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      03-11-2008, 12:32 AM   #1
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Rain Rain Rain

I hate driving when it is wet out... I can barely touch the gas pedal from a stop without having my tires spin... Oh well, I guess things could be worse... I could still be driving a honda
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      03-11-2008, 01:04 AM   #2
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haha i know what you mean, the first week i transititioned from my integra to my e90, i had trouble with overdoing the throttle too. But in all honesty, it's the runflats!!!! they suck so badly.
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      03-11-2008, 01:51 AM   #3
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Originally Posted by daheechang View Post
haha i know what you mean, the first week i transititioned from my integra to my e90, i had trouble with overdoing the throttle too. But in all honesty, it's the runflats!!!! they suck so badly.
the runflats arent too bad, just needs to be warmed up , as for the rain.. yes it sucks..
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      03-13-2008, 12:09 PM   #4
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That's why I drive an xi -- you can pretty much floor it any time in the middle of a corner when it is raining and the car goes like it is on tracks.
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      03-13-2008, 12:16 PM   #5
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335 + PROcede v2 + rain = wheel spin

328 + rain = no wheel spin

the xi probably helps a bit, but i'm pretty sure the wheel spin is due to the increase power of the 335 w/ procede, not to mention the RFT's.
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      03-13-2008, 12:32 PM   #6
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Of course power is also a factor, in that it is much harder to spin an underpowered car. That being said, I have driven the 328i (RWD) and it also slides around during aggressive driving. The fact that the 335xi is faster than a 335i (according to BMW) highlights this point. Unless you have installed a LSD, the BMW RWD cars are really "one wheel drive" -- as opposed to an xi where you have power going to all 4 wheels.
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      03-13-2008, 02:01 PM   #7
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Quote:
Originally Posted by douger View Post
Of course power is also a factor, in that it is much harder to spin an underpowered car. That being said, I have driven the 328i (RWD) and it also slides around during aggressive driving. The fact that the 335xi is faster than a 335i (according to BMW) highlights this point. Unless you have installed a LSD, the BMW RWD cars are really "one wheel drive" -- as opposed to an xi where you have power going to all 4 wheels.

No, you don't have power going to all 4 wheels unless you are driving perfectly straight with all four wheels having identical traction. The sames goes for RWD cars, they have power going to both rear wheels in equal amounts, except when there is an imbalance in traction.

Or, when one wheel is spinning faster than the other. This happens all the time, to both RWD and AWD cars, no matter how sophisticated the system. Every time you make a turn, the outside wheels will spin faster than the inside ones. This is the reason for the differential, and where it gets its name from. If the wheels couldn't spin at different rates, you'd wear down your rear tires in a hurry. If the front wheels couldn't spin at different rates, you would have a very hard time turning.

But that is getting a little technical.......

The xi system does not have LSDs in the front or rear differentials, just like the i series don't have rear LSDs. It uses electronics to control wheel spin, just like the i series does. But if you defeat DSC/DTC fully and place the car on a surface where one front and one rear wheel have zero traction, the car won't move.

So while the i may be called "one wheel drive", the xi should be called "two wheel drive." The only true "four wheel drive" would be a vehicle with front and rear locking differentials and a locking transfer case. You will find that kind of system on a rockcrawler Jeep, but not in a passenger car.
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      03-13-2008, 05:26 PM   #8
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Originally Posted by jdink View Post
335 + PROcede v2 + rain = wheel spin
+ if you don't know how to drive may be?

People (including me) have been driving cars with over 350hp in WA State for years and yet the spin the wheels unintentionally in rain..... So please don't make it sound like it is impossible to drive this car in rain. If you know what you are doing you will be fine even with a 550hp car.
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      03-13-2008, 05:45 PM   #9
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Quote:
Originally Posted by TTG View Post
+ if you don't know how to drive may be?

People (including me) have been driving cars with over 350hp in WA State for years and yet the spin the wheels unintentionally in rain..... So please don't make it sound like it is impossible to drive this car in rain. If you know what you are doing you will be fine even with a 550hp car.
Ouch?

1) I don't quite understand that first sentence, i think you made a typo somewhere... Either way, I think I understand the point you are trying to make...

2) to quote myself:

"I hate driving when it is wet out... I can barely touch the gas pedal from a stop without having my tires spin... Oh well, I guess things could be worse... I could still be driving a honda "

I didn't say it was impossible to drive in the rain. I simply stated that FROM A STOP you can't accelerate hard without the wheels spinning.

I am aware of the technique used by many drivers out there that involves using the gas lightly which will enable me to drive safely in the rain. Still, I find it much more enjoyable to drive my car when it is dry out and I do not have to use this driving technique.
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      03-13-2008, 06:49 PM   #10
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Originally Posted by jdink View Post
Still, I find it much more enjoyable to drive my car when it is dry out and I do not have to use this driving technique.
+1, rain can be fun... I just want some sunshine so I can drive with my windows and and smell the tires
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      03-13-2008, 10:13 PM   #11
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Quote:
Originally Posted by scollins View Post
No, you don't have power going to all 4 wheels unless you are driving perfectly straight with all four wheels having identical traction. The sames goes for RWD cars, they have power going to both rear wheels in equal amounts, except when there is an imbalance in traction.

Or, when one wheel is spinning faster than the other. This happens all the time, to both RWD and AWD cars, no matter how sophisticated the system. Every time you make a turn, the outside wheels will spin faster than the inside ones. This is the reason for the differential, and where it gets its name from. If the wheels couldn't spin at different rates, you'd wear down your rear tires in a hurry. If the front wheels couldn't spin at different rates, you would have a very hard time turning.

But that is getting a little technical.......

The xi system does not have LSDs in the front or rear differentials, just like the i series don't have rear LSDs. It uses electronics to control wheel spin, just like the i series does. But if you defeat DSC/DTC fully and place the car on a surface where one front and one rear wheel have zero traction, the car won't move.

So while the i may be called "one wheel drive", the xi should be called "two wheel drive." The only true "four wheel drive" would be a vehicle with front and rear locking differentials and a locking transfer case. You will find that kind of system on a rockcrawler Jeep, but not in a passenger car.
Thanks for all of the info Scollins. It would be fun to try the "one front one back no traction test" -- I have never heard that. Your knowledge of engineering is clearly better than mine -- but here is what I have read (maybe not correct?). With an xi, power will go to ANY of the four wheels to keep the car moving on the intended path. As I understand it, the power can be applied to any combination, or all of, the 4 wheels. On a RWD BMW with no LSD, my understanding is that power can only be applied via the passenger side rear wheel. If that wheel has no traction, DSC engaged or not, you are not moving. Correct me if I am wrong -- I am sure you will

On a personal experience note -- I have disengaged my DSC before in the snow (just to see what happens) and it sure feels like all 4 wheels are digging.

Below are excerpts from various tech discussions of xdrive found on the web:

In an extreme case, BMW xDrive is even able to fully disconnect the front and rear axle from one another or, conversely, connect them rigidly to one another as one combined drive system. So proceeding from the standard 40 : 60 power distribution front-to-rear, the spread of engine power may be varied infinitely all the way from 100 : 0 or 0 : 100. Without the driver even noticing, therefore, his BMW becomes a rear-wheel-drive-only or – should this be required on account of a very low frictional coefficient at the rear, a front-wheel-drive-only car at least for a few short moments. Should a rigid connection of the two axles be required, on the other hand, xDrive builds up a longitudinal lock, providing permanent all-wheel drive with 50 : 50 power distribution.

Further, when DSC takes corrective braking action on a single wheel, torque is automatically redirected to the wheel opposite it. This means the BMW xi can keep moving even if only one wheel has traction.
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      03-14-2008, 12:47 PM   #12
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Quote:
Originally Posted by douger View Post
Further, when DSC takes corrective braking action on a single wheel, torque is automatically redirected to the wheel opposite it. This means the BMW xi can keep moving even if only one wheel has traction.
That is correct, but the system manages that transfer of power by applying braking pressure to the individual wheels. It attempts to "act" like an LSD or locker, but it will reach a certain point where it cannot apply enough brake pressure to the tire with the least amount of traction. At that point, your car will stop moving, even if one wheel has traction. The braking force on the other 3 wheels will be so great that the one wheel with traction won't be able to drag those 3 wheels along.

More than likely, in everyday driving, you will not encounter a situation where the xi system won't get you moving. And who drives around in the rain with all the stability systems turned off anyway? So on our rain soaked NW roads, the xi system will smoke the RWD cars.

Basically, I'm justing busting your chops for thinking the RWD cars are "one wheel drive" and AWD cars are "all wheel drive" when really they are "two wheel drive!"

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Last edited by scollins; 03-14-2008 at 04:14 PM.
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      03-14-2008, 12:57 PM   #13
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i drive my car with one wheel all the time!
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      03-14-2008, 07:02 PM   #14
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Quote:
Originally Posted by TTG View Post
+ if you don't know how to drive may be?

People (including me) have been driving cars with over 350hp in WA State for years and yet the spin the wheels unintentionally in rain..... So please don't make it sound like it is impossible to drive this car in rain. If you know what you are doing you will be fine even with a 550hp car.
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      03-14-2008, 07:31 PM   #15
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normtrum's 335 has never seen water
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