[Moopai]

Hi, last week I was parked in a mall and when I got back to my car, I noticed this scratch on the carbon fibre piece on the bumper

Is this repairable? Dealer tells me it's not repairable and wants to charge me $2,800 to replace that piece. Any advice would be greatly appreciated especially if you know anyone in the Toronto area that can repair this scratch. It's small but it's bugging the hell out of me when I look on the bumper and see that white scratch...

[Tenac]

Do you believe it is past the clear coat? If not you can have it sanded down and polished to correct it. If it is into the fiber you will need to find a shop that does that type of repair, I've never found one that actually worked out yet...

[Moopai]

I cannot tell if it past the clear coat. It feels little rough when I touch it. What sand paper should I use to try it out? 1500 or higher? Thanks

Originally Posted by Tenac

Do you believe it is past the clear coat? If not you can have it sanded down and polished to correct it. If it is into the fiber you will need to find a shop that does that type of repair, I've never found one that actually worked out yet...

[Tenac]

Originally Posted by Moopai

I cannot tell if it past the clear coat. It feels little rough when I touch it. What sand paper should I use to try it out? 1500 or higher? Thanks

Yeah at that point I would start with 1500 wet and move to 2000 wet.

[danibear]

I would hesitate to sand down per your picture, since it concave inward into the clear, meaning losing too much clear if you wan to sand down to even up the surface.

I would propose to get some auto clear and carefully fill in these scratches, try level with the original clear surface as close as possible.

When new clear is dry, then sand down using wet 1500, 2000, 4000, 6000, 8000. Always wet sand which gives you the smooth finish, never dry sand. And always sand in circle motions. 4000 and up is sand cloth not sand paper.

8000 sand down should be good enough, if not, you can also apply some sand compound.

[Moopai]

Thank you so much for the advice. I will keep searching for someone that can repair CF and if I cannot find any, I will follow your recommendation. Question regarding the sand paper, are you suggesting I start with 1500 and work my way up to 8000? And yes, definitely will NOT sand dry!

Originally Posted by danibear

I would hesitate to sand down per your picture, since it concave inward into the clear, meaning losing too much clear if you wan to sand down to even up the surface.

I would propose to get some auto clear and carefully fill in these scratches, try level with the original clear surface as close as possible.

When new clear is dry, then sand down using wet 1500, 2000, 4000, 6000, 8000. Always wet sand which gives you the smooth finish, never dry sand. And always sand in circle motions. 4000 and up is sand cloth not sand paper.

8000 sand down should be good enough, if not, you can also apply some sand compound.

[Moopai]

FYI in case someone else runs into the same issue as mine! I found this video on Youtube, part of me doesn't want to believe it :-) The damage on this mirror is way worst than what's on my bumper (almost 100 times) and the guy was able to fix it easily by sanding and polishing. In my case I don't think I need to use P600, a 1500 or 2000 should do the job.

Originally Posted by Moopai

Thank you so much for the advice. I will keep searching for someone that can repair CF and if I cannot find any, I will follow your recommendation. Question regarding the sand paper, are you suggesting I start with 1500 and work my way up to 8000? And yes, definitely will NOT sand dry!

[danibear]

Originally Posted by Moopai

Thank you so much for the advice. I will keep searching for someone that can repair CF and if I cannot find any, I will follow your recommendation. Question regarding the sand paper, are you suggesting I start with 1500 and work my way up to 8000? And yes, definitely will NOT sand dry!

Yes, you will have to work with Loewe grit sand patiently to higher grit.

[danibear]

Originally Posted by Moopai

FYI in case someone else runs into the same issue as mine! I found this video on Youtube, part of me doesn't want to believe it :-) The damage on this mirror is way worst than what's on my bumper (almost 100 times) and the guy was able to fix it easily by sanding and polishing. In my case I don't think I need to use P600, a 1500 or 2000 should do the job.

TBH, this is not the best practice to me, as he just sand down the hood/damaged clear as well as the carbon itself, I.e. carbon mass is sacrificed as well.

But, a cheap quick fix, anyway….

BTW, I am building scale car models as a hobby long time, so I know paint, clear, and sanding polishing.

[danibear]

Further more, when using sand paper/cloth, he did not move in circles, this will leave noticeable marks to trained eyes.

Cheap fix and careless, if you ask me.

I will do it in a different way to my own cars, of course, hope I don’t have to….. spent for full car PPF and ceramic already.

[Moopai]

Thanks for your feedback, as I mentioned yesterday, I will keep searching for a shop that knows how to fix CF and if I don't find one, I will follow your recommendation applying some clear coat which I know I don't need a lot as my scratch is not deep enough and then start sanding with 1500 and work my way up.

Originally Posted by danibear

Further more, when using sand paper/cloth, he did not move in circles, this will leave noticeable marks to trained eyes.

Cheap fix and careless, if you ask me.

I will do it in a different way to my own cars, of course, hope I don’t have to….. spent for full car PPF and ceramic already.

[Tenac]

Honestly I think some may be over complicating this minor repair. I bet if you take some buff compound and a wheel you'd get 90% of it out... Just stop by a local detailer shop and have them take a quick look.

[overklok]

Just replace the part yourself, it is a very easy job.

[Moopai]

Hey guys, just wanted to give you a quick update on my CF scratch. So one detailer told me it cannot be done. Then I found a shop that specializes in repairing carbon fibre. They quoted me $900 + tx

I think this is going to be my weekend project. I will start with a rubbing compound first and if that doesn't fix the issue I will follow the recommendation that I received from one of the members.

What I found hilarious in dealing with guy, is when I called the shop, he asked me what kind of car is it. I said BMW, he goes I love working on BMWs. Then he asked which series (in my mind I said oh shit... I'm in trouble now) I said M850GC, he goes oh, you're driving some serious machine that can get one in trouble! Email me the pictures and I'll let you know if it can be repaired and the cost. 20 minutes later I get $1k quote

[mjr24]

I had a similar scratch and a normal polish took most of it out.

[M8Bimmer]

I'd want more than my mirror polished for 1k.

[Moopai]

I'm starting with a polish this weekend and will see what happens.

Originally Posted by mjr24

I had a similar scratch and a normal polish took most of it out.

[Opie55]

I'll add this with the caveat that I've never worked on carbon fiber but have polished lots of interior trim wood pieces, and many other things, as recently as yesterday. I don't think it is accurate to call the coating on a carbon fiber piece "clear coat" except in the literal sense that it is both clear and a coating. But calling it clear coat creates the impression that it is thin and delicate like the clear coat on your paint. It is not. If you have typical glossy wood interior trim - not the newer open pore style - the coating on that is a thick layer of some form of acrylic that is many, many times thicker than the coating on your furniture or your car paint. You can sand through the clear coat on your paint with 1500 grit paper in just a couple minutes if you are not careful. If you tried to sand through the clear on your wood trim with 1500 you'd still be sanding when your grandkids graduate from college. Treat carbon fiber the same way. If you can catch the scratch with a nail, which I assume you can since you said it was "rough", then don't just polish it. It won't work. Even a fairly aggressive polish, like my favorite M105, is only designed to remove 1500 grit scratches, and even that takes a while. The key to successfully removing a defect like that is to ensure you remove all scratches from the previous grits with later grits. If you want to post some very clear closeups from an angle, I can maybe make some more specific recommendations, but by the looks of it I'd start with 800 (all grits with lots of water) and see what happens. Once you wipe it dry with a rag You'll be able to see pretty clearly if you are removing the scratches. If 800 works, I'd then go to 1200, 1500, 2000 and probably 2500, then polish. M105 will polish out 2500 grit scratches by hand in just a few minutes. And the polish you use matters. Polishes/compounds are really just liquid sandpaper. If you use too fine a "grit" for the job it will not work, the same as real sandpaper. For example, M205 is great to follow after M105, but would be useless to remove sandpaper scratches.

[Moopai]

Thanks for the feedback and detailed suggestions, much appreciated... Regarding my clear coat comment, I literally meant clear & coating. I'm not a paint professional but I do know a little about paint and I know CF is a tough material and has many layers of different resins.

Here's a close up pictures of the damage, it looks and feels like a layer of the clear is peeling off due to a deep scratch. That's the best way I can explain it. It would be great if you can tell from the pictures what's the best way to fix it as I'm able to do stuff if someone recommends the steps.

Originally Posted by Opie55

I'll add this with the caveat that I've never worked on carbon fiber but have polished lots of interior trim wood pieces, and many other things, as recently as yesterday. I don't think it is accurate to call the coating on a carbon fiber piece "clear coat" except in the literal sense that it is both clear and a coating. But calling it clear coat creates the impression that it is thin and delicate like the clear coat on your paint. It is not. If you have typical glossy wood interior trim - not the newer open pore style - the coating on that is a thick layer of some form of acrylic that is many, many times thicker than the coating on your furniture or your car paint. You can sand through the clear coat on your paint with 1500 grit paper in just a couple minutes if you are not careful. If you tried to sand through the clear on your wood trim with 1500 you'd still be sanding when your grandkids graduate from college. Treat carbon fiber the same way. If you can catch the scratch with a nail, which I assume you can since you said it was "rough", then don't just polish it. It won't work. Even a fairly aggressive polish, like my favorite M105, is only designed to remove 1500 grit scratches, and even that takes a while. The key to successfully removing a defect like that is to ensure you remove all scratches from the previous grits with later grits. If you want to post some very clear closeups from an angle, I can maybe make some more specific recommendations, but by the looks of it I'd start with 800 (all grits with lots of water) and see what happens. Once you wipe it dry with a rag You'll be able to see pretty clearly if you are removing the scratches. If 800 works, I'd then go to 1200, 1500, 2000 and probably 2500, then polish. M105 will polish out 2500 grit scratches by hand in just a few minutes. And the polish you use matters. Polishes/compounds are really just liquid sandpaper. If you use too fine a "grit" for the job it will not work, the same as real sandpaper. For example, M205 is great to follow after M105, but would be useless to remove sandpaper scratches.

[Opie55]

I'm not sure you will fix that with anything. First, there appear to be small cracks. But from the photos the white marks do not appear to be surface abrasions but subsurface delamination.

[Moopai]

A while back I posted this damage on the CF peace on the lower bumper of my M850. With the weather getting better I decided to take a stab at it. The long story short is I was able to remove the craps completely and return the CF to a reasonable state but for some reason depending from which angle you look at the bumper a small part shows the black and grey colours as gold or light grey or fading. Any idea how I could repair that? I buffet it well with different compounds but no luck.

Any thought as this small area is bugging the hell out of me and I know I’m probably the only person that will see it if I did not point it out, it is the size of a quarter.

Originally Posted by Moopai

Thanks for the feedback and detailed suggestions, much appreciated... Regarding my clear coat comment, I literally meant clear & coating. I'm not a paint professional but I do know a little about paint and I know CF is a tough material and has many layers of different resins.

Here's a close up pictures of the damage, it looks and feels like a layer of the clear is peeling off due to a deep scratch. That's the best way I can explain it. It would be great if you can tell from the pictures what's the best way to fix it as I'm able to do stuff if someone recommends the steps.

[Darth Rust]

Originally Posted by Moopai

Any thought as this small area is bugging the hell out of me and I know I’m probably the only person that will see it if I did not point it out, it is the size of a quarter.

I feel for you. I went back and forth on ordering the CF package because of this issue. It is nearly impossible to make a significant repair with mortal methods and the only practical remedy is replacement. Eventually I relented and got 71C CF exterior package because...reasons...but mostly it's that precious just likes it that way.

It's hard to interpret the image, but if you've not gone through the epoxy to the fiber, then it's possible that the sanding/polishing exposed a different layer of epoxy. Or maybe some amount of UV/weathering/grime got polished away too.

Did the car have a ceramic coat? I'm not real sure what's going on in the chemistry bottomless bonanza on the ceramics market, but maybe that added a slight coloration over time.

If the sanding did get through to the fiber and polished it smooth too then, unfortunately, it is what it is because it's been changed mechanically. In principal, you'd be able to feel the fibers with your finger, but do be careful because CF splinters are pure evil. The irregular appears of the weave and graphite appearance makes me think that's possible but I could be misinterpreting the image artefacts.