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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Floaty 135i



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      03-03-2010, 07:14 AM   #1
RagingKileak
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Floaty 135i

Hello peeps,

I was travelling rapidly across Germany earlier this morning in the 135i when I happened to pass under a flyover type bridge alongside a van.

I was probably doing about 110 - 120 on the Autobahn and obviously the car is generally pretty stable. Traction Control was on etc.

Despite the fact there didn't seem to be any wind (trees totally still etc) when I came out of the otherside of the flyover bridge thing it felt like something had hit the back end of the car and it flew about all over the place...

I have felt this sensation before but usually less so. It's like the faster I go the more it happens and weirder it feels...

Is this the whole 'I need ARB kit' discussion thing? Or something sinister!

Matt
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      03-03-2010, 07:35 AM   #2
HighlandPete
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Do you believe it was an air disturbance thing? Van, bridge, interaction with your car? Or do you suspect it is more than that?

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      03-03-2010, 07:47 AM   #3
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Quote:
Originally Posted by HighlandPete View Post
Do you believe it was an air disturbance thing? Van, bridge, interaction with your car? Or do you suspect it is more than that?

HighlandPete
This is my initial thought, perhaps you lost (some) grip due to the aerodynamics of the car being affected by the already disturbed air from the van you were passing.

I've noticed this when passing lorries in the UK.
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      03-03-2010, 08:40 AM   #4
RagingKileak
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Yeah, I mean basically it was air, no doubt about it...

However, I am talking a long wheelbase tranny, not an artic. The wind seemed very calm outside, no trees moving etc so I don't think it was a crosswind.

My point is, I suppose, that I have heard this linked to the rear Anti-Roll Bar.

People like Doughboy and Tony have suggested that this 'lightness' can be cured with an uprated part which is stiffer and allows less rear end lateral movement (do I mean lateral... ? Horizontal is the term I am trying to suggest)

Matt
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      03-03-2010, 08:41 AM   #5
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I've noticed pressure waves affecting my cars, especially those made buy Merc Sprinters,it feels like they drag me back for a split second, then push me forward.
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      03-03-2010, 08:56 AM   #6
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Originally Posted by creepy coupe View Post
I've noticed pressure waves affecting my cars, especially those made buy Merc Sprinters,it feels like they drag me back for a split second, then push me forward.
For me it's towards them and then away from them (horizontally) as you pass them.

Same with vans (transits and sprinters etc) and even more pronounced with lorries/artics.
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      03-03-2010, 09:03 AM   #7
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Were you driving in a straight line at the time - not cornering, steering wheel straight ahead ?

What temperature was it ? Could you have hit a bit of ground shaded by the flyover, that might always stay shaded ?

D.
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      03-03-2010, 09:07 AM   #8
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Erm, it was pretty cool mate. Probably between 4 - 7c.

Everything totally normal, fast lane, wheels straight ahead etc... I do occasionally feel this floatyness during high speed cornering or when I get hit by a cross wind at speed, but this just seemed weird and with no wind at all I was confused!

Matt
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      03-03-2010, 09:16 AM   #9
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I think the front end of the 1 series is slightly more susceptible to turbulence
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      03-03-2010, 01:14 PM   #10
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Number 2 reason why I got rid of my 1 coupe - was a 123d remapped to 250bhp and the car was so bloody unstable at speed it would shit me up all the time.
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      03-03-2010, 01:44 PM   #11
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Quote:
Originally Posted by RagingKileak View Post
Hello peeps,

I was travelling rapidly across Germany earlier this morning in the 135i when I happened to pass under a flyover type bridge alongside a van.

I was probably doing about 110 - 120 on the Autobahn and obviously the car is generally pretty stable. Traction Control was on etc.

Despite the fact there didn't seem to be any wind (trees totally still etc) when I came out of the otherside of the flyover bridge thing it felt like something had hit the back end of the car and it flew about all over the place...

I have felt this sensation before but usually less so. It's like the faster I go the more it happens and weirder it feels...

Is this the whole 'I need ARB kit' discussion thing? Or something sinister!

Matt
Is that the same Autobahn that we use several times a week?
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      03-03-2010, 02:06 PM   #12
RagingKileak
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Is that the same Autobahn that we use several times a week?
Yeah. I was surprised to see you coming southbound towards Koln the other week!!

Matt
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      03-04-2010, 04:10 AM   #13
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Hah. I enjoyed the trip down the autobahn after go-karting with Carl a few months ago. I got the car up to 147mph on the new stretch between junction 10-6. I forget the name of that autobahn now though.

Autobahns are great.

I have nothing producting to add to this conversation.
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      03-04-2010, 04:57 AM   #14
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I changed the springs on mine as mine often felt floaty on motoryway runs. Went from stock springs to the performance ones. Car definately feels more planted than before.
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      03-05-2010, 07:48 PM   #15
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Presume you have your tyre pressures set accurately. I've noticed even small differences can upset high speed stability.... I'm in the process of buying a RaceX pressure gauge (recommended by Autoexpress).... there is so much variability in the readings of the various other digital and analogue gauges I have otherwise.
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