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PostPosted: Mon Dec 16, 2013 5:01 pm 
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OK, not sure if anyone followed my previous posts but recently got a new fork for my CAAD10 (old one was cut too short by previous owner).

Went to the LBS today who I have a decent level of faith in, also have a few shops around my area so not just a one off place.

The mechanic went about taking the crown race off the old forks and fitting it onto the new ones. However, he found that under a considerable amount of force, the crown race wouldnt sit completely flush with the fork crown on the new forks (max 1mm gap).

The gap is equal all the way around the fork (i.e. not lop slided) and as a result, once the fork is installed the steering is not impaired in any way, nor is there any other abnormal noise etc.

The mechanic said to me that providing that the gap is equal all the way around and the steering isnt hindered, it is completely fine to ride. However, he did offer to do some sanding if I wasnt completely happy.

Just want to get some others opinions - would you ride it, or should I ask for it to be sanded, or perhaps see if it beds in over time?


thanks


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Posted: Mon Dec 16, 2013 5:01 pm 


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PostPosted: Mon Dec 16, 2013 5:21 pm 
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Firstly, don't sand it.......it's not the way to go on Carbon parts unless absolutely necessary.
There is quite a difference between various bottom collars and steerer sizes, it can be a bit of a problem.
You'd be better off taking a Dremmel to the bottom crown ring rather than the fork.
Attention needs to be paid to make sure the crown isn't left with burrs or edges and needs to be a nice fit.
A gap isn't a good idea....it'll lead to an area where the stress levels are raised and could lead to failiure in the longer term.
If neither of these are possible a good solution could be to add a spacer under the crown that'll fill the gap (but that is a final solution really if nothing else works)
Years ago when full carbon forks first arrived on the scene I had a similar problem with a LOOK fork, I ended up filing it down to get a good interference fit. I was working in the Composite and Laminate industry at the time and came to the conclusion that there was enough material around the crown and steerer to make it an acceptable solution. But these days some of the forks are very light in material weight around the steerer area (in the search for weight reduction)
What I'm trying to say is......only mess with the steerer as a last solution.
Regards, Rob. :beerchug:

(edit) If you want to send me some pics or a PM, to assess the state of the fork/crown joint feel free.

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PostPosted: Mon Dec 16, 2013 5:30 pm 
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tinchy wrote:
The mechanic said to me that providing that the gap is equal all the way around and the steering isnt hindered, it is completely fine to ride.


That seems like it's going to create even more stress on what is already a highly stressed area at the junction of the crown and steerer. The crown race has to sit all the way down on the crown. What fork did the race come off of? Also contact the seller and ask them if they had the same problem.



Edited to clarify what I was responding to


Last edited by bricky21 on Mon Dec 16, 2013 6:18 pm, edited 1 time in total.

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PostPosted: Mon Dec 16, 2013 5:39 pm 
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Bottom line is.....there is no way that all forks and all steerer crowns can be made to mate up perfectly. :wink:
That's where the skill of a bike wrench with real engineering background shows over a bike shop monkey with a certificate.
Fork steerer seats can be filed and sanded, but not by some monkey. You need to be sure whoever does the modifications knows what they're doing.
An over compressed headset crown could potentially do more damage to a steerer tube than a bit of light relief to the surface (which has a significant level of resin without fibres)

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PostPosted: Mon Dec 16, 2013 7:14 pm 
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The fork was purchased new from cannondale experts.

Same CAAD10 fork, just different colour scheme.


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PostPosted: Mon Dec 16, 2013 7:35 pm 
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What about splitting the crown race? You can do it with a Dremel. Also makes removing it from a carbon steerer a lot less stressful down the line.

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PostPosted: Mon Dec 16, 2013 8:15 pm 
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+1 to splitting the crown race. I've done it before, fitted the headset and then forgotten all about it. Doesn't seem to cause any engineering difficulty and I have seen a crown race supplied by the manufacturer already split.


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PostPosted: Mon Dec 16, 2013 8:26 pm 
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Yea that is a possibility. If the mechanic has (I'm sure he does) a crown race cutting tool would that not do the job?


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PostPosted: Mon Dec 16, 2013 9:03 pm 
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Do you mean the facing tool? No, that serves a different purpose. I'm not aware of a specific tool for cutting crown races, but I'm prepared to be surprised.

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PostPosted: Mon Dec 16, 2013 9:18 pm 
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http://m.parktool.com/product/crown-rac ... tool-crc-1


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PostPosted: Mon Dec 16, 2013 9:46 pm 
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That's the facing tool. Not suitable for a full carbon fork.

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PostPosted: Mon Dec 16, 2013 10:14 pm 
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I wonder how they would go about 'sanding' it down then?


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PostPosted: Mon Dec 16, 2013 10:42 pm 
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Correct me if I'm wrong but it sounds like he reused the old crown race. Youre not supposed to do that. It could have got distorted on removal.

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PostPosted: Mon Dec 16, 2013 11:02 pm 
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yeah thats what he did, took it off the old one (same fork model fork) and put it on the new one

(im pretty sure its ok to do that...)


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PostPosted: Mon Dec 16, 2013 11:08 pm 
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Splitting the crown or making the Inner diameter larger is by far the best option.
Do not sand or file anything unless the person doing the job knows what they are doing.
The crown race cutting tool is absolutely not for a full carbon fork. (It's an old school tool for steel or alloy forks)

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Posted: Mon Dec 16, 2013 11:08 pm 


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