RTAB pocket reinforcement

[bigjae46]

I'm about to install some monoball RTABs and was planning to reinforce the RTAB mounting points to prevent this...

I was going to just weld around the bolt holes but found a reinforcement plate from Garagistic. Looks like this ties in all 3 threaded inserts to the plate and then weld the plate to the body. Thoughts?

https://www.garagistic.com/collections/e46-performance-parts/products/e46-rtab-pocket-reinforcements

[Estoril]

I had it done when I was having my track-only car caged/seats/harnesses/suspension/SMP done. Street cars don't need it and I believe that only very heavily tracked cars have any need for it.

That VIR failure was in a heavily raced car.

[timmo]

Yeah, I remember reading somewhere that the chassis in that video was a race car pretty much from day 1. You can imagine how much lapping there has been over 15+ years. I wouldn't worry about it unless it's a dedicated race car

[bigjae46]

My car will never be on the street again...so RTAB plates it is.

I was trying to convince myself not to do it since I hate welding upside down.


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[George Hill]

bigjae46 I've seen a couple cars now starting to tear the RTAB pocket out of the car, every RACP reinforcement I do gets the pocket stitch welded at the seams. I personally think that plus adding ball joints at that location is the best option.

[bigjae46]

bigjae46 I've seen a couple cars now starting to tear the RTAB pocket out of the car, every RACP reinforcement I do gets the pocket stitch welded at the seams. I personally think that plus adding ball joints at that location is the best option.

Is the reinforcement plate necessary? Or maybe even counterproductive?

[George Hill]

Is the reinforcement plate necessary? Or maybe even counterproductive?

Honestly, I'm not sure what it is accomplishing that stitch welding the pocket doesn't provide (If someone has data showing its worth I'd love to see it). We also stitch the upper spring pockets as we've seen those tear out of the chassis too and the wheel arch seams. Just giving you some more ideas while you have the welder out, lol.

[bigjae46]

Honestly, I'm not sure what it is accomplishing that stitch welding the pocket doesn't provide (If someone has data showing its worth I'd love to see it). We also stitch the upper spring pockets as we've seen those tear out of the chassis too and the wheel arch seams. Just giving you some more ideas while you have the welder out, lol.

I was thinking that if the tendency is to pull OUT...then wouldn't making the metal thicker and heaver just make it pull out easier? That didn't really make sense to me.

I still have the rubber pads for the springs...might have to take a look. Thx!

[George Hill]

I was thinking that if the tendency is to pull OUT...then wouldn't making the metal thicker and heaver just make it pull out easier? That didn't really make sense to me.

I still have the rubber pads for the springs...might have to take a look. Thx!

I am not an expert on all things RACP, but from what we have seen the issue is the spot welds on the pocket start to fail and allow the pocket to start pulling away. Stitch welding seems to attach the pocket in more places and prevents it from pulling away. Maybe the issue is the pocket metal is to thin and that allows it to flex and kill the spot welds? IDK, I would love to see more data on this. If we are leaving something on the table I would be happy to re-evaluate our method, but for now this seems to be working properly.

Additionally, I think poly or limiters increase the stress on the pocket as the trailing arm moves in (2) axis during up and down travel, so it is trying to twist the pocket out of the car. Rubber bushings and ball joints don't transfer as much of this twist to the chassis but with a hard bushing or limiters that twist goes right into the bracket and into the pocket. At least that's my theory, if I am wrong I'd love to know it.

[bigjae46]

I am not an expert on all things RACP, but from what we have seen the issue is the spot welds on the pocket start to fail and allow the pocket to start pulling away. Stitch welding seems to attach the pocket in more places and prevents it from pulling away. Maybe the issue is the pocket metal is to thin and that allows it to flex and kill the spot welds? IDK, I would love to see more data on this. If we are leaving something on the table I would be happy to re-evaluate our method, but for now this seems to be working properly.

Additionally, I think poly or limiters increase the stress on the pocket as the trailing arm moves in (2) axis during up and down travel, so it is trying to twist the pocket out of the car. Rubber bushings and ball joints don't transfer as much of this twist to the chassis but with a hard bushing or limiters that twist goes right into the bracket and into the pocket. At least that's my theory, if I am wrong I'd love to know it.

Makes sense to me!