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Discussion Starter · #1 ·
My mechanic mate will fit me a set of ARB to my m140i for £210, so starting to look into whether to do this as i would like the car to have less roll.

Few questions i have which im hoping people can answer:

-Will a matched set of ARB'S (Most likely H+R) cause the cars handling to be more 'snappy' and harder to control the rear?

-Do i need to change ARB bushes to stiffer ones? Do they come with their own bushes usually?

-Will they work okay with B8 Dampers + Motech stance + Springs?

-Will i lose lateral grip on fast corners?

My car has the MP LSD.

Anyone have any experiences?
 

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Might find this a good watch.

 

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I had H&R ARBs on my f20 adaptive m135i matched with H&R springs as part of Birds B1S suspension and QLSD package.

Combined with m4 front lower arms - no regrets.
 

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Discussion Starter · #5 ·
I had H&R ARBs on my f20 adaptive m135i matched with H&R springs as part of Birds B1S suspension and QLSD package.

Combined with m4 front lower arms - no regrets.
What was it like? Did it roll a LOT less? What was mid corner grip like, did it oversteer more easily?
 

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Discussion Starter · #7 ·
It rolled less but not so much less that prevented weight shift L&R on fast sweepers.
Ah so it didnt corner 'completely flat' then?

I watched in the youtube video above aswell that it created understeer even on the softer of the two front bar settings.

May go back to the drawing board then, the thing is once my car is in the corner its quite flat, its the turning into the corner and rapidly changing directions where it rolls/sways. Stiffer bushings may help.
 

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Ah so it didnt corner 'completely flat' then?

I watched in the youtube video above aswell that it created understeer even on the softer of the two front bar settings.

May go back to the drawing board then, the thing is once my car is in the corner its quite flat, its the turning into the corner and rapidly changing directions where it rolls/sways. Stiffer bushings may help.
I think the terminology here is confusing but keep in mind 2 basics of vehicle dynamics:

Dampers control rate. (low speed bump/rebound - damper speed not vehicle speed)
Springs / ARB control steady state. (i.e in the corner and loaded up)

i.e. if you are in a corner for a long period of time your body roll will be defined by the springs and anti roll bars. Edit: ive used the term body roll here to make it easier to visulise but don't confuse body roll with weight transfer. Weight transfer is always a fixed amount for a fixed corning g and can only be adjusted front to back to tune your balance. More or less body roll does not mean more or less weight transfer.

quick changes of direction and also entry / exit are where dampers and the feeling your describing comes into play. A really stiff front damper for example will make the car feel responsive as the weight transfer will happen quickly but may induce turn in understeer on the limit.

Ive always found a pointy car feels great on the road, but when you take a track it may well understeer more than expected.

Anyway what you are describing sounds to me like you are after some expensive dampers that allow them to be stiff and responsive but without compromosing ride. like a digressive valve for example.
A posh damper will allow you to run stiffer springs as well without too much ride compromise.
 

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Discussion Starter · #9 ·
Are adjustable droplinks necessary if you fit ARB'S? Was hoping to keep the cost down but annoyingly seems like these are essential if lowered and changing the roll bars.
 

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Personally I would say no as long as they dont hit anything at your ride height ( it shouldn't as BMW would have an issue if the arb contacted something at full droop or over a large bump / compression!) and your corner weighting doesn't change the left to right ride height enough to pre load the bar due to fixed end links.

Secondly the aftermarket bars have different bushes that are not bonded to the bar so having the bar rotate around more due to lowering is not a problem there.

Maybe the ball joints on the links wont last as long, best to ask someone who has tried it! My eibach rear bar is only 1mm larger than stock so can't comment too much.
 

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Are adjustable droplinks necessary if you fit ARB'S? Was hoping to keep the cost down but annoyingly seems like these are essential if lowered and changing the roll bars.
In my experience they were.
I have the Birds-fitted ARBs (H&R)

All was well for 4 years then back in March this year during the usual MoT I was told that at full-droop and with the steering on full-lock the ARBs fouled the steering arms. (They also damaged the steering arm gaiters which I had to replace)
So I had to fit shortened drop-links to resolve this.

To be honest this has left a bit of a sour taste with respect to Birds as they never mentioned this might be an issue.
 

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Discussion Starter · #12 ·
Thank you for everyone who has responded, i think i may change droplinks while im in there.

My other query is, is the body roll on the m140i bad would you say?

Ive always found it an issue but not many people seem to complain about it? It seems that when i go round wide corners at say about 25mph like coming off a wide roundabout it feels like the car is proper leaning to one side and im fighting to stay sat up straight, but it doesent look like it is and it feels like it corners flat at the same time, it makes no sense.

I dont know if its because the seats arent exactly properly supportive even with the bolsters inflated all the way, my friend complained yesterday when i was going round a corner but i wasent going especially quick really just a normal speed but he said it felt like it was way way faster, i dont know if thats again due to roll, lateral g's even though im going slow, or just a sensation because the cars on stiff springs (motech stance plus).⁰
 

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I don't think the addition of stiffer ARBs is purely about reducing body roll, though that is a factor.
As with all things suspension and handling, it's a complex dynamic system with various interdependencies between different paramaters.

One of the chains of thought is as so:
The standard car has no LSD, and because of this the standard rear roll bar is quite soft in order to help traction.
Bearing in mind the general rule of thumb that; not so much in terms of absolute stiffness, but the releative roll stifness beween axles, the axle with the stiffer roll bars will have reduced grip due to it handling a greater proportion of the weight (lateral load) transfer.

So step one is to add an LSD, this then allows you to get away with a relatively stiffer rear roll-bar without hurting the traction or causing excessive inside-wheel spin during power-on cornering (corner exit)

Having a larger proportion of your roll-stiffness on the rear axle in turn means the front axle is handling a smaller proportion of the lateral load transfer, thus increasing its grip and helping the front-end feel more responsive and reducing the understeer that the standard car is prone to.
 

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Discussion Starter · #15 ·
I bet if you fitted a fixed bucket it would feel a whole lot different!
I imagine it would, the stock seats dont feel very supportive side to side.

As far as i know the stock rear springs were exceptionally hard compared to every aftermarket option (even though motech stance+ springs are quite firm), and therefore im wondering if my car has more body roll now than it did before, i honestly cant remember what the roll was like stock.

My only concern with ARB is getting a lot less warning before the car goes.
 

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I've fitted a fair few sets of these so may be able to help.
As for bushes, they come with their own.
Droplinks, MOST suspension kits work fine with the HR arb kit and stock droplinks, KW coilovers need shorter/adjustable droplinks otherwise the ARB rests on the track rods at the front when the car is on the ground, we found this out the hard way.
Body roll may still be there as the B8/B12 kit is still a road suspension kit so while it is a massive improvement its still a fairly softer setup for track use, if you more dedicated to track days then it may be worth changing to an adjustable coilover setup.
Whilst doing the ARB I would personally consider swapping out the subframe bushes for either Powerflex full bushes or Millway aluminium bushes, these will massively improve the feel of the back end.

Marc
 

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Discussion Starter · #17 ·
I've fitted a fair few sets of these so may be able to help.
As for bushes, they come with their own.
Droplinks, MOST suspension kits work fine with the HR arb kit and stock droplinks, KW coilovers need shorter/adjustable droplinks otherwise the ARB rests on the track rods at the front when the car is on the ground, we found this out the hard way.
Body roll may still be there as the B8/B12 kit is still a road suspension kit so while it is a massive improvement its still a fairly softer setup for track use, if you more dedicated to track days then it may be worth changing to an adjustable coilover setup.
Whilst doing the ARB I would personally consider swapping out the subframe bushes for either Powerflex full bushes or Millway aluminium bushes, these will massively improve the feel of the back end.

Marc
Appreciate your response marc as i know you do a lot with the m lites. If there is still some obvious roll present with the H+R ARB's ill probably hold off for now and have a think as its not exactly a cheap job to buy and swap them.

Ive been watching tim williams latest video of his m240i after he had the millway aliminium bushes fitted, i am looking for more 'feel' from the chassis, i dont have a clue what the rear of the car is doing to be honest, even when it lets go i can just about feel that the wheels are spinning, i have powerflex inserts at the moment but im really tempted by a full aluminium bush replacement which i would purchase from yourself, however my concerns are:

Do the subframe aluminium bushes make NVH bad?

Ive heard the diff bushes are the worst for NVH, however if i was replacing the subframe ones id probably want to replace the diff ones too, is there a way to keep NVH to a minimum by maybe just using inserts on the diff, or will the aliminium bushes on the subframe causes too much load on the diff without proper bush upgrades?

Do the solid subframe mounts put pressure on any other area of the car as there is now no subframe movement, will suspension wear quicker etc?

And last of all, would replacing the front control arm bush increase steering feel at all?

Thank you.
 

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Appreciate your response marc as i know you do a lot with the m lites. If there is still some obvious roll present with the H+R ARB's ill probably hold off for now and have a think as its not exactly a cheap job to buy and swap them.

Ive been watching tim williams latest video of his m240i after he had the millway aliminium bushes fitted, i am looking for more 'feel' from the chassis, i dont have a clue what the rear of the car is doing to be honest, even when it lets go i can just about feel that the wheels are spinning, i have powerflex inserts at the moment but im really tempted by a full aluminium bush replacement which i would purchase from yourself, however my concerns are:

Do the subframe aluminium bushes make NVH bad?

Ive heard the diff bushes are the worst for NVH, however if i was replacing the subframe ones id probably want to replace the diff ones too, is there a way to keep NVH to a minimum by maybe just using inserts on the diff, or will the aliminium bushes on the subframe causes too much load on the diff without proper bush upgrades?

Do the solid subframe mounts put pressure on any other area of the car as there is now no subframe movement, will suspension wear quicker etc?

And last of all, would replacing the front control arm bush increase steering feel at all?

Thank you.
The diff bushes do create the most NVH, but I wouldnt say the subframe bushes do, try go for a ride in an F chassis M car, as theyre subframes dont use any bushings.

Front control arm bushes will increase steering feel slightly, we also fitted them to Tims car too
 

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Discussion Starter · #19 ·
The diff bushes do create the most NVH, but I wouldnt say the subframe bushes do, try go for a ride in an F chassis M car, as theyre subframes dont use any bushings.

Front control arm bushes will increase steering feel slightly, we also fitted them to Tims car too
Thank you, is there any issue with replacing the subframe mounts for solid ones without upgrading diff bushes? I.e. is the diff under any more stress or anything if you leave stock bushes in it?
 

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Thank you, is there any issue with replacing the subframe mounts for solid ones without upgrading diff bushes? I.e. is the diff under any more stress or anything if you leave stock bushes in it?
No mate, both totally separate so can do either independantly
 
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