# Crown race won't fit on fork.



## Waspinator (Dec 27, 2004)

I have a Marzocchi fork and a RaceFace Diabolus headset. _Both are brand-new._

The crown race seems to be too small for the fork. That is, it won't even remotely go on with a lot of hand-pressure. Because of this, I did not want to pound it in place using an installation tool.

So just to check, I measured the diameters of the crown race and the steerer tube using a digital caliper.

The inner diameter of the crown race is 29.92 mm

The diameter of the steerer tube at the level of the crown is 30.02 mm.

So, the crown race is a tenth of a millimeter too small in diameter to fit over the steerer tube, and thus it seems that I've got a bit of a problem here.

What's my next step?


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## .40AET (Jun 7, 2007)

It's supposed to be pounded into place. Get the tool out and have at it.


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## SteveUK (Apr 16, 2006)

"_That is, it won't even remotely go on with a lot of hand-pressure._"

That's because it isn't supposed to. Like .40AET says, "get the tool out and have at it.".


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## CharacterZero (May 19, 2004)

Yeah, imagine trying to set a headset without tools...get the tool!


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## Waspinator (Dec 27, 2004)

CharacterZero said:


> Yeah, imagine trying to set a headset without tools...get the tool!


I have all the tools. The thing is, I've never had a crown race that was so difficult to put in place. Usually I'm able to at least press it slightly onto the base of the steerer tube (and then tamp it into place with the proper tool). But this one won't even begin to fit. As the steerer tube gets wider toward the crown of the fork, the crown race won't go any further with hand pressure.


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## sanjuro (Sep 29, 2004)

Let me guess, you have installed, what 10 crown races?


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## Waspinator (Dec 27, 2004)

sanjuro said:


> Let me guess, you have installed, what 10 crown races?


No. I've installed three in the past. This would be my fourth.


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## dereknc (Oct 27, 2007)

According to Park Tool the tolerances should be between .05mm to .15 mm. You're at .10 mm so that should be dead middle in the range. It's probably a good idea to measure again just to be sure but according to what you measured it should be fine.


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## Waspinator (Dec 27, 2004)

dereknc said:


> According to Park Tool the tolerances should be between .05mm to .15 mm. You're at .10 mm so that should be dead middle in the range. It's probably a good idea to measure again just to be sure but according to what you measured it should be fine.


I'm really surprised that the crown race has to be smaller than the steerer tube near the crown. Why the need for such a ridiculously tight fit?


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## dirtmudandrocks (Jun 17, 2007)

You don't want it coming loose on it's own...ever. Pound that sucker on there. Just be sure to use the correct interface between the tool and race, or if you have the slide-hammer type, to check that the tool will impact the race evenly.


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## SteveUK (Apr 16, 2006)

""_I'm really surprised that the crown race has to be smaller than the steerer tube near the crown. Why the need for such a ridiculously tight fit?_

I would guess that the interference fit has something to do with earlier headsets where the part actually worked as a bearing race, with the ball bearings in direct contact. Rotational pressure from the bearings may have been enough to work the race free. Perhaps this is less of an issue with the cartridge bearing designs?

The Hope headsets have a split crown race which can easily be fitted by hand. It needs a small screwdriver to open it up again to be removed.


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## Jerk_Chicken (Oct 13, 2005)

Waspinator said:


> I'm really surprised that the crown race has to be smaller than the steerer tube near the crown. Why the need for such a ridiculously tight fit?


This is called an interference fit:

http://en.wikipedia.org/wiki/Interference_fit


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## SteveUK (Apr 16, 2006)

Thanks JC. I stared at the word 'tolerance' for a while, knowing that it wasn't quite the word I was looking for, but _I_ knew what I meant!!


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## Jerk_Chicken (Oct 13, 2005)

*check yer email


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## seawind161 (May 1, 2008)

Put an ice bag on the crown/steer tube junction for 3 or 4 minutes. 

While that's cooling, boil a cup of water, then drop the crown race in the boiling water.

Give it a couple of minutes, and then fish it out with pliers and install it.

The combination of shrinkage and expansion makes it go on really easy.

Have a beer and congratulate yourself on the practical application of physics. :thumbsup:


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