[Junebug85]

There's a few different threads about fitting F90 Braces/Reinforcements to the G30 540i and 550i, but I thought I'd start my own and try and document it from start to finish.

This all stemmed me having to replace the rear flex disc on the car. While looking at what the job would entail, I read that some of the under body panels and bracing would need to come off. Having a look on here and online, a few have fitted the F90 braces and rear reinforcements as an upgrade and feedback has been positive. There's more focus on the rear as the rear sub-frame is on bushings where as the front sub-frame is not, so it's more stiffer already.

The car is currently on MSS Height Adjustable Springs and this is the only suspension modification on the car, currently. This alone has been a big improvement over stock but I think there is still more improvements to be had.

So what was a task to just have the flex disc replaced has now escalated into sourcing a whole range of F90 parts.... I mean this is what car people do right!?

I placed an order for the below with a BMW dealer yesterday. I was able to get a decent enough discount from them.

F90 Cross Member - 33318064485
F90 Cross Strut/X Brace - 33318064893
F90 Strut Brace Front, Bulkhead - 51618075677
Bolts for cross member (8) - 07119907857
Bolts for cross strut (2) - 33308071664
Nuts for cross strut (2) - 33308073595
Underbody Panel Left - 51758060095
Underbody Panel Right - 51758060096

Flex Disc - 26117610061
Hex Bolts (3) - 326117527475
Hex Nuts (3) - 37106789678
Torx Screws (3) - 26118607971

I will see how the car performs after fitting these and see what difference I can feel. The next step would be to fit the front F90 ARB and also the rear ARB. The F90 one is 32mm compared to the G30 24mm one on the front. The rear F90 one is 30mm compared to the 18mm on on the G30. This should (in theory and with the other parts) aid in making the car more stiffer and sharper as well as increasing rigidity. But I guess I'll only know if it was worthwhile once it's done.

I think the combination of the MSS HAS Kit, F90 front and rear reinforcements and the F90 ARB's should improve things. There are a whole host of other suspension components that can be changed out but I don't think I'm there yet... let's see how this goes.

If I can get the ARB's in time for when I fit the other parts, I'll get it done in one go, otherwise it can be done at a later stage. The good thing is, these brace parts or the exhaust don't need to be removed to fit the front or rear ARB's. Just deciding if I should go for the M5 or M5 Comp ones.

Apologies as I feel I have waffled on a little , but hopefully this might be of some use to someone who is looking to do the same.

[Junebug85]

Few of the parts are german order and should be at the dealer next week. I'll post up some initial pictures once I have picked them up

[CarbonShwarz]

Be interesting to hear how you get on with this!

While doing braces and M LCAs etc are common on 1-4 series, there doesn't seem to be a whole lot documented for the G30.

I also need to do the prop flex disc, got a noticeable vibration between 70-80 so would be good to hear if any of the other changes are worth doing a the same time. Sounds like it's a bigger job than I imagined to change.

[buddyboy]

Originally Posted by Junebug85

There's a few different threads about fitting F90 Braces/Reinforcements to the G30 540i and 550i, but I thought I'd start my own and try and document it from start to finish.

This all stemmed me having to replace the rear flex disc on the car. While looking at what the job would entail, I read that some of the under body panels and bracing would need to come off. Having a look on here and online, a few have fitted the F90 braces and rear reinforcements as an upgrade and feedback has been positive. There's more focus on the rear as the rear sub-frame is on bushings where as the front sub-frame is not, so it's more stiffer already.

The car is currently on MSS Height Adjustable Springs and this is the only suspension modification on the car, currently. This alone has been a big improvement over stock but I think there is still more improvements to be had.

So what was a task to just have the flex disc replaced has now escalated into sourcing a whole range of F90 parts.... I mean this is what car people do right!?

I placed an order for the below with a BMW dealer yesterday. I was able to get a decent enough discount from them.

F90 Cross Member - 33318064485
F90 Cross Strut/X Brace - 33318064893
F90 Strut Brace Front, Bulkhead - 51618075677
Bolts for cross member (8) - 07119907857
Bolts for cross strut (2) - 33308071664
Nuts for cross strut (2) - 33308073595
Underbody Panel Left - 51758060095
Underbody Panel Right - 51758060096

Flex Disc - 26117610061
Hex Bolts (3) - 326117527475
Hex Nuts (3) - 37106789678
Torx Screws (3) - 26118607971

I will see how the car performs after fitting these and see what difference I can feel. The next step would be to fit the front F90 ARB and also the rear ARB. The F90 one is 32mm compared to the G30 24mm one on the front. The rear F90 one is 30mm compared to the 18mm on on the G30. This should (in theory and with the other parts) aid in making the car more stiffer and sharper as well as increasing rigidity. But I guess I'll only know if it was worthwhile one it's done.

I think the combination of the MSS HAS Kit, F90 front and rear reinforcements and the F90 ARB's should improve things. There are a whole host of other suspension components that can be changed out but I don't think I'm there yet... let's see how this goes.

If I can get the ARB's in time for when I fit the other parts, I'll get it done in one go, otherwise it can be done at a later stage. The good thing is, these brace parts or the exhaust don't need to be removed to fit the front or rear ARB's. Just deciding if I should go for the M5 or M5 Comp ones.

Apologies as I feel I have waffled on a little , but hopefully this might be of some use to someone who is looking to do the same.

This is the definition of "sure while im in there", fair play! i was planning to do just the m5 anti roll bars but watching closely to see what your planned mods do for the handling of the g30 and might do similar

[Frozen Fractals]

I've retrofitted and have been driving the entire F90 suspension setup on my G30 540i xDrive for about 2.5 years. IMHO, the following in descending order is what I found to have the most profound impact in terms of driving dynamics.

1.) Springs/dampers
2.) Anti-roll/sway bars (31358074129 and 33558074131)
3.) Front tension strut (31107857017 and 31107857018)
4.) Rear toe arm (33308073973 and 33308073974)
5.) Rear cross strut (33318064893) and connecting member (33318064485)
6.) Front strut brace (51618075677)
7.) Front top wishbones (31108053331 and 31108053332) and bottom wishbones (31107857013 and 31107857014)
8.) Remaining components (e.g. rear camber link, rear subframe rubber mounts, rear differential rubber mount)

Basically, 1 > 2 >> 3 > 4 >> 5 > 6 > 7 >>> 8. If on a budget, just get 1 and 2, and maybe 3 and 4. The rest are nice to haves, but didn't make that drastic of a difference. More detail below.

1.) This mod made the largest positive impact to driving dynamics. I personally have the KW V3 coilovers fitted as it has adjustable compression and rebound settings, and also largely stiffens the suspension's handling while maintaining refinement (something that the cheaper options sacrifice on).
2.) The second most beneficial mod. This really cut down on the body roll at the small sacrifice of ride compliance.
3.) This really stiffened the steering response (a lot less "rubbery" feeling during high G-loads). Introduces a bit more feedback and NVH into the steering wheel.
4.) This made the rear much more planted/less squirrely when applying full throttle and launching (especially useful for the high torque on N63 or tuned B58). Unfortunately, this requires retrofitting the rear wheel hub assembly and consequentially, the rear spring strut assembly as well. There are suitable aftermarket options available (e.g. Hardrace) if you don't want to do this.
5.) Further improves the stiffness of the mid/rear chassis at the slight increase of NVH.
6.) Further improves the stiffness of the front chassis.
7.) Slightly improves the stiffness of the front suspension mainly during very hard cornering.
8.) Makes little to no noticeable difference.

I'll try and do a more thorough write up with some additional notes sometime in the near future.

[Junebug85]

Originally Posted by Frozen Fractals

I've retrofitted and have been driving the entire F90 suspension setup on my G30 540i xDrive for about 2.5 years. IMHO, the following in descending order is what I found to have the most profound impact in terms of driving dynamics.

1.) Springs/dampers
2.) Anti-roll/sway bars (31358074129 and 33558074131)
3.) Front tension strut (31107857017 and 31107857018)
4.) Rear toe arm (33308073973 and 33308073974)
5.) Rear cross strut (33318064893) and connecting member (33318064485)
6.) Front strut brace (51618075677)
7.) Front top wishbones (31108053331 and 31108053332) and bottom wishbones (31107857013 and 31107857014)
8.) Remaining components (e.g. rear camber link, rear subframe rubber mounts, rear differential rubber mount)

Basically, 1 > 2 >> 3 > 4 >> 5 > 6 > 7 >>> 8. If on a budget, just get 1 and 2, and maybe 3 and 4. The rest are nice to haves, but didn't make that drastic of a difference. More detail below.

1.) This mod made the largest positive impact to driving dynamics. I personally have the KW V3 coilovers fitted as it has adjustable compression and rebound settings, and also largely stiffens the suspension's handling while maintaining refinement (something that the cheaper options sacrifice on).
2.) The second most beneficial mod. This really cut down on the body roll at the small sacrifice of ride compliance.
3.) This really stiffened the steering response (a lot less "rubbery" feeling during high G-loads). Introduces a bit more feedback and NVH into the steering wheel.
4.) This made the rear much more planted/less squirrely when applying full throttle and launching (especially useful for the high torque on N63 or tuned B58). Unfortunately, this requires retrofitting the rear wheel hub assembly and consequentially, the rear spring strut assembly as well. There are suitable aftermarket options available (e.g. Hardrace) if you don't want to do this.
5.) Further improves the stiffness of the mid/rear chassis at the slight increase of NVH.
6.) Further improves the stiffness of the front chassis.
7.) Slightly improves the stiffness of the front suspension mainly during very hard cornering.
8.) Makes little to no noticeable difference.

I'll try and do a more thorough write up with some additional notes sometime in the near future.

Thanks for your reply and comments/notes - they are very much appreciated part numbers will/are very helpful too. I did see some of your posts on the other thread and that was what got me thinking about these changes.

One question, did you have to get alignment done on the car again, after fitting some of these components?

[Frozen Fractals]

Originally Posted by Junebug85

Thanks for your reply and comments/notes - they are very much appreciated part numbers will/are very helpful too. I did see some of your posts on the other thread and that was what got me thinking about these changes.

One question, did you have to get alignment done on the car again, after fitting some of these components?

100%! Definitely appreciate the wealth of knowledge in the community and I figured it's my turn to pay it forward. Tbh, I've been meaning to do a full write up a year or two ago, but life has always gotten in the way lol. C'est la vie...

Yes, you'll definitely need an alignment done after retrofitting anything that will modify camber or toe (caster is preset on our cars). This includes most components I mentioned above sans the chassis bracing (#5 and #6), anti-roll bars (#2) and rear subframe/differential bushings (#8).

[Junebug85]

Originally Posted by Frozen Fractals

100%! Definitely appreciate the wealth of knowledge in the community and I figured it's my turn to pay it forward. Tbh, I've been meaning to do a full write up a year or two ago, but life has always gotten in the way lol. C'est la vie...

Yes, you'll definitely need an alignment done after retrofitting anything that will modify camber or toe (caster is preset on our cars). This includes most components I mentioned above sans the chassis bracing (#5 and #6), anti-roll bars (#2) and rear subframe/differential bushings (#8).

It's always the way and trying to find the time is the hard thing even without a full write up, posts like your reply is very helpful to me and others looking to move in the direction you have.

I'm with you thanks again for the help

[Junebug85]

Had a call from the dealer earlier to say the parts were ready to collect...

I can see why those rear subframe bolts are set to 185nm... they're massive!

[PunkMan215]

Originally Posted by Junebug85

Had a call from the dealer earlier to say the parts were ready to collect...

I can see why those rear subframe bolts are set to 185nm... they're massive!

Hey did you get it installed how does it feel?

[Junebug85]

Originally Posted by PunkMan215

Hey did you get it installed how does it feel?

Not yet, just working on sourcing the front and rear antiroll bars. Once I have them I'll get everything installed together.

[Doctor X]

Originally Posted by Frozen Fractals

I've retrofitted and have been driving the entire F90 suspension setup on my G30 540i xDrive for about 2.5 years. IMHO, the following in descending order is what I found to have the most profound impact in terms of driving dynamics.

1.) Springs/dampers
2.) Anti-roll/sway bars (31358074129 and 33558074131)
3.) Front tension strut (31107857017 and 31107857018)
4.) Rear toe arm (33308073973 and 33308073974)
5.) Rear cross strut (33318064893) and connecting member (33318064485)
6.) Front strut brace (51618075677)
7.) Front top wishbones (31108053331 and 31108053332) and bottom wishbones (31107857013 and 31107857014)
8.) Remaining components (e.g. rear camber link, rear subframe rubber mounts, rear differential rubber mount)

Basically, 1 > 2 >> 3 > 4 >> 5 > 6 > 7 >>> 8. If on a budget, just get 1 and 2, and maybe 3 and 4. The rest are nice to haves, but didn't make that drastic of a difference. More detail below.

1.) This mod made the largest positive impact to driving dynamics. I personally have the KW V3 coilovers fitted as it has adjustable compression and rebound settings, and also largely stiffens the suspension's handling while maintaining refinement (something that the cheaper options sacrifice on).
2.) The second most beneficial mod. This really cut down on the body roll at the small sacrifice of ride compliance.
3.) This really stiffened the steering response (a lot less "rubbery" feeling during high G-loads). Introduces a bit more feedback and NVH into the steering wheel.
4.) This made the rear much more planted/less squirrely when applying full throttle and launching (especially useful for the high torque on N63 or tuned B58). Unfortunately, this requires retrofitting the rear wheel hub assembly and consequentially, the rear spring strut assembly as well. There are suitable aftermarket options available (e.g. Hardrace) if you don't want to do this.
5.) Further improves the stiffness of the mid/rear chassis at the slight increase of NVH.
6.) Further improves the stiffness of the front chassis.
7.) Slightly improves the stiffness of the front suspension mainly during very hard cornering.
8.) Makes little to no noticeable difference.

I'll try and do a more thorough write up with some additional notes sometime in the near future.

this is great information.

I think my front tension struts have gone out.. when i apply breaks my car shakes a good amount. I don't think its my breaks

[Junebug85]

Parts Update

The front and rear F90 M5 Comp antiroll bars/sway bars got delivered today. Ended up getting new screws/bolts too as it's recommended they are renewed as they are torqued to 100nm.

I was able to get them from a main dealer with really good discount I also bought new F90 front end links and new G30 rear end links fro. AutoDoc

Looking forward to having all the parts fitted in the coming weeks.

Updated Parts List

F90 Comp Front Sway Bar - 31358074129
F90 Comp Rear Sway Bar - 33558074131
F90 Front End Links - 31308091462
G30 Rear End Links - 33506861482
F90 Cross Member - 33318064485
F90 Cross Strut/X Brace - 33318064893
F90 Strut Brace Front, Bulkhead - 51618075677
Bolts for cross member (8) - 07119907857
Bolts for cross strut (2) - 33308071664
Nuts for cross strut (2) - 33308073595
Underbody Panel Left - 51758060095
Underbody Panel Right - 51758060096
Flex Disc - 26117610061
Hex Bolts (3) - 326117527475
Hex Nuts (3) - 37106789678
Torx Screws (3) - 26118607971

[ashmostro]

This is epic. Looking forward to the installation updates!

[Junebug85]

Update: just waiting on 1 more piece of the 'while I'm upgrading' puzzle then I can get the car booked in for these enhancements/upgrades.

I did notice that I have a dent in my driver side rear Camber Control Arm/Link. I think it was when I drove over a large rock that was unavoidable in the middle of the road (it did make quite a large noise which would explain it)... any how - £372 later, I now have more parts to fit along with new nuts and bolts. The rock also damaged the cover underneath. It kind if did its job as the damage was minimal to a degree.

The car will also need to have alignment done after fitting this new arm. A chance to maybe get it dialled in for a fast road setup.

I'm only doing the one side as the part in question doesn't have any bushings on it and is just all one piece with no moveable parts on it.

[Junebug85]

Front Upper F90 Bulkhead Strut Brace fitted... (first of the F90 Braces/Reinforcement parts fitted today)

This was a straight fitment swap with the G30 one... you do need to remove a few bits first though... side trim covers, wiper arms (using the correct tool) and then trim piece under the windscreen - this then gives you access to all the bolts for the brace.

The F90 one is made from thick aluminium and is very robust and strong - looks like it's laser cut or with water jets maybe? The G30 one is made from a stamped and folded aluminium sheet - which is a little on the thin side (looks flimsy compared to the F90 one &#128516.

I'm not expecting a massive difference with just this piece, but once the other bits are on, they should all contribute to a more sharper driving feel and an improvement in handling.

I still have a few underbody braces and reinforcement parts left to fit, including front and rear F90 anti roll bars... Just waiting on one more part which has been on back order for a while - getting annoying now as it's holding things up.

[ashmostro]

The epicness cannot be overstated

[23109VC]

What was the cost of those braces and WHAT kind of difference did you notice??? I have an M550

[Junebug85]

Originally Posted by 23109VC

What was the cost of those braces and WHAT kind of difference did you notice??? I have an M550

All the braces were around £650 with all the installation hardware and tank cover parts.

The sway/anti roll bars were around £670 with all the installation hardware.

I bought everything new from a main dealer. There are used parts out there but most of them seem to from crash damaged cars. I didn't want to chance it so just bought everything new. I haven't been able fit the rest of the parts, I'm waiting on a Remus midpipe that's been on back order for a while. Once that lands, I'll be able to get on with installing all these.

[PaPaDrew G30]

This is the type of stuff I LOVE reading about. Keeps me interested in doing this type of stuff to mine!

[Dasky_spas]

33318064893

How does this cross brace get put in? Seems like the rear subframe has to get dropped down/supported. In other words, seems quite involved but maybe I'm wrong.

[Junebug85]

Originally Posted by Dasky_spas

33318064893

How does this cross brace get put in? Seems like the rear subframe has to get dropped down/supported. In other words, seems quite involved but maybe I'm wrong.

The 2 rear subframe screws/bolts get replaced by these 2 new ones and torqued to 185nm. They have a little thread on the bottom that the X Brace goes onto. It's then secured with the 2 nuts