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      12-01-2009, 12:38 PM   #1
FusionM
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Weight Distribution or Weight Loss more important?

As we mod our cars, is it important to consider weight distribution to keep it at 50/50 or lose weight?
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      12-01-2009, 12:44 PM   #2
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Depends on the extent of the weight being added...
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      12-01-2009, 07:28 PM   #3
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I would think more weight loss than position within the car except if you are speaking about wheels. Rotational mass is approximately 8X more important than non rotating meaning that each lb that you take off your wheels equals 8 lbs off of any other part of the car. Your easiest weight savings are seats and battery. Probably 60-80 lbs available right there.
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      12-01-2009, 10:06 PM   #4
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Weight reductions

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I would think more weight loss than position within the car except if you are speaking about wheels. Rotational mass is approximately 8X more important than non rotating meaning that each lb that you take off your wheels equals 8 lbs off of any other part of the car. Your easiest weight savings are seats and battery. Probably 60-80 lbs available right there.
True. Only thing about replacement seats is most likely you will lose the side airbags. Not sure I'd make that compormise in a DD. I agree that you probably can't do too much to screw up the front/rear balance.
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      12-02-2009, 12:19 AM   #5
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It's pretty easy to lose weight from the back of the car, but I always wonder what that would do to the balance of the car.
You get a titanium exhaust, plastic/CF trunk, Mini battery and you have a lot of weight out the back of the car.
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Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."
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      12-02-2009, 01:12 AM   #6
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i think if you work out regularly and eat healthy your car should be fine
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      12-02-2009, 02:10 AM   #7
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What about adding a lightweight exhaust, particularly the muffler?
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      12-02-2009, 09:13 AM   #8
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Quote:
Originally Posted by aus View Post
It's pretty easy to lose weight from the back of the car, but I always wonder what that would do to the balance of the car.
You get a titanium exhaust, plastic/CF trunk, Mini battery and you have a lot of weight out the back of the car.
Considering that the car is already designed to carry back seat passengers and a trunk load, it's not too critical for street use. If setting up for the track, adjustments might need to be made, but you're making those anyhow (alignment, tire pressures, etc.).
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      12-02-2009, 10:37 AM   #9
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Both are important....but M3 is one of FEW BMW cars that doesnt have 50:50 from stock.
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      12-02-2009, 10:46 AM   #10
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Difficult question, but less weight is always better and hardly think that lowering weight by say 50 lbs in the rear will make any perceptible difference to the car´s balance. I should say that body rigidity is also very important (fact is someone should have come up by now with a rigidity coefficient and am surprised no one EVER measures this), so, all of these factor in together plus other components such as suspension, wheels/tires, power, etc... to maximize performance. Not an easy task to balance but very exciting to try for sure.
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      12-02-2009, 02:26 PM   #11
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Quote:
Originally Posted by aus View Post
It's pretty easy to lose weight from the back of the car, but I always wonder what that would do to the balance of the car.
You get a titanium exhaust, plastic/CF trunk, Mini battery and you have a lot of weight out the back of the car.
That sounds nice but doesn't that make the car front heavy which equates to less rear wheel traction?
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      12-02-2009, 04:34 PM   #12
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Originally Posted by FusionM3 View Post
That sounds nice but doesn't that make the car front heavy which equates to less rear wheel traction?
You have to keep things in perspective. Even if you take 75 lbs. off the trunk area, that's only 2% of the car weight. It will not make an appreicable difference unless you are tracking and pushing the car hard. Even then, the benefits are still there for less weight.
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      12-03-2009, 03:30 PM   #13
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Do some simple math, our cars are about 9 lb/hp. So it takes losing about 9 lb to gain the acceleration of 1 hp. Now of course weight loss is better than power gain alone since it improves handling. My somewhat coarse evaluation of being able to actually feel and notice a change is something like the weight of a peson ~150lb or very roughly 15 hp. Also losing weight on tires/wheels is more effective than losing no rotating mass but I am very skeptical of these somewhat arbitrary factors of 1 to 8 or 1 to 4 or whatever. I will try some simulation to see if I can get some better numbers.
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      12-03-2009, 03:55 PM   #14
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Quote:
Originally Posted by GTM View Post
Both are important....but M3 is one of FEW BMW cars that doesnt have 50:50 from stock.
Yes BMW states that the distribution is 52.2/47.8% for the sedan, but that is for a fully loaded/optioned vehicle. Now, take for example my car which has no DCT, no sunroof, no NAV/iDrive, no EDC, no heated seats, enhanced audio, plus no fold down rear seats, and all but the fold down seats weight savings is coming from the front half of the vehicle. I am willing to bet that in a this type of optioned M3, the distribution would be closer to 50/50.
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      12-08-2009, 11:04 AM   #15
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Quote:
Originally Posted by ///Metak View Post
Yes BMW states that the distribution is 52.2/47.8% for the sedan, but that is for a fully loaded/optioned vehicle. Now, take for example my car which has no DCT, no sunroof, no NAV/iDrive, no EDC, no heated seats, enhanced audio, plus no fold down rear seats, and all but the fold down seats weight savings is coming from the front half of the vehicle. I am willing to bet that in a this type of optioned M3, the distribution would be closer to 50/50.

Most of equipment you listed are well behind the front axle which pretty much brings down the weight almost same ratio front and rear.
I have corner weighted many cars and tried to adjust it.
Moving around or taking out small equipments like you listed have almost no changes on weight distribution.
Only thing that it can make significant difference is something NOT between front and rear axle.

It's TOUGH to move about 75lb(about 2%) to rear axle which takes WAY more actual weight to transfer that much to rear.
Remember front and rear ARE connected.
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      12-08-2009, 04:34 PM   #16
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depends on what the use of the car is and driver skill.

Yes, technically we should be taking all things into consideration when making any change to the car. But if you're not driving 10/10's on the track, changes that pull the car away from 50/50 weight distribution will go pretty much unnoticed.

In my 2500lbs track car with 185hp, when a passenger sits in the car that's corner balanced for me alone, I feel a huge difference. Why? Because the passenger has added almost 10% body weight to one side of a torqueless car being driven at 10/10's.

To take that idea further. consider how a novice (say 10 or fewer track days) will drive at the track. a 200lbs instructor in the passenger seat does not result in slower lap times.

If you're just driving around on the street, honestly don't worry about the negative impacts of a CF hood or rear diffuser on balance. Your wheel/tire/suspension choice has a much greater impact on how the car actually handles. The rest is along for the ride.
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