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How to fix weight distribution from scale readings.

5
0
Exp. Type
Time Attack
Exp. Level
3-5 Years
Atlanta Georgia
I Have a 2016 Mustang Gt California Special I have been competing in Time Trials racing. I have Pedders XA Coilovers with camber plates and I am not to great with tuning the height or spring rate. I Got the car on a scale and they said the front drivers side weighed in at 1092 pounds while the other corners weight mid to high 800s. How Do I fix the front Drivers Side Corner to match the rest of the corners? Could I fix it if I adjust the height or the spring rate? Looking for any input on how to adjust the coilovers right! Gonna post a picture of the Scale so you can see what I’m working with. Thanks for any input!

3469ED46-AD7A-4B45-9D6C-1073914AFA9C.jpeg
 
442
287
sfo
1st thing is how do you like the car balance now? The answer to this will push you in a direction to adjust your chassis rake and rideheight. Then you corner balance. your balance is way off. You are at 46% cross and you should be at 50% to balance left and right turns and improve the split between LF and Rf wheel for better braking. To corner balance you need adjustable endlinks. many people don't have that. Mustangs need a way to adjust ride height that means things like ground control coils or a real co setup like MCS. I think the pedder's have the adjustments you need but I have never seen them. You also need to know the ride height range your coilovers will allow so that you do not bottom out your shocks when driving. Many coilovers allow you to drop a car low but then you have no travel and the car handles worse than stock and can even damage the car. The S550 has a problem with the rear shock mount area getting ripped out. I believe this problem is due to lack of shock travel putting forces there not designed for. Those of us running proper CO's are not having a problem ripping that area,
 
5
0
Exp. Type
Time Attack
Exp. Level
3-5 Years
Atlanta Georgia
The car is pushing out so a lot of understeer when I’m hitting the apex. The ride height is only 3/4 of an inch lower than stock so there is enough so it doesn’t bottom out the shocks. I am ordering adjustable end links right now. the sway bar is in the fully tight position in the front and it seems really tight. The rear sway bar is in the middle and has no tension like the front. I have Eibach sway bars in front and rear. Also if I adjust the front drivers side height up would it help take the weight off and help take away the understeer at all? Do I need to move weight more to fix it? I am trying to fix this problem without going to a shop.
 
442
287
sfo
How did you determine your RH is -3/4"? Did you measure before and after? Do you measure from frame rail less pinchweld or fender lip to ????

Do you have access to scales? Do you know how to scale a car get flat floor etc?
 
442
287
sfo
It is so hard to do this online but if the front links are tight that means you have added some unknown amount of unpredictabe wheel rate to your spring rate. Without endlinks disconnected or passively connected at RH, your weights posted can be not true meaning your corner balance could be better than posted.

If you have massive understeer there are many things you can control to tray and balance OS or US. An example is to set the front bar to the furthest out hole to soften the bar but use the adjustable endlink to be passive to not add any spring rate of the bar when sitting at RH. So you randomly adjust one endlink in the middle lets say and put it on the passenger side. Then put car at RH and adjust the driver's side link to passively fit. Go drive and see how that feels? You can reduce front US by stiffening the rear bar or lowering the rear RH. You can reduce front US by lowering the front RH. If you have US in the front and outside tire wear more - camber can help too. You can see it gets complicated.
 

racer47

Still winning after 30+ years
335
386
Exp. Type
W2W Racing
Exp. Level
20+ Years
SE WI
First disconnect both sway bars and reweigh, with driver. Your front bar sounds like it is heavily preloaded. Assuming the corner weights are similar, you will need something like 1 turn looser on the LF and RR, plus 1 turn tighter (meaning compressing the spring) on the RF and LR. Reweigh and see what you get. Keep doing this until the sum of the LF and RR equal the sum of the RF and LR. This is 50% cross weight. Like Dave said.

Then reconnect the sway bars (again with the driver seated) such that there is no preload. The links should be adjusted so that they bolt on easily on both sides without having to force the second side after connecting the first side. This will get you a good starting point. The car will likely still understeer but it should understeer equally in left and right turns. From there you start playing the spring rate and swaybar stiffness game until it gets more neutral.

The car will still be left side heavy and nose heavy. You can only change this by moving weight (like moving the battery to the back) or removing weight.
 
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Also, I don't know about the OP's 2016 but at least on my 2011 the front swaybar is actually glued in place. So if you don't disconnect both sides, you are going to get screwy results. The fact that the front bar is glued also has the effect of increasing the effective spring rate whenever you lower the car beyond stock, as the bar increasingly "binds" the more it is twisted outside of its original oem position. Obviously this increase in rate is greater the more you lower the car. Which I suspect could contribute to understeer, as you are effectively making the front rate much greater than the rear, beyond the effect of the springs themselves.

Good luck.
 
442
287
sfo
Also, I don't know about the OP's 2016 but at least on my 2011 the front swaybar is actually glued in place.

This is another dumb Ford thing. Gluing is on the PP1 front bar as an example. I had this on my 2019 PP1. it's goal is to up the rate without making a second stiffer bar. so the PP1 bar is same as non-PP1 bar but the glued thing. I actually cut those off my PP1 bar rewelded the mounts and made the bar swivel. Then the PP1 bar can actually work. The OP has good bars so that's not his issue. That pp1 bar was not enough for me.20200406_142643.jpg
 
The pro's I know do pretty much what @racer47 said, except they put weight in the driver's seat to simulate the driver. The adjustment approach is to balance the car left-right so the load on the tires is the same from side to side. You can't really change front-rear. Your Pedders coil overs, if I read the catalog correctly, have a 400#/inch rate at the front, so lowering the driver's side spring perch a small amount should get it pretty even. Thing is, every adjustment is linked, so if you adjust the left front down a bit, it'll skew the rear balance, so you'll have to compensate back there as well. It's a process...
 

Dave_W

Cones - not just for ice cream
369
351
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
the sway bar is in the fully tight position in the front and it seems really tight

Since you have an aftermarket swaybar, disconnect both end links, then push against one end of the swaybar to try to rotate it. Is it hard to move? Is this what you mean by "seems really tight?" If so, the bushings are probably too tight and binding the bar. You want to be able to rotate the bar easily without it being sloppy in the mounting brackets. You need to remove the bushings and shave/file them to the bar can rotate easily. Not sure on the Mustang, but on other cars I've seen the bushing molded a bit "tall" so extends past the bracket. When the bushing and bracket were installed on the bar, but not bolted into the car, they seemed fine, but bolting the bracket down compressed the bushing enough to bind the bar pretty badly. You may also be able to stack a washer under the bracket bolts to shim the bracket up and eliminate the binding. Other times I've had to shave where the split in the bushing meets because it was being squeezed by the bracket.

As mentioned above, some Mustangs apparently have "bonded" bushings that are molded directly to the swaybar. This means the swaybar doesn't rotate easily, but is designed to be "rising-rate" in each direction of suspension travel, based on the stiffness of the bushing material. Which is completely different than the stick-slip-stick effect you get with a non-bonded bushing that's too tight, causing completely random roll stiffness.
 

ArizonaBOSS

Because racecar.
Moderator
8,545
2,375
Arizona, USA
I have heard that wrapping the bar where it contacts the bushing with teflon tape can also help reduce binding. Truth or old wive's tale?
Judging by my experiences with Teflon Tape, you're more likely to wind up with a wad of tape smashed in your bushing interface. Grease em periodically!
 
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My apologies, I missed OP's post where he said he had Eibach sway bars.
But yes, some models have the front sway glued from the factory and my 2011 is one of them. Apparently other cars from the same year do not, weird.
Maybe the factory glue guy or gal was out sick or on break or something....
Carry on!
 

xr7

TMO Addict?
422
427
Exp. Type
Autocross
Exp. Level
5-10 Years
Minnesota
My 2012 Boss had the bushings bonded to the bar. My thought is it has more to do with assembling cars than anything else. If you look up the OEM front sway bar it is only available as an assembly. You get the bar bushings and brackets fully assembled and ready to install on your car. The bracket that contains the bushing is two piece and is crimped together surrounding the bushing. You cannot purchase bushings or brackets separately. Assembly line part supplied by a vendor.
 
5
0
Exp. Type
Time Attack
Exp. Level
3-5 Years
Atlanta Georgia
How did you determine your RH is -3/4"? Did you measure before and after? Do you measure from frame rail less pinchweld or fender lip to ????

Do you have access to scales? Do you know how to scale a car get flat floor etc?
I measured the middle of the wheel to the fender and that’s how I got the 3/4 measurements. Also used a MM digital ruler and measured the coil over on the inside.
 

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