[Lancelot]

Hi all

Just fitted these on my m550i

- Dinan monoballs on thrust arms

- f90 rear reinforcements, rear tunnel connecting plate and cross brace connecting tunnel plate with rear subframe.
Part list:
M5 Reinforcement for body, rear: https://www.realoem.com/bmw/enUS/sho...diagId=51_8894 - €200 connecting member + €125 cross brace + ~€50 for various bolts required
M5 Underbody paneling, rear: https://www.realoem.com/bmw/enUS/sho...92#51758060095 - €60 x 2


I had previously fitted the f90 front strut bar.


Dinan product is top notch, superb quality. Expensive too.

I have only done 20km back from the shop, city driving on bad roads mostly, so will report back later with more distance behind.
But it's immediately clear that the steering vagueness that was bothering me is gone. steering feedback is night and day, along with expected increase in harshness - no noise or vibration but joints or cracks on the road are much more noticeable to me. I don't think that would be bothering passengers though, and i was prepared to trade this for steering precision so i'm fine with it.

[Lancelot]

Quick update after the weekend

Spirited driving on Sunday morning:
Really nice, the steering is better and makes it even more enjoyable; a bit harsh on cracks and bumps though.

Long haul highway trip :
vibrations coming up from the road, annoying after 1 hour, although no other familiy member mentionned it, and perhaps because part of the vibration comes back though steering wheel and center console.

Do you think runflat tyres transmit significantly more vibrations / harshness than non run flats?

They have to transmit more but I wonder if it's worth switching to non RFT to reduce this?

thoughts?

[Lancelot]

Update #2, now on Michelin PS4, non runflats tyres, ride is good now - quiet, and not harsh, the difference is massive with runflats.

Feels like I'm talking to myself on this thread...
I'm sure that will be useful to someone one day

[choppedliver]

This is useful info. I will likely combine with hardrace subframe brace and sway bar.

Is there a benefit to the underbody panelling?

Thanks

[Lancelot]

Originally Posted by choppedliver

This is useful info. I will likely combine with hardrace subframe brace and sway bar.

Is there a benefit to the underbody panelling?

Thanks

Underbody paneling is to accommodate the X brace that the m550i doesn't have, the original panels wouldn't have the indent

[choppedliver]

Originally Posted by Lancelot

Underbody paneling is to accommodate the X brace that the m550i doesn't have, the original panels wouldn't have the indent

Makes sense. Thanks.

Did you consider the hard race rear subframe brace as well?

[Lancelot]

Originally Posted by choppedliver

Makes sense. Thanks.

Did you consider the hard race rear subframe brace as well?

No that would be beyond my needs, as i don't track the car, i want a bit more rigidity to improve handling but the car is basically very good already.

[Frozen Fractals]

Hey! Thanks for posting this. I've been considering upgrading the cross bracing after doing the full M5 suspension (sans the rear subframe bushings).

Did you notice any appreciable performance improvements from the rear bracings? The cost is quite high at ~$600 USD. Do you think it is a worthwhile upgrade?

Also, to confirm, the below P/Ns are all I need to retrofit onto a G30 540i xDrive?

(1) Cross member: 33-31-8-064-485
(8) Bolt for cross member: 07-11-9-907-857
(1) Cross strut: 33-31-8-064-893
(2) Bolt for cross strut: 33-30-8-071-664
(2) Nut for cross strut: 33-30-8-073-595
(1) Underbody paneling, tank, left: 51-75-8-060-095
(1) Underbody paneling, tank, right: 51-75-8-060-096

Looking at your underbody (from your second picture) is the aluminum rectangular piece part of either cross member (33-31-8-064-485 or 07-11-9-907-857)? I don't think I have that piece on my 540i xDrive.

Thanks!

[Lancelot]

Generally speaking there is an increase in rigidity, though not by much. Was it worth 600? I don't know for sure. But i'm satisfied with it.

I wasn't ready to do more than these bolt on though as the car is mainly used for traveling and I expect it to retain the spirit of the M550i - this dual purpose car, comfortable saloon for traveling, guided missile when you want it to be

I learned my lesson on the F30, where everyone was raving about coilovers which in real life were making the car both hard to live with and less stable (= lower chassis performance) due to excessive stiffness.

I like your approach though, I believe changing the G30 suspension parts with F90 can bring noticeable handling improvements, without compromising drivability and stability, I don't think I would go for KW coilovers though.

The rectangle piece is wielded to the cross strut, though that doesn't show on realoem diagram.

[Frozen Fractals]

Originally Posted by Lancelot

Generally speaking there is an increase in rigidity, though not by much. Was it worth 600? I don't know for sure. But i'm satisfied with it.

I wasn't ready to do more than these bolt on though as the car is mainly used for traveling and I expect it to retain the spirit of the M550i - this dual purpose car, comfortable saloon for traveling, guided missile when you want it to be

I learned my lesson on the F30, where everyone was raving about coilovers which in real life were making the car both hard to live with and less stable (= lower chassis performance) due to excessive stiffness.

I like your approach though, I believe changing the G30 suspension parts with F90 can bring noticeable handling improvements, without compromising drivability and stability, I don't think I would go for KW coilovers though.

The rectangle piece is wielded to the cross strut, though that doesn't show on realoem diagram.

Thanks for your notes and observations! The insight is much appreciated.

I actually have to replace my stock OEM rear cross brace due to hitting some road debris resulting in some damage. The OEM one is ~$50-60, so spending 10x is definitely a hard swallow. However, since I'm already down that rabbit hole, it is something that I am heavily considering doing Is the parts list I posted above exhaustive of all I need to do the rear bracing retrofit?

Have you looked into the cross bracing for the front? It seems like the engine bay has different cross bracing specific to M too. https://bimmercat.com/bmw/en/search/...M5/USA/51_8930



I'm curious as to why you wouldn't consider KW? My reasoning for going down that route was mainly due to availability as the KW V3 was the only real solution available for the G30 at the time. I messaged Bilstein and they didn't have their B12 or B16 kit for the G30 at the time (and I still think they don't). The $2400 price of admission for the V3 is definitely a little rich and in hindsight if KW made the V2 kit, I would've went with that as I don't need the granularity of adjusting rebound and compression separately. However, I think the KW V3 strikes a nice balance between compliance on larger bumps and tightness when cornering. I don't think it's the best setup there is, but given what's available on the market, I don't think it's far from it. In any case, it is miles ahead of the M Sport springs and dampers.

The car is most definitely firmer and less compliant, but personally I was looking for that edge that the stock M Sport suspension setup was lacking. I recently took it on a 5000+ mile cross country road trip with my parents who are in their late 50s (me being in my 20s) and never once did they complain about the ride. Overall, with the KW V3 coilovers and the F90 M5 Competition front/rear control arms, I think my G30 sits around 80% on the spectrum between luxury barge and full-on sports car. And given my goals, this setup has succeeded with flying colors!

[Joe-BMW33]

Originally Posted by Lancelot

Hi all

Just fitted these on my m550i

- Dinan monoballs on thrust arms

- f90 rear reinforcements, rear tunnel connecting plate and cross brace connecting tunnel plate with rear subframe.
Part list:
M5 Reinforcement for body, rear: https://www.realoem.com/bmw/enUS/sho...diagId=51_8894 - €200 connecting member + €125 cross brace + ~€50 for various bolts required
M5 Underbody paneling, rear: https://www.realoem.com/bmw/enUS/sho...92#51758060095 - €60 x 2


I had previously fitted the f90 front strut bar.


Dinan product is top notch, superb quality. Expensive too.

I have only done 20km back from the shop, city driving on bad roads mostly, so will report back later with more distance behind.
But it's immediately clear that the steering vagueness that was bothering me is gone. steering feedback is night and day, along with expected increase in harshness - no noise or vibration but joints or cracks on the road are much more noticeable to me. I don't think that would be bothering passengers though, and i was prepared to trade this for steering precision so i'm fine with it.

Forgive my ignorance, but there was a 2017 M550 offered in France (Europe)?

Some general comments, yes, as you discovered, runflat tires transfer much more of the road imperfections to the suspension and steering. Summer softy non-runflats ride like butter.

There is always a fine line between comport and performance. It seems you are a bit underwhelmed with the vibrations and harshness of your upgrades even though you can corner like a track car. I love the stock M550 for it's ability to ride smoothly and handle adequately.

[Lancelot]

Yes i suppose it was introduced earlier in Europe, mine was first on the road in May 2017.

You're right the stock m550i is well balanced and I'm wary of throwing off this balance!

[Lancelot]

Originally Posted by Frozen Fractals

Thanks for your notes and observations! The insight is much appreciated.

I actually have to replace my stock OEM rear cross brace due to hitting some road debris resulting in some damage. The OEM one is ~$50-60, so spending 10x is definitely a hard swallow. However, since I'm already down that rabbit hole, it is something that I am heavily considering doing Is the parts list I posted above exhaustive of all I need to do the rear bracing retrofit?

Have you looked into the cross bracing for the front? It seems like the engine bay has different cross bracing specific to M too. https://bimmercat.com/bmw/en/search/...M5/USA/51_8930



I'm curious as to why you wouldn't consider KW? My reasoning for going down that route was mainly due to availability as the KW V3 was the only real solution available for the G30 at the time. I messaged Bilstein and they didn't have their B12 or B16 kit for the G30 at the time (and I still think they don't). The $2400 price of admission for the V3 is definitely a little rich and in hindsight if KW made the V2 kit, I would've went with that as I don't need the granularity of adjusting rebound and compression separately. However, I think the KW V3 strikes a nice balance between compliance on larger bumps and tightness when cornering. I don't think it's the best setup there is, but given what's available on the market, I don't think it's far from it. In any case, it is miles ahead of the M Sport springs and dampers.

The car is most definitely firmer and less compliant, but personally I was looking for that edge that the stock M Sport suspension setup was lacking. I recently took it on a 5000+ mile cross country road trip with my parents who are in their late 50s (me being in my 20s) and never once did they complain about the ride. Overall, with the KW V3 coilovers and the F90 M5 Competition front/rear control arms, I think my G30 sits around 80% on the spectrum between luxury barge and full-on sports car. And given my goals, this setup has succeeded with flying colors!

While i do think the comfort mode is a bit boat like, the sports mode is well contained and i'm not sure how that could be better, with the dynamic handling it corners really well thanks to active roll bars and rear wheel steering, so i'm happy

[Frozen Fractals]

Originally Posted by Lancelot

While i do think the comfort mode is a bit boat like, the sports mode is well contained and i'm not sure how that could be better, with the dynamic handling it corners really well thanks to active roll bars and rear wheel steering, so i'm happy

Glad you are happy with the results! I think I am going to move forward with adding the rear cross bracing.

How was the install? I think the rear cross brace should be easy (direct replacement of the stock one). However, the x-brace will be a bit harder, since it requires removal of the left and right underbody paneling. Also, the x-brace requires installation of two (seemingly very long) bolts (33308071664) which does not exist on the G30. I presume these bolts just go right in after removing the underbody paneling? There is no need to create new threading or remove other components?

[Mach550]

I can't tell, does your car have the dynamic handling package? Ordered it with mine and wondering if there is an improvement without any excessive drawbacks like a harsher ride.

[Lancelot]

These bolts take the place of the G30 rear subframe bolts, see part #8 in diagram https://www.realoem.com/bmw/enUS/sho...diagId=33_1976

It's really plug and play

[Frozen Fractals]

Originally Posted by Lancelot

These bolts take the place of the G30 rear subframe bolts, see part #8 in diagram https://www.realoem.com/bmw/enUS/sho...diagId=33_1976

It's really plug and play

Thanks! Makes sense that the x-brace will bolt to the rear subframe carrier to add rigidity!

[430Scud]

Originally Posted by Lancelot

No that would be beyond my needs, as i don't track the car, i want a bit more rigidity to improve handling but the car is basically very good already.

Great thread, thank you for starting this. I just ordered the rear reinforcements online for $645.27 on mybimmerparts.com, with free shipping and no sales tax.

I did a similar upgrade on my E39 540 M-Sport many years ago, adding the M5 "traction rods" which similarly tied the rear subframe to the main chassis with steel rods. It was designed to reduce axle hop on hard acceleration, but I noticed increased rear roll stiffness during spirited cornering. And as suspected, no increase in harshness or downsides with the addition (other than weight of a few pounds).

On the front thrust arms, I used (and continue to use) the Meyle solid thrust arm bushings on my E39, over the oem liquid filled bushings. Much longer wearing, with minimal increase in harshness. I am unsure I am prepared to go to mono balls, but appreciate your feedback on them.

BTW, any pictures or comments on what front bracing or reinforcements you are using? I did a Strong Strut front strut brace on my E39, but found no noticeable improvement.

Thank you again.

[Frozen Fractals]

Originally Posted by 430Scud

Great thread, thank you for starting this. I just ordered the rear reinforcements online for $645.27 on mybimmerparts.com, with free shipping and no sales tax.

I did a similar upgrade on my E39 540 M-Sport many years ago, adding the M5 "traction rods" which similarly tied the rear subframe to the main chassis with steel rods. It was designed to reduce axle hop on hard acceleration, but I noticed increased roll stiffness during spirited cornering. And as suspected, no increase in harshness or downsides with the addition (other than weight of a few pounds).

On the front thrust arms, I used (and continue to use) the Meyle solid thrust arm bushings on my E39, over the oem liquid filled bushings. Much longer wearing, with minimal increase in harshness. I am unsure I am prepared to go to mono balls, but appreciate your feedback on them.

BTW, any pictures or comments on what front bracing or reinforcements you are using? I did a Strong Strut front strut brace on my E39, but found no noticeable improvement.

Thank you again.

Front bracing on G30 is equivalent to F90. G30/F90 has a solid aluminum stiffening/skid-plate which stiffens the front subframe. Further, the front subframe is not riding on bushings like the rear is, so it is inherently already very stiff to begin with. (Technically, F90 has different front strut brace, but I am unsure if this will make any difference to replace on G30.)

I think improvements in G30 can be had by fitting stiffer front anti-roll/sway bars (e.g. F90 Competition or aftermarket). You can also fit the front tension strut, lower wishbone and upper wishbone for increased bushing stiffness, negative camber and caster. On my G30 this made a world of difference with improving steering response and allowing my front end to be extremely planted even when cornering extremely aggressively. If you can find used parts, it will decrease the cost significantly. I believe I paid around $2k USD for entire F90 front-end suspension (including the swivel bearing and wheel bearing for retrofitting the F90 brakes on my G30).

I promised a few on the forum that I would do a full write-up of my retrofit, but I just haven't had the time with personal life and work getting in the way. Hopefully, in the coming weeks I will get some chance to do the write-up as I feel like many are interested in hearing about the process and outcomes (spoiler alert: it really transforms the G30 into a surprisingly capable track weapon!).

[Lancelot]

Originally Posted by 430Scud

BTW, any pictures or comments on what front bracing or reinforcements you are using? I did a Strong Strut front strut brace on my E39, but found no noticeable improvement.

Thank you again.

I'm glad it's useful

I also retrofitted the front strut bar from F90, it really is bolt-on, except you need to remove the wipers to access the bolts on the firewall, which requires a specific wiper removal tool (~$10) to access below the plastic trims.

It made a slight improvement; I'll post some pics later.

[430Scud]

BTW, mybimmerparts.com called me yesterday and said the connecting member was not in stock in the USA and would have to be ordered from Germany...could take up to three weeks. They also advised that the cross strut is large/bulky enough that they may have to add a shipping charge (normally they ship free). I will know more in three weeks when they package everything up and determine if they will surcharge me.

[430Scud]

Originally Posted by 430Scud

Great thread, thank you for starting this. I just ordered the rear reinforcements online for $645.27 on mybimmerparts.com, with free shipping and no sales tax.

I did a similar upgrade on my E39 540 M-Sport many years ago, adding the M5 "traction rods" which similarly tied the rear subframe to the main chassis with steel rods. It was designed to reduce axle hop on hard acceleration, but I noticed increased rear roll stiffness during spirited cornering. And as suspected, no increase in harshness or downsides with the addition (other than weight of a few pounds).

On the front thrust arms, I used (and continue to use) the Meyle solid thrust arm bushings on my E39, over the oem liquid filled bushings. Much longer wearing, with minimal increase in harshness. I am unsure I am prepared to go to mono balls, but appreciate your feedback on them.

BTW, any pictures or comments on what front bracing or reinforcements you are using? I did a Strong Strut front strut brace on my E39, but found no noticeable improvement.

Thank you again.

Received all the parts (special order from Germany) in roughly three weeks, including shipping time. Unfortunately, the seller had to charge me an additional $70 due to oversize/weight of items. Total came to $715.00

So I am ready to install....anyone know the torque values of the various fasteners? Or where I can look them up?