Galapolis
11-07-2020, 08:59 AM
When I did my suspension refresh back in September I checked for RACP cracks and found a small hairline crack at the usual back left fold. A reinforcement had been on my mind for a long time, but since I don't own a garage and need my car as a daily, the lengthy (and expensive if paying someone else!) plate install was out of the question.
Over the summer ZHPizza was like "yo check out these X-Braces, you should totally get one bro" and I was like nah. But obviously seeing the crack recently made me rethink so I looked more into the X-Braces and both ZHPizza and my research confirmed that the X-Brace is actually the better solution compared to the plates. The plates are simply a band aid. They don't address the root cause of the issue. You can read about it in detail here (https://forums.m3cutters.co.uk/threads/subframe-question.173445/page-4) (many examples of cracks after plates were installed) and here (https://cmpautoengineering.com/pages/technical) (some other good reading material too), but basically the subframe mounts are just in the wrong position on our cars.
They are too far in, which means that all the load from acceleration, braking, turning etc. gets transferred into the weak sheet metal of the RACP, leading to the notorious cracks. On properly designed cars, the mounts are below the chassis rails. So the solution, in essence, is to redirect the load path so that the chassis rails absorb all the forces. The chassis rails can easily handle those forces, since they are designed to carry the full weight of the car. You will find the rear springs directly under the chassis rails for this reason.
Now the Vincebar does this in the most direct manner by creating a bridge between the top surface of the rear subframe mounts and the side of the chassis rails. It's a permanent solution, but the installation is quite involved and still requires welding and/or epoxy. This is where the X-Brace comes in.
The X-Brace mounts to the same top surface of the rear subframe mounts, but instead alters the load path to direct the forces to the rear shock towers. These are welded to the chassis rails, so the end result is ultimately the same. The chassis rails absorb all the forces via the shock towers with the X-Brace installed, just as it should be. But unlike the Vincebar, the X-Brace is basically a bolt-on solution that you can also reuse on your next E46.
There are several options for X-Braces on the market, but many are overpriced (*cough* Mason *cough*), overly complicated or very heavy. That's why ZHPizza went with the Specialised Motorsports Engineering X-Brace (https://www.s-m-eng.com/product-page/e46-racp-brace).
ZHPizza coordinated a mini group buy and after some good experiences installing the X-Brace on his very red car, it was time for him to help me install it on my blue car. And by help I mean he basically did the entire install while me and my buddy worked on the Moog RTABs, so many thanks again @ZHPizza for making this possible.
The installation only takes a couple of hours and is very simple compared to the plates. First up, remove everything from the trunk.
37427
Next, drill holes above the rear subframe mounts using the provided guide tool from SME. You can see Pizza hard at work here.
37428
Then, thread the longer subframe bolt, also provided by SME, through the rear subframe mount into the rear trunk.
37429
Time to test fit the brace.
37430
If it's nice and snug, torque down all the bolts and then drill holes into the shock towers. Use the provided bolts and nuts to securely attach the brace to the shock towers.
37431
And that's basically it. If desired, you can adjust your rear trunk floor and liners to fit around the X-Brace.
37432
Finished product.
37433
Since the X-Brace locks the rear mounts into place, it also protects the front mounts. That being said, only the non-folding sedan and convertible have reinforced front subframe mounts, so unless you have one of those two body types, it would still be a good idea to install front reinforcement mounts like those found in the Vincebar kit.
Now I'm sure you're wondering how you too can get such an easy subframe fix. Well, you're in luck! ZHPizza has one more SME X-Brace left over from the group buy, so go flood his inbox with messages about wanting to buy it immediately. In the meantime, I'll be enjoying the extra practicality added by the X-Brace, which protects both my RACP and my groceries from ejecting themselves from the car.
37434
Over the summer ZHPizza was like "yo check out these X-Braces, you should totally get one bro" and I was like nah. But obviously seeing the crack recently made me rethink so I looked more into the X-Braces and both ZHPizza and my research confirmed that the X-Brace is actually the better solution compared to the plates. The plates are simply a band aid. They don't address the root cause of the issue. You can read about it in detail here (https://forums.m3cutters.co.uk/threads/subframe-question.173445/page-4) (many examples of cracks after plates were installed) and here (https://cmpautoengineering.com/pages/technical) (some other good reading material too), but basically the subframe mounts are just in the wrong position on our cars.
They are too far in, which means that all the load from acceleration, braking, turning etc. gets transferred into the weak sheet metal of the RACP, leading to the notorious cracks. On properly designed cars, the mounts are below the chassis rails. So the solution, in essence, is to redirect the load path so that the chassis rails absorb all the forces. The chassis rails can easily handle those forces, since they are designed to carry the full weight of the car. You will find the rear springs directly under the chassis rails for this reason.
Now the Vincebar does this in the most direct manner by creating a bridge between the top surface of the rear subframe mounts and the side of the chassis rails. It's a permanent solution, but the installation is quite involved and still requires welding and/or epoxy. This is where the X-Brace comes in.
The X-Brace mounts to the same top surface of the rear subframe mounts, but instead alters the load path to direct the forces to the rear shock towers. These are welded to the chassis rails, so the end result is ultimately the same. The chassis rails absorb all the forces via the shock towers with the X-Brace installed, just as it should be. But unlike the Vincebar, the X-Brace is basically a bolt-on solution that you can also reuse on your next E46.
There are several options for X-Braces on the market, but many are overpriced (*cough* Mason *cough*), overly complicated or very heavy. That's why ZHPizza went with the Specialised Motorsports Engineering X-Brace (https://www.s-m-eng.com/product-page/e46-racp-brace).
ZHPizza coordinated a mini group buy and after some good experiences installing the X-Brace on his very red car, it was time for him to help me install it on my blue car. And by help I mean he basically did the entire install while me and my buddy worked on the Moog RTABs, so many thanks again @ZHPizza for making this possible.
The installation only takes a couple of hours and is very simple compared to the plates. First up, remove everything from the trunk.
37427
Next, drill holes above the rear subframe mounts using the provided guide tool from SME. You can see Pizza hard at work here.
37428
Then, thread the longer subframe bolt, also provided by SME, through the rear subframe mount into the rear trunk.
37429
Time to test fit the brace.
37430
If it's nice and snug, torque down all the bolts and then drill holes into the shock towers. Use the provided bolts and nuts to securely attach the brace to the shock towers.
37431
And that's basically it. If desired, you can adjust your rear trunk floor and liners to fit around the X-Brace.
37432
Finished product.
37433
Since the X-Brace locks the rear mounts into place, it also protects the front mounts. That being said, only the non-folding sedan and convertible have reinforced front subframe mounts, so unless you have one of those two body types, it would still be a good idea to install front reinforcement mounts like those found in the Vincebar kit.
Now I'm sure you're wondering how you too can get such an easy subframe fix. Well, you're in luck! ZHPizza has one more SME X-Brace left over from the group buy, so go flood his inbox with messages about wanting to buy it immediately. In the meantime, I'll be enjoying the extra practicality added by the X-Brace, which protects both my RACP and my groceries from ejecting themselves from the car.
37434