[HighlandPete]

The most popular engine for the UK, 2.0 diesel.

Interesting comments on the suspension, wheels and ride quality, for UK roads. Seems we are still in the same place as the F10.

http://www.autocar.co.uk/car-review/...520d-se-review

Explaining how the 5 Series copes with UK roads is a little trickier than you might expect. Opt for an M Sport car on 19in wheels and non-adaptive suspension, and you might be more than a little disappointed, because it'll pick up on most of the surface imperfections you'll find on a typically tortured stretch of British blacktop.

The trick is to avoid the temptation of speccing wheelarch-filling rims, and stick to 17in or at most 18in wheels. Combine the thicker sidewalls these bring with the optional £985 adaptive dampers, and you suddenly have a car that all but floats down the road when left in Comfort mode.

[Chuckyarla]

They still haven't driven a car without VDC so how can they compare?

[SpencerP]

I've driven an M Sport with 19's and no VDC and in my opinion it rides just fine. Any blame lays with our poor roads, not the car! One more thing that maybe someone with more technical knowledge might be able to answer! If the car has run flat tyres that stay up even with no air in (because of the reinforced sidewall) then surely the tyre sidewall ratio would have very little effect on the ride?

[HighlandPete]

Originally Posted by SpencerP

I've driven an M Sport with 19's and in my opinion it rides just fine. Any blame lays with our poor roads, not the car! One more thing that maybe someone with more technical knowledge might be able to answer! If the car has run flat tyres that stay up even with no air in (because of the reinforced sidewall) then surely the tyre sidewall ratio would have very little effect on the ride?

I agree the problem is with our roads, hence we will see varying assessment of ride quality, due to where tests are conducted. It's one reason motor magazine testers like to get back onto UK roads, before passing the final judgement on how a car rides, compared with some exotic launch location with different hardtop.

You comment on tyre sidewall ratio is a very valid point, in 'run-flat land' not all normal rules apply. It is true the weight has to be carried whether we run a smaller diameter rim, or the largest rim possible, so at first thinking the ride shouldn't be much different. In fact some setups, the larger rim can give the feeling of a better ride, due to requiring less structural support than a higher ratio tyre.

But it isn't that simple, ride on a given 'decent surface' may be very similar. As road quality deteriorates, that's where the impact on ride quality changes across the rim sizes. The higher aspect ratios do typically have more 'give'. Taking more shock out of the road imperfections. So a higher aspect ratio (on the smaller rim) will have a wider working envelope before ride quality deteriorates. The tyre spring rate will clearly be different at say 3kN impacts, across the different sidewall heights. The softer the rate at a given load, (at correct air pressure) the better the ride quality.

I tried 19" wheels on an F10, on surfaces typical of my normal driving routes. Pretty good on decent surfaces, but much too harsh and crashy over the poor stuff. Dropping back to 18", gives an improvement, adding VDC better still. So a combination of variable damping, plus a bit more sidewall dimension cushions the worst impacts and saves the crashy feel. Road imperfections can be far worse before ride quality deteriorates, even then the fall off of ride quality is not so dramatic.

Winter time I drop back to 17" run-flats, (deliberate decision) on the same suspension setup. The ride quality is even better, less intrusion from road imperfections, even when running at low ambient temperatures, when the tyres are cold and clearly more rigid in structure.

To illustrate the difference in tyre flex due to more sidewall, on the 17" run-flats, I can drive over cat's eyes with no difference in feel than many cars with normal tyres. Try the same on a 19" run-flat (I've tried it) and you know you are doing it.

[HighlandPete]

Originally Posted by SpencerP

I've driven an M Sport with 19's and no VDC and in my opinion it rides just fine. Any blame lays with our poor roads, not the car!

Problem is, we can drive the car of a variety of roads, so a car is not really any good unless it can cope with the roads we drive.

I speak for myself here, but if I lived down south where I used to be, suspension and tyres would not be half as critical as it is up here. My roads are much more challenging and to get a BMW riding well, it is either get the 'best' setup, (which widens the working envelope), or modify myself. I modified my E91 suspension (and wheels) to get a better compromise than BMW could offer out of the box.

I'm interested to try some G30/31 setups to see for myself. But I still suspect to get what I want, across a wide range of driving conditions, it will be a repeat of what I'm driving in the F11.

[Shakespere]

Originally Posted by HighlandPete

Problem is, we can drive the car of a variety of roads, so a car is not really any good unless it can cope with the roads we drive.

I speak for myself here, but if I lived down south where I used to be, suspension and tyres would not be half as critical as it is up here. My roads are much more challenging and to get a BMW riding well, it is either get the 'best' setup, (which widens the working envelope), or modify myself. I modified my E91 suspension (and wheels) to get a better compromise than BMW could offer out of the box.

I'm interested to try some G30/31 setups to see for myself. But I still suspect to get what I want, across a wide range of driving conditions, it will be a repeat of what I'm driving in the F11.

Just took a two hour drive. 520d xdrive and luxury line. Weather was slushy as temp just risen above zero. Grip and ride was very comfy. Despite icy patches and not so smooth roads. Much better then my current f10 xdrive of same spec. However, yes. The steering wheel feedback was artificial and too light. More like a Volvo s90. Car was on standard suspension and no IAS

[HighlandPete]

Originally Posted by Chuckyarla

They still haven't driven a car without VDC so how can they compare?

Do you mean they haven't published any reviews with the standard suspensions? Or haven't tried any?

Some of the UK motoring journalists have had access to the G30, even before release. Driving and sitting with engineers who were fine tuning the chassis here in the UK. Had a wide range of chassis setups to drive. For example, had engineers changing the EPS with laptops, between runs, to show how BMW work towards the best compromise, for all driving situations.