# Attn: All xi's - Bad News ... Good News



## CH_325xiT (Dec 21, 2001)

BAD NEWS:
just found out today from our dealer that as of Sept '01 BMW is cautioning against placing steel wheels on its AWD vehicles, due to the fact that under heavy and intense braking the wheels get hot enough that they loose their strength and could eventually break.

GOOD NEWS
This means that those using steels for thier winter tires should consider getting an extra pair of alloys for the winter 

If anyone has more info please post.


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## Mike 325xi (Dec 19, 2001)

CH_325xiT said:


> *BAD NEWS:
> just found out today from our dealer that as of Sept '01 BMW is cautioning against placing steel wheels on its AWD vehicles, due to the fact that under heavy and intense braking the wheels get hot enough that they loose their strength and could eventually break.
> 
> GOOD NEWS
> ...


Why would the brakes get any hotter on an xi?


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## Guest (Jan 10, 2002)

*Re: Re: Attn: All xi's - Bad News ... Good News*



Mike 325xi said:


> *
> 
> Why would the brakes get any hotter on an xi?  *


Here's why... (And it's also why Audi's AWD system is superior - Sorry Mike...)

Unlike Audi, that uses some form of 4-way mechanical computer controlled differential to modulate power between all four wheels, BMW simply uses a variation of the DSC system to apply the brakes on the wheels that are slipping. Basically, rather than actually cutting the power TO the wheels, it's cuts the power AT the wheels. This means than the Xis, in inclement weather, are using their brakes A LOT. And it also means that, in a deep snow or bad ice, you could theoretically overheat your brakes and essentially strand yourself.

Sadly, the X5 uses a variation of this system too.


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## CH_325xiT (Dec 21, 2001)

That was my initial question as well.

TD is right
It has to do with how the AWD system works to slow the wheels.

However in deep snow BMW does say to deactivate the system when starting off. The same for if you have to use snow chains.


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## Spiderm0n (Dec 19, 2001)

Alloy wheels it is then! I have decided to wait out this winter with the stock Eagle's my 330xi came with, and buy new tires/wheels next winter.


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## Mike 325xi (Dec 19, 2001)

*Re: Re: Re: Attn: All xi's - Bad News ... Good News*



TD said:


> *
> 
> Here's why... (And it's also why Audi's AWD system is superior - Sorry Mike...)
> 
> ...


OK...now I understand, wasn't thinking of the traction control. To be honest in all of the snow and ice that I drove in last year, I found that I had to push the car intentionaly beyond it's limits to get the traction control to activate at all. I guess it comes with 20+ years of driving in the snow without AWD and that I still drive cautiously with AWD.

I certainly had no plans on buying steel wheels anyway.


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## Spiderm0n (Dec 19, 2001)

*Re: Re: Re: Re: Attn: All xi's - Bad News ... Good News*



Mike 325xi said:


> *
> To be honest in all of the snow and ice that I drove in last year, I found that I had to push the car intentionaly beyond it's limits to get the traction control to activate at all. I guess it comes with 20+ years of driving in the snow without AWD and that I still drive cautiously with AWD.*


I was the exact opposite! One of the first this I did (in a safe environment) was to see the limitations of the tires/AWD system. I have found that once I know the limits I can then drive within them confidently.

One thing I liked (while driving in the snow) was the ability to swing the rear end around in corners - I couldn't do that with my friont wheel drive Integra. My wife didn't like that trick as much!


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## Mike 325xi (Dec 19, 2001)

*Re: Re: Re: Re: Re: Attn: All xi's - Bad News ... Good News*



Spiderm0n said:


> *
> 
> I was the exact opposite! One of the first this I did (in a safe environment) was to see the limitations of the tires/AWD system. I have found that once I know the limits I can then drive within them confidently.
> 
> One thing I liked (while driving in the snow) was the ability to swing the rear end around in corners - I couldn't do that with my friont wheel drive Integra. My wife didn't like that trick as much! *


I did the same thing the first time it snowed...I went to an empty part of the parking lot at work and had a blast. I wanted to know the capabilities of the car too..well that and I wanted to play in the snow


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## Alex Baumann (Dec 19, 2001)

*Re: Re: Attn: All xi's - Bad News ... Good News*



Mike 325xi said:


> *
> 
> Why would the brakes get any hotter on an xi?  *


I've read an article on the AWD system that comes on the BMWs. The overheating of the brakes, as TD said, is the result of the AWD structure, it cuts the power at the wheels rather than to the wheels.

But I've noticed something else in that article. In order to avoid overheating of the brakes, the engine power is cut by reducing the butterfly valve opening.


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## Plaz (Dec 19, 2001)

I thought there were no butterfly valves in the Valvetronic...


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## Alex Baumann (Dec 19, 2001)

Plaz 330i said:


> *I thought there were no butterfly valves in the Valvetronic...  *


Valvetronic is available only on 4 cylinder models and on the new 7 Series, for the moment.


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## Plaz (Dec 19, 2001)

I see... my misconception. Thx.


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## ·clyde· (Dec 26, 2001)

*Re: Re: Re: Attn: All xi's - Bad News ... Good News*




TD said:


> *
> And it also means that, in a deep snow or bad ice, you could theoretically overheat your brakes and essentially strand yourself.
> *


But if my brakes are overheated, they won't work right? And if they don't work, they won't stop my car, right? And if my car won't stop, then I'll be moving around, right? If I'm moving around, I won't be stranded, right? Problem solved!


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## Nick325xiT 5spd (Dec 24, 2001)

*laughs*


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## AF (Dec 21, 2001)

*Re: Re: Re: Re: Attn: All xi's - Bad News ... Good News*



clyde325xiT said:


> *
> 
> But if my brakes are overheated, they won't work right? And if they don't work, they won't stop my car, right? And if my car won't stop, then I'll be moving around, right? If I'm moving around, I won't be stranded, right? Problem solved!  *


uhhhhh . . . very interesting point . . . I wonder if your right though


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