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I'm trying to reassemble my mountain bike fork making sure to put the bottom crown race and assorted pieces back together, but I can't quite figure it out:

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Here are all the parts I have:

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(click the images for full size)

Am I missing something? For some reason, these don't feel like they fit together correctly no matter which way I try it.

  • Well, you need two bearing sets, one for the top and one for the bottom. – Daniel R Hicks Aug 16 '19 at 21:03
  • @DanielRHicks Okay so I have a complete set on the top and I'm trying to figure out how to reassemble the set on the bottom. Do you know if I'm missing any parts? I can't get it to fit together properly. – SurpriseDog Aug 16 '19 at 21:15
  • Did you start by removing the fork and disassembling the bearings? If so you're not missing any parts (unless you have misplaced something) and they will fit together. – Argenti Apparatus Aug 17 '19 at 1:10
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Picture by picture: in the first photo, the bearing retainer is facing the wrong way. The more open side (the side with the little hooks that contain bearing balls in between them) faces up, where it will interface better with the top race.
Photo number 2 of the fork crown: it looks to me that you've either placed the top race and it's compression ring where only the crown race should be. The top race and crown race can look pretty similar. The fork's crown race is an interference fit meaning it's a very tight fit an has to be pounded into place. There is a specific bike tool for this however you can utilize an appropriately sized length of pipe and hammer to set this. Also carefully tapping it down using a punch works if you bring it down level by working around the race, moving the punch with each tap. So, if this is a mix up, obviously that needs correction.

Picture three of the leftovers:. The bearing retainer ring will go open side down onto the fork crown race and the fork's steerer can be slid up the bike's head tube. A generous amount of grease (preferably water proof) should be placed within the the bike's top and bottom cups prior to assembly. When the steerer tube is through the headtube's top cup, the headset's top assembly goes on. Bearing retainer, open side up, top race, the compression ring (appears to be the uppermost part in photo 3, a split ring with tapered sides to slip within the center of the top race). Next item coming down the steerer tube is the top dust cover and any spacers needed*. Then the threadless stem is placed on the dust cover and spacers and the top cap with the bearing loading bolt tops it off. * You should note that the top of the fork steerer tube comes to within 5 mm--or just below-- the top of the stem. If it sticks above, spacers should be used under the stem to achieve that 5 mm gap. You could cut down the steerer tube as well. The key point is that this whole fork and steering assembly will be held together by the stem's pinch bolts so it's extremely important that BOTH the upper and lower stem bolts can squeeze the steerer tube. The top Cap's role is to "load" the bearings prior to the stem being tightened.

I'm unsure about the crown race issue. My thoughts about it above are suspect based on the presence of a compression ring in your picture 3. The crown race picture however doesn't look right to me. There may be a part around the circumference of the crown race that acts to seal the bottom cup, but all crown races I'm familiar with are press-fit as described above and there isnt any part or material between the race and steerer tube.

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  • >"The fork's crown race is an interference fit meaning it's a very tight fit an has to be pounded into place." -- I suspect this was the issue. It didn't seem to fit right because I wasn't forcing it into place properly. Anyway thanks for your help, but I'm afraid the bearings got wrecked by all this monkey business, so off to the bike shop it goes. What a nightmare. – SurpriseDog Aug 17 '19 at 1:19
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There are a number of different schemes for fork headsets, but this seems pretty close to what you have:

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Here is a different image of an older design, but with the same basic components, and a little easier to understand. What's called the "crown race" in the first image is called the "bottom cone" in the second.

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And this link may help you understand things a bit better.

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  • The above diagram is somewhat confusing. The "crown race" is what you have more or less permanently mounted at the bottom of your steering tube in the second picture. It looks like you've placed the other race against it. That one should go on top. What you want on top of the crown race is one of the two sets of ball bearings. – Daniel R Hicks Aug 17 '19 at 0:14
  • (Edited in a second diagram.) – Daniel R Hicks Aug 17 '19 at 0:20

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