[Tengocity]

Myself and Guy met this evening for a little evening entertainment by way of a 30 mile car swap. Watesy joined us as a passenger and also had a drive of Guy's car (and has driven mine before).

For those who don't know (where have you been?) then my car is a 335d tourer with DMS remap, ACS springs and Birds anti-roll bars. Guy's car is a 335d with ACS RS coilovers.

We were interested to have a good drive to really see how these compared.

So this is my thoughts, and I'm sure they'll be along soon with their opinions.

The RS kit is based on KW v3 coilovers, so a serious bit of kit, which are adjustable for ride height and damping stiffness. They're currently set to the softer end of the scale. Even so, around town there is a certain firmness to them as you might imagine. Not harsh unless you hit a deep set drain or failed road patch, but certainly not soothing in a way that my car is in comfort mode.
Head out of town and things improve considerably, and indeed it's safe to say that the faster you go the better these feel. It was raining tonight and we were on typical bumpy B-roads (Henley to Reading), and in another person's car so not the time to test the limits!
The RS car is absolutely tied down, in a way that a standard F30 driver can barely imagine. Turn the wheel and the front just turns- not delay, no roll to the outside and wait for it to settle, no slop, and resolutely no understeer, just a nice neutral flatness.
Despite the firmness you can carry great speed across crappy roads and the feeling of body control is super, though at times you do feel as though 'breathing' with the road a little wouldn't be a bad thing. And I did feel at times, especially under braking, that it had more of a tendency to tramline/follow road cambers than mine.

Overall I was impressed by them on the back roads. They are undoubtedly more capable, when pushed, than what my car offers but I think that that level would only make a difference on track or seriously going for it on a public road. I can't see my driving like that down South, only on quiet roads I know well in Scotland for example, so I struggle to make the case for them over what I have, as this just doesn't reflect my needs and typical usage of the car.

In my car the roll is well contained on road, and the handling very neutral also. It's not quite as quick to turn in, but still way better than a car with just ACS springs only. Where my car would fall behind is on a really challenging road for body control, as the standard adaptive dampers just reach the limit of what they can control as the bumps come thick and fast. On track then my car still seems quite soft, but with the RS kit then Guy would be able to turn those up considerably from there.

My feeling is that for most people then my car would be more than enough- it's much cheaper to do it, and it retains the comfort and sport damping options, which I like for crappy British roads. That's with those who have a diesel saloon car as daily family transport with a requirement for it to be an all-rounder.
For me I think the RS kit is something I'd put on a weekend E46 M3 that I planned to use mainly on track days or for back road fun! I think for the UK the springs are probably just that little bit too stiff, and even on softer damper settings it's probably still just that little bit too firm for me.

I've also been for a passenger ride in NISFAN's car with Bilstein PSS10 coilovers and I think it felt more like my car. It has KOMFORT springs which I expect are a bit softer than the ACS RS ones, but you still have a large range of adjustment with ride height and damper settings. I think this is more likely where I would go next if I went any further.

Hopefully Guy and Ian will be along with their thoughts soon...

[....,,,,..,,..]

Nice write up.

I assume Guys car is still without the ACS power kit?

The RS kit does sounds a serious bit of make over for the suspension.

As you say likely overkill for a lot of owners.

Will wait for the others to pen something down, particularly Watesy as the 'independant'.

[gtsussex]

Just got in and so thought I'd write my thoughts over a quick (and well earnt) beer! Good to see you again Terry and thanks for the swap - was very interesting.

I'd love to write something different to Terry's account but it's pretty much spot on. Getting in his car, immediately it was more soothing in Comfort mode and I'll admit, I do miss that for pottering around, no question.

Switch to Sport and things are different and actually pretty good. On PSS and ACS springs before I had the RS kit, the dampers had a nasty habit, when pushed outside their comfort zone, of ruining things. I suspect the compliancy in the non runflats fooled them into thinking there was too much travel and therefore were closing down unnecessarily, almost like hitting a bump stop.

I am delighted to say that the ARB kit that Terry has on his car absolutely transforms this (don't ask me why because I'm not clever), helping the dampers out no end and really turns the car into what most would want most of the time. Turn isn't as crisp as mine but it is perfectly acceptable (and beyond what most would expect of an xDrive or actually most F30's). Body roll is well contained. You can catch out the dampers but it's not a regular occurrence. Overall I was hugely impressed with it and I can see this being a perfect 'next step' for those keen drivers with ACS springs thinking about changing over to PSS tyres.

As Terry says, the difference between the two is that his is happy at what we were doing today - 6/10ths (maybe 7/10ths at times) and realistically on most roads (certainly in the wet), that is more than acceptable pace. But, this is where my setup really starts to come alive and make sense.

Would I do it again or go for Terry's setup? I thought that was a tricky one for me to answer as by time I'd driven Terry's car for 40 mins ,I'd convinced myself I'd go for Terry's setup and save the money. I then let Ian drive my car back to Henley and even from the passenger seat could see why I like my setup.

From a practical point of view, my car is LOW and if you're aiming to do Touring things with a Touring (i.e go on a bit of grass), you've had it with my car! So you really need to want that last bit from the car and believe me, it truly turns the 335d into something that you wouldn't quite believe. Think of it as a 335d RS and it kind of paints the picture. Now some would save such an extreme setup for a tractor engined salesman's car is daft. I can see their point totally. Have to say there isn't a huge difference between the ride of my car and our M235i (and it's certainly better than one of the Mini's) so it's all relative.

The biggest compliment I can pay to Terry's car is that it feels like the Alpina D3 I tried but with a lot of extra traction where you want it. His mapping on the engine is hugely impressive (disclaimer - I actually never went about 3.5k but below that it was very good). I think it could well be close to the ultimate estate. Just sort out the brakes Terry!!!!

I'm going to leave Ian to finish this as his thoughts on my car are interesting (especially as an sDrive driver) and it was him that came up with the best conclusion at the end of night (and I don't want to spoil his punchline).

Good to meet you Ian - will have a rematch once back to full power!!

[jumperjohn]

Good write up!
For a family car i'm happy with the ACS springs but do you suggest the Birds ARBs will eliminate the rest of the car's wallow? I remember reading how with the birds ARBs the car is much firmer, is there a detriment to ride quality?
How much thicker are they compared with the M Sport arbs?

[gtsussex]

Originally Posted by jumperjohn

Good write up!
For a family car i'm happy with the ACS springs but do you suggest the Birds ARBs will eliminate the rest of the car's wallow? I remember reading how with the birds ARBs the car is much firmer, is there a detriment to ride quality?
How much thicker are they compared with the M Sport arbs?

I'll answer this as I'm not biased in any way at all. The ride is still absolutely superb in comfort mode and yes it does eliminate a lot of the remaining wallow when on Sport setting - in Comfort setting it's still there (but everything is relative and I am used to absolutely no wallow RS suspension!!).

BUT this is based on having PSS tyres. I suspect it might be the wrong side of harsh on run-flats.

[Tengocity]

Originally Posted by jumperjohn

Good write up!
For a family car i'm happy with the ACS springs but do you suggest the Birds ARBs will eliminate the rest of the car's wallow? I remember reading how with the birds ARBs the car is much firmer, is there a detriment to ride quality?
How much thicker are they compared with the M Sport arbs?

Yes it would. A little firmer but really not much- my wife can't tell any difference!
The car is stiffer across the rear axle I notice, more when you cross uneven bumps at slow speed.
They're 28/19 thick front/rear v 23/11 as standard I think.

[jumperjohn]

Originally Posted by Tengocity

Yes it would. A little firmer but really not much- my wife can't tell any difference!
The car is stiffer across the rear axle I notice, more when you cross uneven bumps at slow speed.
They're 28/19 thick front/rear v 23/11 as standard I think.

Thanks for the quick reply!

The thickness is increased quite a lot!

I have the ACS springs with passive suspension and MSS but there is still roll when cornering at speed, not as much as before though!


I'll have a chat with Birds and see what further info they have and any deals, the arbs are expensive fitted.

[Tengocity]

Originally Posted by jumperjohn

Thanks for the quick reply!

The thickness is increased quite a lot!

I have the ACS springs with passive suspension and MSS but there is still roll when cornering at speed, not as much as before though!


I'll have a chat with Birds and see what further info they have and any deals, the arbs are expensive fitted.

Yes and the resistance to a twisting force is not a linear relationship to diameter but to cross sectional area... So the bar is several times stronger!

[teaston]

Originally Posted by jumperjohn

Good write up!
For a family car i'm happy with the ACS springs but do you suggest the Birds ARBs will eliminate the rest of the car's wallow? I remember reading how with the birds ARBs the car is much firmer, is there a detriment to ride quality?
How much thicker are they compared with the M Sport arbs?

I really can't imagine they'd make a difference on an sdrive M Sport considering how much thicker the standard arb's are than the "thinner than SE" arb's that the xdrives come with!

[Mattyk]

Nice write up!

My yearning is switching from eco tune to birds I think....

[Tengocity]

Originally Posted by teaston

I really can't imagine they'd make a difference on an sdrive M Sport considering how much thicker the standard arb's are than the "thinner than SE" arb's that the xdrives come with!

Nonsense, they're still way bigger!
The MSport ones are only a mm or so larger. Plus it's the larger relative increase in the rear one that really goes to dial out the understeer characteristics.

[MarkG_M5Comp]

Guy, in interested in your comment on the pre-RS setup and 'hitting the bump stops'.

I'm feeling this a lot right now on the rear; where the front can cope with a bump on the motorway for example, the rear seems to crash through it and feels like it's too soft. The result is it can be rather uncomfortable at speed. Is this similar to what you experienced?

I'm going no further with my car as it'll only be with me for 9 or 10 months now; I had considered a remap but now I'm going to save for the next car - So I won't be fixing it and just interested.

[gtsussex]

Originally Posted by MarkG335

Guy, in interested in your comment on the pre-RS setup and 'hitting the bump stops'.

I'm feeling this a lot right now on the rear; where the front can cope with a bump on the motorway for example, the rear seems to crash through it and feels like it's too soft. The result is it can be rather uncomfortable at speed. Is this similar to what you experienced?

I'm going no further with my car as it'll only be with me for 9 or 10 months now; I had considered a remap but now I'm going to save for the next car - So I won't be fixing it and just interested.

Mine was more when pushing on bumpy roads but either way, I just don't think the standard dampers are happy once you move away from non runflats. Terry's is a huge improvement over what mine was without ARB's and for whatever reason, the dampers are much closer back to their comfort zone.

[MarkG_M5Comp]

Interesting, leads me to believe I either need a passive or M car next time around...

[davyk31]

How do you sort insurance for a swap like that. Wouldn't want to be doing it on third party road risks cover!

[tjlees]

Interesting, but obvious I suppose, that the dampers have been tuned to run flats. I hate harshness of them compared to standard tyres.

The ACS sounds a good, particularly if it resolves the suspension settle 'delay' that Ive encountered on twisties with lots of direction changes.

The turn in, for me, is fine on the 19s though this maybe an issue if I go over to michelins, which is my intention once I've worn out the run flats.

The only issue stopping me at the moment, is that I do a lot of towing and my last tow car grounded on the speed humps while trailering 1.5t - this one does not. The ACS springs lower the car by a further 15mm (?) on the xdrive, and given the trailer compresses the rears by around 10mm this could be a scraping problem!

[Tengocity]

Originally Posted by davyk31

How do you sort insurance for a swap like that. Wouldn't want to be doing it on third party road risks cover!

Guy's car is covered for anyone over 25.

I arranged 24 hour cover for Guy on my policy, and he kindly went halfers on the cost with me!

[Watsey]

So here are my thoughts as the unbiased independent in last night's back-to-back road test. It was very interesting and thanks Guy for the chance to drive your car.

Terry and Guy have covered things well, so I'll try and add what I feel are the key differentiators which have really helped with my decision-making.

Focussing on ride and handling, i.e leaving other things like power and brakes to one side, my starting point is the base car (in my case F31 330D sD). There are several problems with the stock build :

- RFTs are so hard that the ride quality is nadgety, they don't key into the road surface so they can scrabble for grip, straight line traction is compromised on wet/damp roads, and there's a horrible combination of understeer and weight through the bends.
- Spring rates and dampers (adaptive on mine) are not working in harmony, resulting in wallow/floating (bump is 'OK', but rebound is very poor especially in Comfort), and mid-corner bumps can result in very unsettling barrel-roll. Rapid direction changes tend to easily expose the shortcomings.
- The overall capability of the suspension set-up has a fairly limited performance envelope and on UK A/B roads it can be more a case of blind faith, rather than confidence that keeps you going.

The stock package is very compromised, to the extent that it really spoils my enjoyment of the car.

I drove Terry's car a few weeks ago and the combination of Birds' ARBs, ACS springs and MPSS makes a significant difference in ride quality, cornering neutrality, and roll. The three of us were talking before heading home last night and we all agree that the ARBs are helping the adaptive dampers massively. The ride is firm, the benefit of having adaptive dampers is retained, understeer is hugely reduced (also helped by the excellent Michelin Pilot Super Sports), and the car feels composed. The car can now be hustled down a bumpy twisty road, rather than wrestled. IMO the suspension will tackle British roads, with good control (driver limitations excepted...), up to, say, three figures.

For the majority of drivers who want to improve their car but still retain the comfort of a daily driver, this will tick most of the boxes.

On to Guy's ACS RS setup. No doubt about it, the ride is very firm around town and up to low-moderate speeds (say 50-70 mph) you feel every irregularity in the road surface BUT the suspension doesn't crash; it's busy, but not unpleasant. The dampers do an outstanding job of controlling body movement at speed, and handle primary and secondary inputs with aplomb. The car is absolutely tied-down to the road surface and there is a sense of 'immediacy' - no float, no wallow; you can feel exactly what's going on. Turn-in and neutrality are spot-on. Very impressive.

To me, and I'm no racing driver, the capability of the suspension felt very linear. From 50-70 mph the car really comes alive and, leaving aside the safety and moral aspects of big speeds on public roads, the cross-country capability could embarrass full M-cars; no doubt.

The more I drove Guy's car the more I liked it. The ride is very focussed, uncompromising, and if it was just me in the car I would be very tempted with the ACS RS setup; the additional confidence when one is 'on it' is worth having. However, I think it's just that bit too firm as an 'all day every day' car, and in reality I'd probably get an earful of complaints from my wife and kids when we all travel together, especially rattling along Devon roads where we visit regularly.

My car is going into Birds' next week for ARBs, ACS springs, and MPSS. This package makes such a positive difference to the car's capabilities that it is the sensible compromise (and actually not that big a compromise; I don't track my car) and won't cause any disappointment. It's also better value for money. Having driven each setup, they are similarly matched at sensible speeds and it's clear that a relatively modest amount of money can transform the ride, composure and capability - these are meant to be driver's cars, not boats. There will be moments, when I'm having a cracking drive on my own, when I will remember driving the RS setup and I'll think "what if...?", but for >90% of the time the car will still bring a smile to my face.

When I've had the work done, we must meet-up again and see how the sD and xD setups compare, and see how much the sD gives away in terms of traction versus what it gains in terms of steering feel and turn-in.

Bring it on !

[....,,,,..,,..]

Excellent independant review.

Would be interesting having Evo etc do a decent write up on Guys car.

Obviously not going to happen, however would be good seeing a positive 'wow' piece.

I bet Birds/ ACS would like that as well

[gtsussex]

Good review Ian. I think we're all rather in agreement here. Will be interesting to see how yours is transformed.

[gtsussex]

Originally Posted by Brigand

Excellent independant review.

Would be interesting having Evo etc do a decent write up on Guys car.

Obviously not going to happen, however would be good seeing a positive 'wow' piece.

I bet Birds/ ACS would like that as well

Funnily enough Lorcan and I were talking about spring setup a while back. ACS lent Evo their M135i with RS kit on (and that was with dampers set tighter than mine which I would have thought made the ride uncomfortable) and they loved it!

More than happy to lend mine for the cause if you want Lorcan :-)

[Lorcan]

Great review chaps

I'd just like to add that the RS suspension is adjustable over a wide range so if you find it a little firm and uncompromising you can always back it off. Just one click makes a significant difference. If I remember rightly Guy has the rebound at our recommended setting and the compression at 6 clicks front and 7 clicks rear (out of 16).