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Sanding Carbon Fork?

Old 03-24-21, 10:24 AM
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Sanding Carbon Fork?

Hey folks, recently upgraded the drive train and fork ($80 Chinese carbon special via eBay) on my old commuter bike. Everything is peachy, but the integrated disc brake mount on the fork is just a tad off so the disc rotor occasionally rubs against it.

Is it safe to sand down that area about 1mm to accommodate for the rotor?
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Old 03-24-21, 10:32 AM
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Let the shelling begin !

Any question regarding Ebay'ed Carbon results in "I WON'T USE THAT" replies
Heads-up.... incoming!

Last edited by Barry2; 03-24-21 at 10:39 AM.
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Old 03-24-21, 11:13 AM
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Originally Posted by nel e nel View Post
Hey folks, recently upgraded the drive train and fork ($80 Chinese carbon special via eBay) on my old commuter bike. Everything is peachy, but the integrated disc brake mount on the fork is just a tad off so the disc rotor occasionally rubs against it.

Is it safe to sand down that area about 1mm to accommodate for the rotor?
If it is occasional, figure out why it is occasional, and fix that.
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Old 03-24-21, 11:15 AM
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no. do what phughes posted.
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Old 03-24-21, 11:21 AM
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Are you sure the rotor is contacting the fork's brake mount? Maybe post a pic.
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Old 03-24-21, 12:26 PM
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If your rotor is only occasionally bumping the fork, then the rotor is likely warped and that needs to be fixed first. Otherwise just leave the warped rotor alone and it'll make it's own custom fit grove in the fork after a few thousand miles.
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Old 03-24-21, 12:41 PM
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Originally Posted by Iride01 View Post
If your rotor is only occasionally bumping the fork, then the rotor is likely warped and that needs to be fixed first. Otherwise just leave the warped rotor alone and it'll make it's own custom fit grove in the fork after a few thousand miles.
Late 2019 I had a rear-end collision (ran into the rear/side of racer in front of me as he was crashing out in a greasy corner) in lap 2 of 7 at a local CX race and bent my front rotor. It was bent enough to rub the inside of the fork leg but not so much that the wheel still rotated. I completed the remaining 5 laps to finish the race (+/- 5km) and when I looked at the fork the rotor had cut through the paint and put a -1mm deep groove in the carbon fork leg. So I managed to pry the rotor back to a straight-ish position, rode home from the race, cleaned up the bike, and touched up the damage with a few coats of nail polish.
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Old 03-24-21, 12:44 PM
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All this to say it can take substantially less than a few thousand miles for a bent rotor to cut a custom fit groove in a carbon fork...but you should fix the rotor ASAP.
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Old 03-24-21, 01:01 PM
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Originally Posted by nel e nel View Post
Hey folks, recently upgraded the drive train and fork ($80 Chinese carbon special via eBay) on my old commuter bike. Everything is peachy, but the integrated disc brake mount on the fork is just a tad off so the disc rotor occasionally rubs against it.

Is it safe to sand down that area about 1mm to accommodate for the rotor?
Make sure you have life insurance so your family is cared for.....

I had a recent issue with the rotor hitting the brake mount occasionally when I shifted weight to NDS. I assumed for some reason it hits the brake pads. but it turned out it hit the brake mount of the fork. I investigated the Shimano hub (100mm QR) and it seems the one one side spacer with the cone nut is wider. I swapped them so the wider one is on the NDS. that problem had existed a few years. i have no idea if my fix made it right, or if it came assembled wrongly from factory, or if I did it wrong when servicing the hub. I had built the wheel myself. that swap moved the rotor about 2mm inwards and resolved the occasional " ding". so i would check that. but with a knockoff fork, it also could be a weird fork issue.

Good luck. With a fork like that you will need it.
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Old 03-25-21, 11:27 AM
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Originally Posted by Barry2 View Post


Let the shelling begin !

Any question regarding Ebay'ed Carbon results in "I WON'T USE THAT" replies
Heads-up.... incoming!
Oh yes, was fully prepared for those. Honestly, I did a lot of research before pulling the trigger and the only consensus I could find was that the majority of people making those kinds of posts had never even used the products in question. What I did find was a lot of information that the majority of carbon bike parts - brand name and generic - are made in China, and that even the generic brands have gotten really good over the past decade. Any actual anecdotes about carbon part failures didn't lean in either direction (brand name vs. generic) and usually was just general warnings about the cons of carbon in general.

As I said, it's my commuter bike, 2017 Specialized Hardrock that I've basically ridden to the ground, and the stanchions on the crappy Suntour shocks have rusted into place, so wasn't looking to spend more than what I paid for the whole bike in replacing.

"Cheap" is probably a bad term, 'affordable' would be better, because cost does not always correlate with quality. I've been riding with it for almost 2 weeks now, inspecting it every couple of days and it seems to be holding up great. Only issue is the slight niggles with the fit, but otherwise I'm happy.

I do appreciate the insight on checking the rotor, so thanks all for that!
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Old 03-25-21, 11:49 AM
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You can't post pictures yet, but if you upload some pictures into an album in your gallery we can post them here for you. Or you could wait until you make two more posts. But I don't think anyone can make an informed opinion about this until we see what's going on.

Many bike shops have a tool to flatten brake mounts. That might be what needs to happen.
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Old 03-25-21, 01:12 PM
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Originally Posted by unterhausen View Post
Or you could wait until you make two more posts.
Post 1
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Old 03-25-21, 01:12 PM
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Originally Posted by nel e nel View Post
Post 1
Post 2!
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Old 03-25-21, 05:30 PM
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Anyone who makes fake posts just to up their post count instead of contributing to the forum should maybe reconsider checking the name of the website compared to the name of the website they were looking for and realize they are extremely different.

Google and BikeForums do share an "E" and an "O" but that is about it

If you are having rotor problems take it to a shop and see if they can try and help true the rotor for you. It sounds like your main issues are due to allowing your bike to get destroyed by leaving it outside in the elements or somewhere without some form of air conditioning or humidity regulation. That could cause issues with your carbon fork as well, sitting out in the sun and elements all the time which could potentially delaminate the carbon.
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Old 03-26-21, 02:33 PM
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Anyone who makes a sarcastic response without reading the entire thread should maybe reconsider how clever they think they are.


Making assumptions about how I store my bike - indoors by the way - is not a great way to establish credibility.



unterhausen I have pics below.




EDIT: ugh, seeing that rotor zoomed in I probably need to replace those too.
EDIT 2: just measured the thickness, and the rotors are still at 1.75ish mm

Last edited by nel e nel; 03-26-21 at 02:50 PM. Reason: Update
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Old 03-26-21, 02:47 PM
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i cannot see what the pictures are suggesting. It's dark making it unclear.
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Old 03-26-21, 04:40 PM
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Originally Posted by nel e nel View Post
Anyone who makes a sarcastic response without reading the entire thread should maybe reconsider how clever they think they are.


Making assumptions about how I store my bike - indoors by the way - is not a great way to establish credibility.

unterhausen I have pics below.

EDIT: ugh, seeing that rotor zoomed in I probably need to replace those too.
EDIT 2: just measured the thickness, and the rotors are still at 1.75ish mm
It could be just a weird fork design, but you should read my above post because it looks exactly like what my problem was.
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Old 03-26-21, 07:14 PM
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Originally Posted by HerrKaLeun View Post
It could be just a weird fork design, but you should read my above post because it looks exactly like what my problem was.
Thanks, I missed that rebuild part of your post. That was actually my first assumption, but this fork had an extremely tight fit when putting the front wheel back on. Had to flex it just a tad to fit the quick release into the dropouts. It seems to be better now than when I first installed, but will investigate putting a washer/spacer in.

While Iíve stored the bike indoors itís entire life, I havenít treated it as nicely as I should have in terms of maintenance, and I noticed the rubber covers on the axel is dry/cracked, so thinking thatís part of the issue as well. Appreciate the insight.
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Old 03-26-21, 07:38 PM
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Originally Posted by nel e nel View Post
Thanks, I missed that rebuild part of your post. That was actually my first assumption, but this fork had an extremely tight fit when putting the front wheel back on. Had to flex it just a tad to fit the quick release into the dropouts. It seems to be better now than when I first installed, but will investigate putting a washer/spacer in.

While Iíve stored the bike indoors itís entire life, I havenít treated it as nicely as I should have in terms of maintenance, and I noticed the rubber covers on the axel is dry/cracked, so thinking thatís part of the issue as well. Appreciate the insight.
Just so you don't kill yourself... I didn't add a spacer. I just swapped the cone nuts since the one on the rotor side was narrower (which like in your picture brought the rotor closer to the tap). With the wider one on the rotor side, it moved the rotor 1-2mm away from the tab. this doesn't change overall width of 100mm. So no spacer ADDED. Obviously adding something will widen the hub over 100mm and can break your fork.

I'm not sure I follow what you mean by you flexing... but I would consider getting a proper fork. If your chainstay breaks, you still can survive and stop the bike in most cases. surviving is what you want, in case i wasn't clear. If the fork brakes.... you may look into buying one of these bicycle airbags

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Old 03-26-21, 07:49 PM
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Thanks for the clarification HerrKaLeun , and just to clarify myself, I guess I misspoke about adding width to the hub, and meant what you indicated: shifting the hub to the drive side to compensate.
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Old 03-26-21, 10:19 PM
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Originally Posted by nel e nel View Post
Anyone who makes a sarcastic response without reading the entire thread should maybe reconsider how clever they think they are.


Making assumptions about how I store my bike - indoors by the way - is not a great way to establish credibility.



unterhausen I have pics below.




EDIT: ugh, seeing that rotor zoomed in I probably need to replace those too.
EDIT 2: just measured the thickness, and the rotors are still at 1.75ish mm
Wow!

Making assumptions about how you store your bike? You said your stanchions RUSTED IN PLACE. That doesn't happen with proper indoor storage, things like that don't rust unless you have completely abused the bike in some way and every time I have seen rusty stanchions it is because the bike was left outside. If you don't want people to make those assumptions maybe don't tell us that they are "rusted in place". Bikes don't generally get damaged indoors unless near a leak or a radiator or something like that and if they are in such bad shape like that the bike needs to be maintained and hence why I mentioned taking it to a shop. Someone doing some basic maintenance at home wouldn't likely cause anything to rust in place or you would notice something before it gets that bad and would probably be asking questions before it got so bad you are replacing the fork already. I have seen people with forks from the 1990s that were still going (or needed some new seals or oil or elastomers) but weren't rusted in place or damaged in that way and certainly weren't babied.

Also I did read the thread and provided useful help even though you literally just post "post 1 and post 2" which is a clear sign you have ZERO interest in this forum and are using this as a place to google things rather than participate. People wouldn't make fake posts like that if they were interested in this forum, they would get that post count up by being a contributor to the forum like a normal person. You can be pouty and mad all you want but you made the posts not me not someone else. Now maybe you meant to use us like Ask Jeeves or Altavista or maybe Yahoo! Answers or something like that but the concept is the same.
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Old 03-27-21, 05:28 AM
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Just looking at it, something seems misaligned. Is it possible the fork has the wrong spacing for that hub (e.g. a 110 fork on a 100 hub, or vice versa)?
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Old 03-27-21, 10:17 AM
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Originally Posted by bitpuddle View Post
Just looking at it, something seems misaligned. Is it possible the fork has the wrong spacing for that hub (e.g. a 110 fork on a 100 hub, or vice versa)?
No, the fork isn't quite that off, but it was much more snug than the OEM fork it came with.

HerrKaLeun I ended up taking off the cone nuts and servicing the bearings (which hadn't been done since I purchased in 2017). While my cone nuts were the same I adjusted them to give a bit more room on the NDS and now have more clearance, and readjusted the caliper on the mount as well.

Last edited by nel e nel; 03-27-21 at 11:14 AM.
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Old 03-27-21, 02:24 PM
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Looks like someone missed his nap again...
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