F31 - X Drive or not?
Discussion
msej449 said:
My previous road cars included the Millennium VVC Lotus Elise (so that's oversteer with a vengeance) and Porche Carrera S4. I did driver training at both Lotus and various racing circuits, including Formula Ford etc. On circuits like Hethel, spinning-off when you get it wrong is no problem and what you learn gets built into your ordinary road driving. Handling oversteer on track training helped me recover from otherwise fatal driving errors on public roads on a couple of occasions. FWD I've had an RS2000 (madness) Saab 911 Turbo (also madness) and as a daily car the over-powered 170BHP A3 FWD which always liked to exit roundabouts somewhat ahead of the actual road itself :-)
{Any car given enough beans round a corner will do one of those things.}
No - in an AWD car you get a 4-wheel-drift, where the whole car moves outwards at right angles to the direction of travel: it is a fairly graceful event and powering-off is all that's needed to recover, rather than a careful combination of steering and throttle adjustment needed to bring the front/back into line.
An AWD 'at the limit' won't understeer or oversteer - it does a 4-wheel-drift (The overall weight distribution does have to be balanced evenly between front and back, however - not all AWD cars are).
Modern cars electronically cosset the driver to such an extent that you never really see the chassis and drivetrain dynamics fully unleashed anyway. And you probably don't want to, as they are relatively heavy: I'm fairly sure that my first 320i Touring in 1990 weighed about half a tonne less than my current 330d - No amount of engineering can compensate for that middle-age-spread (but don't get me wrong - I wouldn't want to go back to the 1990 model). What you do get on a modern RWD car are electronics which substantially obviate the downsides of RWD. Somehow FWD cars don't seem to have advanced to the same degree in this respect i.e. I'd always go for a modern RWD car rather than a FWD.
With the 330d the fairly hefty engine power meant that I opted for xDrive. But with your 320d there's less of a problem putting its power down to two rather than four wheels, and the difference in handling may either not be noticeable or unwelcome. So give both a try and see.
Most AWD cars understeer in extremis actually. Ask Audi who have taken to fitting wider tyres at the front to compensate in the RS3 (although latest one much better in this respect){Any car given enough beans round a corner will do one of those things.}
No - in an AWD car you get a 4-wheel-drift, where the whole car moves outwards at right angles to the direction of travel: it is a fairly graceful event and powering-off is all that's needed to recover, rather than a careful combination of steering and throttle adjustment needed to bring the front/back into line.
An AWD 'at the limit' won't understeer or oversteer - it does a 4-wheel-drift (The overall weight distribution does have to be balanced evenly between front and back, however - not all AWD cars are).
Modern cars electronically cosset the driver to such an extent that you never really see the chassis and drivetrain dynamics fully unleashed anyway. And you probably don't want to, as they are relatively heavy: I'm fairly sure that my first 320i Touring in 1990 weighed about half a tonne less than my current 330d - No amount of engineering can compensate for that middle-age-spread (but don't get me wrong - I wouldn't want to go back to the 1990 model). What you do get on a modern RWD car are electronics which substantially obviate the downsides of RWD. Somehow FWD cars don't seem to have advanced to the same degree in this respect i.e. I'd always go for a modern RWD car rather than a FWD.
With the 330d the fairly hefty engine power meant that I opted for xDrive. But with your 320d there's less of a problem putting its power down to two rather than four wheels, and the difference in handling may either not be noticeable or unwelcome. So give both a try and see.
Edited by msej449 on Thursday 2nd July 11:23
msej449 said:
Evidence? I would disagree. Actually. Have you driven 'Most AWD' cars?
Wish I had driven most.We have two though - 997 C4S and BMW 330d Xdrive. And I was out in a RS3 today. And have had or driven most of the big Audis over the years (RS2/4/6 etc).
You can get them to under steer, oversteer or drift but most (road cars) are set up to understeer. And in some they understeer despite the engineers' best efforts. The first RS3 being the classic example. Just read the write ups.
Try Googling road test, understeer, and Impreza, Quattro, Porsche C4S, xdrive etc etc. That should cover most of the interesting ones.
Custard test
Edited by drmark on Thursday 2nd July 20:13
Edited by drmark on Thursday 2nd July 20:28
PS although I freely admit they normally understeer much less than FWD if you go in too hot, and understeer much less than RWD if you get back on the power too quickly / heavily. Still understeer in most road situations though if you over cook it.
The "drifting" at 90 degrees to the direction you travel that you describe = running wide = understeer IMO. True 4 wheel drift follows exact direction of travel but with car at angle (attitude) to that direction (eg 45 degrees with nose inside line)
Not being a troll. And all IMO. I am no driving God - just keen on physics.
The "drifting" at 90 degrees to the direction you travel that you describe = running wide = understeer IMO. True 4 wheel drift follows exact direction of travel but with car at angle (attitude) to that direction (eg 45 degrees with nose inside line)
Not being a troll. And all IMO. I am no driving God - just keen on physics.
Edited by drmark on Thursday 2nd July 21:14
JNW1 said:
julian64 said:
comments were tongue in cheek pointless
Corrected that for you then! Edited by JNW1 on Wednesday 1st July 15:45
julian64 said:
I can categorically tell you now that an F30 335xd with runflats is far better in the countryside snow than an E39 with a full set of winter tyres is.
Winter tyres are good, without them my E39 wouldn't even get out of my road in my area, but the minute you have enough loose snow to coat the rear tyres you're sunk. Snow tyres are good on fairly compact snow or ice, but not the fluffy stuff.
Whereas by contrast I drove 1000km around Switzerland (They have proper, actual winter, not the crap we get here and then pretend we need winter tyres for) in an RWD 320d on winter tyres and it was absolutely fantastic.Winter tyres are good, without them my E39 wouldn't even get out of my road in my area, but the minute you have enough loose snow to coat the rear tyres you're sunk. Snow tyres are good on fairly compact snow or ice, but not the fluffy stuff.
I have to agree, xdrive on summers in snow isn't great and no where near a RWD drive car with winters on, for start the grip is the same as a RWD on summers so braking and cornering grip is dreadful, yes the torque can be vectored to give you more traction but the same limitations apply.
Winters are always better than summers regardless of how many wheels are being driven.
Winters are always better than summers regardless of how many wheels are being driven.
Wills2 said:
I have to agree, xdrive on summers in snow isn't great and no where near a RWD drive car with winters on, for start the grip is the same as a RWD on summers so braking and cornering grip is dreadful, yes the torque can be vectored to give you more traction but the same limitations apply.
Winters are always better than summers regardless of how many wheels are being driven.
This Autocar video sums your point up well. 4WD and summer tyres can give better traction / acceleration due to shared load through all wheels, but much poorer in lateral g during cornering, and braking.Winters are always better than summers regardless of how many wheels are being driven.
https://m.youtube.com/watch?v=7l2cMlNRX_A
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