Obioban's 2005 IR/IR Coupe

[0-60motorsports]

Been a while since I got to do a mod on the M3. Been busy with house construction/e60 M5/never ending Land Cruiser refresh.

Anyway, made my trunk a bit less practical.

Love it.

[Obioban]

Haven’t actually driven the car yet. Been doing shake down on a friends e38 750il rebuild the last week of DDing

I’d expect WAY less benefit from this than the Slon wall. But, the price was nearly free, so…

also debating tying it to the subframe mount points. Currently chatting with Vince about if that’s viable with the Vince bar installed. But, that would REALLY reduce trunk functionality.

[Obioban]

I do wonder if the Slon wall makes a rear strut tower brace more effective— the rear spring mounts are positioned between the bulkhead and the shock towers, so maybe this boxes out the load path?

[Bry5on]

I think it does a while lot of nothing, especially with the Slon wall. If you want to tie it to the Vince bar, some rivet nuts into the bar should do it. I’d go inward of the subframe mounts and cross the brace to the other side for maximum stiffness. But my sense is that this is a diminishing returns situation.

[George Hill]

Agreed, I think the Slon wall is doing the heavy lifting. Certainly can't hurt but IDK if its worth loosing the trunk space over.

[Obioban]

My assumption was that they didn't do a ton, until I noticed BMW has one on the M3 GTR street car.



From: https://www.youtube.com/watch?v=rKm0FPh3UtQ

[heinzboehmer]

My assumption was that they didn't do a ton, until I noticed BMW has one on the M3 GTR street car.

All coupe chassis came with folding seats from the factory right? I know all M3s did and I think the same is true for non-Ms, but not 100%.

Super hard to tell from that video, but I doubt BMW retrofitted a rear bulkhead for the GTR. Sounds like that might have been grounds for extra crash testing, which I'm sure they were very eager to avoid doing.

No doubt that style of bracing does something on a coupe chassis with the huge hole behind the rear seats, just unsure if it'll be meaningful with a structural bulkhead in place.

Edit: Found a picture of the GTR trunk and brightened it up:



I'd say that's very... inconclusive.

There's something back there, but still hard to tell if it's just the trim panel for the rear seat delete or if it's a structural piece.

[Obioban]

All coupe chassis came with folding seats from the factory right? I know all M3s did and I think the same is true for non-Ms, but not 100%.

Super hard to tell from that video, but I doubt BMW retrofitted a rear bulkhead for the GTR. Sounds like that might have been grounds for extra crash testing, which I'm sure they were very eager to avoid doing.

No doubt that style of bracing does something on a coupe chassis with the huge hole behind the rear seats, just unsure if it'll be meaningful with a structural bulkhead in place.

Edit: Found a picture of the GTR trunk and brightened it up:



I'd say that's very... inconclusive.

There's something back there, but still hard to tell if it's just the trim panel for the rear seat delete or if it's a structural piece.

Non M coupes also had fold through seats as standard.

As for what's going on with the GTR... hard to tell. It has no back seats, as you say, and that is very much not the standard fold through seat view from the trunk side. But, also doesn't really look like a sedan without fold through from the factory.

[Obioban]

actually, no, that looks like exactly the carpet panel of a non fold through sedan:



... but what lays between :P

[heinzboehmer]

actually, no, that looks like exactly the carpet panel of a non fold through sedan:

Interesting!

Well, looking forward to hear what you think of the brace.

[George Hill]

Yes, agreed, that is a non fold down panel for sure.

It also looks like the GTR brace is tied into the RACP, I do think that is a benefit even with the Slon brace

[0-60motorsports]

Yes, agreed, that is a non fold down panel for sure.

It also looks like the GTR brace is tied into the RACP, I do think that is a benefit even with the Slon brace

100%! Are we all still thinking BMW didnt know that subframe failure was going to happen LOL.

[Obioban]

All told, feels like I should tie into the subframe or remove it completely...

[Obioban]

Last week I had a misfire, traced it to a coil.

I have always been under the impression that coils either work or don't, no middle ground. I've also not seen a ton of correlation between mileage and failure. Between the two, I've always ignored them till they failed, then replaced only the one that failed-- which meant that 4 of my 6 coils were original, 170k miles, 22 year old coils.

This time, however, I replaced all 6. Lots of OE BMW part production has been moving to China, and these have not yet. The OEM parts were also super cheap! So, decided to do them all before they were downgraded.

Today I drove the car for the first time since replacing them. Wow did it make a huge difference! The car is smooooooother than it has been for years. Going forward I am 100% treating these as a maintenance item, instead of wait for failure item. I don't have any idea what the mechanism is, but with 100% confidence there is something more than go/no go here.

I was going to keep a couple of the non failed originals in my trunk as spares, but tossing them instead.

[oceansize]

On my titanium m3 I replaced mine as preventative maintenance at 105k miles as I've noticed a difference in smoothness on other cars I own. I used the carbahn (dinan) ones.