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I have a 90’s Cannondale 2.8 Aluminum that I have been renovating. Just added a Campagnolo Veloce groupset with Zondas. It looks and feels amazing, almost better than brand new. But here’s the thing...

I purchased a full carbon fork to replace the aluminum one. The fork steering tube is 1” but it will only accept a 27mm (JIS) crown race. I got this particular fork because it perfectly matched the candy red paint job and I was unable to find another 1” like this anywhere. You think there would be more demand for 1” carbon forks in different colors but I guess not.

I wanted to purchase a high quality 1” threadless headset, like a Chris King to replace the old threaded Shimano 105. The problem is that Chris King doesn’t make a headset to fit a 27mm crown race, or anyone else really. SO, I have these options. Which is best?

• Sand down 0.6mm of the carbon fork steering tube to accept the 26.4mm crown race. I heard from some places that this is possible but not advisable and most likely dangerous, but could work if done precisely. Or...

• Get a Chris King headset with 26.4mm baseplate and machine off 0.6mm of the inner diameter of the crown race (precisely) so that it fits on the 27mm steering tube. Or...

• Just get a lesser quality headset that fits the headtube (was it 30.2 or 30mm, I forget at the moment?) and that can sit on the 27mm crown race. I guess Origin 8 makes a headset that comes with a 26.4 and a 27mm crown race. And there are maybe 1 or 2 other no name headsets with the: Threadless 1”, 30.2mm (or 30.0?) x27mm ID. But this would mean having to sacrifice bling/ride quality. OR...

Find a new 1” fork that accepts a 26.4mm crown race, but it has to match the Cannondale’s candy red color. And I haven't found one anywhere. Been looking a long time.

SO, should I:
• Alter the 27mm carbon fork?
• Alter the high quality 26.4mm headset crown
• Get a low quality headset to fit?
• Search for a different fork?
• Or none if these things?

Oh great and wise bike sages, please advise!

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I have a 90’s Cannondale 2.8 Aluminum that I have been renovating. Just added a Campagnolo Veloce groupset with Zondas. It looks and feels amazing, almost better than brand new. But here’s the thing...

I purchased a full carbon fork to replace the aluminum one. The fork steering tube is 1” but it will only accept a 27mm (JIS) crown race. I got this particular fork because it perfectly matched the candy red paint job and I was unable to find another 1” like this anywhere. You think there would be more demand for 1” carbon forks in different colors but I guess not.

I wanted to purchase a high quality 1” threadless headset, like a Chris King to replace the old threaded Shimano 105. The problem is that Chris King doesn’t make a headset to fit a 27mm crown race, or anyone else really. SO, I have these options. Which is best?

• Sand down 0.6mm of the carbon fork steering tube to accept the 26.4mm crown race. I heard from some places that this is possible but not advisable and most likely dangerous, but could work if done precisely. Or...

• Get a Chris King headset with 26.4mm baseplate and machine off 0.6mm of the inner diameter of the crown race (precisely) so that it fits on the 27mm steering tube. Or...

• Just get a lesser quality headset that fits the headtube (was it 30.2 or 30mm, I forget at the moment?) and that can sit on the 27mm crown race. I guess Origin 8 makes a headset that comes with a 26.4 and a 27mm crown race. And there are maybe 1 or 2 other no name headsets with the: Threadless 1”, 30.2mm (or 30.0?) x27mm ID. But this would mean having to sacrifice bling/ride quality. OR...

Find a new 1” fork that accepts a 26.4mm crown race, but it has to match the Cannondale’s candy red color. And I haven't found one anywhere. Been looking a long time.

SO, should I:
• Alter the 27mm carbon fork?
• Alter the high quality 26.4mm headset crown
• Get a low quality headset to fit?
• Search for a different fork?
• Or none if these things?

Oh great and wise bike sages, please advise!
Not sure of this but a frame builder (or a well-equipped bike shop) would have a tool to chase the fork crown race. The tool is designed to cut steel and so would have no problem cutting the CF. The challenge might be getting a smooth cut without chipping the CF fork crown.
 

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You don't want to cut that steerer. While some carbon steerers may be designed for machining, I can't imagine that one is.

Buy a headset with a 26.4mm crown race and have it machined to size. If you blow it, it's cheaper to find another headset than that rare fork you have.

Note: Campy spec for the crown race 26.30-26.40mm. Campy spec for the fork column base is 26.45-26.55mm.
The Asian (JIS) spec for the crown race is 26.9-27.0mm. The Asian (JIS) spec for the fork column base is 27.05-27.15mm.

These specs are from the Barnett's Manual.

I provide these specs should you decide to do the work or farm it out and need to know the limits when measuring the work.

If the crown race is machined oversize, resulting in a loose fit, you can use Loctite RC680 to secure it to the fork column.

If you try to do it yourself, I'd try to chuck up by the O.D. in a drill somehow and use sandpaper, stopping often to check. Obviously you want to keep it concentric.
 

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Discussion Starter · #4 ·
Not sure of this but a frame builder (or a well-equipped bike shop) would have a tool to chase the fork crown race. The tool is designed to cut steel and so would have no problem cutting the CF. The challenge might be getting a smooth cut without chipping the CF fork crown.
Im most hesitant about cutting the carbon steering tube but if i find someone that can do this with confidence It would be the easiest option. I need to find a frame builder because I called R&A cycles here in Brooklyn and they said they couldn’t do it because of “liability issues”.
 

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Discussion Starter · #5 ·
You don't want to cut that steerer. While some carbon steerers may be designed for machining, I can't imagine that one is.

Buy a headset with a 26.4mm crown race and have it machined to size. If you blow it, it's cheaper to find another headset than that rare fork you have.

Note: Campy spec for the crown race 26.30-26.40mm. Campy spec for the fork column base is 26.45-26.55mm.
The Asian (JIS) spec for the crown race is 26.9-27.0mm. The Asian (JIS) spec for the fork column base is 27.05-27.15mm.

These specs are from the Barnett's Manual.

I provide these specs should you decide to do the work or farm it out and need to know the limits when measuring the work.

If the crown race is machined oversize, resulting in a loose fit, you can use Loctite RC680 to secure it to the fork column.

If you try to do it yourself, I'd try to chuck up by the O.D. in a drill somehow and use sandpaper, stopping often to check. Obviously you want to keep it concentric.
This is very informative and exactly why I came here. Thank you. I think I will try to find a frame builder here in NYC who can machine a 26.4 crown race for me. I dont want to settle for a lesser headset and if it works then I’ll be very happy and I’ll thank you all properly.

I did just order a digital caliper so I will double check the fork base size so I can machine the crown race exactly. To really make it a nice tight fit it should be just slightly smaller, correct? Like .1mm or something like that? The loctite would be a nice backup just in case but hopefully we measure right and tight. Again, I appreciate the knowledge.
 

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I have trouble believing Cannondale would have used a JIS headset on anything. By your fork "accepting" a JIS crown race do you mean it pushed on by hand while an ISO is not a slip fit? Remember, most crown races require a fair bit of force to seat them. Ever seen a crown race setting tool? It's basically a fairly heavy tubular slide hammer. You may indeed have an ISO fork.
 

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Discussion Starter · #7 ·
I have trouble believing Cannondale would have used a JIS headset on anything. By your fork "accepting" a JIS crown race do you mean it pushed on by hand while an ISO is not a slip fit? Remember, most crown races require a fair bit of force to seat them. Ever seen a crown race setting tool? It's basically a fairly heavy tubular slide hammer. You may indeed have an ISO fork.
Yes I know Cannondale doesn’t use JIS anything. I purchased a Carbon fork to replace the old aluminum one. The fork I bought is JIS standard, so my problem is i have an ISO standard headtube and a JIS 1” carbon fork that will only accept a 27mm crown race. So I need a solution that can join the two in harmony.

I have seen no name brand headsets that I could get but Id rather find a way to use a chris king or campy record headset because I want the best for my ride. And its all campy everything so far. If you think i could just slam a 26.4 on the 27mm carbon steering tube id do it but my LBC said dont do it bc it could damage the carbon and potentially cause failure. I have experience setting crown races as well as removing them. But i might be looking to alter one at this point.
 

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... Like .1mm or something like that? The loctite would be a nice backup just in case but hopefully we measure right and tight. Again, I appreciate the knowledge.
Re-read my post. The min/max acceptable dimensions for your crown race are listed. If the result is not an interference/press fit, then the Loctite is called for. And yes; you're right-don't even think of trying to force a 26.4 crown race onto a 27.0 seat. If you can't find a framebuilder in NYC, try e-mailing some. Most are pretty savvy, have a lathe, and understand what you're trying to do. You could mail the crown race to them and costs would be minimal.
 

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I had a similar scenario with a bike. Steel Ritchey frame, carbon fork. I used a smooth file to reduce the crown diameter on the fork down to accept the crown race. Worked just fine. This was 8+ years ago and it's been perfectly fine. Just sharing my experience here, not making suggestions. The diameter difference is 0.023", so it was super easy to file down the carbon to the correct size. Didn't use a lathe, or any other sophisticated cutting tools.
 
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