E39 5201, 97 skidding

I had a hair raising moment the other day, going right unto a roundabout I took the sharp exit left and all of a sudden the car was on skates. left, right, left again. Lucky for me the oncoming driver
stopped, but the look on his face said it all..Following that, I'm doing about 70 on but then the road feel abit uneven and suddenly I feel the back starting to feel like its about to fly i.e. like it was losing traction. So I slowed down.
This is a bit frustrating as my previous car could easily maintain 70 without me worrying that its about to spin out of control.
Any one know what could be causing this problem, i.e. suspension, tyres, system fault etc.
I've got low profile 235,R18' tyres so I would have thought that it would hold even in the wet conditions alas I was wrong. I've read that the BMW's are quite tail happy but I would have expected that at speeds like maybe 90mph not 70mph. Please help, I didn't get any lights ABS, ASC etc I don't know how to test these, I know I ASC light works as I can turn it on or off, I might just go down to the stealers but I would rather have an idea of what it was dirst....
I would say the problem I've noticed seems to happen if I'm at speed and over uneven surfaces, as the car rocks a bit, I start to feel like its loosin its hold. HELP.
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Was your previous car front wheel drive? Rear requires a slightly different driving style, you need to corner using the throttle as one of the major inputs to control the car.
The brand of tyres and pressure makes a big difference too.
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Email: snipped-for-privacy@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland
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John G.Burns B.Eng, Bonny Scotland

My diagnosis is that the tyres pressures are all wrong. True it is very easy to kick the tail out in the wet (although this is only a 520), but going wobbly at 70mph in a straight line - no European car* has done that for over 50 years. Given the E39 was used for engines up to ~200kW, I would expect it to be very stable at more than twice that speed!
* but US cars had "shimmy" over ~55mph due to a lack of independent front suspension until at least the late 60's. More recent US cars were better, but still way behind EU cars.
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If it has got stability control then it's impossible to 'kick the tail out' in the wet unless switched off. And even then it's probably much more stable than most cars - if on decent tyres - and easily caught even if you do. Certainly more so than a FWD where the weight distribution is uneven.

Perhaps you'd give the model(s) of US cars without independent front suspension in the '60s? The last new car I can think of with a beam front axle was the E93 Ford Popular sold in the UK until '69 or so, and virtually unchanged since before WW2.
If you meant *rear* suspension, a well located beam axle can work pretty well, handling wise, and certainly better than early semi trailing arm IRS setups. But the E39 has a very sophisticated multi-link rear suspension which is better than either.

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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Hmmmm....now you mention it, I did adjust the tyre pressure only just recently when I was doing a check, and it might be I was using the pressures from a 17' as there was none on the listings for 18' matching mine exactly. Anyone know what the values should be for 18' tyres I believe they are R18/235.. or which way to adjust them up/down, note that the car is hardly ever loaded i.e. only driver....Thanks
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Hydro-planing can happen at almost any speed, certainly from 30-40mph or above. I'd say that your car slipped when it hit pavement markings, which are quite slippery. Additionally, if it hadn't rained for a few days oil/grease/tire rubbings can build up and become quite slippery for the first day of rain.

Your low-profile high performance tires aren't built for rain, would be my guess.
Floyd
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the light will then come on. The ASC is normally on (no light) unless manually turned off.
Tom
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Yep, know that. Its on as the ASC light is off. I only toggled the switch to make sure the light would come on.. I think I need to adjust tyre pressure but not sure what values to use for these R18 wheels
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Yep, know that. Its on as the ASC light is off. I only toggled the switch to make sure the light would come on.. I think I need to adjust tyre pressure but not sure what values to use for these R18 wheels
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Yep, know that. Its on as the ASC light is off. I only toggled the switch to make sure the light would come on.. I think I need to adjust tyre pressure but not sure what values to use for these R18 wheels
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