Odd chassis behaviour

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huytonman
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Odd chassis behaviour

Post by huytonman » Tue Nov 14, 2017 5:09 pm

Twice today on dry roads I had a weird sensation from the steering in low speed for tight corners, once on a roundabout, the other as I joined a slip road off a roundabout. The steering "felt" like it had stuck at one angle which gave the impression that I was snapping into oversteer (I wasn't), it then "unstuck" and the car behaved normally. I'm fairly sure that Ive noticed this before but not as pronounced as today, on both occasions it caused a bit of a pulse leap as I wasn't expecting any oversteer. My car is a 35iS with Adaptive dampers and 18" wheels fitted with Michelin Pilot Sports so non RFT's. In both cases I was in normal drive mode, comfort setting and was applying gentle throttle. I am running the tyres at less than the recommended pressures, I just struggle with the levels that BMW spec for RFT's, so in my case Im around 0.5 bar less front and probably around 0.25 bar less on the rear. I planned to up the pressures to standard tomorrow once the car is cold to see if I can replicate the issue but as it doesnt always happen I wont be sure that tyre pressures are the issue until I drive for quite a while.
Anybody else had this sensation with the steering?
Thanks
Keith

mcbutler
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Odd chassis behaviour

Post by mcbutler » Tue Nov 14, 2017 6:59 pm

I would definitely get the car down to a garage and let someone have a look underneath, better safe than sorry.

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buzyg
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Odd chassis behaviour

Post by buzyg » Tue Nov 14, 2017 8:16 pm

Well if you had one I would suspect a dodgy power steering pump. As you don't, I would get the steering system thoroughly checked out.
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huytonman
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Odd chassis behaviour

Post by huytonman » Tue Nov 14, 2017 8:38 pm

buzyg wrote:
Tue Nov 14, 2017 8:16 pm
Well if you had one I would suspect a dodgy power steering pump. As you don't, I would get the steering system thoroughly checked out.
Hmm...lighting doesnt strike twice but maybe it does, my old e35 needed a new rack in July...maybe its a trend..

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Odd chassis behaviour

Post by Maniac » Tue Nov 14, 2017 8:39 pm

The iS has servotronic so this could be electric steering assistance (motor or sensor) failure or a software issue.

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Nanu
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Odd chassis behaviour

Post by Nanu » Tue Nov 14, 2017 8:41 pm

Why guess when you need to be certain. Get down to the dealership ASAP especially if it's still under warranty
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huytonman
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Odd chassis behaviour

Post by huytonman » Wed Nov 15, 2017 10:53 am

Nanu wrote:
Tue Nov 14, 2017 8:41 pm
Why guess when you need to be certain. Get down to the dealership ASAP especially if it's still under warranty
Who said anything about guessing, Im asking if anybody else has experienced similar issues, thats why we have forums with like minded people

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Nanu
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Odd chassis behaviour

Post by Nanu » Wed Nov 15, 2017 8:43 pm

huytonman wrote:
Wed Nov 15, 2017 10:53 am
Nanu wrote:
Tue Nov 14, 2017 8:41 pm
Why guess when you need to be certain. Get down to the dealership ASAP especially if it's still under warranty
Who said anything about guessing, Im asking if anybody else has experienced similar issues, thats why we have forums with like minded people
It's us that's guessing. Until someone actually has a look see, you won't know for certain
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huytonman
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Odd chassis behaviour

Post by huytonman » Thu Nov 16, 2017 4:47 pm

Nanu wrote:
Wed Nov 15, 2017 8:43 pm
huytonman wrote:
Wed Nov 15, 2017 10:53 am
Nanu wrote:
Tue Nov 14, 2017 8:41 pm
Why guess when you need to be certain. Get down to the dealership ASAP especially if it's still under warranty
Who said anything about guessing, Im asking if anybody else has experienced similar issues, thats why we have forums with like minded people
It's us that's guessing. Until someone actually has a look see, you won't know for certain
Its due an inspection in February so I've brought it forward to this month and will get them to check it out plus the noisy fuel pump which is beginning to drive me mental. My local suspension guru checked it over yesterday on the ramp and couldn't see anything obvious that was wrong (certainly nothing loose or broken), he also double checked the alignment and it was in spec. So lets see if BMW can shed any light.
Keith

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Odd chassis behaviour

Post by huytonman » Wed Nov 29, 2017 1:11 pm

Short update - Cooper Reading was surprisingly intrigued by the symptoms with the chief technician wanting to discuss it with me personally when I took the car in yesterday. After checking the suspension and steering system they could find no fault with the car and the guy took it home on his commute drive (40 miles each way) and called me to confirm that no odd behaviour arose during that time. I drove it myself last week for four hours to the Aston Martin factory in Gaydon and back and also didnt notice the fault so maybe it was one of those strange glitches that sometimes happens :headbang: The good news is that there is no obvious safety related issue so I'll monitor it and see if it reoccurs.

One outcome from the time with Cooper is that they agree with my diagnosis that the fuel pump is on its way out and will replace that under warranty.

Keith

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