[J_MENIS]

Do they make a big difference ? And which would you all recommend ? I'm lowered on H&R SS springs with stock M sport suspension. But cornering isn't as good as I'd hope.

[Polo08816]

Originally Posted by J_MENIS

Do they make a big difference ? And which would you all recommend ? I'm lowered on H&R SS springs with stock M sport suspension. But cornering isn't as good as I'd hope.

If you already have the 704 Sport Suspension, the stock roll bar should be sufficient.

To reduce roll, you need a higher spring rate. To get a quality ride with a higher spring rate, requires a well tested system - matched springs/struts.

Consider either the M Performance Suspension Kit or the Ohlins Road and Track coilovers.

Both these only drop the car about 10mm compared to stock suspension because they've done their research... more than a 10mm drop hurts performance more than it helps.

[J_MENIS]

Originally Posted by Polo08816

If you already have the 704 Sport Suspension, the stock roll bar should be sufficient.

To reduce roll, you need a higher spring rate. To get a quality ride with a higher spring rate, requires a well tested system - matched springs/struts.

Consider either the M Performance Suspension Kit or the Ohlins Road and Track coilovers.

Both these only drop the car about 10mm compared to stock suspension because they've done their research... more than a 10mm drop hurts performance more than it helps.

I heard the B8 shocks are good pairs for the H&R springs. Do you think that'll help with the cornering? Not as worried about comfort.

[Polo08816]

Originally Posted by J_MENIS

I heard the B8 shocks are good pairs for the H&R springs. Do you think that'll help with the cornering? Not as worried about comfort.

I've heard the H&R SS + Bilstein B8 combo results in a lot of blown tophats which is exactly what to expect when driveway mechanics start mixing and matching springs and struts thinking they can do better than engineers from BMW or Ohlins.

[RM7]

I have the dinan anti-sway bars. I really like em, but they don't do m-sport suspension on the x-drives, so these should be roughly equivalent to that. Really nice cornering traits now, car stiffens up nicely in response to throwing it into a corner. I would agree with the others though, if you already have m-sport, you need to look elsewhere. I'd look at shocks and tires. Question is to ask why isn't cornering as good as you want. Is it because of grip, or is it because of weight shift upsetting the grip during rapid directional changes? It's probably not weight shift upsetting the grip, which would be soft springs and weak anti-sway bars. There might be other things to help with the directional changes IF you really believe that to be an issue, like a M3 type strut bar, but your best bet is probably wider sticker (summer!) rubber and coil-over shocks, both of which can make a dramatic difference by themselves.

Of course, it would help to know what you mean by "cornering". Do you want to go faster through the turn, kick the rear end out a bit and have some controllable slide, make quick reactions left and right? These things are not all the same and one may sacrifice the others.

[lens]

Originally Posted by Polo08816

I've heard the H&R SS + Bilstein B8 combo results in a lot of blown tophats which is exactly what to expect when driveway mechanics start mixing and matching springs and struts thinking they can do better than engineers from BMW or Ohlins.

Also doesn't help that H&R springs in general are absolute garbage overall.

IMO they're just to lower the car and provide looks.

After driving two 335i with H&R springs+H&R SS springs vs my Dinan, I can feel the ride quality difference.

[Lancelot]

Originally Posted by JamesNoBrakes

I have the dinan anti-sway bars. I really like em, but they don't do m-sport suspension on the x-drives, so these should be roughly equivalent to that. Really nice cornering traits now, car stiffens up nicely in response to throwing it into a corner. I would agree with the others though, if you already have m-sport, you need to look elsewhere. I'd look at shocks and tires. Question is to ask why isn't cornering as good as you want. Is it because of grip, or is it because of weight shift upsetting the grip during rapid directional changes? It's probably not weight shift upsetting the grip, which would be soft springs and weak anti-sway bars. There might be other things to help with the directional changes IF you really believe that to be an issue, like a M3 type strut bar, but your best bet is probably wider sticker (summer!) rubber and coil-over shocks, both of which can make a dramatic difference by themselves.

Of course, it would help to know what you mean by "cornering". Do you want to go faster through the turn, kick the rear end out a bit and have some controllable slide, make quick reactions left and right? These things are not all the same and one may sacrifice the others.

Your sir provide very sound advice

[J_MENIS]

Originally Posted by JamesNoBrakes

I have the dinan anti-sway bars. I really like em, but they don't do m-sport suspension on the x-drives, so these should be roughly equivalent to that. Really nice cornering traits now, car stiffens up nicely in response to throwing it into a corner. I would agree with the others though, if you already have m-sport, you need to look elsewhere. I'd look at shocks and tires. Question is to ask why isn't cornering as good as you want. Is it because of grip, or is it because of weight shift upsetting the grip during rapid directional changes? It's probably not weight shift upsetting the grip, which would be soft springs and weak anti-sway bars. There might be other things to help with the directional changes IF you really believe that to be an issue, like a M3 type strut bar, but your best bet is probably wider sticker (summer!) rubber and coil-over shocks, both of which can make a dramatic difference by themselves.

Of course, it would help to know what you mean by "cornering". Do you want to go faster through the turn, kick the rear end out a bit and have some controllable slide, make quick reactions left and right? These things are not all the same and one may sacrifice the others.

The car just has a heavy feel when taking turns, I want to reduce roll and get a more direct turn in. When going through slight turns at high speeds there is no problem though.

[RM7]

Originally Posted by J_MENIS

The car just has a heavy feel when taking turns, I want to reduce roll and get a more direct turn in. When going through slight turns at high speeds there is no problem though.

Well, anti-sway will help with that, but also bushings, front strut bar, etc. Stiffer springs would make it ride worse everywhere, helping here but causing a hit in your compliance, running springs stiff enough to eliminate weight transfer would negate the purpose of having springs in the first place, which is why we have anti-sway bars. But most likely a combination of better damping and maybe something like a strut bar. Given you have the 704, I wouldn't jump right into stiffer anti-sways. There's a fine line between what works well on the street and what is unlivable when only one side of the car goes over a bump (like pothole, bump, etc). It exaggerates the bump and is almost like running a solid axle, because the anti-sway bars think the car is "leaning", rather than just one spring compressing. I don't know much about those springs, but I did some research and bought the ACS because it seemed they were tuned for my exact car and model, in that the springs they offer for other similar 4-series are a different part number. Things like x-drive vs. not, 4cyl vs. 6, etc., add or subtract significant weight. A "one-size-fits-all" approach is likely to have some poor results at some point. But, dampers go hand in hand with springs, so you need the higher damper rates too, otherwise the car just ends up "bouncy".

[Polo08816]

Originally Posted by JamesNoBrakes

Well, anti-sway will help with that, but also bushings, front strut bar, etc. Stiffer springs would make it ride worse everywhere, helping here but causing a hit in your compliance, running springs stiff enough to eliminate weight transfer would negate the purpose of having springs in the first place, which is why we have anti-sway bars. But most likely a combination of better damping and maybe something like a strut bar. Given you have the 704, I wouldn't jump right into stiffer anti-sways. There's a fine line between what works well on the street and what is unlivable when only one side of the car goes over a bump (like pothole, bump, etc). It exaggerates the bump and is almost like running a solid axle, because the anti-sway bars think the car is "leaning", rather than just one spring compressing. I don't know much about those springs, but I did some research and bought the ACS because it seemed they were tuned for my exact car and model, in that the springs they offer for other similar 4-series are a different part number. Things like x-drive vs. not, 4cyl vs. 6, etc., add or subtract significant weight. A "one-size-fits-all" approach is likely to have some poor results at some point. But, dampers go hand in hand with springs, so you need the higher damper rates too, otherwise the car just ends up "bouncy".

If you already have the 704 Sport suspension, there's not that much to gain vs. effort required by switching to stiffer roll-bars.

Stiffer springs are fine as long as dampening matches it. This is why Ohlins Road and Track coilovers have such high spring rates but feel as comfortable as the factory ride.

In fact, increasing the stiffness of the roll-bars will negatively impact the ride. The idea of roll-bars is to distribute weight more evenly through a turn by transferring the weight to the outside. However, it does this by linking the left and right suspension components. What this also means is that if you hit a pothole on one side, the noise and vibration is transferred more effectively to the other side of the car as well which negates the point of an independent suspension as it would exhibit behavior associated with live axle setups.

[Lancelot]

Originally Posted by Polo08816

If you already have the 704 Sport suspension, there's not that much to gain vs. effort required by switching to stiffer roll-bars.

Stiffer springs are fine as long as dampening matches it. This is why Ohlins Road and Track coilovers have such high spring rates but feel as comfortable as the factory ride.

In fact, increasing the stiffness of the roll-bars will negatively impact the ride. The idea of roll-bars is to distribute weight more evenly through a turn by transferring the weight to the outside. However, it does this by linking the left and right suspension components. What this also means is that if you hit a pothole on one side, the noise and vibration is transferred more effectively to the other side of the car as well which negates the point of an independent suspension as it would exhibit behavior associated with live axle setups.

This.
To share my experience, the stiffer bars i have (h&r) do well on track with an even surface. But come the irregular normal street surface, you both lose comfort but also stability: when hitting an uneven surface, instead of being locally absorbed by a single wheel assembly, it is transfered to the entire car body, making it twist which is very bad for overall stability and communicates to the steering as well.

Then when you consider this it isn't surprising that more advanced cars like high end McLaren's are getting rid of ARBs altogether in favour of electronic dampers;

I myself took the wrong road with H&R anti roll bars, having suffered a bit from weight transfers when cornering, and i'm now rectifying this by having fitted firmer coilovers with EDC (KW DDC coilovers, my car has EDC), and reverting to stock ARBs in 10 days.

The interesting thing with EDC is that there are constant adjustments that will stiffen your dampers according to the information feed from acceleration sensors for all three axes, pitch, yaw and roll, but the stock dampers and springs are too weak for a good spirited driving or a bit of track.

[D041987]

First to reduce body roll you want to go with ARB's.

GO with the M135 LCI Set. It's a 25MM front bar and a 15MM rear. SHould be a upgrade from your current setup which I think is at a 23mm front and 12mm rear. Or if you track I would just get the front ARB at 28MM MAX and leave the rear stock so see if you like the handling. If you want later than upgrade to the 15MM rear ARB.

Than get coilover suspension, like Auto Fortune, KW V2+, Bilstein, Ohlins.

[eddiehatchblack]

Originally Posted by D041987

First to reduce body roll you want to go with ARB's.

GO with the M135 LCI Set. It's a 25MM front bar and a 15MM rear. SHould be a upgrade from your current setup which I think is at a 24mm front and 13mm rear. Or if you track I would just get the front ARB at 28MM MAX and leave the rear stock so see if you like the handling. If you want later than upgrade to the 15MM rear ARB.

Than get coilover suspension, like Auto Fortune, KW V2+, Bilstein, Ohlins.

Does the M135 LCI set fit an F31? Looking on RealOEM, it looks like the front is 23.x not 25. Can you confirm the part numbers? I saw the rear 15mm being correct though.

[eddiehatchblack]

Originally Posted by eddiehatchblack

Does the M135 LCI set fit an F31? Looking on RealOEM, it looks like the front is 23.x not 25. Can you confirm the part numbers? I saw the rear 15mm being correct though.

Found my answer. The xDrive front ARB is thinner than on the RWD models. I have a US F31 so I have xDrive. Hrmmm... something to think about.

[Dmitry83]

Originally Posted by eddiehatchblack

Found my answer. The xDrive front is thinner then the RWD models. I have a US F31 so I have xDrive. Hrmmm... something to think about.

I suppose this is made to adjust the grip balance towards the front to compensate front wheels torque. But the same is the reason xDrive rolls that much, being 10mm taller on springs in addition.

[D041987]

It all depends on if you have standard or M sport suspension for the ARB as they range from 22 to 24MM. If it is stock X drive than you might be at a 22 or 23mm front and a 12 or 13 mm rear just depending on the car and suspension. A few members have upgraded to the LCI sets as they went to the 25mm front and 15MM rear and the F32 LCI and M series have had nothing but glowing reviews on their handling but this was for a Rear Wheel Drive car. For X Drive you would just need to look at the REALOEM parts list and see what bar sizes are available from the LCI or newer cars or another alternative to go with would be the Eibach kit as it gives you a beefy front bar at 28mm and the rear is a good middle of the road upgrade at 16mm. Most other companies sport the 28mm front and a bigger 19mm rear bar but that is if you are full on race spec. If you want good driving characteristics for road use and some track time I would just upgrade with middle of the road with the LCI sets or the Eibach if you want a more sporty feel but even with LCI you will have a good change for the car!

[Dmitry83]

Originally Posted by D041987

It all depends on if you have standard or M sport suspension for the ARB as they range from 22 to 24MM. If it is stock X drive than you might be at a 22 or 23mm front and a 12 or 13 mm rear just depending on the car and suspension. A few members have upgraded to the LCI sets as they went to the 25mm front and 15MM rear and the F32 LCI and M series have had nothing but glowing reviews on their handling but this was for a Rear Wheel Drive car. For X Drive you would just need to look at the REALOEM parts list and see what bar sizes are available from the LCI or newer cars or another alternative to go with would be the Eibach kit as it gives you a beefy front bar at 28mm and the rear is a good middle of the road upgrade at 16mm. Most other companies sport the 28mm front and a bigger 19mm rear bar but that is if you are full on race spec. If you want good driving characteristics for road use and some track time I would just upgrade with middle of the road with the LCI sets or the Eibach if you want a more sporty feel but even with LCI you will have a good change for the car!

Other thing which is interesting reagrding xDrive:

For both M135i & M140i (LCI) the rear wheel drive version offers only 25.2/22.2 front and 15mm rear.
While the xDrive has two options for the rear ARB- 15mm for passive and 14mm for adaptive suspension. Front ARB stays the same in both types- 23.6/20.8mm .

However for 420i xDrive LCI the picture is even more interesting compared with the 320i xDrive LCI:
Standard rear ARB on F32 LCI is 13mm, while M-Adaptive comes with 15mm bar.
But the F30 LCI does not have thicker bar option anymore and got 12mm with both standard and M-Adaptive suspensions.