E46 rear subframe

[Deffed 10]

Iv heard convertibles and estate/wagon have a beefier rear subframe,im about to start m60b40 transplant. Also iv read bmw use these sub frames in the m cars.

[Sammo 2544]

Someone more knowledgable may chime in but pretty sure that isn't the case, and with how much M3s like eating subframes with less torque than an M60B40 I would look to re-bush, reinforce and brace your 330i subframe.

[BreakMyWindow 1874]

The subframe itself isn’t the problem on e46. It’s the flawed design of the chassis the subframe bolts to. 
 

 

[exextatic 111]

As above, it's the RACP (rear-axle carrier panel) itself that has the issue, not the subframe.

Take a read through this: https://cmpautoengineering.com/pages/part-1-will-my-e46-subframe-crack-how-will-i-know

I'm personally running CMP's underfloor plates and topside beam kit on my E46 M3 Sedan build.

[Sammo 2544]

2 hours ago, exextatic said:

As above, it's the RACP (rear-axle carrier panel) itself that has the issue, not the subframe.

Take a read through this: https://cmpautoengineering.com/pages/part-1-will-my-e46-subframe-crack-how-will-i-know

I'm personally running CMP's underfloor plates and topside beam kit on my E46 M3 Sedan build.

That makes for some sobering reading 😆

Thoughts on preventative subframe / RACP solutions for a non-M?

Planning on getting my subframe bushings done later in this year.

[zero 1162]

I'm planning on epoxying on the plates, and also using structural epoxy foam inside the racp.

Both are bmw approved methods.

[m325i 709]

On 2/10/2021 at 2:17 PM, zero said:

I'm planning on epoxying on the plates, and also using structural epoxy foam inside the racp.

Both are bmw approved methods.

Won't fix it mate

[zero 1162]

10 hours ago, m325i said:

Won't fix it mate

Have you any hard evidence to back that up, because alot of top repairers have used that method, including reddish motorsport? 

[Harper 547]

@zero not any hard evidence necessarily but there is anecdotal evidence of people still getting cracking after epoxy foam and underside plates. The issue is that it does not solve the problem and just redirects the load path to the wheel arches where there are spot welds that start to pop and separate the RACP from the chassis. The biggest dissuader for me is that the epoxy foam makes it incredibly difficult to weld any cracks or solve the issue properly because it catches fire when welding and creates toxic fumes. 

However, it's hard to recommend a full top mount kit on a non-m when the cost of the kit + installation could eclipse the value of the car. CMP has a chassis rail plate which works quite well as a midrange option (https://cmpautoengineering.com/collections/all/products/e46-subframe-racp-to-chassis-rail-plates) in addition to underside plates. 

Edited February 14, 2021 by Harper

[Deffed 10]

Ok,so iv got the strengthing of the body sorted for the 46,xtra plates strut tower strengthed. So is it best to strengthen or build a subframe replacement with items stengthed? Thanks for you import its all good knowledge. 👍

[Cement 871]

2 hours ago, Deffed said:

Ok,so iv got the strengthing of the body sorted for the 46,xtra plates strut tower strengthed. So is it best to strengthen or build a subframe replacement with items stengthed? Thanks for you import its all good knowledge. 👍

I think it was mentioned previously but the subframe itself is not the issue, its the car floor (RACP = rear axle carrier panel) and surrounds where the subframe mounts to. CMP Automotive have the most comprehensive articles I have seen regarding the issues. Part 2 of their material linked below, to follow on from part 1 linked above.

https://cmpautoengineering.com/pages/part-2-it-s-not-just-the-subframe-mounts

[Deffed 10]

Yea i have researched modifications necessary to strenghten the structural integrity of body in and around subframe mounts,also have made alterations and provisions for triangular dry sump tank. 

[Deffed 10]

On 3/16/2021 at 6:31 PM, Cement said:

I think it was mentioned previously but the subframe itself is not the issue, its the car floor (RACP = rear axle carrier panel) and surrounds where the subframe mounts to. CMP Automotive have the most comprehensive articles I have seen regarding the issues. Part 2 of their material linked below, to follow on from part 1 linked above.

https://cmpautoengineering.com/pages/part-2-it-s-not-just-the-subframe-mounts

Do you think a standerd 330i subframe will handle 500hp?

[Sammo 2544]

14 minutes ago, Deffed said:

Do you think a standerd 330i subframe will handle 500hp?

Would ask the question here - loads of boosted M54s running 450plus WHP - mostly on a budget so doubt they are doing much more than reinforcing.

https://www.facebook.com/groups/134785066905933/

[NZ00Z3 187]

There is a "Vince Bar" group buy going on over at E46Fanatics.  Don't know if it applies to your car?  https://www.e46fanatics.com/threads/vincebar-group-buy.1288206/