Karbonius CSL Roof – Tips for DIYers

[SQ13]

There are a lot of online resources for roof installs on the E46, but I felt that there was some missing information, especially for the Karb roof. So I’m making this thread to hopefully address the missing stuff as well as outline the steps I took to hopefully help out some future DIYers. Is the install difficult? I don’t think so. Just a job that’s time consuming and requires care and high attention to detail. But I’ve also been working on this M3 since 2013 and have also done four header installs on it, so I’m prob somewhat of an experienced DIYer. Huge thanks to heinzboehmer for holding my hand thru the entire process and answering my endless stream of dumb questions.

First, I’m going to link resources that were helpful. I’ve also attached the official BMW instructions for carbon roof install on the E46 M3 CSL and F87. I would suggest reading thru these first then the third party resources, so you can come up with a game plan that’s somewhat close to the BMW install methods. The MunichVenom vid and Bimmersport forum thread were really good IMO.
1. https://forums.m3cutters.co.uk/threa...-install.9539/
2. https://e46m3.bimmerpost.com/forums/...d.php?t=877448
3. https://bimmersport.co.nz/topic/6789...unroof-delete/
4. https://euroconnex.co/blogs/the-phoe...ut-glasses-out

1. https://youtu.be/Bny08_GKhNk
2. https://youtu.be/0jdThGJtem0
3. https://youtu.be/wF4-oLDS50Y
4. https://youtu.be/wmC-gooNM0M
5. https://youtu.be/ESjX2BCyzIQ
Don’t waste your time watching the YouTube video of the dude with the LSB M3..it’s a half assed install.

1. 41 31 000 Replace roof outer skin (CFRP roof equipment specification).pdf
2. Carbon Roof Panel Retrofit Installation Instructions.pdf


Edit: I can rent out the bolded tools. If in Houston, I can also offer installation, BUT I’m also busy with med school so scheduling and the actual work may take some time.

Tools
18” locking C-clamps
1” C-clamps (would recommend 6-8 more if you're going to over clamp like I did)
Paint mixing sticks
Blair 11096 spot weld cutter
Blair 11750 lubricant for cutter
Lisle 51900 chisel
Belt sander
3M 80 grit sanding belts (33446)
Two part epoxy/caulking gun
Standard caulking gun
Rivet tool
Drill bits
Shop vac
Step stool for the short kings and queens
Plastic razor blades
Big boi razor blades and/or other sharp cutting tools

Consumables
Sika Force 7888 panel bonding adhesive (K3 adhesive) -- this has a six month expiration time; 3M 08115 is a good alternate
DuPont U-418 windshield adhesive
DuPont 5504G primer -- would recommend getting more daubers bc you don't want to double dip them and contaminate the primer
3M/Dynatron seam sealer
Scuff pads (BMW recommends Scotchbrite ultra fine)
Shop towels
Tack cloth
Isopropyl alcohol
Acetone
Wax and grease remover
Clear plastic sheeting
2x queen top bedsheet
Automotive masking tape
Duct tape

PPE
3M respirator with 60923 filters (if you're worried about counterfeits like me, have Home Depot price match)
Safety glasses/goggles
Earplugs/muffs
Face shield
Disposable coveralls
Latex dipped gloves for acetone handling
Leather work gloves

Parts
Rubber gasket/seal for front and rear glass
Windshield cowl
Slicktop headliner and correct coat hanger brackets


Karbonius roof-specific info
1. Karb recommends cutting the roof corners at an angle (like OE) to clear the nubs
2. Karb recommends cutting the front overhang
3. Karb recommends using clamps every 10-15 cm on the front and rear edges
4. Stock roof rails can be used since the roof has attachment points for them. Or spend $400 on CSL rails. Whatever your heart desires
5. The underside of the roof does NOT come marked
6. The 1x1 carbon weave is perfection tbh, and none of the other popular options I’ve seen match the quality of these pieces. Pricey? Yes. Worth it? 100% This is pretty much a permanent install, so you might as well do it right.


And now what I did and/or recommend in chronological order. Take what you like and ignore what you don’t like…or use it as your DIY guide. Whatever works best for you. TLDR/high yield points will be bolded.

Pray to the gods that your new glass doesn’t crack when being removed. Now would be a good time to redo the tint if yours is failing. My glass guy was cool and offered to take my front and rear glass to a tint shop. Rear deck is easy to remove now, if you plan on doing anything with it.



Remove one or both front seats if they’re fixed back seats. Draping will be easier if you have both removed. The rear door cards do not need to completely come off in order to remove the B pillar cover—you can just pull off the top front corner to get to the two plastic rivets that hold the cover.

I’d highly recommend thoroughly draping exterior and interior with clear plastic sheets. For the interior, also suggest adding throwaway cloth sheets to help take up the majority of the metal shavings and other debris; this will make cleanup much easier. I used two queen sized bedsheets, but you might be able to get away with one if both front seats are removed. Plastic sheet + cloth sheet = slippery, so try not to slip and fuck up your knees.

For the areas I thought could easily get damaged by my tools, I added 2-3 layers of masking tape plus a layer of duct tape. Definitely do this to the roof rail area in case your drill bit walks off. I also covered the side finishers to prevent damage from dropped tools.



Seam sealer on the sides can be easily removed with a flathead screwdriver. Once seam sealer is removed from the roof rack holes, remove them. They’re just bolts

Handheld belt sander with 3M 80 grit belt works well to expose the spot welds. Center punch, Blair spot weld cutter, lube for cutter, and chisel should be enough to cut the spot welds. You could use belt sander to remove the spot welds if you don’t want to mess with the spot weld cutter. IIRC there are 96 spot welds. Try not to cut past the first layer/roof.

My method for the front and rear edges was to cut a spot weld, separate it from the layer below with chisel and hammer, then move on to the next one. Couldn’t really do this with the sides, so I just drilled them all out then started at one corner and moved along the edge using chisel and small pry bar.

Windshield adhesive is used to hold the roof in three places if your car has a sunroof (2x front bow and 1x back bow). You can either lift the roof panel until the adhesive fails or cut them from the cabin. The roof can come off now.





I used the belt sander to flatten the spot welds - super quick and easy. You can also use it to clean up the areas with windshield adhesive. Wire brush cup was used to clean up the perimeter and roughen the surface.

Used a combination of shop vac, magnets, acetone, and IPA to clean everything.

Roof bow
I decided to rivet and bond the roof bow. You should buy an extra mixing nozzle for the adhesive if you’re doing this. I drilled five holes. There’s about 1 cm of allowable forward/backward movement, so I made the bottom middle hole larger and used it with a small bolt to allow for adjustment. Drill bolt hole only on B pillar. Find a position you’re happy with, tighten down the bolt on either side, then drill thru the roof bow holes and into the B pillar—this method ensures the holes for the rivets will line up perfectly. Scuff bonding surfaces, clean with solvent of your choice, apply adhesive, somewhat loosely install bolt (enough to allow movement to line up holes), rivet, tighten bolts if you decide to keep them in place. FYI if you use the same bolts that are used to secure the surrounding airbag brackets, the brackets WILL clear the bolt head.


Roof rack holes
I was not going to cut up the Karb roof to reuse the roof rack bolts. So I grabbed M10x1.5 set screws and M4 washers (I think, just grab something that’s slightly smaller than the 12 mm hole) to plug them. I adjusted set screw height so that washer would sit somewhat flush with surface. Then I bonded the screw to the washer and used the belt sander to make sure it sits perfectly flush with the surface. FYI the threaded portion of the roof rack hole is not fixed in place. It’s a separate piece that will move around and make noise unless you fix it in place; bonding the set screw to the washer took care of that in my case.


Nubs
There are nubs on the body at each corner. I think these help align the OE roof. The problem with the Karb roof is that the corners are not cut at an angle to clear the nubs, so it won’t sit flush as is. To achieve flush fitment, you can either grind down the nubs or cut the roof corners at an angle (Karb recommends the latter). Be aware that the nubs start to hollow out when ground flat with the surrounding surface, so you may need to fill them in with adhesive.


Clamps
BMW recommends using five clamps on front/rear edge and two clamps on each side. You can use more if you want—just don’t use less. I’ve seen some installs that use a grand total of four clamps…they might be totally fine but why half ass something like this? Be sure to have them pre-adjusted and staged for quick and easy placement after bonding. On front and rear edge, Karb recommends having clamps every 10-15 cm.

I placed wood paint sticks between the roof and clamps. The feet on the 18” clamps were too big for the roof rail section, so I taped some paint sticks together and cut them into blocks. This worked pretty well except for the fact that the adhesive liked to stick to the tape. Duct or aluminum tape might work better.



Roof alignment
Snap on the roof rails to help with alignment. Place some weight on the center section of the roof to help it sit properly. You want the contour of the pillars, roof rails, and roof to match. Once you think the alignment is good, clamp the roof down the same way you plan to clamp when bonding. Double check alignment and fitment of roof rails.

I then used tape to mark the alignment. Roof to roof rail to quickly check roof alignment after bonding. Roof to body on all four edges and corners. You can use a thinner piece of tape or paper on the underside of the corner tape to reduce cross contamination with the bonding surface. I think tape at the corners (not pictured) and roof rail are all that’s needed. Skip the tape on the edges for roof to body alignment.
Also mark the position of the clamps on the roof.
On the underside of the roof, draw an outline of the front, middle, and rear bows.

The front edge of the Karb roof is longer than the lip on the chassis, so I had 6-7 mm of overhang. Karb recommends cutting the excess off. I believe most people just leave the overhang and don’t experience issues with windshield fitment.

Now you can remove everything. On the roof rails slide the clips out of correct position, so when roof with adhesive is placed on car, you can quickly throw the rails without snapping them in to check the alignment.




continued in next post

[SQ13]

Prep for bonding
The photo below was taken from BMW’s instructions. I’ll list what I did for each area and what I would recommend. DO NOT apply the adhesive yet..I’m just describing the *prep* for bonding and order of operations right now.


1. I have seen many people use a thin bead of panel bonding adhesive here. This likely does nothing due to the large gap between the body and roof. You could probably get away with applying a thiccc bead of panel bonding adhesive. I would recommend using windshield adhesive as suggested by BMW bc it will work with the large gap if applied correctly. I went with DuPont Betaseal U-418 with 5504G primer. Scuff, clean, primer, apply windshield adhesive in a triangular shape that’s 10 mm wide and 12 mm tall. When the roof is put in place, this triangular shape flattens to make a thick bond with the roof. To do this, just cut a V-shaped notch on the adhesive tip.
Also, there’s no point in applying the adhesive to the most posterior lip of the front bow (blue X). Yellow lines are where you’ll apply new windshield adhesive, and red line is where K3 adhesive will go.

2. After bringing this area down to bare metal and scuffing with wire brush, I cleaned thoroughly, applied K3 adhesive and brushed it on to cover the bare metal, applied extra in the special areas outlined in the BMW instructions, then applied adhesive in a zigzag pattern on the roof’s perimeter with extra in the corners. All of this is hard to do with the OE adhesive bc it’s very difficult to brush on and the working time is very short. If following this method, I’d suggest using an adhesive that’s easier to work with. If I were to do it again, I would apply K1 adhesive (83190413015) to the bare metal instead of brushing on K3 adhesive, or use a 3M panel bonding adhesive that is meant to be brushed on before an additional bead is applied (like 3M 08115). I’ve used 08115 for RACP reinforcement in the past, and it was stupid easy to work with.

3. Scuff, clean, and apply two thick beads of K3 adhesive in a straight line

On the roof itself, I’m pretty sure the underside was already scuffed by Karbonius. I scuffed the bonding points anyways, cleaned thoroughly, and applied 5504G primer where the windshield adhesive would bond.

The 5504G primer can also be used on exposed metal elsewhere for rust prevention. Just don’t apply it to where the K3 adhesive will go. A solvent like acetone will remove it if you make a mistake.



Clean, clean, clean, and clean some more

I did a couple of passes on all bonding surfaces with tack cloth, a few passes on bare metal with acetone, and a few passes on all bonding surfaces with IPA. I kept going til my cleaning towel had no visible residue.

Time to bond 😅
1. Do a final wipe down or two on all bonding surfaces with IPA, if some time has passed since your last wipe down.

2. Apply windshield adhesive on bows. I made a continuous straight TRIANGULAR bead and joined the beads if I had to pause/readjust. Make sure the beads are thick and tall.

3. Apply K3 adhesive to bare metal and brush to coat all bare surfaces.

4. Apply K3 adhesive on the seven recessed areas and two roof rack holes on each of the long edges, 2.5 cm bead on recessed areas where the A and C pillars meet the bows (four total).

5. Apply K3 adhesive on most posterior aspect of raised portion of rear bow. Two thick beads.

6. You have 10-15 mins to do the following: Apply K3 adhesive in a zig zag pattern on the perimeter of the roof, and be sure to apply extra adhesive in the corners. Put roof on car, add weights on center of roof, throw roof rails on, align roof, once happy with position begin clamping roof (start from center of edge and move outwards), remove weights.

7. IMMEDIATELY use IPA or mineral spirits to remove adhesive from any surface where it shouldn’t be, like the exposed section of the roof

8. BMW states that the clamps can be removed after two hours and recommends removing excess adhesive; I didn’t follow this. Instead, at 3-4 hours I began trimming the excess adhesive one area at a time and reinstalled the clamp before moving on to the next area.

9. Clamps were removed after about 24 hours

10. Shine light over roof rail area, and from the cabin look for any light passing thru between the roof and body. Do the same for the corners, where step compensation was performed. Add extra adhesive to close any gaps.

11. Treat any remaining bare metal with 5504G

12. Add seam sealer with both sides taped off on long edges for more finished look. I tried to make it sit level with the roof; the little lip that protrudes out from the roof rail is short and doesn’t touch the seam sealer. Do not add seam sealer where the glass goes. Your glass guy should bridge the transition from roof to A/C pillar with windshield adhesive.

Clean up

Paint/wrap stock roof rails gloss black or buy CSL roof rails and install

Install glass. Bridge the transition from roof to A/C pillar with windshield adhesive.

For headliner install, you’ll want to secure it from back to front. If you don’t have someone to hold up the front end, you can feed the wiring for sun visor thru the headliner then hook up the sun visor to it, and let the sun visors just hang. This will hold the headliner up enough to let you screw everything in without wanting to commit violent acts. If using the ultrasonic sensor, feed the wiring to the center of headliner and install. At the rear, make sure the two holes for third brake light cover are lined up evenly with headliner, then snap in the cover—this will prevent the headliner from sliding off as you work. Install coat hangers, grab handles, and sun visors.



Protruding adhesive = good IMO bc you know the edge has sufficient adhesive and shouldn’t leak.


Roof bow with windshield adhesive






Buy a Karbonius CSL airbox. 10/10 would recommend

[heinzboehmer]

Amazing collection of info, thanks a bunch for compiling all of this.

I'll be following this process closely when the time comes to do my install (i.e. when I find a stupid slicktop headliner). Only thing I'm gonna try differently is to bond some strips of CF sheet in the places where the windshield adhesive is supposed to go (both to the chassis/roof bow and to the roof). Should result in increased chassis torsional rigidity.

(pls someone tell me if this is a stupid idea, I'm by no means an expert on this kind of stuff)

[AWE46M3]

Avedis 👀

[Bornacane]

Wow i Need to get one of these.

[bigjae46]

Awesome work man! Drilling spot welds makes no sense. If you start slow, it walks. If you start on an angle, it walks. I've found the best way is to go full speed and slowly lower the bit. Then if it walks...it WALKS!

Any reason why you didn't use 3M panel bond? 3M's directions say you don't have primer any metal....just saves a little hassle.

[SQ13]

Awesome work man! Drilling spot welds makes no sense. If you start slow, it walks. If you start on an angle, it walks. I've found the best way is to go full speed and slowly lower the bit. Then if it walks...it WALKS!

Any reason why you didn't use 3M panel bond? 3M's directions say you don't have primer any metal....just saves a little hassle.

Honestly…only because it’s the OE adhesive. I knew about the short working time, but I didn’t realize it’s hard to brush on until it was too late. 🙃 If I could do it again I would have most likely gone with 3M adhesive—meant to be and easy to brush on AND much longer working time = lower risk of rushing and installing the roof crooked.

[bigjae46]

Just got my roof off once I figured out the roof rack mounts screw out 😫. I was charging the sawzall batteries when I was like hmm…that looks like a hex head under the seam sealer. 10mm socket and they screw out. 🤦♂️

Removing the roof with a roll cage…my only option was to pull from the outside.

Maybe I can use those bolts to just bolt the roof in! 🤣🤣🤣🤣🤣

[0-60motorsports]

Just got my roof off once I figured out the roof rack mounts screw out 😫. I was charging the sawzall batteries when I was like hmm…that looks like a hex head under the seam sealer. 10mm socket and they screw out. 🤦♂️

Removing the roof with a roll cage…my only option was to pull from the outside.

Maybe I can use those bolts to just bolt the roof in! 🤣🤣🤣🤣🤣

Nice one!