Subframe Dropped and cracks found

[scotty737]

My bad. Yes, its a similar topside reinforcement concept to the CMP Rail Plates

Yeah, they are nearly identical to those.

[poss]

What does the bar really do differently than this in terms of racp movement? If you really wanted a bar you could easily weld a piece of metal to both of these plates.

The design flaw addressed by both solutions is that the RACP structure (a kind of gusseted box girder structure made out of sheet metal) is indirectly tied to the chassis rails via the wheel arches - i.e.: it's effectively sprung to the chassis rails rather than directly connected, introducing enough movement to induce metal fatigue in the sheet metal structure (usually starting around the gusset welds).

Simply tying the RACP directly to the chassis rails is likely going to eliminate the majority of the flexing and prevent catastrophic metal fatigue during the serviceable lifetime of the car. Adding a bar and bolting the rear subframe mounts to it is going to pretty-much eliminate any remaining flex in the RACP due to its sheet metal structure, and adding rigidity to the rear end. Is it necessary to eliminate RACP cracking? Probably not, but it absolutely guarantees it will never happen. Will it improve the car's feel? Yes.

PS: I wouldn't wait for signs of cracking before doing topside reinforcement. I'd be doing it immediately if you plan to keep the vehicle and can afford it, 'cos cracking is not a matter of if, but when.

[scotty737]

The design flaw addressed by both solutions is that the RACP structure (a kind of gusseted box girder structure made out of sheet metal) is indirectly tied to the chassis rails via the wheel arches - i.e.: it's effectively sprung to the chassis rails rather than directly connected, introducing enough movement to induce metal fatigue in the sheet metal structure (usually starting around the gusset welds).

Simply tying the RACP directly to the chassis rails is likely going to eliminate the majority of the flexing and prevent catastrophic metal fatigue during the serviceable lifetime of the car. Adding a bar and bolting the rear subframe mounts to it is going to pretty-much eliminate any remaining flex in the RACP due to its sheet metal structure, and adding rigidity to the rear end. Is it necessary to eliminate RACP cracking? Probably not, but it absolutely guarantees it will never happen. Will it improve the car's feel? Yes.

makes sense. I am hoping what I did removed enough of the flex to not crack again.

[poss]

makes sense. I am hoping what I did removed enough of the flex to not crack again.

You should be fine. You've addressed the fundamental cause of the problem. Only doing underside plates without any topside reinforcement can see the cracking migrate to the wheel arches

[Nate047]

Waited for my welder to show for about a month

Hope he had a good reason lol.

Can I jump in and ask something related, my car has plates on the underside from the previous owner, they are on there with epoxy and the job looks like it was done alright as far as anyone can know from just looking. I have been considering a topside bar reinforcement, and I was just wondering if there's any reason to be concerned about cracks if there are none visible from the top? I just don't know how good a job the last guy did. I will not be tackling this as a DIY regardless but I'm just curious.

[poss]

Hope he had a good reason lol.

Can I jump in and ask something related, my car has plates on the underside from the previous owner, they are on there with epoxy and the job looks like it was done alright as far as anyone can know from just looking. I have been considering a topside bar reinforcement, and I was just wondering if there's any reason to be concerned about cracks if there are none visible from the top? I just don't know how good a job the last guy did. I will not be tackling this as a DIY regardless but I'm just curious.

The wheel arch spot welds typically fail before anything is visible in the boot. If the boot floor is coming apart the damage is probably extensive by that stage. As per my previous post I would not wait to see failures before doing topside reinforcement as its a matter of when not if.

[Thoglan]

Hope he had a good reason lol.

Can I jump in and ask something related, my car has plates on the underside from the previous owner, they are on there with epoxy and the job looks like it was done alright as far as anyone can know from just looking. I have been considering a topside bar reinforcement, and I was just wondering if there's any reason to be concerned about cracks if there are none visible from the top? I just don't know how good a job the last guy did. I will not be tackling this as a DIY regardless but I'm just curious.

Underside plates are not enough unfortunately. I was in a similar situation and purchased my car with only underside plates. about a year into ownership of normal driving there was cracking on the wheel arches.

[Nate047]

Yea I kind of figured this would be inevitable. I'm just trying to see if the old plates need to come off or if I can keep them and do the top bar. Aside from checking for bad spot welds in the wheel arches... What else?

[poss]

Yea I kind of figured this would be inevitable. I'm just trying to see if the old plates need to come off or if I can keep them and do the top bar. Aside from checking for bad spot welds in the wheel arches... What else?

If you stop the fundamental cause of the metal fatigue I can't see any reason to take the band aids off. My advice is to forget about wasting time and money checking for the start of what is likely an inevitable failure, but instead prevent it with top side reinforcement.

[MTiz]

scotty737 Thanks for this thread. Mind sharing the total price of this job (parts, labor) as well as the links to everything that you bought? I think it will be helpful for people like me looking into getting their subframe done. Thank you!

[scotty737]

scotty737 Thanks for this thread. Mind sharing the total price of this job (parts, labor) as well as the links to everything that you bought? I think it will be helpful for people like me looking into getting their subframe done. Thank you!

I don’t have an easy list of everything with links and pricing, but you can figure it out yourself with google.

It’s just the redish plates, Wurth self etching primer, a 2k primer, 3m seam seal, Wurth underbody coating, 3m cavity wax, SEM EzCOAT in light green as redish says it’s the closest to oe color, and a can of your body color to dust the trunk to replicate the factory color. This is about 400-25$.

Labor was free since I did it myself and the welder was 400$. Redish rates the job at 28-32 hours to get oe like finish so you can factor what a shop would charge using that.

I also am doing everything in the rear end, the giubo, the csb and a new diff cover. I think in total it’s about 1800 in parts/welder+ alignment.

[scotty737]

Hope he had a good reason lol.

Can I jump in and ask something related, my car has plates on the underside from the previous owner, they are on there with epoxy and the job looks like it was done alright as far as anyone can know from just looking. I have been considering a topside bar reinforcement, and I was just wondering if there's any reason to be concerned about cracks if there are none visible from the top? I just don't know how good a job the last guy did. I will not be tackling this as a DIY regardless but I'm just curious.

You need to drop the subframe either way to install the top side bar, so you can weld the plates, stitch wheel well, repair bad spot welds, and rtab pockets. Then you have no worries about the PO job. Not sure how hard it is to remove that epoxy though, I’m sure it is a lot of work.

[tnord]

Labor was free since I did it myself and the welder was 400$. Redish rates the job at 28-32 hours to get oe like finish so you can factor what a shop would charge using that.

holy hell, at basic shop rates of $100/hr this is sounding more like a $5k job than the $3k I was kinda planning on. curious if others who have had this done have any feedback?

[scotty737]

holy hell, at basic shop rates of $100/hr this is sounding more like a $5k job than the $3k I was kinda planning on. curious if others who have had this done have any feedback?

I mean you can do it for less. It just depends on the level of finish you are after. I had a quote of 1250 for labor of underside plates. The interior removal, cutting and masking was pretty time intensive.

I was just worried about the shops job on the underside coating and I would rather be the one cutting my car. I didn’t want to have to drop it again to repair rust in the near future, because that is basically all the labor.

I will also say that I got a 6800$ quote from Kassel for doing all the work I’ve done, so at the end of the day I have saved quite a bit. Although, they were going to do their own top side reinforcement kit. I can’t imagine the labor is really much different. I think I am going to end up at about 40-50 hours for all this though.

[tnord]

I've never welded a thing, so I don't think this is the job to learn on.

I'm also planning on top side reinforcement, so I guess it's just going to cost more than I had thought.