[Frozen Fractals]

Originally Posted by 430Scud

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?

Thanks for the update! Which parts did you end up buying? The rear cross and x braces?

The (4) M8x30 bolts for the rear cross brace are 30 Nm. The (4) M8x30 bolts for the rear x brace are also 30 Nm. BMW also recommends applying Loctite on the threads for these (8) M8x30 bolts. The (2) M14x64 bolts that goes on the rear subframe mount are 185 Nm. The (2) M10 nuts for the rear x brace are 62 Nm.

If you don't mind, can you take pics during the install process? I'd be curious to see what the process is like as I plan on doing this too in the near future.

[430Scud]

Originally Posted by Frozen Fractals

Thanks for the update! Which parts did you end up buying? The rear cross and x braces?

The (4) M8x30 bolts for the rear cross brace are 30 Nm. The (4) M8x30 bolts for the rear x brace are also 30 Nm. BMW also recommends applying Loctite on the threads for these (8) M8x30 bolts. The (2) M14x64 bolts that goes on the rear subframe mount are 185 Nm. The (2) M10 nuts for the rear x brace are 62 Nm.

If you don't mind, can you take pics during the install process? I'd be curious to see what the process is like as I plan on doing this too in the near future.

Yes, the cross brace and X brace. Will be installing in the next week or so. Thanks for the torque numbers, that makes things much easier. Will definitely take plenty of photos. It will be difficult to get them, as I will probably be doing this on jack stands, unless I drive to a friends house with a lift.

[430Scud]

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

Please reconfirm the underbody panel part numbers. I special ordered them and I clearly have the wrong items. I trusted Frozen Fractals who summarized the parts list, but he obviously got it wrong in post #8. Hopefully he can go back and edit the error.

Looks like the correct parts are


No. Description Supp. Qty From Up To Part Number Price Notes
01 Undershield for tank, left 1 51758060095
01 Undershield for tank, right 1 51758060096

[430Scud]

Originally Posted by Frozen Fractals

Thanks for the update! Which parts did you end up buying? The rear cross and x braces?

The (4) M8x30 bolts for the rear cross brace are 30 Nm. The (4) M8x30 bolts for the rear x brace are also 30 Nm. BMW also recommends applying Loctite on the threads for these (8) M8x30 bolts. The (2) M14x64 bolts that goes on the rear subframe mount are 185 Nm. The (2) M10 nuts for the rear x brace are 62 Nm.

If you don't mind, can you take pics during the install process? I'd be curious to see what the process is like as I plan on doing this too in the near future.

Just finished. Pictures in a moment.

A couple tips on the fasteners. To remove the stock cross brace, you need an EP10 Torx socket.
The M14x64 subframe bolts require a 21mm deep socket to install the new replacements.
The two M10 nuts that secure the X brace to the new subframe bolts require a 16mm socket

Other bolts are standard sizes in any normal socket set.

[430Scud]

So this took me about 2 hours using jack stands. I'm pretty slow and methodical and not one to rush a job. I also only use hand tools, no powered ratchets or wrenches. If I had the correct under panels, that would have only added 10 or 15 minutes to the job. I'm sure a shop with a two post lift, and powered tools could easily do this in one hour. You save a ton of time not having to slide under and back out from the car all the time...

This is a pretty basic parts swap. Compared to the chassis braces used on the E39 and E60 M5s that I am familiar with, this is much more robust. I did not weigh it, but the X brace piece is not insignificant in weight, even though made of aluminum.

Thanks to Frozen Fractals for the torque values and where red Loctite is required. The new subframe bolts have red Loctite on them where the nuts go on to secure the X brace.

Here are the pictures. I did not take pictures of every step.
But the basic order of things:
1) Remove the plastic under trays on each side
2) Remove the stamped aluminum center cross brace
3) Install new machined aluminum cross brace, but leave out the four bolts that will attach the X brace (all 8 bolts that secure the cross brace you are to apply a drop of red Loctite per Frozen Fractals.
4) Remove the two rear subframe bolts and install the new bolts (you will need a decent sized breaker bar to loosen the two bolts) Per Frozen Fractals, they are set at 185NM, I don't doubt that.
5) Install the X brace (four bolts up front (remember the red Loctite on the four front ones that go through the cross brace), two nuts in the rear)
6) Install the new under tray panels

[Lancelot]

Originally Posted by 430Scud

Please reconfirm the underbody panel part numbers. I special ordered them and I clearly have the wrong items. I trusted Frozen Fractals who summarized the parts list, but he obviously got it wrong in post #8. Hopefully he can go back and edit the error.

Looks like the correct parts are


No. Description Supp. Qty From Up To Part Number Price Notes
01 Undershield for tank, left 1 51758060095
01 Undershield for tank, right 1 51758060096

Here are the correct part numbers:

[Frozen Fractals]

Thanks, 430Scud!

My apologies on getting the wrong P/N as I too was confused on which one was needed. Thanks for clarifying the correct one, I will modify my post for future reference.

Also, I do appreciate the quick writeup and pictures! Definitely looking forward to your thoughts on improved handling characteristics, etc. I presume you haven't retrofitted the rest of the F90 suspension yet?

Some questions on the install process:

- Did you support the subframe when removing the front two bolts or are the three remaining bolts sufficient to hold it up?
- Is it possible to modify the existing underbody panelling to accomodate the new X brace?

[430Scud]

Originally Posted by Frozen Fractals

Thanks, 430Scud!

My apologies on getting the wrong P/N as I too was confused on which one was needed. Thanks for clarifying the correct one, I will modify my post for future reference.

Also, I do appreciate the quick writeup and pictures! Definitely looking forward to your thoughts on improved handling characteristics, etc. I presume you haven't retrofitted the rest of the F90 suspension yet?

Some questions on the install process:

- Did you support the subframe when removing the front two bolts or are the three remaining bolts sufficient to hold it up?
- Is it possible to modify the existing underbody panelling to accomodate the new X brace?

No, and I have no intention of doing any further suspension changes at this time. I have DHP.

No additional support needed.

I don't believe so, if you want a nice, integrated look. I suppose you can use tin snips and trim out the existing panel...but I would not even consider that.
You WILL lose about 2 or 3 CM of ground clearance and the old panel will probably be stretched trying to clear it.

[430Scud]

Finally did some driving last Thursday evening. About 60 miles of highway, city, country roads. On the highway or driving in the city, there is little difference noticed. While it perceptibly "felt" more stiff or firmer in the rear, it could be just in my head I will admit.

But out on country roads, or whipping around a quick 90 degree turn the car definitely felt more controlled and I could actually feel the rear tires biting and building up some g forces. The car felt more planted with more feedback. I like it a lot. There are similar parts on the E39 M5 I retrofitted on my E39 540 M-Sport, but this feels more significant.

I have the DHP suspension option, and never been particularly happy with it. Especially when on familiar roads with sharp turns. I felt the rear wheel steering felt odd and you got little feedback from the rear tires, you just never felt what was going on in back... with most cars you can feel the rear tires bite and build g forces in a turn...with rear wheel steering the car remains flat and the rear just follows and whips around the corner with no drama. Neat, but uninspiring. Now I have some feel of the rear, and it is great. You feel much more in control of the car. I'm a lot happier with this car now, then I was before...seriously. I was considering dumping the car for one without DHP. No longer considering that now.

I don't have the under body panels for the gas tanks installed yet, as I am still waiting for them from Germany...perhaps in a couple more weeks. Won't be driving in the rain until they are in. Was surprised to find a decent accumulation of mud inside the existing ones when removed. My car only has 10k miles and the underside is pretty clean otherwise. (granted I bought the car with 6700 miles, so previous owner may have driven over some local mtn passes in British Columbia where the car originated from)

[Lancelot]

Thanks for your write up!
I agree with what you say

I did not know the car well enough before this mod to have a real before/after feel, but i've spent the last two weeks on vacation in the mountains, the car was a blast, so well in control at every turn!

I also like the monoballs on the front arms a lot, there's no « dead » center zone, it gives precision to steering.
No NVH issues now that i'm on non runflats.

[PetieD 7]

Hello all,

I have been thinking about getting Hardrace engine bay strut brace recently, and was wondering if this particular part will provide immediate difference (or greatly improves) in handling of this vehicle (besides enhancing the looks of the engine bay). Welcome your comment(s) and opinion(s)!

https://www.hardrace-europe.com/engi...ace-q0659.html

[Lancelot]

Originally Posted by PetieD 7

Hello all,

I have been thinking about getting Hardrace engine bay strut brace recently, and was wondering if this particular part will provide immediate difference (or greatly improves) in handling of this vehicle (besides enhancing the looks of the engine bay). Welcome your comment(s) and opinion(s)!

https://www.hardrace-europe.com/engi...ace-q0659.html

Well it should, i haven't tried because it doesn't fit the 8 cyl engine of the m550i.

i went with the m5 brace which is sturdier than the m550i, although it remains a hinged design.

[430Scud]

I am suspect that this rear brace will do anything....
https://www.hardrace-europe.com/rear...ace-q0479.html

Look at where it attaches, and what it is attached to. It attaches to an already rigid structure. Am I missing something here??

[23109VC]

Originally Posted by 430Scud

I am suspect that this rear brace will do anything....
https://www.hardrace-europe.com/rear...ace-q0479.html

Look at where it attaches, and what it is attached to. It attaches to an already rigid structure. Am I missing something here??

What was the total cost to install this M5 sub brace? All parts? If I had someone install it for me what would I expect to pay at a reputable shop?

I'm also thinking of getting hard races rear sway bar… I read another review from a different BMW for him or a guy installed it and said it made big improvements and turn in and cornering

Thx

[choppedliver]

Originally Posted by 23109VC

What was the total cost to install this M5 sub brace? All parts? If I had someone install it for me what would I expect to pay at a reputable shop?

I'm also thinking of getting hard races rear sway bar… I read another review from a different BMW for him or a guy installed it and said it made big improvements and turn in and cornering

Thx

I’m thinking to do the following;
1) mono ball… I expect this makes a massive difference to the steering as others mentioned.
2) Hardrace rear brace
3) Hardrace rear sway bar
4) Hardrace front brace
5) X-brace
6) M5 strut brace - need to research this

I gather with AWD you can’t add a front sway bar or it seems Hardrace don’t sell one. Does one exist?

I’m in Australia and might grab the Hardrace stuff as it’s pretty cheap here.

[choppedliver]

Digging on the internet I stumbled on this.

https://parts.bmwsydney.com.au/p/BMW...All%20Products

I wonder if that would fit our cars? I’m confused by the picture and the description being for right only.

Does anyone have a link to an M5 brace?

[Lancelot]

This one is the secondary part from strut tower to front, it's got a hole in the middle to fit the admission pipes, the 530hp m550i has it, and it doesn't fit the 462 hp m550i.

I fitted the main strut brace from m5 however which fits very well on all m550is

[Lancelot]

Originally Posted by choppedliver

I gather with AWD you can’t add a front sway bar or it seems Hardrace don’t sell one. Does one exist?

Try the M5 ones I suspect they fit, although I don't think anyone has tried yet (or reported here)

[choppedliver]

Originally Posted by Lancelot

This one is the secondary part from strut tower to front, it's got a hole in the middle to fit the admission pipes, the 530hp m550i has it, and it doesn't fit the 462 hp m550i.

I fitted the main strut brace from m5 however which fits very well on all m550is

Ah, I get it now.

https://parts.bmwsydney.com.au/showA...sembly=9052513

I just looked and the 2020 M550i has the left and right braces. What it doesn't appear to have is the main brace, thought it looks like I need to remove a few things to be able to see clearly.

I must say it's pretty cheap.

Thanks

[choppedliver]

I had another look on that site and the rear M5 stabilizer bar is unavailable. But the front for the M5 is available. Not terribly cheap but begs the question if it will work well with a Hardrace rear stabilizer bar. Be better to go full m5 i would think.

[Lancelot]

It's probably better to have a balanced set from M5, looks like it's about 600 for the pair, similar to aftermarket parts - not sure where you can source it for Australia, ebay can be a place to start:
https://www.ebay.com.au/itm/303776060518
https://www.ebay.com.au/itm/304080599906

[choppedliver]

Originally Posted by 430Scud

I am suspect that this rear brace will do anything....
https://www.hardrace-europe.com/rear...ace-q0479.html

Look at where it attaches, and what it is attached to. It attaches to an already rigid structure. Am I missing something here??

I was thinking the same thing and wondered if the M5 has something similar from the factory and it doesn’t. Seems like a waste of money. I think the front suspension brace, strut brace, x brace and sway bars are likely the best options. I’m concerned the mono balls will make the ride harsh.