FRONT subframe reinforcement?

[jareds941]

My M3 is a full on track car...not registered and trailered to events only. Pretty sure motor and trans mounts are 160k miles old so I’m looking at taking advantage of Black Friday sales on some new mounts. As it’s a track car, I’m looking at solid mounts and realized that both Turner and BW call out a need for front subframe reinforcement plates. I’m only about a year into this platform, but I’ve never once heard of any comments about the front subframe needing attention...only the rear.

Who has the solid motor/trans mounts? Did you reinforce your front subframe? Is this actually necessary or a disclaimer each brand is making “just in case”?

[Jersey_M3]

So I just did my rod bearing service and thought I should order this and weld them up. Upon taking the subframe down and inspection I found it not needed to be reinforced. The front subframe is made of pretty substantial metal. It is no where near the thickness of the 22 gauge metal holding the rear end of our cars together. I did not take a gauge to it but I would guess the front subframe is 1/8th steel all around. Maybe someone else can chime in here about the failure and if it ever actually happens on a track car or these cars in general. My guess is the failure happens when you go high hp, like 600+

Side note. You can buy the kit I never installed from me pm me

[mrgizmo04]

I've heard of front swaybar mounting points ripping out (reinforcement for which I think these kits are missing), I can't say I've heard about front engine mounts ripping out (which is what these kits focus on).

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[jareds941]

Yeah I've been doing some searching online and can't really find any mention of this being an issue. Now if it's a racecar issue, especially those running big power, I wouldn't expect it to necessarily make it to a forum, as the team would just deal with it and move on.

[Luong7]

I had my front sway bar mounting points completely rip off on the passenger side. Driver side was starting to crack. Car isn't tracked but is on air ride. Ended up welding it with custom plates to reinforce it.

[jareds941]

I had my front sway bar mounting points completely rip off on the passenger side. Driver side was starting to crack. Car isn't tracked but is on air ride. Ended up welding it with custom plates to reinforce it.

Interesting. I’m not super familiar with the geometry under there...where are the fsb mounts relative to the motor mounts / front subframe.

[timmo]

I had my front sway bar mounting points completely rip off on the passenger side. Driver side was starting to crack. Car isn't tracked but is on air ride. Ended up welding it with custom plates to reinforce it.

Did you make the plates, if so do you happen to have the dimensions still?

Interesting. I’m not super familiar with the geometry under there...where are the fsb mounts relative to the motor mounts / front subframe.

It's actually on the chassis itself, and the metal is very thin gauge so the weld studs can easily pull out with larger sways.

I just bought a 30 mm front sway and I'm thinking of fab'ing some plates and epoxying them in

[Rich022]

larger/stiffer front sway bar can cause this to happen on e46 platform. Rare, but I've seen it happen to a forum member. However, I believe this is much more common in the e36 platform.
I'm running a Hotchkis bar with plates. No issues for the past 2+ yrs. now.

[jareds941]

larger/stiffer front sway bar can cause this to happen on e46 platform. Rare, but I've seen it happen to a forum member. However, I believe this is much more common in the e36 platform.
I'm running a Hotchkis bar with plates. No issues for the past 2+ yrs. now.

But any issues from solid motor mounts causing this on a 46? Seems like the sway bar mounting location is not connected to front subframe, correct?

[EthanolTurbo]

Don't the front strut towers deform and mushroom sometimes? It's not the front subframe but it's pretty closely connected...

[timmo]

Don't the front strut towers deform and mushroom sometimes? It's not the front subframe but it's pretty closely connected...

Yeah, but that's easy solved with factory reinforcement plates. They are bolt-in as well as they just sandwich between the strut mount and the strut tower - no welding required!

[Rich022]

Chad knows his stuff- here's his guide on reinforcements in a racing environment

https://www.moreheadspeedworks.com/bmw-e46-chassis-reinforcement-guide/

[Luong7]

Did you make the plates, if so do you happen to have the dimensions still?

unfortunately I don't have sizes of the plates. A buddy of mine came out to make them and weld them in for me.