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On some headsets which use a cartridge bearing in the lower assembly, the crown "race" is split. Also, I know a lot of people split their crown race for the ease of installation.

Perhaps I'm overly concerned, but I'm wondering about two things.

  1. Has anyone ever cracked a crown race during use? If this is something that can happen, a split crown race might shatter into pieces..
  2. The crown race is held somewhat snug by the chamfered edge of the bearing, which suggests it might prevent a broken crown race from falling of the fork. Has anyone ever crashed due to the crown race / lower headset assembly failing?

Edit: I ask this because I consider splitting a race. I'm switching out a RS Reba for a Surly 1x1 fork, both of which have a crown seat diameter of approx. 30mm (as do all 1.125" forks, as far as I know). I tried setting it using my "specialized race setting tool" (i.e. some PVC piping and a mallet) and plenty of lube. No luck however, the pipe started to shatter but the race wouldn't set :-(. It seems like the seating is just a hair too wide for the race to seat. As far as I see there are two options: file down the crown seating a bit, or split the race. The latter seems easier; also I'd rather modify a 3€ part than a 50€ one. But only if I won't loose my teeth over it :-P.

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The actual Park Tools crown race tool is basically a metal pipe with a beveled insert at the bottom that is sized to fit your crown race. You could try metal pipe cushioned at the bottom with a 1/2" or so piece of pvc. I would think that should transfer a lot more energy to the race with a lot less stress on the pvc. –  jimirings Feb 2 '13 at 18:44
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1 Answer

up vote 3 down vote accepted

I've never cracked a crown race after assembling many different bikes with different fork/headset configurations. Split crown race makes things far easier and it means one less specialty tool that you need to own or access to get the job done. I've never had an issue with split races either.

As for splitting your own, lots of people do it without issues, if you go this route, I would make sure you gently file the edges to make sure it is deburred with no sharp edges. For how infrequently you need to install/fiddle with a crown race, splitting would however be a last resort for me since you can usually set them with a piece of appropriately sized PVC pipe and a mallet.

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Specialty tool? You mean a pvc pipe? :p Seriously though, I know they make a specialty tool but I've never installed a split crown race and I've always used a pvc pipe and it works fine. –  jimirings Jan 31 '13 at 19:01
    
My comment got cut off for some reason, I meant to add the bit about the PVC pipe at the end :). It has worked for me as well. –  nspace Feb 1 '13 at 14:44
    
I tried the PVC pipe + mallet method without luck; see my edited opening post. Perhaps I'm overlooking some other options, but I think splitting the race is the easiest solution in my case. –  ZulfiqarIII Feb 1 '13 at 22:58
    
The bottom race, and the top for that matter, are both under constant pressure and a non moving part in a sealed bearing headset. They could be in several parts and it wouldn't matter. –  alex Feb 2 '13 at 3:27
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