. This is because lowering the height at one corner (decreasing the weight) will also decrease the weight at the opposite corner (thereby increasing weight on the other tires).
Now it is still possible to get a 50% cross weight, however per the equation these are merely the ideal numbers for that car. When I got corner weighted, the final equation was a bit different from the one I posted here, not to mention that the final numbers also added up with a two pound difference in total weight. So make sure when you get your car's corner balanced, the guy doing it actually knows the concepts behind it, and doesn't simply use a computerized weight scale to do the "work" for him.
Last edited by belizelittle39439; Jun 11, 2007 at 08:27 AM.
Jun 11, 2007, 10:57 AM
#22
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You need to measure the ride height off the pinch seam under the car rather than from the fender lips.
If you want to keep the factory rake, then find a stock sprung evo and measure the ride height from the pinch seams to the ground at the front and rear on a level surface and use that difference (front to rear) as your guide
If you want to keep the factory rake, then find a stock sprung evo and measure the ride height from the pinch seams to the ground at the front and rear on a level surface and use that difference (front to rear) as your guide
Jun 11, 2007, 11:19 AM
#23
You need to measure the ride height off the pinch seam under the car rather than from the fender lips.
If you want to keep the factory rake, then find a stock sprung evo and measure the ride height from the pinch seams to the ground at the front and rear on a level surface and use that difference (front to rear) as your guide
If you want to keep the factory rake, then find a stock sprung evo and measure the ride height from the pinch seams to the ground at the front and rear on a level surface and use that difference (front to rear) as your guide
I did however, lower the rear to reduce the rake a bit since then. I wanted the car to sit a little flatter. Right now, she's got a barely noticeable front rake...and is for the most part balanced. I'm waiting for the scales to come in to double check my work.
Jun 12, 2007, 09:24 AM
#26
What I did is set each coilover at exactly the same length, installed them, and measured at the fenders for a base measurement to go off of. This should be fine because unless the subframe is bent, each side of the front should be the same height, and each side of the rear should be the same height. I get it visually where I want it and from there it's up the corner balancing to determine where the ride height will be.
I did however, lower the rear to reduce the rake a bit since then. I wanted the car to sit a little flatter. Right now, she's got a barely noticeable front rake...and is for the most part balanced. I'm waiting for the scales to come in to double check my work.
I did however, lower the rear to reduce the rake a bit since then. I wanted the car to sit a little flatter. Right now, she's got a barely noticeable front rake...and is for the most part balanced. I'm waiting for the scales to come in to double check my work.
. Just make sure do the your roll center correction, it is as important as the rest of the set up. What wheel/tire/spacer combo are you running? Also, what is the purpose of the build autocross/ road-racing and what are your spring rates?
Jun 12, 2007, 10:35 AM
#27
You are headed in the right direction . Just make sure do the your roll center correction, it is as important as the rest of the set up. What wheel/tire/spacer combo are you running? Also, what is the purpose of the build autocross/ road-racing and what are your spring rates?
. Just make sure do the your roll center correction, it is as important as the rest of the set up. What wheel/tire/spacer combo are you running? Also, what is the purpose of the build autocross/ road-racing and what are your spring rates?As far as spacers...I'm not a big fan of them. I think it's better to simply use wider rims/tires. I'll use them if I absolutely have to.
And you're spot on as far as the purpose of the build. Autocrossing and roadracing. That's also why I went with the FPgreen instead of a 35r.
Jun 12, 2007, 12:27 PM
#29
I'll be doing the roll center correction soon. I still have stocker wheels and tires, will be keeping the stock rims and going with a 245/45 Falken Azenis as my next set of rubber. Spring rates are 10kg all around.
As far as spacers...I'm not a big fan of them. I think it's better to simply use wider rims/tires. I'll use them if I absolutely have to.
And you're spot on as far as the purpose of the build. Autocrossing and roadracing. That's also why I went with the FPgreen instead of a 35r.
As far as spacers...I'm not a big fan of them. I think it's better to simply use wider rims/tires. I'll use them if I absolutely have to.
And you're spot on as far as the purpose of the build. Autocrossing and roadracing. That's also why I went with the FPgreen instead of a 35r.
Jun 12, 2007, 12:32 PM
#30
Perhaps...I'll try everything else before I do the spacers. But thanks for the heads up! The green isn't installed yet, still waiting for it to get here. From what I understand though lag is just about non-existent. I'll be getting all the last stuff in my sig installed at once and then Chris (AMS) is going to come down and tune the car on the 8th of next month. So for now I'm just daily driving while everything is in limbo.