H&R ARBs on MRs ?

[swamper]

ok guys has anyone done this mod...?
i know the coupe guys have a thread going on at the minute and its been discussed greatly at lenth over their .
but im after people that have fiited them to MRs.
theres a lot of conflicting reports about droplinks , boot floors , mounting faults ..ect?
obvously the couple has a much stiffer chassess anyway so would this help with the anti roll?
mine is set on H&R springs and B8s...and TBH is fairly flat through the corners....but ive read reports that the ARBs can make it twitchy...as us MR owners know..the arse can snappy at the best of times.
if the car rolls from front to rear and the MR would being less stiff than the coupe would this help with traction ?

anyway this is open to the coupe lads as well for there input on the mod and there findings..all i want if for pros and cons to be discussed as this could be my next mod

 

[Stormy_be]

I don't know if this article has already been looked at, but it explains the working and results of the arb's very well.http://iracing.wikidot.com/components:anti-roll-bar-sway-bar

 

[swamper]

yeah Stormy ive read it......its more the stresses and strains and handling on the MR compaired to say the coupe.
IE if the MR flexes more than the coupe would the stain on the components be exaggerated..that kinda thing

 

[Stormy_be]

The stress on mounting points and on bushes etc would be exactly the same.
The stress on the chassis will be picked up differently by the coupe and the roadster chassis.

Personally I wouldn't be able to tell anything on this topic as my full blown roll cage will add more strength then the coupe's roof.

 

[swamper]

The stress on the chassis will be picked up differently by the coupe and the roadster chassis.
.

this is an intresting point...do you want to elaborate ?

 

[swamper]

i was hoping this might be the start a bit of a good thread...maybe the MR chap dont use them that much

 

[Dino D]

I think most don't get driven let alone cornered hard enough to generate any lean!
The way values are going and all that, you sir are an increasingly rare breed, an M car owner that drives it!


@Brian H runs them in his 3.0 and tracks it so could have relevant feedback. @zedonist runs then on his 1.9 but I don't know if he tracks it too but he's very pleased with them I believe.

I've read somewhere that beefing up the ARB mounting brackets is a good idea if the existing ones are tired.

In the US there a few who 'autocross' the M roadsters with lots of suspension changes. I think I've seen reference to some running with the ARB's disconnected too for certain disciplines/suspension set ups.

 

[zedonist]

I don't know about the MR but the standard Z3 rolls really bad, it is particularly bad at going around traffic islands. Changing the ARB's transformed the car, it now handles as good as it looks, they are that good I am looking to put a set on the Van...

 

[swamper]

i do drive it hard sometimes...when nobodys looking so i can get it all wrong without anybody seeing haha
the thing with the M and the way its set up is its very easy to overstep the mark....however...get it right and it sticks like glue..!!
i do get some lean with it even though ive got the B8s and H&R springs on.

the 3.0 has a diffrent set up on the shocks and drop likns to the M so i wonder if they have suffered the same problems ?
would making the rear roll less make it more skittish...hmm im trying to work out if it would loose traction more by taking the pressure off the loaded tyres

 

[zedonist]

The ARB function is to keep both the driven wheels on the ground, therefore it is the front bar that does the work on the Z3 as it prevents the nose dipping, and the tail lifting, go to hard and you end up with no roll, and like a go cart the back end will come round to say hello the front. If you are tracking a car then you want the ARB to be adjustable, as they will work different on a flat track, compared to a hilly track, due to loading into the corners being different, it's why all races have practice sessions such as F1, so they can make decisions on how much ARB to run, I expect @Brian H is building up a book of settings?

 

[swamper]

this is something i was thinking about Zed.
the M has much thicker ARBs than a zed so the uprated H&Rs would probly best be left on the softest settings for road running..?

 

[zedonist]

Yes, I see no reason to put them on the hard setting, what a lot do is put the rear on hard setting which is wrong and ends up ripping the trailing arm brackets. Your car looks quite flat in the pictures. I suppose the question you need to ask is do you think it has more to give in the corners, if yes I would look at corner weighting and tyres

 

[Stormy_be]

this is an intresting point...do you want to elaborate ?

Chassis-flex is a torsional force. Not having a roof will make it more flexible: it is easier to flex a sheet of paper or a sheet of metal, than a box or a square tube.
That is why most convertible weigh more than saloons. They have to compensate the loss of strength from removing the roof, by adding additional chassis reinforcements under the car. And even then it is hard to get the same strength you automatically get from the shape of a saloon. Therefore, most convertible have worse handling than their saloon versions.

With my roll cage, I recreated that saloon-type structure. Even more, the roll cage is stronger than a normal roof. So I will have less fix in my chassis then a "roofed-car".

With bigger ARB's the chassis will get more flex-forces. This because the wheels don't take the force, the force goes via the ARB to the chassis.
This is confirmed by some people with bigger ARB's bend their mounting points: because of the additional force.
The forces need to go somewhere.

Regards, Koen

 

[Brian H]

I have mine set on soft, front and rear, the difference out of the box was enough to leave them alone, I would also need different drop links to achieve the hard setting as the stock units would not reach the hard hole setting!

@swamper, just had a look on realoem, the S50 ///M has a 23mm front ARB as stock, the 3.0 has a 25mm ARB as stock and the m-sport a 25.5mm ARB as stock, somewhere along the line BMW decided to uprate these it seems.

The roll in your picture does not look too excessive but granted the new ARBs will help.

 

[Stormy_be]

I have mine set on soft, front and rear, the difference out of the box was enough to leave them alone, I would also need different drop links to achieve the hard setting as the stock units would not reach the hard hole setting!

@swamper, just had a look on realoem, the S50 ///M has a 23mm front ARB as stock, the 3.0 has a 25mm ARB as stock and the m-sport a 25.5mm ARB as stock, somewhere along the line BMW decided to uprate these it seems.

The roll in your picture does not look too excessive but granted the new ARBs will help.

I suppose you are taking about the front measurements? H&R's are 29mm at the front, right?
To be complete, what about others? 1.9's, etc.
What about the rear? any differneces their? I would suspect so.

M-front-suspension doesn't need other droplinks (as they have the same droplink-connection as we have on our BC-Shocks, it is directly on the shocks).
At the back, we all would need other droplinks to be able to put it on the hard setting.
I will have mine in 1 week

 

[swamper]

Now that's very interesting Brian.
The S50s came way before the 3.0s.
So the 3.0s have updated ARBs.
So quite a bit thicker so more resistance in the bends.

Koen ..that's food for thought...I'm wondering where the strengthening would be on an MR.
The same as a coupe or with it being an MR it would have to be more.

 

[Stormy_be]

Now that's very interesting Brian.
The S50s came way before the 3.0s.
So the 3.0s have updated ARBs.
So quite a bit thicker so more resistance in the bends.

Koen ..that's food for thought...I'm wondering where the strengthening would be on an MR.
The same as a coupe or with it being an MR it would have to be more.

Not sure if the MR has any.
That is maybe the reason some are fitting the underbody braces (http://www.strong-strut.com/body-brace.htm or like @Anthony Cherry is making), which are actually the same type of reinforcements.

 

[Stormy_be]

Think I looked them all up in realoem:
-----------------Front------------------------------------------Rear
-----Non-M-Pack-------M-Pack--------------Non-M-Pack----M-Pack
1.8-----22.5----------------23.5---------------------14---------------14
1.9-----22.5----------------23.5---------------------14---------------14
2.0-----24-------------------25-----------------------15----------------15
2.2-----25-------------------25.5---------------------15----------------16
2.5-----25-------------------25.5---------------------15----------------16
2.8-----24-------------------25-----------------------15----------------15
3.0-----25-------------------25.5---------------------15----------------16
3.2-----23-------------------23-----------------------18.5--------------18.5

Editor deletes double spaces, so had to put "-" in.

 

[zedonist]

The 3.0 may not be uprated over the //M, diameter only plays a part if the bars are all the same material, for example the H&R bars are made from alloy steel and heat treated to higher hardness (more torsional rigidity). I expect the //M products are similar...

 

[zedonist]

The dimensions for H&R are:

28mm front both Z3 and Z3M, the diameter and alloy steel certainly explains why they make so much difference

19mm rear on Z3 and 21mm on the Z3M, I assume the 19mm gives you neutral handling.