Gravel and MTB: What film to use to protect for rocky riding? and what parts?

Carbon is not as fragile as many think. The tubes on such bikes will be built to handle typical riding for that bike - for gravel bikes this is probably not smashing the down tube onto a rock, but it will handle rocks flicking up and hitting the down tube without suffering structural damage, A typical Carbon MTB should be able to handle a reasonable knock to the bottom of the down tube with no damage, even though this is rare. Anything that risks smashing the down tube is unridable, and the chain ring usually gets in the way first if the timing of a jump bunnyhop etc is that far out.

Adding protection robust enough to make a difference comes with the cost of extra weight and ugly. You would probably get a lighter total setup with an alloy frame.

There are clear wraps available, that stick onto frames, for those who like to prevent chips and scratches and keep their bikes looking as close to showroom new as possible. These do provide good cosmetic protection.

More aggressive bikes, both carbon and aluminum, often come with moulded plastic or rubber downtube guards. They prevent rocks from slowly eroding the paint and relatively light BB strikes. The drive side chain stay is usually protected too by a rubber guard.

I personally have the car vinyl wrap on my downtube. It does help protect against rock chips and works well.

Chain stay protectors are standard equipment on MTBs, and I use a piece of road bike tire for mine. Higher end bikes usually come with beefy molded rubber guards made specifically for that bike, while lower end bikes usually only have a thin vinyl sticker on the chainstay. Aftermarket products are available as well if you don’t want to go the DIY route to add a better protector.

Helicopter tape. Underside of down tube and bottom bracket shell, plus anywhere your bags or housings rub.

Have you heard of RideWrap? https://www.ridewrap.ca/ They make options to cover any kind of bike. You can cover just the essential high wear areas like the down tube and top tube and chain and seat stays, or the entire bike from head tube to rear axle.

I am not sure how helpful paint protective or any film will be from a hard impact on a mountain bike trail. However, for things like rocks being kicked up or a light scrap, I think paint protective film will work well.

I used XPEL Track Wrap on my Road Bike and it works well to protect the paint from rock chips and cable rub. It is easy to apply (i.e. no soap sprays like other films, etc.) by just pressing it to the surface and it peels off without residue easily if you want without the need for a heat gun or hairdryer. Also, it is pretty cheap vs. other options if you are willing to cut it to size yourself.

I have never had issues with it pealing off and have had it on my bike for over 1.5 years and several thousand miles. Also as a bonus tip, I use it on my car with my trunk mount bike rack to prevent the feet from marring the paint. So far that has worked well too.

I put sections of the film on the following areas:

• Top Tube
• Under Bottom Tube to Protect Against rocks from the front wheel
• Where cables rub the front of the bike before they enter the internal grommets on the frame. It definitely prevents marring of the paint there. I forgot to do it on the rear brake cable under my seat and see the difference.
• You could possible use this too on the chainstay or use something like Lizard Skin which I now use after some chain suck smacked my chain into the stay.

You can see from the pic below it is clear enough that it cannot be noticed unless you get inches away from the frame. I also use a cutting board to cut long straight sections of the wrap in straight lines to make applying it easier and the results better looking.