[dape90]

Hi All,

Can someone tell me what kind of result I could expect from fitting the F22 rear suspension brace on my MY 2015 F20 M135i (the one that goes underneath the car).

I keep reading a lot about people doing this mod on their cars but without a clear description as to what the difference is.

Also, does it affect the warranty in any way?

Thank you all.

D

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[AndyKnight]

I think it's the f21 brace you are talking about, I.e. putting the 3 door underbody brace on the 5 door. From what I have read it tightens the rear end up reducing chassis flex. I'm somebody who has done it will be along to enlighten us lol

 

[dape90]

I think it's the f21 brace you are talking about, I.e. putting the 3 door underbody brace on the 5 door. From what I have read it tightens the rear end up reducing chassis flex. I'm somebody who has done it will be along to enlighten us lol

Yes, thank you for the correct. The f21 brace is what I meant.

I just wanted to know if it's worth it and the warranty implications.

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[br0wny]

I'm sure Blind Pugh has knowledge know this

 

[Quadrapete]

I'd be interested to know how much the brace costs too

 

[DFKMT]

I'm also interested and I'm sure I came across a thread that had all the part numbers you need too.

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[Paul CS]

Fitted.

Paul

 

[dape90]

Fitted.

Paul

Hi Paul,

On your five door right?

How much was this and has it affect your warranty?

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[Paul CS]

Yep 5 door. I think all the bits cost about £200. Zero effect on warranty I'd say, but I'm sure I'll be challenged on that. I won't tell BMW you don't.

Paul

 

[Paul CS]

 

[marco_polo]

Yep 5 door. I think all the bits cost about £200. Zero effect on warranty I'd say, but I'm sure I'll be challenged on that.

I guess technically you could invalidate your suspension warranty, but I'd be very impressed if any Techie noticed the braces as additional.

Mine went in for an oil change, and they didn't even notice the TMC, let alone the M4 LCA's or M235i springs!

 

[Paul CS]

I was going to keep it a secret but I have a special agreement that I can do anything I want and they won't question it. Now I will have to shoot you all.

 

[Fong]

Looks good Paul. How did the addition of the brace change the cars handling? Is it noticeable?

 

[dape90]

Does anyone know why this is on the three door and not the five door also as standard.
It give the impression that the three door is more focused in setup.

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[marco_polo]

Man-spec vs Mummy spec!

The assumptions are either:

a) the 5 door is stiffer and doesn't need bracing
b) the rear doors add quite a bit of weight, so it needed to go on a diet
c) the rear doors are expensive, and they needed to save cost
d) all of the above

The 5 door could be better as a track-slag, as making the frameless front windows from Lexan would be comparatively tricky.

 

[Paul CS]

Looks good Paul. How did the addition of the brace change the cars handling? Is it noticeable?

Back end feel ever so slightly less scrabbley (is that a word?) when powering out of a bend or roundabout. I guess I'm trying to say it feels nicely planted.

I'm glad I did it.

Building on what Marco said, we have both tried to find the torsional stiffness of the F20/21 but it is not published like it is for most other cars. That would help answer why the brace is on the 3dr and not the 5dr.

Paul

 

[marco_polo]

i suspect the extra weight might have pushed it over the edge into the next tax bracket.

You can't even spec 19" wheels on an M135i for the same reason, but it's fine for the rest of the range!

 

[dape90]

Looks good Paul. How did the addition of the brace change the cars handling? Is it noticeable?

Back end feel ever so slightly less scrabbley (is that a word?) when powering out of a bend or roundabout. I guess I'm trying to say it feels nicely planted.

I'm glad I did it.

Building on what Marco said, we have both tried to find the torsional stiffness of the F20/21 but it is not published like it is for most other cars. That would help answer why the brace is on the 3dr and not the 5dr.

Paul

This is great information.

Thanks for this.

I am going to be looking into this as soon as I get back from this weeks business trip.

Did you fit it yourself? If so how long did it take?

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[Paul CS]

Re fitting, a mate has a garage and did it for me on the ramps. It's not hard. The trickiest bit is the removal of the plastic trim near the back wheels. By the way, I would not bother with the additional aluminium brace even though I did fit it.

Paul

 

[Blind Pugh]

Hi Dape,

I have installed the F80 plate and rear underbody cross brace for F21.

My F20 5dr has quaife LSD and JB4 with ~ 400bhp/460lbft and the rear brace positively locates rear subframe to the underbody.

More power and QLSD putting more reactions into the rear subframe bushes meant occasionally worming under hard acceleration. With underbody chassis bracing the rear is now much more stable with any and all of the aforementioned wobbles now gone and

My car is now even more composed especially over bumpy roads, typical of what we have here in the UK.

BP