Is the cross brace necessary?

[jmz135]

Hi all,
I installed a custom midpipe and the x-brace won't fit without hitting the midpipe and causing some serious vibration/rattle.

I took it off and went for a drive and it all seems good now. Is the x-brace necessary? I'm not entirely sure the purpose, does it help hold up the stock midpipe to reduce the stress on the spring bolts?

[rhodesman]

I would put the cross-brace back in and do this (see image) to the diff-exhaust hanger. Just my $0.02, but if BMW put it there, there's a reason for it. Adding this to the hanger will 100% raise it off that x-brace, works 100%.

[6MT_Addict]

Originally Posted by jmz135

Hi all,
I installed a custom midpipe and the x-brace won't fit without hitting the midpipe and causing some serious vibration/rattle.

I took it off and went for a drive and it all seems good now. Is the x-brace necessary? I'm not entirely sure the purpose, does it help hold up the stock midpipe to reduce the stress on the spring bolts?

Part No. 17 - Tension Strut?

Yes, it's fairly important. As rhodsman pointed out, BMW (or any auto manufacturer for that matter) isn't in the habit of adding parts for no reason. Especially suspension components that 99% of the general public will never see. This brace likely acts in a similar way to the strut tower cross brace in your engine compartment and transfers load laterally from one side of the car to the other.

Also there is a specific torque spec + specific degree turn to install these bolts (18 + 19) but I can't remember off hand. The service manual calls for new bolts when re-installing as well - fyi.

[jmz135]

Thanks for the responses guys - yes I figured BMW didn't add it for no reason, I just wasn't sure what the point was, it doesn't seem like a very rigid piece to be involved with side to side load transfers, but hey I'll take your word for it.

I'll try and figure out how to fit it back on...@rhodesman - I'm not exactly sure what you're depicting there in your picture - i see you have a hose clamp on an exhaust hanger?

[Yeineken]

Originally Posted by jmz135

Thanks for the responses guys - yes I figured BMW didn't add it for no reason, I just wasn't sure what the point was, it doesn't seem like a very rigid piece to be involved with side to side load transfers, but hey I'll take your word for it.

I'll try and figure out how to fit it back on...@rhodesman - I'm not exactly sure what you're depicting there in your picture - i see you have a hose clamp on an exhaust hanger?

This may give you a better idea of what he is talking about.

[rhodesman]

Originally Posted by jmz135

...@rhodesman - I'm not exactly sure what you're depicting there in your picture - i see you have a hose clamp on an exhaust hanger?

Yeah, basically, tighten up the hose clamp around the hanger and it will "squeeze" the hanger pulling up the exhaust. My mechanic came up with this and I've had it on for nearly a year now and has been flawless. Might take a couple different ones to find the right fit and I had to "re-tighten" after 100 miles and the exhaust got warm/hot (started to rattle a tad at idle). However since I've done that, the exhaust fitment has been butter!

Good luck!

[The Wind Breezes]

It's not "necessary" in the slightest. You can run without it. I've had mine off for a while and there's no difference in handling on a stock car. People are so goddamn dumb when it comes to these braces. GUESS WHAT, the chassis is already super stiff compared to something like an E36, braces or no.

The purpose of this part more than anything is to keep your exhaust from dragging on the ground if something fails.

[6MT_Addict]

Originally Posted by The Wind Breezes

It's not "necessary" in the slightest. You can run without it. I've had mine off for a while and there's no difference in handling on a stock car. People are so goddamn dumb when it comes to these braces. GUESS WHAT, the chassis is already super stiff compared to something like an E36, braces or no.

The purpose of this part more than anything is to keep your exhaust from dragging on the ground if something fails.

If you're comparing the E82 chassis and body to something as old as the E36, then it's a tank. Technology has come leaps and bounds since then, and unless you were an engineer on the E82 chassis design team, perhaps there is something you've overlooked... Like reinforcing in a roll over, T-bone collision, or high stress at the rear subframe.

According to the subframe explosion diagram and torque specifications (excerpt below), the 'V Shaped Brace' is in place as body reinforcing. I'm sure it would help keep the exhaust from dragging, but according to Real OEM and the diagram below, it does look to be a structural element.

[jmz135]

Thanks everyone for your responses. Clearly BMW wouldn't add it for no reason, it's just somewhat hard to believe it's for structural rigidity. If you pick it up it's easy to bend it with your hands, it's clearly not meant for rigidity. I've tried to do a bit of research but haven't found any data actually from BMW on what the point of it is. I'm still planning on seeing if I can figure out how to get it on without rubbing.

[vtl]

The bar is called a tension strut for a reason. When you hit a bump on on the rear this strut goes under tension and reduces the flex of the body.

[The Wind Breezes]

I've been hooning my car around on totally stock suspension and bald rear tires for over a week now with the brace removed, DSC off 100% of the time. If anything the rear is a little more stable due to less rigidity but honestly there's very very little change. You certainly won't BREAK the car by running without this piece--it's like really really thin icing on your cake and is totally optional.

[Solo_M_Tech]

Originally Posted by The Wind Breezes

I've been hooning my car around on totally stock suspension and bald rear tires for over a week now with the brace removed, DSC off 100% of the time. If anything the rear is a little more stable due to less rigidity but honestly there's very very little change. You certainly won't BREAK the car by running without this piece--it's like really really thin icing on your cake and is totally optional.

I don't think BMW puts "Optional" Chassis braces on the car.

Not trying to insult you in particular, but it never fails that users here think they know more than BMW engineers.

Do whatever you want with your car, but it's there for a reason.

[The Wind Breezes]

Originally Posted by Uber///Madd

I don't think BMW puts "Optional" Chassis braces on the car.

Not trying to insult you in particular, but it never fails that users here think they know more than BMW engineers.

Do whatever you want with your car, but it's there for a reason.

I'm not saying I know more than BMW's engineers about this car. I'm just saying that:

1) the brace makes the car very very slightly stiffer, it's not the huge difference some people claim
2) the car won't fail with the brace removed because the unibody is fully and completely strong enough by itself, without the crossbrace, by a factor of several times the minimum necessary to avoid being torn apart.

I also removed my midpipe and all the ducting and shrouds in front of the airbox. All "optional" in my world.

[NORAGRETS]

Originally Posted by rhodesman

I would put the cross-brace back in and do this (see image) to the diff-exhaust hanger. Just my $0.02, but if BMW put it there, there's a reason for it. Adding this to the hanger will 100% raise it off that x-brace, works 100%.

LOVE this thx

[iminhell1]

Perspective:
BMW engineers also put RFT's on the car. So we all should stick to only that tire. Anything else will destroy the car.

also per the "manual"

The specially arranged floor system causes impactforces to be transmitted to the side of the vehicle opposite the impact. In the door area, the doors themselves, the reinforced Bpillar, the seats and the instrument carrier between the A-pillars provide the stability ofthe side structure in connection with the roofframe. All the measures listed enable the vehicle to remain below significantvalues, such as the maximum permissible intrusion speed, in the event of a side impact.

I would say that the tension strut may be part of the crash worthiness system.

[The Wind Breezes]

Originally Posted by iminhell1

Perspective:
BMW engineers also put RFT's on the car. So we all should stick to only that tire. Anything else will destroy the car.

I would say that the tension strut may be part of the crash worthiness system.

That's a fair perspective.

Originally Posted by iminhell1

I would say that the tension strut may be part of the crash worthiness system.

No, because it's a tension strut, shifting side impacts to the other side like that quote is talking about would put it under compression.

[jmz135]

Thanks everyone for your suggestions - I went ahead and tried the hose clamp method and it worked well, I've now got the clearance I need

[christian_128i]

I had the same problem with my 128i and thought Id scrap the cross brace. But after reading this thread I'm going to try the method with the worn gear hoses.

Can I reinstall the cross brace with a singular jack and jack up the driver's side? or should it be done with 4 jack stands if a lift is inaccessible?

[Papa Popov]

Originally Posted by christian_128i

I had the same problem with my 128i and thought Id scrap the cross brace. But after reading this thread I'm going to try the method with the worn gear hoses.

Can I reinstall the cross brace with a singular jack and jack up the driver's side? or should it be done with 4 jack stands if a lift is inaccessible?

Just my $0.02, but don't ever work under a car unless its evenly supported on jack stands or ramps. Even then you still have to be careful. One of my plastic jack points broke while using a jack stand and the stand slid out from under the car. Fortunately I wasn't under it, but it dented the hell outta my rear quarter panel. Needless to say I use ramps w/ the wheels on the ground chocked for everything that doesn't require the wheels to come off now. Much easier and safer for most jobs IMO and still allows you to access most things on the underside.

Thanks for coming to my Ted Talk. To answer you question, yes, this'll be ezpz without a lift, just use a couple ramps or jack stands.
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