Reinforcement plates vs structural foam ?

[repoman89]

Agree. I was speaking from my personal perspective - not for everyone. I have a low mileage car in pristine condition that I plan to keep for the foreseeable future. I would have preventatively dealt with it even without any visible cracking - however, even my low mileage never-tracked 'vert had cracks. The CMP dude says every M3 he is now seeing has them, and I recall a UK shop saying some time back that every CSL they inspected had the issue.

If you're regularly lowering the subframe to diligently clean and check for hairline cracks then, by all means feel free to wait until the issue actually manifests if that's your plan - but we've seen over the years that the first time many owners become aware is when the issue has become quite advanced and expensive to repair (and even dangerous).

I tend to side with CMP's reasoning on this - fundamentally, the design of the RACP cannot withstand fatigue failure. Sure BMW has made some tweaks to prevent failure within the warranty period, but in the end it all comes down to the number and severity of duty cycles applied to the RACP. If you baby your M3 or mainly do highway cruising then the metal fatigue will take longer to manifest, but if you track or have a lead foot your RACP will fail much sooner.

Personally, I didn't buy an M3 to baby it :-)

The guy who did my plates and Vince bar a couple years ago told me my car was the first he’d seen in many years without cracks, and it still had popped spot welds so it was on its way. He’s done somewhere north of 200 reinforcements. Car had 40k when I took it in for that and I was always kind of anxious thrashing on it, now I don’t worry about it at all. Well worth it.

[poss]

maybe i missed a response to this question, but for those that already have the foam injection (like myself), what options exist. mine is an '06 fwiw and it was foamed prior to purchase. it has been inspected numerous times w/no cracks discovered. since reinforcement plates can't be done, will the foam with vincebar be sufficient?

thanks.

BTW the foam tends to move the failure point to the wheel arch seams, so make sure you're inspecting all the right spots!

(and as ATB88 said, you can use epoxy as an alternative to welding plates etc)

[poss]

Just to clarify, because I don't think everyone knows/realizes, AussieE46M3 is CMP, he frequents the forums and helps the community.

Yes. He helped me considerably even after I decided to go with a custom hidden brace solution rather than the CMP brace, and has approached analysis of the failure points and stresses involved from an engineering perspective.

Can highly recommend the CMP plates I used - they offer more comprehensive coverage/strengthening than others I have seen.

[AussieE46M3]

maybe i missed a response to this question, but for those that already have the foam injection (like myself), what options exist. mine is an '06 fwiw and it was foamed prior to purchase. it has been inspected numerous times w/no cracks discovered. since reinforcement plates can't be done, will the foam with vincebar be sufficient?

thanks.

Although it makes things quite a bit harder and riskier, it is still possible to weld plates onto a car that has has foam injected into the RACP.

I have never done it myself however, I've had two customers within Aus do so and I provided what guidance I could remotely.

I literally just figured that out five minutes ago as I sent CMP an email. 🤦🏻♂️
Thanks for the clarification haha.
I do like your top mount kit pricing. 👋🏻 AussieE46M3

Thanks!

I plan on doing a sale next month (conditional on a new batch of parts arriving in time) so they'll be even better if you're after anything.

Yes. He helped me considerably even after I decided to go with a custom hidden brace solution rather than the CMP brace, and has approached analysis of the failure points and stresses involved from an engineering perspective.

Can highly recommend the CMP plates I used - they offer more comprehensive coverage/strengthening than others I have seen.

Thanks for the kind words. I'm glad I can help!


On a separate note about cracking, I inspected a very nice, stock 02 LSB car yesterday with only 80k km/~50k miles with some pretty significant cracking at the front right/rear left mounts and spot weld failure in an abundance of places. It was a weekend car so although not driven much, it had been driven hard.

[martin.oconnor]

I recently installed structural foam on my M3. (I enclose a PDF of the write-up I did at the time since the image links from my original threads are no longer live.)

I did a lot of reading before deciding on this route. There were many high-quality threads on the various solutions on different boards available to read (though many are now gone since the demise of m3forum.net).

While there was a consensus that the foam-based solution was somehow an inferior approach, I was not remotely convinced by the evidence.

At the time I did the research (last year) I could not find a single report of failure on a car that had foam injected.

Specialists like Redish Motorsports in the UK, who appear to have done a crap ton of foam procedures on M3 back in the day, also did not report any failures (even though they now seem to have abandoned this procedure since they had trouble sourcing the foam).

Reading this thread has not changed my mind. Yup - there is now a single report on this thread of the failure points now being moved to the wheel arches in a car that had foam injection - though, frankly, if the chassis design is really that compromised it might be time to find a different car.

It is worth noting that the foam injection procedure is extremely easy to do (it can be done in an afternoon) and relatively cheap (and the foam is now readily available online).

[poss]

I recently installed structural foam on my M3. (I enclose a PDF of the write-up I did at the time since the image links from my original threads are no longer live.)

I did a lot of reading before deciding on this route. There were many high-quality threads on the various solutions on different boards available to read (though many are now gone since the demise of m3forum.net).

While there was a consensus that the foam-based solution was somehow an inferior approach, I was not remotely convinced by the evidence.

At the time I did the research (last year) I could not find a single report of failure on a car that had foam injected.

Specialists like Redish Motorsports in the UK, who appear to have done a crap ton of foam procedures on M3 back in the day, also did not report any failures (even though they now seem to have abandoned this procedure since they had trouble sourcing the foam).

Reading this thread has not changed my mind. Yup - there is now a single report on this thread of the failure points now being moved to the wheel arches in a car that had foam injection - though, frankly, if the chassis design is really that compromised it might be time to find a different car.

The problem with the foam is, although it will help prevent cracking around the subframe mounts it doesn't correct the load paths and moves the problem elsewhere (like the wheel arches) which people aren't necessarily looking for Redish didn't realise at first that underside reinforcement plates similarly moved the issue to the secondary failure points. Now Redish include stitch welding the wheel arches as a standard part of their procedure (they're a workshop not an engineering company).

CMP on the other hand is an engineering company and advise:

"For permanent peace of mind, additional chassis structure installed from above the RACP is required to provide reinforcement, correct load paths, eliminate stress risers and increase structural integrity overall."

Just like underside reinforcement plates, foam ain't reinforcing your wheel arches or changing the load paths. There are plenty of examples of secondary failures after plates have been installed and sound engineering advice as to why you need topside reinforcement to actually fix the problem - which was more than enough evidence for me when I went through the same investigative process last year.

[martin.oconnor]

CMP is a company selling a product. By all accounts, it is a good product - but I would definitely not treat such a source as definitive.

The BMW foam injection procedure has been around since 2003 - and when I searched last year (over many E46 boards) I could not find a single report in that 16 year period of post-foam failure. Not one.

The theory now appears to be the foam actually works but that it moves the failure points to the wheel arches. I don't really understand how it could have taken 16+ years to discover this if it is at all a common failure mode. I am not saying that it is not possible - I'm just questioning how likely it is given the massive evidence gap.

[poss]

CMP is a company selling a product. By all accounts, it is a good product - but I would definitely not treat such a source as definitive

CMP is not merely a company selling a product. The CMP dude is a qualified engineer who designed the product(s) after analysing the structure and forces at play when his own car suffered secondary failure

As I said - people know about the subframe issue and inspect there - but not so many know about the secondary failure points.

Personally, I wouldn't buy a car with foam as its more difficult to fix properly.

[old///MFanatic]

CMP is not merely a company selling a product. The CMP dude is a qualified engineer who designed the product(s) after analysing the structure and forces at play when his own car suffered secondary failure

Curious who came out with this type of brace design first between VInceBar or CMP?

How many years LATER than a racing company like Turner Motorsport did they add the plates to their product line?

(So no confusion, I completely support upstart businesses in the E46 community) 👍🏻

*analyzing not analy-sing

[eacmen]

Curious who came out with this type of brace design first between VInceBar or CMP?

How many years LATER than a racing company like Turner Motorsport did they add the plates to their product line?

(So no confusion, I completely support upstart businesses in the E46 community) 👍🏻

*analyzing not analy-sing

AFAIK Turner was the first to bring plates to market. They saw this failure before a race weekend, rapidly designed the plates then started selling them soon after.


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[AussieE46M3]

I can dig up some pics of a few post foam failures if you'd like? Doesn't seem fruitful given you've already gone ahead with it.

The foam doesn't just move it to the wheel arch and between. The original procedure was to weld small cracks then foam. The cracks eventually re-formed in in the same place following that procedure.

I appreciate your support guys and it's good to see people do read those tech articles

I do stand by that statement that topside reinforcement is 100% necessary for permanent peace of mind. The reason I stated I don't always encourage this which I saw quoted earlier is because a full topside reinforcement can land half way to 5 figures which most Non-M's aren't worth and thus it would be a major over capitalisation.

This is where I suggest the underside plates and chassis rail plates then do more if justified depending on long term plan, intended use, mods etc. I don't want to push an huge upsell down someone's throat and risk their financial position.

In terms of who originated the idea of a topside reinforcement that credit actually goes to a guy in South Australia named AJ. He had an incredible M3 that he super charged, then swapped for twin turbo's and eventually pulled the lot out and went with blown 7 point something litre LS from memory. If I recall correctly he did it way back in 07 or 08?

I discovered this when I was part way through working on my own topside reinforcement and sharing progress on some Australian E46 Facebook pages.

Here's a pic of his car from a while back from a summernats event. I don't believe the blower was on their for too long.


As eacmen said, I believe the original underside plate manufacturer for the E46 chassis was Turner as I recall reading about them having to slap something together over night in order to make a race weekend and that's the product they ended up selling. In saying that, I suspect it was inspired by the underside plates for E36's so maybe the original credit lies with BMW?

The first product I made was the topside beam kit which I started on back in 2016. I installed Redish plates in late 2015 as per their direction and video's at the time and just kept finding more damage that wasn't detailed anywhere and needed a solution for my own car. It was only meant to be a 1 off but I got a bit of interest from a few other M3 owners and decided to get a small batch made and the rest is history.

[old///MFanatic]

AFAIK Turner was the first to bring plates to market. They saw this failure before a race weekend, rapidly designed the plates then started selling them soon after.

Yes thank you for reply. But I was asking how many years after TMS. (Sorry wording wasn’t more clear.)
Was not sure if it was a decade and a half or just a decade..

[old///MFanatic]

In terms of who originated the idea of a topside reinforcement that credit actually goes to a guy in South Australia named AJ...If I recall correctly he did it way back in 07 or ‘08.

Actually my question was between “VinceBar” and “CMP” who came out with this first? (since you’re one of the companies I’m sure you can answer)

As I posted before, way back even before my post of ‘06 Active Autowerks was doing a bolt through supported by a cross bar. They were getting some early ‘00 E46s with their high boost supercharger to crack at the RACP mounting blocks. So not sure AJ was the first in ‘07-‘08.
More the point who was making and selling it first.

[poss]

Actually my question was between “VinceBar” and “CMP” who came out with this first? (since you’re one of the companies I’m sure you can answer)

Wearing my asbestos undies here, I believe Vince was first to sell a rear (stealth/hidden) RACP mount topside bar solution - then CMP came out with their H-Bar solution which extended rigidity with another bar directly between chassis rails and the addition of a completely new topside bar to strengthen the front mounts (for coupes).

[kaiv]

Just a single datapoint but some years ago I would occasionally do the structural foam service according to the factory BMW instructions.
I saw one of those cars again more recently. No problem where the foam was but it had developed cracks elsewhere.