Where does all the rear weight come from?

[SUB-FT86]

Originally Posted by Miniata

No. Moving the stock battery to the trunk means adding even more weight with cables and a box. A better solution (unless running a big stereo) is putting a small lightweight battery in the stock location. Save 20+ lbs over the front end with few downsides. I have a 2 lb lithium battery for my Miata for autocrossing, and my normal street battery for the Miata is a 7 lb AGM battery.

The cables certainly can't be heavy enough to offset the battery. And part of the cables will lead onto the rear side of the car.

2760 lbs

55% is 1518 and 45% is 1242.

What happens when you shift a 30+ lb battery from front to rear?

54% is 1490.4 and 46% is 1269.6

The balance is increase to 54/46 instead of 55/45.

How much weight does the cable add? Like less than 5 lbs?

[regal]

Originally Posted by SUB-FT86

The cables certainly can't be heavy enough to offset the battery. And part of the cables will lead onto the rear side of the car.

2760 lbs

55% is 1518 and 45% is 1242.

What happens when you shift a 30+ lb battery from front to rear?

54% is 1490.4 and 46% is 1269.6

The balance is increase to 54/46 instead of 55/45.

How much weight does the cable add? Like less than 5 lbs?

No offense but calculating weight distribution is not this simple. The weight distribution change depends on how far the change is from cog which changes when you move the weight around , the constant is the wheelbase. I am sure someone has an excel spreadsheet on the web that will do it for you if you are this concerned about it.

[SUB-FT86]

Originally Posted by regal

No offense but calculating weight distribution is not this simple. The weight distribution change depends on how far the change is from cog which changes when you move the weight around , the constant is the wheelbase. I am sure someone has an excel spreadsheet on the web that will do it for you if you are this concerned about it.

What does the cog have to do with F/R balance? It doesn't make a bit of sense. A car can have a low cog and still have terrible balance F/R.

[regal]

Originally Posted by SUB-FT86

What does the cog have to do with F/R balance? It doesn't make a bit of sense. A car can have a low cog and still have terrible balance F/R.

You are confusing vertical COG with horizontal COG with COG (x,y, and z) just use wikipedia.

Here is a spreadsheet I found in 15 seconds with google. Didn't review it. If you are interested check it out.

http://www.smithees-racetech.com.au/...worksheet.html

[Miniata]

Originally Posted by SUB-FT86

The cables certainly can't be heavy enough to offset the battery. And part of the cables will lead onto the rear side of the car.

2760 lbs

55% is 1518 and 45% is 1242.

What happens when you shift a 30+ lb battery from front to rear?

54% is 1490.4 and 46% is 1269.6

The balance is increase to 54/46 instead of 55/45.

How much weight does the cable add? Like less than 5 lbs?

even if the calculations were that simple (they aren't) you're still adding at least 5 lbs with appropriately sized cables and a box to move a small bit of the weight balance to the rear when you could achieve the same effective result by using a 5-7 lb battery up front and also reduce the overall weight of the car.

[SUB-FT86]

Originally Posted by Miniata

even if the calculations were that simple (they aren't) you're still adding at least 5 lbs with appropriately sized cables and a box to move a small bit of the weight balance to the rear when you could achieve the same effective result by using a 5-7 lb battery up front and also reduce the overall weight of the car.

I guess BMW is retarded for putting a battery in the back then. But then that's one of the reasons BMW cars are known for the 50/50 weight distribution.

Also a 5-7 lb battery doesn't sound like one you would daily drive with.

[Miniata]

Originally Posted by SUB-FT86

I guess BMW is retarded for putting a battery in the back then. But then that's one of the reasons BMW cars are known for the 50/50 weight distribution.

Also a 5-7 lb battery doesn't sound like one you would daily drive with.

Not retarded at all. Neither is Mazda for putting the battery in the trunk of my Miata - from the factory. I have no issue when manufacturers do it, just don't see it as being necessary to move the battery to the trunk when it didn't come there from the factory, except for specific applications like when a race car is under required weight for its class and ballast is needed, and a big heavy battery in the trunk could be one way to achieve that.

As to the daily-drivability of a small lightweight AGM or lithium battery? They actually work better on daily driven cars than on cars that are parked and only driven every week or two. Not keeping the small batteries charged up is what kills them, not using them daily. I've been using smaller, lighter batteries in daily driven (and rarely driven autocross/track cars) for 10+ years, from Neons to Mustangs to my Miata.

[raul]

Another thing that helps with weight distribution is the fact that the hood is aluminum, while the trunk lid isn't.

[Dadhawk]

Originally Posted by Miniata

even if the calculations were that simple (they aren't) you're still adding at least 5 lbs with appropriately sized cables and a box to move a small bit of the weight balance to the rear when you could achieve the same effective result by using a 5-7 lb battery up front and also reduce the overall weight of the car.

It can make a huge difference, easily offsetting the weight of the cables. The battery in the car now sits relatively close to the COG, which means it has minimal impact on COG, at least the horizontal component.

If you move it further out on the rear ARM (moving it towards the rear of the car and further from the COG) the same weight gets amplified and move the the COG much more effectively. As someone above mentioned, its just like a see-saw (basic lever).

This is used in experimental aircraft all the time. you can offset a significant portion the weight of a 200lb engine just by putting the battery in end of the tail cone.