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Old 04-04-2013, 08:15 PM   #1
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Default 4 scale balancing questions

So i'm using 4 scales for the first time to set my weight balance how do i setup the car before i put it on the scales? Shocks off? Do i push it down to settle the suspension? Any tips would be great.

I adjusted my shock collars so they are all turned out the same amount and placed it on the scales wih out pushing down with eerythingon it ready to run body and all. My numbers are as follows:
RF 313
RR 330
LF 343
LR 321

Total 1307 so i gotta add 73 grams so do i just add 30 on the RF and 10 on the LR then another 35 or so in the middle? Or are all these wrong cause i set it up wrong on the scales? Any help would be awesome thanks
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Old 04-04-2013, 08:37 PM   #2
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That is actually a lot closer to perfect than my car was... I was off by like 100g in crossweight, but just adding weight where you think it needs it won't be a perfect fix.

I learned that before trying to get the scales to read right to check the tweak then take the swaybars off and make sure the chassis is actually level and at the height you want it, then start setting the spring collars while always paying attention to the chassis height at different ends of the car. Once balance is there with the collars, reinstall the swaybars and adjust the links from the swaybar to the arms to make sure the swaybar is under no tension at rest. Now the car should be right in this sense.
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Old 04-04-2013, 08:49 PM   #3
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Scales should not be used to get the left to right and front to rear balance of your car. The only way to use scales this way is to replace the shocks with exact equal length solid rods so you take the springs out of the equation. the best thing to do is balance your car by hanging it from the center point. most cars have holes or dimples in the shock towers for this. if not the chassis probably has two holes on the bottom for balance. Set your ride height, droop, etc as you normally would then you can use the scales to fine tune. make sure the axle passes over the center of the scales or your measurement won't be accurate. Your numbers should be pretty close. if there is a drastic difference between the fronts or the rears your chassis is probably tweaked. you can now adjust the shock collars to fine tune the weights. screw down to increase the number and up to decrease. one thing to remember though is that you need to adjust the opposite corner the opposite adjustment to keep the ride height. ex. if you turn the right front down a quarter turn then the left rear must go up a quarter turn. you probably won't get a 100% even number but you can get pretty close. after you finish check your ride height and droop to make sure things are still where you want them. this method can be a pain but it works very well.
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Old 04-05-2013, 12:22 PM   #4
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The numbers are a lot easier to make sense of if you write them like this:

LF 343 + RF 313 = Front 656
LR 321 + RR 330 = Rear 651
Left = 664
Right = 643
LF + RR = 673
RF + LR = 634

So, your car is heavy on the left. A heavier battery, or lighter electronics, or moving your battery out, or moving your electronics in, would do well. But since you have to add weight anyway, you can just do that.

Your car is pretty balanced front to rear, actually a bit front heavy. I haven't experimented a ton with front/rear weight balance, but I usually run more weight to the rear. Rear corners about 10g heavier than front corners. More rearward seems to give the car more steering in the first half of the corner, but less in the second half of the corner. It also seems to be a bit easier to drive. Going too far back seems to make traction roll worse, though. In any case, I'd start by adding weight on the right rear.

Also important to note: because the left side is 20g heavier than the right, and the front/rear is roughly even, you'd expect to see the left front ~10g heavier than the right front, and the left rear ~10g heavier than the right rear. That is, you'd want LF + RR == RF + LR. But what you see is a ~40G difference, meaning either the scales aren't sitting evenly, or something is fairly tweaked. You'd probably notice that amount of tweak on track. That can come from a lot of things. Assuming the scales aren't sitting really unevenly, the most likely causes are tweak in the chassis (top deck most likely), uneven spring lengths (common on associated and Schumacher springs), and tweaked swaybars.

For getting a good reading off the scales, you'll have to experiment to see how your car and scales react to different ways of settling the car. You can try lifting the car and letting it settle back down. You can try pressing down and letting it come back up. I usually end up with a combination of gently tapping on the center of the shock towers, and rolling forward/back a bit to get it settled. The readings can vary quite a bit (like 5-10g per corner) based on how you get the car settled. So you just need to play with it and find what it likes to give you the most balanced and consistent readings.

From here, I'd suggest the following steps:
- Play with orienting the car differently, spinning the tires differently, moving scales around, and different settling techniques to get a feel for how reliable your readings are.
- Back off your droop screws a bit, so that droop isn't affecting the readings.
- Put on some setup wheels if you have them.
- Disconnect the swaybars
- Go ahead and add the weight you need to add
- Play with weight to get total left/right weights the same (within ~5g is close enough). Don't worry too much about cross weights just yet.
- Now take the car off the scales, and re-set your ride height and droop. Get the droop spot-on using a droop gauge and blocks, or blocks and measurement off the setup board.
- Put the car on the setup board with tires on
- Lift the car slowly from under the center of the rear with a wrench, and watch the way the tires lift. If the left tire lifts first, tighten the right front spring slightly, and loosen the left front the same amount. If the right tire lifts first, do the opposite.
- Now spin the car around and do the same thing lifting the front, and adjusting the rear springs.
- Put the car back on the scales, and your cross weights should be very very close.
- Reconnect swaybars one at a time and make sure it's still good. If connecting a swaybar throws off the cross weights, de-tweak that swaybar.
- Re-check ride height again, and then re-check with the tire-lift technique.

I prefer to use scales to get the car balanced the way I want, and for sanity-checking tweak, but I use the droop + lift technique to de-tweak. Whenever I try to use the scales to de-tweak, I end up going in circles with the spring adjustments, and sometimes end up with really weird adjustments, because the scales don't tell you which end of the car the tweak is coming from. The droop + lift technique is really simple, and it's closest to what the car is actually going to be doing when it's on the track, which is what really matters. However, that technique doesn't work at all if the car's left/right balance is off, because it'll look tweaked on both ends, and you'll make some screwy adjustments. It also doesn't work if your droop isn't spot-on using blocks. Sometimes I'll lift one end of the car when it's on the scales to try and figure out which end is tweaked, but even then it can still lead to some weird adjustments.

Some people may disagree with me, but my recommendations are based on tips and tricks I've picked up from top-tier drivers along with my own experience of what works to get the car to work properly and consistently on track. There may be other things that work, too. There are also some factors (like actual symmetry of weight placement and its effect on chassis tweak) that I just don't worry about, because I usually can't really do anything about them. The bottom line is to understand what assumptions you're making with different measuring techniques, and making sure you get the most basic measurements and adjustments right first, before making down-stream measurements and adjustments. Otherwise, you'll get things screwed up pretty quickly and have a car that you think is set up correctly, but drives like a bag of poo. The absolute most important first thing is chassis tweak. The chassis has to sit flat on blocks, because if it doesn't, the droop numbers will be off. Then the droop numbers have to be spot-on, because if they're not then my suspension de-tweaking will be off. Etc, etc....

Also, if your club has an official scale for tech purposes, be sure to weigh your car on that. Our club's scale reads a good 15-20g lower than my 4 combined scales.

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Old 04-05-2013, 05:39 PM   #5
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Corner Weight Balance Calculator.zip

With your numbers input =

4 scale balancing questions-arf.jpg
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Old 04-06-2013, 01:01 AM   #6
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Make sure your scales are on perfectly flat surface as even a very small amount out can make a difference on the scales
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Old 04-08-2013, 10:44 PM   #7
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Originally Posted by r king View Post
Make sure your scales are on perfectly flat surface as even a very small amount out can make a difference on the scales
I concur.

Also use setup wheels when measuring weights. Tires are too compliant and misshapen, I think. You wind up with funky answers which largely become unfunked when you switch to the more perfectly shaped and rigid setup wheel.
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