E46 Arches

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BMW E46 M3 Rear Wheel Arches Rusting

The 2nd most common E46 enquiry we receive (after RACP work) is 'Rear Arch Rust'.

E46 rust in rear arch, advice please. Reply Reply Author. Original Poster. Monday 10th September 2012. Hey Guys, Was washing the car today, and to. BMW E46 GTR Coupe Body Kit. Geoff Steel Racing have used this kit for many years. Designed to be lightweight, durable and cost effective. Will house 12J Rear and 11J Front width wheels using 325 Rear and 265 Front Tyres (possibly wider if required) The kit comprises of: 2x front wings/fenders/front and rear bumper/pair side skirts/pair rear arches.

Extreme Dimensions Duraflex Replacement for 2001-2006 BMW M3 E46 Circuit Wide Body Kit - 6 Piece Ruien Universal Fender Flares Over Wide Body Wheel Arches 4pcs 2inch (50mm) 4Pcs 3.5'/90mm Universal Flexible Car Fender Flares Extra Wide Body Wheel Arches.

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.

Redish offer 2x different E46 Rear Inner Wheel Arch Repairs:

  • New BMW Metal Inner Wheel Arch Panels £2895.
  • 3M Panel Bond Adhesive (aka CSL style) Inner Wheel Arches £1595.

(Prices are for both sides, and include all paints/materials/labour, and VAT).

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:

What is the purpose of fender vents?

The main purpose of fender vents is to relieve built-up air pressure from inside the wheel arches which causes aerodynamic lift. Typically, there are air intakes in the front of the bumper directing air over the brakes to cool them. This air gets trapped in the wheel arches and creates high pressure. High pressure results in lift over the front wheels reducing traction. Relieving this built up high-pressure system in the wheel arches reduces front axle lift thus increasing safety and grip.


In addition to high pressure,tTrapped air in the wheel arches also creates aerodynamic drag. Drag is the force of air pushing in the opposite direction of the vehicle, reducing efficiency. Some research suggests wheel arches account for up to 30% of aerodynamic drag of a vehicle. With fuel efficiency ratings becoming increasingly more strict on modern vehicles, you can understand why so much attention is being directed towards the reduction of this inefficiency. Efficiently routing air into and out of the wheel arches increases fuel economy through the reduction of drag.

Another benefit of fender vents is to efficiently vent hot air generated by heavy breaking out in the air stream. Fortnite ninja wallpaper. Quickly relieving hot air generated from the brakes makes room for more cool air to pass over the brakes, thus increasing efficiency. Finally, it is worth mentioning that trapped air in the wheel arches also contributes to cabin noise. Reduction of cabin noise is more pleasant to drivers on long trips reduces driver fatigue.

* For another topic on aerodynamic efficiency and lift reduction, read our article on rear diffusers. It explains what they are used for and how they work, click the link HERE.

Do the fender vents vent hot air from the engine?


No, not on BMWs. Some vehicles tie in the fender vents exhausting hot air trapped under the hood and out the fender but on BMW models the fender vents are not related to venting hot air from under the hood.

Are all BMW fender vents functional?


No. Some are just for show. The E46 M3, for example, has nonfunctional fender vents. The original design was intended to use functional fender vents however the engineering team decided the vents were not needed through testing. The final vehicle design was already approved by the marketing team however and as a result, the fender vents stayed with the design of the vehicle but were made nonfunctional. Since the E46 M3, each subsequent generation M3 has had the fender vents become an iconic design element of the car. The M4, however, does have functional fender vents.

What does BMW call their solution to efficient air flow?


BMW is marketing these new aerodynamic features as “Efficient Dynamics”. 'BMW EfficientDynamics is the name of the strategy from BMW to minimize fuel consumption and CO2 emissions while, at the same time, increasing dynamics and driving pleasure. It is a package of functions covering the drive system, energy management, and vehicle concept – and is a standard feature in every BMW.' - BMW.com

Where can I learn more BMW fun facts?

E46 Flared Arches

Learn more BMW fun facts by clicking HERE

E46 Armrest Cover

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