Quote:
Originally Posted by exdos
So how do you corner weight the car without adjusting the suspension heights at each corner? Surely this must alter the position of the body of the vehicle relative to the road which may alter the rake angle?
In the case of 3002 tii's car, how come it appears to have zero rake after corner weighting when OEM has some positive rake?
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Corner balancing only requires VERY small adjustment on, at most, 2 corners out of 4. You're talking about a couple of turns of the collar at best.
Typically, these cars come from the factory "fairly" balanced, however they do not account for variances in driver's weight or other modifications. The end result, say, your left front+right rear is about 50 lbs heavier than the right front+left rear, then one of the adjustment collars will be moved slightly to tilt the car one way or another. Keep in mind, the OP's car came with 450/550lbs springs. That means to alter the ride height of one corner by no more than 1/10" to achieve the desired effect.
One. Tenth. Of an inch.
If that 1/10th of an inch alters the dynamic height enough to reduce the front aerodynamic force enough to be a concern upon acceleration squat, I've got another calculation for ya.
Our car makes 265ft-lbs of torque at the crank. Let's call it 240 at the wheels to be generous. Given that aerodynamic forces aren't significant on this chassis under 80MPH, we'll call it middle of 3rd gear. 3rd gear multiplication is 1.66 * 3.65 = 1,454.16 ft-lbs of potential twisting force being applied at the rear wheels, since the overall radius of the wheel/tires is pretty darn close to 1'. The MZ4 has a wheelbase of 96" (8.06'), so that means the leverage that 1,454.16 ft-lbs of torque being applied at the rear wheel translates to a whopping 180.27 lbs at the front axle. So at full throttle, on OP's car, with front springs at approximately 450lbs/in, the car will lift or squat...Wait for it...
4/10th of an inch. At full throttle. In 3rd gear. That number decreases at even higher speeds, in higher gears, where aerodynamic forces are more important.
The next thing I want y'all to do, is go out and measure the height of the chassis right in front of the rear wheel, and right behind the front wheel. Tell me what the difference is there. Then I want you to measure the clearance between the mid point of the front bumper to the ground, then measure the midpoint of the REAR valance to the ground. And tell me the difference there.
I'm willing to bet even on OP's car, the rear valance clearance is
inches higher than the front.
And then go ahead and tell me that it's going to make a difference AERODYNAMICALLY if you move one of the front or rear collar 1/10th of an inch.
I'm going to let you all in on another secret. I'm not proud of it, but I will share it to make a point.
Right after I got my MZ4 Coupe corner balanced, I didn't like the "stance" of the car. Plus on straight roads it pulls to the right, or I have to crank the wheel to the left. So I figure I can probably HACK this by adjusting the easiest parameter I can mess with, by turning the right front adjustment collar to raise that corner just a bit. I turn the collar 3 turns, which in turn, move the right front up by about 1/8". Didn't do sh*t for the issue with the car pulling to the left (I'll explain this later). I took the car back to the place that CB'ed the car. Kept my mouth shut, and the owner of the shop came back and said "I don't know why but your setting was all f*cked up, especially the front right corner. We had to go through the whole process again." He was going to suggest I check the rest of my suspension to find out why, especially the front right setting, was way off from where they set it a few weeks ago.
1/8th of an inch.
Turns out the car was simply following the crown of the road, but since the front end was toe-ed out slightly it dramatically enhanced this effect. I drove the car on a road that crowned to the left (the sewer drains were in the middle of the road) and sure enough, it pulled to the left and I had to crank the wheel to the right.
This is why I insist that corner balancing has zero effect on rake, and rake is irrelevant. It's far more important you set the cross weight correctly. Rake is important only to those who are far more obsessed with stance than functionality, I've never in my life seen any club racer worry about the car's rake. Because, even if you set the rear axel height of the car lower, the front facia is still much lower than the rear opening. And it's hard to set the car so far out of wack that the rear of the car is LOWER than the front, since the rear of the car is several inches higher than the front to begin with. Corner balancing does not alter the ride height enough to lower the rear by inches and raise the front by inches.
You'll have a bigger negative effect on static rake and dynamic aero lift by going with the WRONG aspect ratio tires than corner balancing, IMO.
And I am going to address your last point by pointing out you're looking at a picture taken with what likely is a wider angle lens commonly found on cell phones. At an angle. Which typically exaggerates the dimensions of objects closer to you and diminishes those same dimensions of objects far away from you. If you can accurately say that his car has zero rake from a simple picture taken by a simple camera posted on a simple forum, I applaud you for your super human deduction skills. Because frankly, I can't see it.
