Driving without UnderBody Brace

[Jumbo401]

hi everyone i just recently bought a z4m for pretty cheap, and it doesnt come with the diagonal brace that connects to the differential.

when driving the car feels a bit looser in the rear end but otherwise is still driveable and handles well enough.

are there any affects of driving or tracking the car without this brace? any affect on chasis twist etc...?

 

[B21]

I suggest it’s extremely dangerous…as well as lack of integrity it could lead to structural failure of one or more chassis components..

I’m not an expert on the E85 chassis bit similar bracing on the E89 is mandatory…and that’s a stronger chassis..

 

[Zedebee]

The diagonal braces at the rear, the aluminium reinforcement plate and the diagonal braces in the engine bay are all structural and your car shouldn’t be driven without them.

It sounds as though your Z4M may have been cheap for a reason.

 

[Jumbo401]

The diagonal braces at the rear, the aluminium reinforcement plate and the diagonal braces in the engine bay are all structural and your car shouldn’t be driven without them.

It sounds as though your Z4M may have been cheap for a reason.

just trying to gauge the importnace of the brace. i think bmw refer to them as pull-rods.

i never drive without the engine bay struts.

i got the M for 6.5k knowing all the issues she has. going to do rod bearings soon as well as preventative.

there is a noteable difference in handling from my 3.0si coupe which has the brace.

trying to figure out what the worse case scenario of drving without them long term is :?

i also dont like how the brace connects to the rocker panels. just another place for rust and corrosion to occur. where every other BMW doesn't have them joining there. Perhaps i should look at alternative ways to brace the rear whether thats from the rear strut towers or finding another place on the underbody to fit some aftermarket braces.

Also compared to older BMWs like the e36 z3 etc. Our chassis are multiple times more rigid, so unsure how it could cause any serious problems when you have cars that are tracked and driven without them like the (s2000) maybe im reaching here idk?

decisions decisions...

 

[Umfaan]

Depending where you are located i have the missing bits available ....i will PM you.

 

[B21]

The diagonal braces at the rear, the aluminium reinforcement plate and the diagonal braces in the engine bay are all structural and your car shouldn’t be driven without them.

It sounds as though your Z4M may have been cheap for a reason.

just trying to gauge the importnace of the brace. i think bmw refer to them as pull-rods.

i never drive without the engine bay struts.

i got the M for 6.5k knowing all the issues she has. going to do rod bearings soon as well as preventative.

there is a noteable difference in handling from my 3.0si coupe which has the brace.

trying to figure out what the worse case scenario of drving without them long term is :?

i also dont like how the brace connects to the rocker panels. just another place for rust and corrosion to occur. where every other BMW doesn't have them joining there. Perhaps i should look at alternative ways to brace the rear whether thats from the rear strut towers or finding another place on the underbody to fit some aftermarket braces.

Also compared to older BMWs like the e36 z3 etc. Our chassis are multiple times more rigid, so unsure how it could cause any serious problems when you have cars that are tracked and driven without them like the (s2000) maybe im reaching here idk?

decisions decisions...

 

[Jumbo401]

The diagonal braces at the rear, the aluminium reinforcement plate and the diagonal braces in the engine bay are all structural and your car shouldn’t be driven without them.

It sounds as though your Z4M may have been cheap for a reason.

just trying to gauge the importnace of the brace. i think bmw refer to them as pull-rods.

i never drive without the engine bay struts.

i got the M for 6.5k knowing all the issues she has. going to do rod bearings soon as well as preventative.

there is a noteable difference in handling from my 3.0si coupe which has the brace.

trying to figure out what the worse case scenario of drving without them long term is :?

i also dont like how the brace connects to the rocker panels. just another place for rust and corrosion to occur. where every other BMW doesn't have them joining there. Perhaps i should look at alternative ways to brace the rear whether thats from the rear strut towers or finding another place on the underbody to fit some aftermarket braces.

Also compared to older BMWs like the e36 z3 etc. Our chassis are multiple times more rigid, so unsure how it could cause any serious problems when you have cars that are tracked and driven without them like the (s2000) maybe im reaching here idk?

decisions decisions...

Thanks for the diagram B21

I’m talking about the V shaped Brace excuse the badly drawn circles

 

[Umfaan]

Yip ... i have a few kicking about of those ....where you located ?

 

[Jumbo401]

Yip ... i have a few kicking about of those ....where you located ?

Cheers Umfaan. I’m located in Wembley. : )

 

[B21]

just trying to gauge the importnace of the brace. i think bmw refer to them as pull-rods.

i never drive without the engine bay struts.

i got the M for 6.5k knowing all the issues she has. going to do rod bearings soon as well as preventative.

there is a noteable difference in handling from my 3.0si coupe which has the brace.

trying to figure out what the worse case scenario of drving without them long term is :?

i also dont like how the brace connects to the rocker panels. just another place for rust and corrosion to occur. where every other BMW doesn't have them joining there. Perhaps i should look at alternative ways to brace the rear whether thats from the rear strut towers or finding another place on the underbody to fit some aftermarket braces.

Also compared to older BMWs like the e36 z3 etc. Our chassis are multiple times more rigid, so unsure how it could cause any serious problems when you have cars that are tracked and driven without them like the (s2000) maybe im reaching here idk?

decisions decisions...

Thanks for the diagram B21

I’m talking about the V shaped Brace excuse the badly drawn circles

Yes not having those are even worse from a structural perspective..they provide a significant degree of triangulation support to the body and attached parts…definitely required under all circumstances..well on an E89 they are…and an E85 isn’t as strong as an E89 body..

 

[Jumbo401]

Thanks for the diagram B21

I’m talking about the V shaped Brace excuse the badly drawn circles

Yes not having those are even worse from a structural perspective..they provide a significant degree of triangulation support to the body and attached parts…definitely required under all circumstances..well on an E89 they are…and an E85 isn’t as strong as an E89 body..

I thought they would be more crucial for the roadsters than the coupes. Since the coupes have more structural rigidity due to the fixed roof? And they just decided to keep the brace on the coupe because every little helps.

The e46 and z3 didn’t get the v brace (except m3) . :?

I believe the coupe as a torsional strength of 32000nm
While the roadster is 16000nm which is a pretty big difference. (Even though it is still very good for a roadster)

I can definitely see how they are absolutely necessary on roadsters though.

 

[B21]

Thanks for the diagram B21

I’m talking about the V shaped Brace excuse the badly drawn circles

Yes not having those are even worse from a structural perspective..they provide a significant degree of triangulation support to the body and attached parts…definitely required under all circumstances..well on an E89 they are…and an E85 isn’t as strong as an E89 body..

I thought they would be more crucial for the roadsters than the coupes. Since the coupes have more structural rigidity due to the fixed roof? And they just decided to keep the brace on the coupe because every little helps.

The e46 and z3 didn’t get the v brace (except m3) . :?

I believe the coupe as a torsional strength of 32000nm
While the roadster is 16000nm which is a pretty big difference. (Even though it is still very good for a roadster)

I can definitely see how they are absolutely necessary on roadsters though.

Roof structure has precious little to do with it..

Anyway I'm out of here..

 

[Jumbo401]

Yes not having those are even worse from a structural perspective..they provide a significant degree of triangulation support to the body and attached parts…definitely required under all circumstances..well on an E89 they are…and an E85 isn’t as strong as an E89 body..

I thought they would be more crucial for the roadsters than the coupes. Since the coupes have more structural rigidity due to the fixed roof? And they just decided to keep the brace on the coupe because every little helps.

The e46 and z3 didn’t get the v brace (except m3) . :?

I believe the coupe as a torsional strength of 32000nm
While the roadster is 16000nm which is a pretty big difference. (Even though it is still very good for a roadster)

I can definitely see how they are absolutely necessary on roadsters though.

Roof structure has precious little to do with it..

Anyway I'm out of here..

Roof structure alone doubles rigidity from 16knm/degree to 32knm

 

[paddy wright]

Why do you want to drive without them??

 

[Mr Tidy]

£6.5k was dirt cheap for an MC.

I'd just get the parts from Umfaan and get them fitted. BMW didn't put them there for decoration!

 

[Zedebee]

are there any affects of driving or tracking the car without this brace? any affect on chasis twist etc...?

Yes, the car will be looser and less rigid, and more prone to shaking itself to bits. The chassis will twist more. The torsional rigidity quoted is likely to include the braces, so your rigidity will be much reduced. To suggest that it is still more rigid than the roadster may be correct in absolute terms, but it will be weaker in places where the braces are absent.

It doesn’t make any sense to run the car without these structural components and will almost certainly invalidate your insurance.

 

[Jumbo401]

£6.5k was dirt cheap for an MC.

I'd just get the parts from Umfaan and get them fitted. BMW didn't put them there for decoration!

I got pretty lucky there, fair bit of rust on the fenders hatch and roof. and a few damaged suspension components. Mechanically she’s fine. Think I got a pretty good deal off the geezer

 

[beanie]

Given BMWs track record with panels pulling themselves apart (E46 and Z3), I wouldn’t be doing anything more than a gentle trip to the MOT station without them.

 

[Mr Tidy]

Mr Tidy wrote: ↑Fri Jun 07, 2024 8:08 pm
£6.5k was dirt cheap for an MC.

I'd just get the parts from Umfaan and get them fitted. BMW didn't put them there for decoration!
I got pretty lucky there, fair bit of rust on the fenders hatch and roof. and a few damaged suspension components. Mechanically she’s fine. Think I got a pretty good deal off the geezer

TBH on the face of it you stole it! Although given those issues you might not have.

I thought I got a good deal on mine but I'd love to know a bit more about yours, like condition and history, etc.

 

[Jumbo401]

Mr Tidy wrote: ↑Fri Jun 07, 2024 8:08 pm
£6.5k was dirt cheap for an MC.

I'd just get the parts from Umfaan and get them fitted. BMW didn't put them there for decoration!
I got pretty lucky there, fair bit of rust on the fenders hatch and roof. and a few damaged suspension components. Mechanically she’s fine. Think I got a pretty good deal off the geezer

TBH on the face of it you stole it! Although given those issues you might not have.

I thought I got a good deal on mine but I'd love to know a bit more about yours, like condition and history, etc.

No accidents as far as report tells. Doesn’t look like she was looked after though, especially living most her life near the sea.
going over to a mates garage next Wednesday to do a compression test. I’ll be replacing all the steel body panels as well. (Including the hatch (£2k) smh

I’m sure more problems will rear their ugly head soon
But I have my trusty 3.0si Coupe and Supra to daily

I’m also a contemplating buying another 2J and swapping it into my 3.0si, but I’ve heard e46 mounts make the engine sit too far forward, and the wiring problems are a Pita. So lots of custom fabrication would be needed on that project.

Anyways back to the topic.

My fear is when I get the V Brace . When I try fitting it maybe the bolt holes won’t align :gulp