"In this Special Series, I'm taking another step towards the M5 CSL conversion. I document the development, features and conversion process of the E60 M5 CSL carbon roof kit.

In this entry, I document the underlying benefits to the carbon roof conversion. I review the required Genuine BMW hardware, and we test fit the carbon roof to understand how it's aligned. Lastly, accessories get painted and slight repairs are performed."
- Matt

Wind noises, be gone - amongst other things.  

The E60 M5 is my only car equipped with a sunroof. I understand why some owners appreciate the glimpse of rays, I personally always felt it was annoying for my year round use. 

The panel tends to slide backwards half an inch due to hard SMG3 shifts. The slight gap increases the baseline for wind noises, which was already slightly higher than the E92 M3 with carbon roof. In addition, the sliding panel lets light creep into the cabin in unforeseen circumstances and it creates a cold air pocket during Winter time.

The sunroof seals would eventually rot, and be a potential water infiltration problem that can be a cause of fried sound system amplifiers.

While worth mentioning, these are minor annoyances that don't drive most of the value to this carbon roof conversion. It does present the opportunity to improve upon the M5's comfort. 

Improved slicktop insulation. 

With the E46 M3 CSL carbon roof conversion, I learnt BMW uses larger insulation pads for their sunroof-less cars. From reviewing diagrams, this was also the case for the E60 M5. Unfortunately the diagrams weren't clear.

The novelty of this conversion meant we had to patiently blaze the trail. We awaited until the original metal roof was removed to better understand whether some pads would be re-used, and which would be needed.

Ultimately, none of the sunroof insulation pads would be re-used. I ordered 2x insulation pads and 3x sound absorbers from BMW.

These are required for street driven M5s, and are included as part of the conversion kit.

The insulation pads from the metal sunroof panel were all discarded. 

The roof bow - or bar. 

BMW's slicktop roof cars usually feature a roof bow: a transversal metal component that connects the B pillars of the chassis. The E46 M3 uses a roof bow that is bolted, and glued to the B pillars directly. You can learn more in my entry here. 

According to diagrams, the E60 did also use a roof bow - but its design is more of a bar. It's straight, with added ribbed section to improve rigidity. It does not angle inwards into the cabin, nor does it required bolts to install. 

Whether the roof bow is considered a structural component can be partly deducted from BMW's evolution in carbon roof design. The F87 M2 CS introduced a new carbon roof design that extended to the edges of the roof's chassis.

The results were increased rigidity, improved comfort, and reduced weight by 4.0 kg / 8.4 lbs by discarding the roof bar, roof rails and some insulation in the process. 

BMW M's brochure stated the following:

"The new roof, with its sandwich design, makes the body more rigid and appears to have been cut from the same mould as the rest of the car; no trim strips are needed, meaning no visible join[t]s either.

This has the additional effect of enhancing acoustics, both inside and outside the car. And dispensing with the customary roof bows and insulation also saves weight." 

The availability problem. 

Worryingly, BMW USA had the roof bow listed as No Longer Available (NLA). Luckily, I was able to find 2x in the BMW Germany network. One was ordered for my conversion, while the other stayed in Germany to be kept for the development of a carbon variant similar to the E46 M3 unit we previously manufactured. 

The metal roof bar is included as part of the conversion kit. If availability changes, we will have a plan B. The carbon roof bar can also be optioned if you want further weight reduction. 

For documentation purposes, I used the original BMW part. It has a slight curvature that makes it clear which side is up, and down. 

The roof chassis rails have indents in the sheet metal layers to allow the easy installation of the bar. 

It snaps in, sandwiching the rail in the process. 

It is snapped in very firmly. 

We noticed our mistake at this stage. The bar does have an orientation. Can you see any indication?

The center section has an offset cutout that needs to be oriented towards the back of the chassis. It is used to install the headliner and support it into place.

The alignment mechanisms. 

Prior to proceeding with gluing the roof panel, we practiced! We prepared the surfaces but did not apply adhesives to any section. 

We proceeded with inspecting the roof panel and roof chassis rails to better understand how the alignment of the panel would be completed. The roof panel was dropped onto the chassis rails and we fiddled with its position. 

We found BMW integrated 2x main alignment mechanisms on the E60 chassis.

The first mechanism are the angled indents at all 4x corners. The angle provides the alignment, and matches with the roof panel. 

The 2nd mechanism are dimples shaped onto the roof chassis rails, and on the original metal roof skin. As the carbon panel is an exact replica, those dimples were retained. 

They come in pairs, and are located at 1/4 and 3/4 of the way through each rails. 

The unofficial 3rd mechanism is a paint shop trick. The E60's roof rails have a curvature that will fit with the roof's chassis rails and the roof panel. It isn't a perfect solution, and should be used in conjunction with other methods. 

Do not try this trick with the E46 M3. The CSL roof panel used different shaped roof rails specific to the CSL.

Prior to gluing the roof panel, the original Sepang Bronze rails and antenna were prepared and painted to Gloss Black finish. 

The color and finish mimics how BMW M complements its carbon roof on the E92 M3.  

Paint repairs. 

This type of repair can be performed without a complete respray of the quarter panels and pillars' section. 

I highly recommend you personally inspect the roof's chassis rails after the removal of the metal roof skin to ensure no bare metal is visible as you will not notice if the roof rails are installed. However, corrosion will still erode away at the metal. 

The roof's chassis rails were sanded, prime and resprayed in Sepang Bronze as original. 

With the process understood and preparations made, it was time for permanence. 

Up next: the carbon roof gets glued and sealed, and the antenna gets fitted.