[peetee]

Hi Guys,

I've got a f31 335d with adaptive suspension and ACS springs. Handles great and body roll is much improved. Is there anything I can do to improve body roll and make the car sit more flat around the bends. Much appreciated


Thanks

[Cootie]

Probably Birds anti-roll bars, albeit without ditching the run flats you might find a bit of a ride penalty. Another favourite on the forum seems to be fitting a stiffer rear ARB from the M135i/M140.

[APJ]

Originally Posted by Cootie

Probably Birds anti-roll bars, albeit without ditching the run flats you might find a bit of a ride penalty. Another favourite on the forum seems to be fitting a stiffer rear ARB from the M135i/M140.

Yep, a rear arb makes the rear spot on with much much less roll, problem is though you still get roll from the front end, which is far more annoying, I'd love to know how to cure it, but not sure what to do !

[Watsey]

Originally Posted by peetee

Hi Guys,

I've got a f31 335d with adaptive suspension and ACS springs. Handles great and body roll is much improved. Is there anything I can do to improve body roll and make the car sit more flat around the bends. Much appreciated


Thanks

"Birds" ARBs are actually made by H&R. They are very stiff and although the car will corner very flat there can be some downsides, i.e. issues with traction and snap oversteer. On track you can really lean on the car, but on a bumpy road they're not ideal.

My recommendation, based on experience, is to fit Eibach ARBs front & rear. Stiffer than OEM but still retaining some compliance.

[cramsnik]

I had the 15mm rear arb fitted last week, I also have acs springs and adaptive dampers. I have to say the thicker roll bar has been the most noticeable improvement so far.

[Rasco]

In terms of front stiffness are there options for strut brace bars? I'd be interested for my 440i

[Techno 9000]

There's some about, but it won't do anything for body roll (the reason for this thread) and given the inherent chassis stiffness of the F36 it won't be anywhere near as obvious an improvement as it was on cars of 20 years ago.

For instanceWatseys comment on a strut brace

[APJ]

Originally Posted by Techno 9000

There's some about, but it won't do anything for body roll (the reason for this thread) and given the inherent chassis stiffness of the F36 it won't be anywhere near as obvious an improvement as it was on cars of 20 years ago.

For instanceWatseys comment on a strut brace

You could be right Techno, but Watsey also states the brace was his last suspension modification, his car is pretty sorted already, so when someone is fitting it as an early modification i'm sure the difference is a lot more noticeable, if the gent is not going to track his car, then the brace 'may' be enough for him.

[Techno 9000]

I'd be surprised that Watsey (with the springs/dampers he's running likely to be placing greater loads into the chassis and doing track days etc) would not notice an improvement - if one was to be had.
People running standard springs/dampers are putting lower loads into the chassis so, in my logic, would be even less likely to notice an improved chassis stiffness.

[APJ]

Well, not in my logic, he may have a better feel for his car than many on here and most definitely better than myself and can feel very small movements. But surely when a car is lowered and stiffer than standard, you will feel less movement than a car that is higher and and has a much softer suspension, the softer car has more travel therefore it is likely to move more. The guy from Kies motorsport on YouTube thought the strut was one of the best mods he'd done to his car. So obviously different people have their own opinions.

[HighlandPete]

Originally Posted by Techno 9000

I'd be surprised that Watsey (with the springs/dampers he's running likely to be placing greater loads into the chassis and doing track days etc) would not notice an improvement - if one was to be had.
People running standard springs/dampers are putting lower loads into the chassis so, in my logic, would be even less likely to notice an improved chassis stiffness.

That's where my thinking is as well. (Engineering experience in 'damping' systems).

The softer 'more yielding' components will contribute much more to roll.

Body with a defined 'stiffness' will be the last to give. Body will move more (torsional) as higher loads are applied, with stiffer suspension setups.

[Ennoch]

My experience of every car I've ever played with is that on the roads ARB's make the biggest difference on softer suspension; as you get progressively stiffer so the relative effect of the bar drops. Obviously on track they can still have a dramatic effect as the loads can be higher, generally without such sudden surface changes as you get on a public road. Granted none of this is experience on the F30 chassis but a car is ultimately a car and the rules are generally the same even if the tools you use to achieve the solution of those rules might be slightly different.

[Watsey]

Originally Posted by Techno 9000

I'd be surprised that Watsey (with the springs/dampers he's running likely to be placing greater loads into the chassis and doing track days etc) would not notice an improvement - if one was to be had.
People running standard springs/dampers are putting lower loads into the chassis so, in my logic, would be even less likely to notice an improved chassis stiffness.

Correct

I've had the front strut brace connected/disconnected when trying to find the cause of persistent knocking on the car, and there's very little difference either way. It was a cheap mod but it also makes very little difference.

I can only feel the difference because I've had the car as my DD for 8 years, but it's imperceptible even with a much stiffer sprung and damped suspension setup than OEM.

As for roll resistance, it won't make any difference at all.

[Watsey]

Originally Posted by APJ

Well, not in my logic, he may have a better feel for his car than many on here and most definitely better than myself and can feel very small movements. But surely when a car is lowered and stiffer than standard, you will feel less movement than a car that is higher and and has a much softer suspension, the softer car has more travel therefore it is likely to move more. The guy from Kies motorsport on YouTube thought the strut was one of the best mods he'd done to his car. So obviously different people have their own opinions.

Bear in mind that the front suspension turrets are already braced to the bulkhead so, in that sense, they already benefit from from some triangulation.

Connecting the turrets on these cars does increase the steering precision a smidge, but you'll only feel the benefit if you also replace the hydro bushes in the radius arms. The OEM bushes are very soft and they rob steering precision and feel.

[APJ]

Originally Posted by Watsey

Bear in mind that the front suspension turrets are already braced to the bulkhead so, in that sense, they already benefit from from some triangulation.

Connecting the turrets on these cars does increase the steering precision a smidge, but you'll only feel the benefit if you also replace the hydro bushes in the radius arms. The OEM bushes are very soft and they rob steering precision and feel.

Which bushes is it that you replace and do Super pro do a kit for this ?

[Watsey]

Originally Posted by APJ

Which bushes is it that you replace and do Super pro do a kit for this ?

Item 7.

SuperPro do a poly bush SPF4306K for that location and it has lasted OK on my car.

I've had several problems with SuperPro components, so I certainly wouldn't attest to its reliability or customer service.

Millway Motorsports have a sealed monoball press-fit bush for the same location (https://www.millway.se/front-control...0-x-drive.html) which should provide very good steering precision.

[HighlandPete]

Originally Posted by Ennoch

.... but a car is ultimately a car and the rules are generally the same even if the tools you use to achieve the solution of those rules might be slightly different.

I tend to agree. ARBs are not an, 'all positive' solution on a road car. As you suggest, there's a cost on bumpy and irregular surfaces.

Stiffer ARBs are a compromise, like all suspension tuning. You may gain in one area or function, lose in another.

Single wheel bumps are one of our biggest problems in the UK, where our road edges are typically irregular. We can lose comfort and induce cross axle oscillations, and unpleasant 'roll-rock'.

[Kal101]

From experience trying to reduce the body roll , biggest change was to replace the standard adaptive dampers with Bilstein B6 damptronics.

Not for everyone and probably not the most focused option but work for me.

Already done the ACS springs , rear ARB upgrade and added the rear underbody brace of a F31 not to mention the front strut brace.

[Ennoch]

Originally Posted by HighlandPete

I tend to agree. ARBs are not an, 'all positive' solution on a road car. As you suggest, there's a cost on bumpy and irregular surfaces.

Stiffer ARBs are a compromise, like all suspension tuning. You may gain in one area or function, lose in another.

Single wheel bumps are one of our biggest problems in the UK, where our road edges are typically irregular. We can lose comfort and induce cross axle oscillations, and unpleasant 'roll-rock'.

Yup, it can very much be a double edged sword - and I say that as someone who has stuck some very large bars on cars over the years. My old Vectra ST200 had OEM Koni coilovers and 19 year old me decided to stick a custom solid 28mm rear bar on it. That thing was tail happy in the extreme (but once I shoehorned the 3.2 V6 into the bay it had enough poke to pull itself straight in any situation). Then there was the time I stuck a 25mm bolt on bar to my Mk1 vRS octavia and drilled extra holes in it to make it stiffer. It massively helped turn in and, because it wasn't IRS, it didn't suffer much detriment on the single wheel bump issue, just better turn in. In contrast my Impreza stock was a 19mm rear bar and I went to 24mm with the coilovers as they didn't have much travel anyway so like the Octavia, the single wheel bump wasn't really impacted. However, when I went to Koni inserts and RB320 springs to gain wheel travel back the 24mm bar was a noticeable detriment to the rear end. So I dropped to 22mm on its softest which is about 20mm in OEM terms and added 10mm rear spring spacers to increase the positive rake and generate turn in that way (this moves the roll centre forwards and increases rotation of the car in corners) without impacting the ability for each corner to act reasonably independently on bumps.

In contrast, the single biggest improvement in handling to any car I've owned with ARB tweaks was when the front drop link snapped on my '02 CRV. Turn in was massively improved, at the expense of roll, but well worth the downside of scraping door mirrors on the tarmac - the thing could be pushed so much harder. In fact it snapped 1 week after an MOT and the only thing that made me replace the link was the following year's MOT!

ARBs can definitely improve roll control but so can digressive or adjustable low speed compression valving and spring changes. I've never been too bothered by roll and tend to focus on balance and handling - the cars of mine which have handled best on the public road are invariably not the ones with the flattest cornering but the best control of the wheel travel, as well as actually having a decent amount of travel (hence returning to struts and playing with the rake on the Impreza). Given I've got a warranty with the F31 and already have modified cars to play with I've not even looked at what options there are for this car other than to know that the ACS springs are allegedly warranty safe.

[McBeemer]

Originally Posted by cramsnik

I had the 15mm rear arb fitted last week, I also have acs springs and adaptive dampers. I have to say the thicker roll bar has been the most noticeable improvement so far.

It is something I've been considering for some time now ... I had adaptive, but ditched it for the ACS dampers to match the springs I already had fitted. It is really good, but I would like a touch less understeer ... wouldn't want to spend a fortune though as it's pretty good already.

Last mod I am considering too is the Alpina gearbox map

[Rasco]

Originally Posted by McBeemer

It is something I've been considering for some time now ... I had adaptive, but ditched it for the ACS dampers to match the springs I already had fitted. It is really good, but I would like a touch less understeer ... wouldn't want to spend a fortune though as it's pretty good already.

Last mod I am considering too is the Alpina gearbox map

What does the alpina gearbox map give you? What does it do? And how would if affect warranty? I'm interested to hear as we know that Alpina are masters of tuning these cars.

So reading through this thread it seems to be that the rear ARB upgrade is the best bang for buck? And bracing the front could help but less impactful?

Sharpening the steering response would be great so which bushings & other mods would aid this?

[APJ]

Looks like the Bushing for the radius arm to chassis kit is out for any of those with an Xdrive, not sure whether OP is rear wheel or all wheel drive.
Watsey had kindly supplied the code of SPF4306K for the bushing kit, so i looked it up, and noticed it was recommended for rear wheel drive only, so last night i contacted Super pro who replied back this morning with this -

'Thank you for your email, unfortunately the T4306K does not fit the X-Drive platform BMW’s. The original BMW bush is a hydro bush which is designed to adsorb vibration, one of the things SuperPro take into account when designing a bush is can they ensure NVH is not going to be increased if this is the case then they will advised best to stick with OEM bush. Other PU manufactures may make bushes for the X-Drive because they do not worry to much about increased Noise, Harshness and Vibration.'

Just thought I'd mention it on here, as i imagine there's possibly a few on here who are interested in this bushing kit, i certainly was !, but its only suitable for the rear wheel drive cars and not the Xdrives.

(I did email him back about the T4306K, and he apologised and said it was a typo, it is SPF4306K)