Paint bubbles and white residue on carbon fork?

My beloved 2017 Trek 720 has done well over 10,000 miles on commuting and winter bike duties. At this point pretty much the frame fork, and contact points are the only original bits left. I love it though.. Perfect fit and by far the best frame I’ve ever owned.

Recently noticed some darker spots of paint on the fork, and almost white powdery stuff starting to come out the fork arch where my mudguard meets it. Any idea what’s caused this? Just succumbing to general road crap over the years? It’s definitely not road salt, sweat etc.. It’s slowly coming out the fork, but the fork is carbon so I wouldn’t expect white stuff to be there!!

Added complication is the bike shop I got it from is now closed (RIP Craig H 😔), so I took it to a different Trek dealer who said they weren’t sure they could do warranty claims from a closed shop but will see what they can do. Double-added complication is the model isn’t made any more and didn’t exactly sell like hot cakes so I’m concerned Trek UK might not even have a replacement fork (especially as it has special mountings for fork-attached bags).

Anyone reckon I can keep riding this in the meantime until I do(not) hear from the dealer I took it to? Am I screwed for Trek’s like time warranty due to original shop closure?

Do I still need to reply to this for it to appear on the forum list, as it’s not visible currently!

Do I still need to reply to this for it to appear on the forum list, as it’s not visible currently!

No, you don’t. I’d seen your post (and was looking for info) before you did that.

The fork will have an aluminium crown so that could be corroding.
Trek list this as a replacement fork for that bike…

They have 2 in their Netherlands warehouse (so would take anywhere from 3 days to a couple of months to arrive at a dealer).

Cheers that’s super encouraging they have a replacement fork.. With the mounts for my weird fork bag cages too ( I think..as mine seems to have 2 bolts on the fork) 😃. Just hope the shop can do something. Is there a risk they might say I haven’t maintained it well enough and that’s caused the corrosion? The bike looks like an absolute shed, but I do look after the moving parts!

Edit – I think it might have been 2015 actually.. Time flies!!

Its really hard to tell from the photo. I’m reasonably confident the white powdery substance would be from corrosion of aluminium. Where it is and you let description suggest the paint has been damaged by the mudguard rubbing so the aluminium has been exposed and started to corrode.

It’ll probably be fine. I’d take a good look, clean it and understand the extent of damage. Probably just touch it up and carry on. There will be a good bit of aluminium there and the corrosion rate minimal. I’ll caveat that and say I’ve not seen it, I’m not qualified to assess its strength and it may snap and kill you 😉

I would agree ^ paint rubbed off due to mudguard and exposed aluminium alloy on fork crown has some surface corrosion (white powder) and best remedy would be to clean off the fork, abrade the exposed metal to remove the aluminium oxide and bubbled paint, apply some sort of suitable primer and then paint. Also carefully examine the fork to check that there’s no further damage.
Maybe put some helicopter tape on both areas of fork once repainted to protect the paint. Doubt it’s a warranty issue because it is caused by “wear and tear” not a design or manufacturing fault.

Brilliant thanks all! I’ll take off the mudguard at the weekend and give it a good clean around to try and see the full extent. I don’t think the exposed bit was caused by the mudguard rubbing directly: there’s a fair few mm of clearance. Wonder if corroding from the inside out with water dripping/sitting down the steerer after lots of wet scottish commutes? Not heard back from the shop yet, and I doubt it’s a major priority for them given I didn’t buy from them in the first place.

I love the frame so much, even if the fork is damaged and not a warranty job, I may buy that fork anyway..although most of the (replaced twice over) groupset is gubbed, I need to get new brakes(again) to replace the cable discs, and the post mounts mean it’s a pain to get decent hydros, so it might not be cost effective. The Hope wheels are in decent nick though!

Small update. Local Trek dealer have taken frame number and photos to send to Trek. They said they aren’t sure if covered or not (2 year paint warranty long gone, and corrosion isn’t covered), but they will see what Trek say.

In the meantime I’ve confined it to turbo duty so stripped the mudguard and gave the area a clean. Bit better photo below if it helps any analysis.

… And managed to snag the closest Trek to my old 720 on the C2W scheme. Checkpoint ALR5.