M3/M4 Yellowing or Oxidation of your Carbon Fiber Roof roof

[Yuille36]

This thread is to give you some advice if your experiencing this issue on your M3/M4, and what I did to mitigate this issue. My detailer told me that my CF roof was starting to oxidize, I think he meant yellowing.

But stated that he used aggressive rubbing compounds and polishes to restore the luster in the clear coat, then wrapped it in STEK PPF.

He also stated it is the best PPF on the market currently, and has a 10 yr. warranty, he then coating it in 9H Ceramic Coating which is good for 6 yrs. My M3 went thru an enhancement polish which corrected the minor swirls and light scratches in the paint, before its ceramic coating.

He also did the same thing on my CF mirrors. And honestly, I couldn't be more satisfied. Something about that ceramic coating, my paint just pops in the sun.

So, if your are having this issue, and looking for a solution, then I suggest that you follow this similar approach. For the PPF and Ceramic Coating will set your back about $1000, it is worth it, compared to letting your CF roof delaminate or the clear coat starts peeling away. What is the price to having it sanded down and re-cleared? Probably a lot more than my approach.

[M3SQRD]

The yellowing is caused by UV damage to the CF gel coat. I’m not sure whether adding PPF and a ceramic coating to an already UV damaged gel coat will stop the yellowing. It certainly won’t hurt anything, except your wallet, by adding them to the roof.

[Yuille36]

Originally Posted by M3SQRD

The yellowing is caused by UV damage to the CF gel coat. I’m not sure whether adding PPF and a ceramic coating to an already UV damaged gel coat will stop the yellowing. It certainly won’t hurt anything, except your wallet, by adding them to the roof.

M3SQRD,

As I stated in my post, my detailer used compounding creams and polishes to remove the top layer of the UV damage to the gel coat, and it turned out beautiful. Then he applied UV protected PPF then ceramic coated it. I think that with these steps my CF roof will be protected for years to come. The alternative would be to do nothing. Which doesn't sit right with me. What would you have done differently?

[M3SQRD]

Originally Posted by Yuille36

M3SQRD,

As I stated in my post, my detailer used compounding creams and polishes to remove the top layer of the UV damage to the gel coat, and it turned out beautiful. Then he applied UV protected PPF then ceramic coated it. I think that with these steps my CF roof will be protected for years to come. The alternative would be to do nothing. Which doesn't sit right with me. What would you have done differently?

There’s a clearcoat on top of the gel coat. The gel coat is thick compared to the clearcoat. So your Detailer removed all of your clearcoat? That would be very bad. Gel coats don’t respond to paint a correction like a clearcoat does.

[Yuille36]

Originally Posted by M3SQRD

There’s a clearcoat on top of the gel coat. The gel coat is thick compared to the clearcoat. So your Detailer removed all of your clearcoat? That would be very bad. Gel coats don’t respond to paint a correction like a clearcoat does.

NO, he didn't remove all the clear coat, just a layer to remove some oxidation. But regardless, I looked at the roof in the direct sun, and it looked really good, before he PPF and coated it.

[Yuille36]

I've seen photos of some M3/M4 owners with CF roofs, where you could see the CF layers delaminating, and where the intense sun started wearing away the clear coat and the gel coat. At which point would require a complete restoration of the CF, and that is expensive.

[masayoshi]

I own a body store. Basically, clear coat does not yellow. Gel coat will yellow and deteriorate because it is sensitive to UV rays. Clear coat protects it.
Unlike normal body paint, carbon fiber and gel coat are more likely to peel off than normal body paint due to expansion and contraction problems caused by heat. In the case of a carbon roof, delamination is more likely to occur between the gel coat and the clear coat. Certainly the protection film will protect the clear coat, but the protection film itself will yellow. And when you remove it, the clear coat may peel off.
High quality clear coat is the best choice for UV protection. Protection film is recommended for stepping stones. Afterwards, if you get hit by a skipping stone, please close it with clear coat as soon as possible, even if it is just a touch-up. It may peel off rapidly from there.

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[Yuille36]

Originally Posted by masayoshi

I own a body store. Basically, clear coat does not yellow. Gel coat will yellow and deteriorate because it is sensitive to UV rays. Clear coat protects it.
Unlike normal body paint, carbon fiber and gel coat are more likely to peel off than normal body paint due to expansion and contraction problems caused by heat. In the case of a carbon roof, delamination is more likely to occur between the gel coat and the clear coat. Certainly the protection film will protect the clear coat, but the protection film itself will yellow. And when you remove it, the clear coat may peel off.
High quality clear coat is the best choice for UV protection. Protection film is recommended for stepping stones. Afterwards, if you get hit by a skipping stone, please close it with clear coat as soon as possible, even if it is just a touch-up. It may peel off rapidly from there.

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Thank you for that explanation, very helpful for us none body and paint guys.

[jp2001]

Originally Posted by masayoshi

I own a body store. Basically, clear coat does not yellow. Gel coat will yellow and deteriorate because it is sensitive to UV rays. Clear coat protects it.
Unlike normal body paint, carbon fiber and gel coat are more likely to peel off than normal body paint due to expansion and contraction problems caused by heat. In the case of a carbon roof, delamination is more likely to occur between the gel coat and the clear coat. Certainly the protection film will protect the clear coat, but the protection film itself will yellow. And when you remove it, the clear coat may peel off.
High quality clear coat is the best choice for UV protection. Protection film is recommended for stepping stones. Afterwards, if you get hit by a skipping stone, please close it with clear coat as soon as possible, even if it is just a touch-up. It may peel off rapidly from there.

Translated with DeepL.com (free version)

I have the roof PPF’d (XPEL), ceramic coated (gtechniq) And the car had always been garage kept and is low miles (12k). Roof seems to be in good condition. When did others see yellowing / peeling start? Anything else I should do to protect it while it’s healthy?

[Yuille36]

Originally Posted by jp2001

I have the roof PPF’d (XPEL), ceramic coated (gtechniq) And the car had always been garage kept and is low miles (12k). Roof seems to be in good condition. When did others see yellowing / peeling start? Anything else I should do to protect it while it’s healthy?

Brother...you've done all the same things as I. To my knowledge there isn't anything else that you can do. I think that they are referring to cars that have been left out in the sun, without any sort of protection, like PPF or CC.

[masayoshi]

Although practically difficult, we still want to avoid exposure to UV light as much as possible.
PPF itself also yellowing when exposed to UV light.
I saw a comment on this forum that XPEL's PPF yellowed after 2 years.
When PPF turns yellow, it must be reapplied. However, when you peel it off, the clear underneath may come off with it.
(This may not be a problem if the PPF instructor is primed for easy removal).
In my personal opinion, if the original clear has deteriorated, it is advisable to apply a high-quality clear at that stage.
Some of the recent automotive repair clears are quite UV resistant.
Incidentally, there are coatings that claim to provide UV protection, but I don't think they have any real effect.
(One Japanese site tested a number of coatings claiming UV protection, but found them to be largely ineffective.)
This is where automotive clear is completely different from coatings.
By no means do we think PPF is bad. However, I stopped using PPF because of the risk of yellowing, cost, and peeling.
If I see signs of deterioration in the factory clear, I apply a clear coat at that stage.
(Two coats, if possible, will further increase UV resistance.)
My concern is that since I drive a Heritage, the three colored lines on the roof will disappear when scraped off.
Well, I gave up on this.
Again, PPF protects the original clear even if it yellows and has excellent resistance to the stepping stone problem.
So I'm not going to say PPF is useless or no good.
But it will still yellow, so be careful with UV light.

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[deemack79]

My preferred tactic is keep the car out of the sun as much as possible. It is a 2016 and the roof shows no sign of yellowing. 95% of the year the car is under a car cover or parked under a canopy when it is out. I know that this will not apply to most, especially those that daily.

[Yuille36]

I would think that BMW is aware of this issue, as they been using CF roofs since the E9X, if my memory serves. So, I would hope that their clears would be up to the challenge of protecting our CF roofs. But I do believe that these are worst case scenarios, for cars that see a ton of sunlight. That's just my opinion, and I'm no expert.