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Carbin fork dropout problem

Old 12-03-22, 04:37 AM
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alexk_il
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Carbon fork dropout problem

My LBS installed my own new carbon fork, also new 185mm rotors. Top quality service, no reason to doubt their skills.

Took the bike to bed in the brajes, got quite aggressive with the front brake at the very end, lifted the back wheel a couple of times.

Then I found then that the wheel slightly leaned to the left in dropouts. I will check if internal QR helps to secure the wheel. The current cheap ones need to be overtightened to keep the wheel in place both with the new and the old fork.

More important I found this tiny chipping on the outer/front side of the right side dropout.

Is it a serious issue? Not sure if it arrived like that or if it is due to the hard braking. I could imagine the loose wheel damaging the back side of the dropout, but not the front.

Don't care about cosmetics, but safety is important. I shall be able to replace the fork under the warranty.

Update: I received full refund from the shop, will be shopping for another fork.



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Old 12-03-22, 07:49 AM
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The drop-outs on my CF fork are alloy and I would assume yours are as well. However that chipping does look unusual IMHO and i can't imagine right off how braking would created it but I suppose an incorrectly tightened or installed QR may have.
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Old 12-03-22, 08:27 AM
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Originally Posted by Chuck M View Post
The drop-outs on my CF fork are alloy and I would assume yours are as well. However that chipping does look unusual IMHO and i can't imagine right off how braking would created it but I suppose an incorrectly tightened or installed QR may have.
There are plenty of carbon forks out there that have carbon dropouts. I own 2 Look bikes that have forks with carbon dropouts. What happens with a fork with conventional quick releases and disc brakes is that when the brake is applied the axle is forced down. The damage I see is exactly what I would expect to see using open cam quick releases. A good quality closed cam quick release would help with this problem. This is why for the most part bikes with disc brakes have migrated towards thru axles.
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Old 12-03-22, 03:05 PM
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Disc brakes behind the blades cause a downward reaction force on the axle. This is more pronounced on the left side.

So, at first glance, the chipping and wheel tilt are consistent with the axle moving under hard braking loads.

Start by confirming that all is right with the wheel fully pocketed in the slot. The best way is to mount the wheel on the floor so gravity pushes the fork home.

Assuming the fork is fine, and it's a movement issue, a better QR isn't likely to solve it.

There's a mistaken assumption that the QR secures the wheel from moving within the dropout. In truth, the QR's job is to compress the dropout against the axle's face, and that's where the hold happens.

Rather than spending on a skewer, focus in improving the bite of the left axle face. If you can find a thin steel serrated washer, try that. If it works, you might glue it on for convenience.

My preferred solution for things like this is traction paint, like they sell for stair treads. No need to buy a gallon, you can mix some fine sand or similar into nail polish, and paint the axle faces.


PS the minor chipping doesn't matter, but use some "paint" to seal the damage.

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Old 12-03-22, 04:21 PM
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Originally Posted by FBinNY View Post
There's a mistaken assumption that the QR secures the wheel from moving within the dropout. In truth, the QR's job is to compress the dropout against the axle's face, and that's where the hold happens.
I can see clear and accurate marks from the axle's serrated surface on the inner side of both droputs, no marks/scratches consistent with the wheel moving around the dropouts.

The serration in my QRs is very subtle, I'm not convinced it creates enough friction to prevent anything from moving. Do I need to get a better QR locking nuts? It is serration on the axle that is doing the job, right, QR's serration should be irrelevant, right?

I can see minor marks on the lawyer lip, maybe the locking nut wasn't sitting flash on the dropouts. Chances of that are slim too my LBS that installed the wheel and the fork know what theybare doing.

Originally Posted by FBinNY View Post
PS the minor chipping doesn't matter, but use some "paint" to seal the damage.
Thanks, just wanted to confirm that this chipping doesn't comprise the structural integrity of the fork.
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Old 12-03-22, 05:36 PM
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Originally Posted by alexk_il View Post
.....
The serration in my QRs is very subtle, I'm not convinced it creates enough friction to prevent anything from moving. Do I need to get a better QR locking nuts? It is serration on the axle that is doing the job, right, QR's serration should be irrelevant, right?
........
Yes, it's axle, not QR, bite that counts.

Since you don't see evidence of movement, it follows that the wheel might have been improperly seated all along.

So, do nothing for the moment, except for correctly mounting the wheel. Then go ride, including a few hard stops along the way. If the wheel stays put, all is good. If not focus on improving the axle's bite.

BTW - unfortunately it's not rare for dealers not to fully seat front axles. That's because they work on repair stands, and therefore against gravity when mounting wheels. So, be methodical, and finish wheel installation on the floor so gravity is your friend.

Last edited by FBinNY; 12-03-22 at 05:40 PM.
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Old 12-04-22, 05:50 AM
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Is that fork rated for a 185 rotor? QR forks with disc brakes is not ideal, even with metal dropouts, and carbon dropouts makes it worse. Increasing the rotor size increases the force trying to eject the axle from the dropout.
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Old 12-04-22, 07:58 AM
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Originally Posted by dsaul View Post
Is that fork rated for a 185 rotor? QR forks with disc brakes is not ideal, even with metal dropouts, and carbon dropouts makes it worse. Increasing the rotor size increases the force trying to eject the axle from the dropout.
The specs on the internet mention 160-183mm rotors. I guess a couple of extra mm won't make a significant difference.
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Old 12-04-22, 09:17 AM
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I see no evidence of high friction movement by the skewer.

That fork looks like it dropped out of the frame & landed on the dropout resulting in damage.

I don't like the look of how the metal was inset into the epoxy. Looks a rush job.

There should be an excess of epoxy.
The excess epoxy should be faired for a nice smooth transition effectively encapsulating the part.

It is clear that the part that chipped away was unsupported & not bonded to anything. (Void)

Of the part that did have epoxy, there was no bond to the metal.
This indicates proper manufacturing cleanliness standard was not obtained.


A quality drop out is more than a thin metal washer placed by bare hands with the tiniest possible squirt of epoxy.

Bargain internet brand?

Safe is not a word I would associate with this fork.

Last edited by base2; 12-04-22 at 09:43 AM.
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Old 12-09-22, 07:14 AM
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Originally Posted by FBinNY View Post
Yes, it's axle, not QR, bite that counts.

Since you don't see evidence of movement, it follows that the wheel might have been improperly seated all along.

So, do nothing for the moment, except for correctly mounting the wheel. Then go ride, including a few hard stops along the way. If the wheel stays put, all is good. If not focus on improving the axle's bite.

BTW - unfortunately it's not rare for dealers not to fully seat front axles. That's because they work on repair stands, and therefore against gravity when mounting wheels. So, be methodical, and finish wheel installation on the floor so gravity is your friend.
Re-seated the wheel, locked the QR as hard as I could, unfortunately after 2-3 rides the wheel started to lean to the left again. Not as bad as it was before, but still it's not perfect.

Here is a "forks for dummies" style question. I just realized:
  • The fork specs mention "9mm QR, Hub spacing 100mm".
  • My 27.5 MTB wheel comes with QR that measures 5mm instead
Am I confused or is it the root of the problem? On the closer inspection the surface of the wheel axle that presses against the dropout feels a bit narrower that I would hope.
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Old 12-09-22, 07:18 AM
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Originally Posted by FBinNY View Post
Yes, it's axle, not QR, bite that counts.

Since you don't see evidence of movement, it follows that the wheel might have been improperly seated all along.

So, do nothing for the moment, except for correctly mounting the wheel. Then go ride, including a few hard stops along the way. If the wheel stays put, all is good. If not focus on improving the axle's bite.

BTW - unfortunately it's not rare for dealers not to fully seat front axles. That's because they work on repair stands, and therefore against gravity when mounting wheels. So, be methodical, and finish wheel installation on the floor so gravity is your friend.
Re-seated the wheel, locked the QR as hard as I could, unfortunately after 2-3 rides the wheel started to lean to the left again. Not as bad as it was before, but still it's not perfect.

Here is a "forks for dummies" style question. I just realized:
  • The fork specs mention "9mm QR, Hub spacing 100mm".
  • My 27.5 MTB wheel comes with QR that measures 5mm instead
Am I confused or is it the root of the problem? On the closer inspection the surface of the wheel axle that presses against the dropout feels a bit narrower that I would hope. The lawyers lip is definitely not holding the wheel.
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Old 12-09-22, 08:11 AM
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It's the skewer that measures 5mm.
Front axles measure 9mm with a 5mm hole for the skewer to go through.
Rear axles measure 10mm with a 5mm hole for the skewer to go through.
The 9mm front or 10mm rear should nest in intimate contact in the mating 9mm or 10mm slot in the bike.

Of course everything being +/- a tiny bit so the parts can slide past each other for installation.

Are you sure you are using the skewer properly? Not treating it like a wing-nut are you?


Last edited by base2; 12-09-22 at 08:19 AM.
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Old 12-09-22, 08:30 AM
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Originally Posted by alexk_il View Post
The serration in my QRs is very subtle, I'm not convinced it creates enough friction to prevent anything from moving. Do I need to get a better QR locking nuts? It is serration on the axle that is doing the job, right, QR's serration should be irrelevant, right?
No, QR is not irrelevant. Some grip better than others. We don't know what QR you have so some info and a photo would help but if you can beg/borrow a good Shimano or Campy QR to test it out you can at least determine if yours is the problem before buying anything. If it's not the issue you can at least move on to finding another cause of the slipping.
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Old 12-09-22, 10:31 AM
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Originally Posted by alexk_il View Post
The specs on the internet mention 160-183mm rotors. I guess a couple of extra mm won't make a significant difference.
What is the specific fork brand/model or to be more direct is it a brand name or a no name from where ever?

you are pushing rotor size in an an already less than optimal set up ( Drop out with QR for disc brakes...there are lot of reasons the standard is now thru axle)

I would at minimum get good quality internal cam QR's,
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Old 12-09-22, 11:38 AM
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Originally Posted by base2 View Post
Are you sure you are using the skewer properly? Not treating it like a wing-nut are you?
😂

First time it happenned, the wheel was installed by my LBS. When I reinstalled it, the wheel actually stayed significantly longer in dropouts.

If anything, my QR installation skills should be on par with the skills of the LBS owner. He is more knowledgeable and skilled though in pretty much every other aspect of servicing the bikes.
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Old 12-20-22, 04:16 PM
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Originally Posted by alexk_il View Post
My LBS installed my own new carbon fork, also new 185mm rotors...

Took the bike to bed in the brakes, got quite aggressive with the front brake at the very end, lifted the back wheel a couple of times.

Then I found then that the wheel slightly leaned to the left in dropouts.
...
After unsuccessfully trying a good Shimano MTB inner QR, I contacted the shop and got the full refund for the fork. I explained that the wheel moves in dropouts under heavy braking.

They suggest to get a new fork from them after Xmas to try (same model). I might do that, but I just realised the inner side of the dropouts is actually made out of carbon. I originally thought it's a painted alloy, but unfortunately it's the same piece of carbon that makes the fork. Is this the root of the problems? Bad design?

I can't imagine how carbon can possibly have enough friction with the axle to hold the wheel under heavy braking.

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Old 12-20-22, 05:14 PM
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We don't know what angle the fork's dropouts are at WRT the reaction forces the disk brake creates, it's this force that tries to eject an axle from the drop out. Independent of the dropout or QR materials good dropout design can go a long way. Andy
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Old 12-20-22, 06:28 PM
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Originally Posted by Andrew R Stewart View Post
We don't know what angle the fork's dropouts are at WRT the reaction forces the disk brake creates, it's this force that tries to eject an axle from the drop out. Independent of the dropout or QR materials good dropout design can go a long way. Andy
Not sure if this helps, but the advertised fork was supposed to have alloy dropouts inside and outside. The rear one came with alloy only outer sides.


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Old 12-20-22, 07:16 PM
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The missing paint on the fork's dropouts might be from masking and not a different material. But there's likely a catch along the lines of "specifications subject to change..." somewhere in really tiny font Anyway I think you did the right thing given your issues and lack of faith in the fork. Andy
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Old 12-20-22, 07:51 PM
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I would just get a quality known brand fork, even if not carbon

$130 surly https://www.jensonusa.com/Surly-ECR-29-Fork

$130 salsa https://www.jensonusa.com/Salsa-Cro-Moto-Grande-29-Fork

This specific fork has already shown problems and the weight shown of 525 grams is less that of a brand name like fork that is 400 to 500 dollars https://www.jensonusa.com/WHISKY-No9-MTN-Fork-29-Boost
everything points to the "toseek" fork being low quality


IIRC OP is not in north america so options may be limited
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