BMW E46 M3 Rear Wheel Arches Rusting

'Rear Arch Rust' is the 2nd most common E46 enquiry we receive, after RACP work.

All E46 Rear Arch corrosion starts from the Inner Arch area.
Regardless if you can only see a small blister on the Outside Arch area.
We can guarantee you that the epicentre is hidden under Seam Sealer on the Inner Arch area.
This means if you aren't tackling the Inner Arch area then the corrosion will return.

We've been tackling E46 Rear Arch corrosion for many years now and if you've followed us on our YouTube channel, and Facebook/Instagram pages you would have seen several of our repairs


Having now been working with E46 M3 Inner Rear Wheel Arches since 2015, we have found many different ways to complete this work, including copying the CSL style.

We're currently working on a new way of helping owners understand which style of Rear Arch repair they will require and therefore the costs involved.

This is a time consuming process as we have identified 8 versions of the repair.

We are building a flow chart to help decipher which 'option' you may require.
We're also working on a new picture set of each version, along with one of our detailed videos to explain this, and if all goes to plan, pricing.

We're still taking on Arch Repair bookings and currently working on Arch Repairs here in the workshop right now, but we just can't give exact pricing currently.

So, if you require pricing first before booking in with us, we recommend that you wait until we've finished the revision of this webpage before booking.

We don't yet know when this page will be updated next, but we are working on it.

Please note:
To rid a wheel arch completely of corrosion sometimes the outer arch needs bare-metalling.
It's common that the outer painted arch (body-coloured) will require repainting at a bodyshop.
We are not a bodyshop and cannot paint the outside of the vehicle (body-coloured paint).
This means that in some cases you may need to have outer body paint.
We are unable to offer outer bodypaint and you would need to deal with this separately.

By far the most popular version is our 3M Panel Bond Adhesive (aka CSL style) modification.

This is where we remove a section of the Inner Wheel Arch Panel - especially the 'U shape channel' which removes 99% of E46 Inner Arch rust.

We leave this cut as that's how it is on the CSL Wheel Arches.

Once all the remaining loose corrosion has been removed/cleaned from the Outer Wheel Arch 'U shape channel' we treat any bare metal with a chemical to stop it further corroding.

We then improve tyre-to-arch clearance by gently closing some of the Outer Wheel Arch 'U shape channel' (all hidden on the inside of the arch system).

Then the area is thoroughly dried and inspected before we protect it with Etch Primer.

Then we carry out our pioneering-repair to bond the Inner and Outer Wheel Arch Panels together using 3M Panel Bond Adhesive - just like a CSL.

We also ensure the remaining Outer Wheel Arch 'U shape channel' is not only completely filled with continually-joined 3M Panel Bond Adhesive, but also envelopes the entire front face of the 'U shape channel'.

This means the vehicle retains it's strength of the 'U shaped channel' but it's completely flat and therefore water/salt/mud cannot collect and instead simply slide down the newly created vertical line and fall onto the ground.

Once cured we further protect the repaired area (Inner Arch area) with High Build Primer, Sprayable Seam Sealer (textured), and 'Redish E-coat' OEM colour.

Finally we treat the internal hidden sections to copious amounts of high performance Cavity Wax for total protection.

Once cured our repair is rock-solid, and will not allow corrosion to form.

This is a repair which Redish Motorsport have pioneered after years of experience with the E46 chassis and especially chasing corrosion, as well as having utter confidence to open up BMW chassis's to component metal form and produce adequate solutions to common problems.

We are soon-to-release a brand new video detailing our 'Rear Arch modification aka CSL style'

In the mean time please feel free to watch our old way of the repair using New BMW Metal Arch Panels: