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      02-21-2008, 11:25 AM   #1
JerezBlue!
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Full Fuel Tank, Road Holding?

It's been quite icy of late where I live.

I've found that when the car is near empty traction controll will step in just the little bit more often and my confidence around turns is slightly diluted as a result.

Then, last night after fulling the tank to the brim, I found it all came back as it should.

The questions is: Is the car so finely balanced that the weight of fuel will make this sort of difference?
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      02-21-2008, 11:27 AM   #2
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Originally Posted by JerezBlue! View Post
It's been quite icy of late where I live.

I've found that when the car is near empty traction controll will step in just the little bit more often and my confidence around turns is slightly diluted as a result.

Then, last night after fulling the tank to the brim, I found it all came back as it should.

The questions is: Is the car so finely balanced that the weight of fuel will make this sort of difference?
A difference of over 100 lbs. near the rear axle is bound to have a big influence. Always good to fill the tank when things are slippery.
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      02-21-2008, 11:47 AM   #3
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I remember during my college days in the U.S, we had to place bricks in the trunk in the depth of winter to give the car greater traction so that we can drive up a particular slope in the snow
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      02-21-2008, 11:54 AM   #4
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I remember during my college days in the U.S, we had to place bricks in the trunk in the depth of winter to give the car greater traction so that we can drive up a particular slope in the snow
Bet you miss that!
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      02-21-2008, 12:08 PM   #5
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Bet you miss that!
Hell yeah! There was once in my freshman year when a senior drove me in his 325i in the snow, and we spun 720 degrees down a gentle slope

The windchill is freaking cold at -20 degree C in IU Bloomington .
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      02-21-2008, 12:13 PM   #6
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200 pounds out of 1800-ish pounds (on the rear wheels) is insignificant. If you are running PS2s a couple of degrees difference at these temps will have a greater impact
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      02-21-2008, 12:18 PM   #7
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Quote:
Originally Posted by JerezBlue! View Post
It's been quite icy of late where I live.

The questions is: Is the car so finely balanced that the weight of fuel will make this sort of difference?
Not surprising. I find my daily drive (E60 530 Sport) handles best with greater than 1/4 tank but less than 3/4 tank of fuel. This is especially evident when I play around the corners and the degree which the car leans and grips, off and on power.
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      02-21-2008, 12:50 PM   #8
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Quote:
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200 pounds out of 1800-ish pounds (on the rear wheels) is insignificant. If you are running PS2s a couple of degrees difference at these temps will have a greater impact
That is just over 10% difference... that is pretty substantial IMO.
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      02-21-2008, 01:26 PM   #9
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That is just over 10% difference... that is pretty substantial IMO.
Probably not that high though. 200 pounds assumes that 100 pounds of fuel is substantially behind the rear wheels, causing a weight shift from the front to back of 100 pounds. I don't see it happening. It also does not assume that acceleration will shift a LOT more weight to the back, so it is more like 130 pounds out of 2200 pounds. 10% would a highly overexaggerated number. Tire temp will be a bigger factor me thinks
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      02-21-2008, 01:26 PM   #10
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200 pounds out of 1800-ish pounds (on the rear wheels) is insignificant. If you are running PS2s a couple of degrees difference at these temps will have a greater impact
16 gal @ 6.2 lb./gal is just about 100 lb., so that's the maximum differential between empty and full. I do think it makes a noticeable difference under low traction conditions, though.
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      02-21-2008, 03:21 PM   #11
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Quote:
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Tire temp will be a bigger factor me thinks

Come to think of it, you may have a point here. It is true to say my experience was in icy conditions.
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