[E39] Floaty steering at hwy speeds

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"adder1969" wrote

The Maxx is the top of the max performance tire in the Dunlop lineup with very good reviews on TireRack. I wouldn't call them cheap. Besides, I observed the same issue on my previous set of tires - the OEM ContiSportContact.
Pete
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Pete;341397 Wrote: > "pfloding" wrote > > Yeah, but for the other case (pulling to one side) they recommend a > > relatively (compared to the toe-out) large toe-in. BTW, I wonder if > BMW > > loaded down the car as recommended before alignment, and if not using > it > > with the same total load and distribution affects things. Especially > if > > some suspension component is worn out. > > The alignment was done by an indy shop, but they did follow the > procedures, > ie. full tank of gas, loading the car with extra weights, etc. > However, it > is only me driving the car and I weigh 140 lbs. Probably much less > than the > weights required in the procedure. > > After that, I did take it to a BMW dealer and the tech drove it and > said "I > don't know what you're talking about". So, I have a feeling these cars > may > just handle like this. But then again, it's hard to believe with BMW > being > the 'ultimate driving machine' and all. I'm repeating myself here, but > my > old Audi A4q felt more confident at high speed. > > > > I assume the rear axle was checked for wear as well? > > Yes. > > Regards, > Pete
The best thing would be if you could test someone else's car -a car that that person regards as a normal E39. Here in UK doing this is a b-tch due to insurance laws, but the US may be different.
I'm not sure what speeds you drive at, and the condition of the roads there, but my 2002 530i is extremely stable at up to, hrmmm, 90-100 mph. Haven't tried much higher. (On the German Autobahn, naturally)
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pfloding
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"pfloding" wrote

One of these days, I might try to test drive another e39 from the BMW dealer's used car lot, if they let me.

I'm talking about speeds of around 90 mph. Roads are smooth.
Pete
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I was specifically thinking about your problem whilst driving the E39 today. I've had E39s now for about 7 years, and I'm so used to them. I did notice a sort of fairly high frequency floating or bobbing at around the 1 Hz mark. I believe this must be a natural fenomenon due to the E39 subframe design? Not sure other car's use this design to isolate from road intrusion? (I'd be happy to be corrected.)
Anyway, I'm used to it, and I don't apply any steering corrections due to it. Perhaps you feel you have to correct the car even though it won't be necessary?
About my own car, I suddenly noticed that the steering felt lighter than it has done lately, at low speed, as I pulled out from my street today. I could more easily feel the center point of the steering, and it centered a bit more willingly (although not perfectly). I could even let the car self-steer along some roads.
All this leads me to suspect the power steering. Perhaps some speed sensitive regulation of the level of assist is not working as it should? (I'm not even sure if I have that or not on this car.)
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"pfloding" wrote

Are you sure it was 1 Hz? That would mean 1 oscillation per second. Definitely not "high frequency" and definitely not something a human can hear or even feel. :)

I don't know. Maybe I am just not used to driving a large car. I mean, if a rental Nissan Sentra can provide me with a more confident straight-on ride behavior, something is not right. Maybe I just need to sell this thing and go back to something smaller.
Pete
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Pete;341556 Wrote: > "pfloding" wrote > > I was specifically thinking about your problem whilst driving the E39 > > today. I've had E39s now for about 7 years, and I'm so used to them. > I > > did notice a sort of fairly high frequency floating or bobbing at > around > > the 1 Hz mark. I believe this must be a natural fenomenon due to the > E39 > > subframe design? Not sure other car's use this design to isolate from > > road intrusion? (I'd be happy to be corrected.) > > Are you sure it was 1 Hz? That would mean 1 oscillation per second. > Definitely not "high frequency" and definitely not something a human > can > hear or even feel. :) > > > > Anyway, I'm used to it, and I don't apply any steering corrections > due > > to it. Perhaps you feel you have to correct the car even though it > won't > > be necessary? > > I don't know. Maybe I am just not used to driving a large car. I > mean, if > a rental Nissan Sentra can provide me with a more confident straight-on > ride > behavior, something is not right. Maybe I just need to sell this thing > and > go back to something smaller. > > Pete
No, I'm not sure about the frequency. Could be 0.5 Hz to 2 Hz or so. Of course you could feel a 1 Hz oscillation! (And, no, you can't hear it.)
What happens if you do not correct the steering so often? Does the car immediately wander off the lane?
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"pfloding" wrote

Yes.
Pete
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Is it you with the castor out of spec? If your car's been hit in the past and the chassis is twisted, it's not going to help.
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"adder1969" wrote

Yes.
past and the chassis is twisted, it's not going to help.
That is my fear. CarCheck did not show any accidents on record, but some time after I bought the car, when I went to a guy that does polishing work, he told me that my front left fender had been repainted. However, I have no way of knowing how extensive the damage was and if the wheel was hit or just the fender. I wonder where I could find a specialized shop that could assess if my subframe is bent. Can the dealer's service dept. make such an assessment?
Pete
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You'd expect the castor to be out more than it is but you could just measure wheel centre to wheel centre on both sides as a check. I think we've reached a stalemate on this one. You need to drive another car and see if it's different or spend some money on getting the car stripped and inspected. ..or put more than 20psi in the tyres :-)
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"adder1969" wrote

I didn't catch that last part. What did you mean by that? I run about 35 psi all around.
Pete
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Pete;342142 Wrote: > "adder1969" wrote > > or put more than 20psi in the tyres :-) > > I didn't catch that last part. What did you mean by that? I run about > 35 > psi all around. > > Pete
He probably meant a simple fault like the wrong tire pressure can give a lot of your symptoms. Anyway, shouldn't the rear wheels have significantly higher pressure compared to the front wheels? And 35 psi sounds high for the front wheels.
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"pfloding" wrote

The manual recommends 33 front and 41 rear, but since I don't carry any load (apart from myself), I don't inflate the rear so much.
As for the front, I played around with various psi in order the reduce flatspotting (these Dunlops tend to flatspot like crazy), although it didn't really help much.
Pete
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You need to look at the smiley. Pointless repalcing suspension etc if your tyres are all flat, which I'm sure they're not :-)
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message de

For some reasons, when my Z3 has been delivered, the rear wheels were inverted and the tire sculptures pointing backwards. The car was floating a lot. Where I was driving 130 kph with the old E30, the Z3 was badly handling. I realized the mistake some weeks later, looking at pictures I took of the car ! Large tires have a tendency to tramlining on the ruts, especially on the right lane :-)
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The tramlining of my Z3 was reduced considerably when I replaced the OEM Michelin MXM tires with Conti SportContacts.
Tom K.
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