F30 M Sport ARB

ar68 · 07-17-2016, 11:34 AM

Has anybody replaced the front ARB on their xDrive with one from a M Sport model (25mm dia against 22.5mm dia on xDrive). Need to improve the handling of this car but don't want to go too far from stock ie fitting Birds ARB. Ordered ACS springs and they should be here any day now. Wondering if I should fit better ARB before I get alignment and headlights checked.

Watsey · 07-18-2016, 03:20 AM

Quote:

Originally Posted by ar68

Has anybody replaced the front ARB on their xDrive with one from a M Sport model (25mm dia against 22.5mm dia on xDrive). Need to improve the handling of this car but don't want to go too far from stock ie fitting Birds ARB. Ordered ACS springs and they should be here any day now. Wondering if I should fit better ARB before I get alignment and headlights checked.

What aspects of the handling are you trying to improve ? If you want better turn-in then a stiffer rear ARB would be a better bet.

If you want flatter cornering stiffer front & rear ARBs will help hugely, depending upon what you choose.

Subframes have to be dropped to install the ARBs so definitely wait until afterwards (plus, say, 50-100 miles for things to settle down) for the geometry and headlight alignment.

teaston · 07-18-2016, 03:45 AM

As Watsey says either change both or just the rear. Just a stiffer front ARB would likely cause the car to understeer more.

ar68 · 07-18-2016, 03:52 AM

Quote:

Originally Posted by Watsey

What aspects of the handling are you trying to improve ? If you want better turn-in then a stiffer rear ARB would be a better bet.

If you want flatter cornering stiffer front & rear ARBs will help hugely, depending upon what you choose.

Subframes have to be dropped to install the ARBs so definitely wait until afterwards (plus, say, 50-100 miles for things to settle down) for the geometry and headlight alignment.

Thanks for info. I just want an all round improvement as I have no confidence in the handling or braking of this car compared to previous models I have owned.
I didn't realise fitting new ARBs was such a big job so I might just fit ACS springs and see how I go on.

ar68 · 07-18-2016, 03:56 AM

Quote:

Originally Posted by teaston

As Watsey says either change both or just the rear. Just a stiffer front ARB would likely cause the car to understeer more.

Thanks.
I don't have adaptive suspension on my car. Are you happy with how yours handles after fitting ACS springs. Planning to fit mine myself like you did too.

teaston · 07-18-2016, 03:58 AM

Quote:

Originally Posted by ar68

Quote:

Originally Posted by teaston

As Watsey says either change both or just the rear. Just a stiffer front ARB would likely cause the car to understeer more.

Thanks.
I don't have adaptive suspension on my car. Are you happy with how yours handles after fitting ACS springs. Planning to fit mine myself like you did too.

Yes I'm happy with it, but i do have adaptive.

Best to fit the ACS springs first and see how you like it.

tbenn1 · 07-18-2016, 06:25 AM

If your near Shropshire you welcome to come out in mine, acs springs and birds antirollbars

ar68 · 07-18-2016, 07:44 AM

Quote:

Originally Posted by tbenn1

If your near Shropshire you welcome to come out in mine, acs springs and birds antirollbars

Appreciate the offer. I will give you a shout if I'm ever down your way.

M40CCA · 07-18-2016, 04:49 PM

Quote:

Originally Posted by ar68

Has anybody replaced the front ARB on their xDrive with one from a M Sport model (25mm dia against 22.5mm dia on xDrive). Need to improve the handling of this car but don't want to go too far from stock ie fitting Birds ARB. Ordered ACS springs and they should be here any day now. Wondering if I should fit better ARB before I get alignment and headlights checked.

Which engine do you have ?

Tengocity · 07-18-2016, 05:02 PM

I had birds ARBS all round, then changed them back to standard when I changed to the ACS RS coilovers. Except instead of the standard rear xdrive bar I put in the sdrive one which 1mm thicker 13v12mm.

Whilst the car handles better overall now on the RS suspension I think the turn in was sharper with the beefy birds ARBs.

So in summary I would change the rear one or I'd change them both, but definitely not the front one only. I'd get ACS springs first though!

There is an adage that suspension engineers use- if you think it's the rear that's the issue then it's the rear, if you think it's the front that's the issue then it's still probably the rear...

ar68 · 07-19-2016, 12:55 AM

Quote:

Originally Posted by M40CCA

Which engine do you have ?

Same as you mate except mines a pre LCI.

ar68 · 07-19-2016, 01:08 AM

Quote:

Originally Posted by Tengocity

I had birds ARBS all round, then changed them back to standard when I changed to the ACS RS coilovers. Except instead of the standard rear xdrive bar I put in the sdrive one which 1mm thicker 13v12mm.

Whilst the car handles better overall now on the RS suspension I think the turn in was sharper with the beefy birds ARBs.

So in summary I would change the rear one or I'd change them both, but definitely not the front one only. I'd get ACS springs first though!

There is an adage that suspension engineers use- if you think it's the rear that's the issue then it's the rear, if you think it's the front that's the issue then it's still probably the rear...

I will fit the ACS springs and see how I go. Having owned an E46 M3, E83 X335d Msport, E46 M3 CS, E60 M5, E92 335i Msport and an E84 X125d xLine before this car, its the first time I haven't had confidence in a cars abilities and that's including that X1 mistake I owned for 4 weeks.

Tengocity · 07-19-2016, 02:35 AM

That list of cars are some of the best cars BMW have ever made though so perhaps not the best comparisons! However, this 335d is the only BMW I've had that I've felt the need to modify the hell out of, so I know what you mean.

ar68 · 07-19-2016, 05:12 AM

Quote:

Originally Posted by Tengocity

I had birds ARBS all round, then changed them back to standard when I changed to the ACS RS coilovers. Except instead of the standard rear xdrive bar I put in the sdrive one which 1mm thicker 13v12mm.

Whilst the car handles better overall now on the RS suspension I think the turn in was sharper with the beefy birds ARBs.

So in summary I would change the rear one or I'd change them both, but definitely not the front one only. I'd get ACS springs first though!

There is an adage that suspension engineers use- if you think it's the rear that's the issue then it's the rear, if you think it's the front that's the issue then it's still probably the rear...

Does the extra 1mm diameter on rear ARB make that much difference. Makes you wonder why BMW would spec two different items so similar too each other rather than just standardising them all.

Tengocity · 07-19-2016, 05:13 AM

It made a small difference with reducing understeer. Not sure it's worth doing on its own but I wa taking the birds arbs off anyway.

teaston · 07-19-2016, 04:02 PM

Quote:

Originally Posted by ar68

Quote:

Originally Posted by Tengocity

I had birds ARBS all round, then changed them back to standard when I changed to the ACS RS coilovers. Except instead of the standard rear xdrive bar I put in the sdrive one which 1mm thicker 13v12mm.

Whilst the car handles better overall now on the RS suspension I think the turn in was sharper with the beefy birds ARBs.

So in summary I would change the rear one or I'd change them both, but definitely not the front one only. I'd get ACS springs first though!

There is an adage that suspension engineers use- if you think it's the rear that's the issue then it's the rear, if you think it's the front that's the issue then it's still probably the rear...

Does the extra 1mm diameter on rear ARB make that much difference. Makes you wonder why BMW would spec two different items so similar too each other rather than just standardising them all.

It's an 8.3% increase in diameter,. You'd be happy if the car came with 8.3% extra power wouldn't you?

ar68 · 07-19-2016, 04:08 PM

Quote:

Originally Posted by teaston

It's an 8.3% increase in diameter,. You'd be happy if the car came with 8.3% extra power wouldn't you?

Good point well made.

XK140 · 07-19-2016, 04:33 PM

Quote:

Originally Posted by ar68

Good point well made.

Personally I wouldn't have a clue to what difference it makes.
If you fit a rear arb to a front drive car which did not have any bar at all,as I have in the past,by what percentage do you improve it?

NISFAN · 07-19-2016, 04:53 PM

Quote:

Originally Posted by teaston

Quote:

Originally Posted by ar68

Quote:

Originally Posted by Tengocity

I had birds ARBS all round, then changed them back to standard when I changed to the ACS RS coilovers. Except instead of the standard rear xdrive bar I put in the sdrive one which 1mm thicker 13v12mm.

Whilst the car handles better overall now on the RS suspension I think the turn in was sharper with the beefy birds ARBs.

So in summary I would change the rear one or I'd change them both, but definitely not the front one only. I'd get ACS springs first though!

There is an adage that suspension engineers use- if you think it's the rear that's the issue then it's the rear, if you think it's the front that's the issue then it's still probably the rear...

Does the extra 1mm diameter on rear ARB make that much difference. Makes you wonder why BMW would spec two different items so similar too each other rather than just standardising them all.

It's an 8.3% increase in diameter,. You'd be happy if the car came with 8.3% extra power wouldn't you?

Actually it's something like 40% stiffer. So quite a difference.

teaston · 07-20-2016, 03:14 AM

Quote:

Originally Posted by NISFAN

Actually it's something like 40% stiffer. So quite a difference.

So an 8.3% increase in diameter equates to 40% increase in stiffness?!

NISFAN · 07-20-2016, 04:07 AM

Quote:

Originally Posted by teaston

Quote:

Originally Posted by NISFAN

Actually it's something like 40% stiffer. So quite a difference.

So an 8.3% increase in diameter equates to 40% increase in stiffness?!

Yep, don't forget in cross sectional area you've gone up 17.4% or thereabouts.

Also the outer diameter plays a large part in the equation, from memory D to the power of 4 is in that torsion equation.

ar68 · 07-20-2016, 04:56 AM

Quote:

Originally Posted by NISFAN

Yep, don't forget in cross sectional area you've gone up 17.4% or thereabouts.

Also the outer diameter plays a large part in the equation, from memory D to the power of 4 is in that torsion equation.

So its well worth doing then?

07-17-2016, 11:34 AM	#1
ar68 First Lieutenant 149 Rep 379 Posts Drives: F36 440i Join Date: Jun 2016 Location: Lancashire iTrader: (1)	F30 M Sport ARB Has anybody replaced the front ARB on their xDrive with one from a M Sport model (25mm dia against 22.5mm dia on xDrive). Need to improve the handling of this car but don't want to go too far from stock ie fitting Birds ARB. Ordered ACS springs and they should be here any day now. Wondering if I should fit better ARB before I get alignment and headlights checked.
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07-18-2016, 03:45 AM	#3
teaston Banned 10994 Rep 32,881 Posts Drives: X3 M40d Join Date: May 2012 Location: The High Seas iTrader: (1)	As Watsey says either change both or just the rear. Just a stiffer front ARB would likely cause the car to understeer more.
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07-18-2016, 06:25 AM	#7
tbenn1 Second Lieutenant 23 Rep 293 Posts Drives: f31 335d Join Date: Sep 2013 Location: shrewsbury iTrader: (0)	If your near Shropshire you welcome to come out in mine, acs springs and birds antirollbars
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07-18-2016, 05:02 PM	#10
Tengocity General 8566 Rep 19,982 Posts Drives: 911, Cayenne Turbo, Disco 4 Join Date: Sep 2013 Location: Crieff, Perthshire, Scotland iTrader: (0)	I had birds ARBS all round, then changed them back to standard when I changed to the ACS RS coilovers. Except instead of the standard rear xdrive bar I put in the sdrive one which 1mm thicker 13v12mm. Whilst the car handles better overall now on the RS suspension I think the turn in was sharper with the beefy birds ARBs. So in summary I would change the rear one or I'd change them both, but definitely not the front one only. I'd get ACS springs first though! There is an adage that suspension engineers use- if you think it's the rear that's the issue then it's the rear, if you think it's the front that's the issue then it's still probably the rear... __________________ Current: Porsche 911 991 C4S, Porsche Cayenne Turbo, Land Rover Discovery 4. Gone...G01 X3 M40i, Cayman S 987, F31 340i, Cayman GT4, F82 M4 CP, Lotus Exige V6, G20 330e, F30 330e, Boxster S 987, F31 335d, Mini Cooper SD, E89 Z4, E90 330d 320d, E60 520d, E46 330d 320d, MX5s, E30 325i
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07-19-2016, 02:35 AM	#13
Tengocity General 8566 Rep 19,982 Posts Drives: 911, Cayenne Turbo, Disco 4 Join Date: Sep 2013 Location: Crieff, Perthshire, Scotland iTrader: (0)	That list of cars are some of the best cars BMW have ever made though so perhaps not the best comparisons! However, this 335d is the only BMW I've had that I've felt the need to modify the hell out of, so I know what you mean. __________________ Current: Porsche 911 991 C4S, Porsche Cayenne Turbo, Land Rover Discovery 4. Gone...G01 X3 M40i, Cayman S 987, F31 340i, Cayman GT4, F82 M4 CP, Lotus Exige V6, G20 330e, F30 330e, Boxster S 987, F31 335d, Mini Cooper SD, E89 Z4, E90 330d 320d, E60 520d, E46 330d 320d, MX5s, E30 325i
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07-19-2016, 05:13 AM	#15
Tengocity General 8566 Rep 19,982 Posts Drives: 911, Cayenne Turbo, Disco 4 Join Date: Sep 2013 Location: Crieff, Perthshire, Scotland iTrader: (0)	It made a small difference with reducing understeer. Not sure it's worth doing on its own but I wa taking the birds arbs off anyway. __________________ Current: Porsche 911 991 C4S, Porsche Cayenne Turbo, Land Rover Discovery 4. Gone...G01 X3 M40i, Cayman S 987, F31 340i, Cayman GT4, F82 M4 CP, Lotus Exige V6, G20 330e, F30 330e, Boxster S 987, F31 335d, Mini Cooper SD, E89 Z4, E90 330d 320d, E60 520d, E46 330d 320d, MX5s, E30 325i
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