Current recommend rear bracing and bushings for a vert?

[Gregdepot]

I have the DMG rear Comp-V super lite RACP brace to install. I was thinking the Vince Gussets and not sure which plates or bushings would be a good option? I sent a message to Vince at Practical Performance RnD and few days ago and have not gotten a response yet, but not sure if that is a good way of contacting him.

[ATB88]

Vincebar's front gusset cups are not designed for verts -- only the bar itself can be installed.

[Gregdepot]

I have only ever herd of the opposite, interesting

[Slideways]

Copied from Vincebar GB thread:

This thread seems like it has some good info for topside reinforcement on verts (see post #8) - https://nam3forum.com/forums/forum/m...t-subframe-bar

Edit (added part of post #8):

"From what I learned this kind of bar is essential to stop cracking. Putting reinforcement plates on the underside to repair cracks is treating the symptom not the cause. The bar directly couples the rear mounts to the chassis rails, thereby solving the chassis design flaw that relies solely on sheet metal to do the job (which flexes and eventually fails due to fatigue)"

[Gregdepot]

I already have a rear bar from DMG

[poss]

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[Gregdepot]

The pic of the 'vert boot above is from my vehicle. I spoke at length with the engineer at CMP before choosing this solution. His advice is that the 'vert only needs added bracing on rear mounts as the rear seat is a fixed bulkhead that offers significantly more rigidity against vertical flex in the front mounts.

The bar pictured above was custom made. I used the CMP underside plates and can recommend them.

I also put in Powerflex black RACP bushings (left diff bushings stock). I am very happy with the overall result. The backend feels noticeably tighter and no noticeable increase in noise/vibration

I have my doubts as to the effectiveness of using an X-brace-style solution transferring forces to the rear turrets instead of attaching the rear RACP mounts directly to the chassis rails - especially in a 'vert.

If you look at the design of the brace you plan to install it is plain that it is strongest in transferring forces diagonally from the RACP mounts to the top of the opposite turret - but the 'verts fixed rear seat is already probably doing a pretty reasonable job of preventing such a twisting motion.

RACP cracking is caused by an up/down flexing of the rear left subframe mount relative to the front right - not a twisting of the entire rear end of the car. An X-brace design is at its weakest stopping these forces.

I understand an X-brace is easy to fit and does not require the kind of surgery a brace does - but its sub-optimal and takes a chunk of your boot space too.

I think you could call what I have an X brace?

https://dmg-autosport.myshopify.com/products/new-comp-v-superlite-fixed-racp-brace?pr_prod_strat=copurchase&pr_rec_pid=4316178677812&pr_ref_pid=4308889993268&pr_seq=uniform

[poss]

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[Gregdepot]

Yep.

A strut brace is (usually) designed to solve quite a different problem - the strut towers moving closer together when you hit a bump.

It may well also help prevent your RACP from cracking, but to what degree who knows? you're still transferring forces indirectly rather than directly to the chassis rails. For vertical movement the weak points of an X-brace design are the center of the X, the mounts onto the strut towers, the strut towers themselves, and the use of tubular steel. This cannot hope to compare to the structural rigidity of a substantial square-section steel bar connecting the Subframe mounts to the chassis rails via the most direct route possible.

As an example of the insidious nature of metal fatigue, some have reported that RACP reinforcement plates merely caused the failure to later spread to their wheel arches.

If you're planning on keeping your M3 for awhile I'd suggest fixing it properly/permanently.

Fix it properly how? I will have X brace, vert rear seat backing, plates underneath, poly bushings etc. what else is there? Maybe front gussets if they fit?