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E46 m3 subframe reinforcement epoxy crack#
I'd prefer to fix the problem rather than having to keep lowering the subframe to inspect on a regular basis - and then one day discovering a crack and having to do it anyway - and your probably much better off dealing with it before your RACP is weakened to the point of cracking.Yes that is fair. It's not a matter of if but when - so I would have pre-emptively reinforced mine even if there was no sign of cracking. I'd prefer to fix the problem rather than having to keep lowering the subframe to inspect on a regular basis - and then one day discovering a crack and having to do it anyway - and your probably much better off dealing with it before your RACP is weakened to the point of cracking.Īs CMP say on their website, all E46's RACPs will eventually fail due to metal fatigue. It’s much more involved and not something I’d consider doing as an “already in there” time saving overlap.As CMP say on their website, all E46's RACPs will eventually fail due to metal fatigue (except for the compact). Not to mention disconnecting driveshaft and rear brake lines. Heck you have to drop the gas tank to do the welding responsibly.
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I don’t feel the inspection time is close to being equivalent to the repair time when welding in plates. You don’t need to fully “drop” it/remove it like when doing plates. Done inspections many times over the decade plus. I see your reasoning but one only needs to “lower” the subframe marginally to have access to clean and inspect. You'll find cracks around the threaded anchors under the back seat and spot weld failure where the bench seat base meets the frame rail and in extreme cases where the front edge of the RACP meets the seat base under the sound deadener.Ī bolt through design does nothing for these areas nor does a tube linking the bench seat to the mount IMO.Ĭheck out figure 19 onwards if you want examples of what I'm referring to: This also assumes you're using a non standard bush which is known to lunge into the chassis which also requires a plate to increase thickness and thus shear strength of the underside face.Ĭracking at the front mounts is also a lot more complex than just the top welds and underside.
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I personally would go for a larger plate as I do see cracks creep along the radius and would prefer to be a bit more comprehensive. You don't need a substantial plate in this case (provided you've reinforced from above) as it needs to only function like a large washer. My concern is simply that cracks form around the stud hole due to what I assume to be the contacting pressure. Cracks grow perpendicular to stress and cracks seem to form at the top and bottom of the top welds so would suggest this could be the cause. I've seen a few people say that the stud gets bent left to right and that is the result of the cracking underneath however, the front subframe mounts are secured in double shear so the stud doesn't have the ability to flex side to side? There still would be lateral loading on the insert with some eccentricity could cause the top welds to fail. I understand how a top nut can prevent the top welds from tearing out in the earlier cars however, the later cars had additional welds securing the threaded insert within the chassis and thus the inserts no longer tore out. When you pair them with a set of chassis rail to RACP plates you yield more or less the same result at a more budget friendly price. Something to keep in mind is that a good enough set of underside plates provides almost as much rigidity as most of the slender hidden bar solutions as they have just much material equally as far from the neutral axis. Technically the rear two mounts don't once you've done enough up top however, if you're doing the front two, the rear two aren't optional unless you want to subframe to sit funny.Įvery M3 I've ever inspected has had cracks present so they're more or less always needed for the purpose of strengthening the fatigued steel to prevent the same cracks from forming again at the stress concentrations. But that’s not to say it would not be “worthwhile” to do them while in there for some.Plates are still entirely needed regardless of the topside reinforcement as the front two mounts are still prone to fail underneath. If doing as preventative you do not “need” the plates.
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If the metal was cracked/highly fatigued you’d want to use the plates then. Have not seen the VinceBar design stating plates would be needed since it holds from the top across both rear mounting blocks and further along to the sides.