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Old 01-10-13, 05:53 PM   #1
jeffpepperdine
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Headset Help. Tolerance in regards to stack height.

I've been reading past threads about headsets, stack heights and the like. I'm having a hard time answering my question, so I thought I'd pose it here in the new thread.

I've got a frame and fork which has a stack height that measures ~35mm. It seems most of what I've been reading suggests and ideal headset would be 1-2mm larger stack height than measured from the frame. Unfortunately, the headset I'm most interested in is the Tange Levin NJS campy copy which has a stack height of 38.4mm.

Would I be pushing my luck? Is the 3.4mm going to stop me from getting enough threads on the lockring?

The alternate would be the Tange Levin CDS which has a stack height of 33.4, and would require a spacer.

What are you thoughts? Should I risk it?

- Jeff
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Old 01-10-13, 06:37 PM   #2
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If you are saying that the fork column (from bottom seat to top) is 35mm longer than the head tube then you may be OK. the top 1mm or more of a headset nut is not threaded anyway, so you are probably only losing a bit more than one thread, and you will have enough for sure if there is a non-keyed spacer that can be removed. What would be helpful to know is the stack height without the locknut. That will tell you how many threads will be available, roughly 1 per mm.
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Old 01-10-13, 09:40 PM   #3
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Figuring that a top nut typically has less than 7mm of thread, you're playing it pretty tight. But since you only need another millimeter or two you have options. First put it together and find out exactly how it fits. Then consider dropping a spacer to get 1.5mm or so. Another option may be to face the head tube down a bit.

One way or another, I'm pretty sure this can be made to work.
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Old 01-11-13, 05:50 AM   #4
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If you dry fit the headset in place and find it to be 1-2 mm short, a headset mill can accomplish two things. One, it will allow the cups to seat into the frame correctly, aligning them and ultimately all the pieces in the headset. The second is that the milling process will remove paint and a bit of material.

Done correctly, the mill will remove the same amount of material from both the top and bottom of the headtube.

Also, take care when installing the cups. While a section of 2x4 and a hammer can be used to put the cups into the frame, a proprer headset press will install and align the cups correctly.

This could be the difference between a good fit and a precise one.
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Old 01-11-13, 07:47 AM   #5
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It seems the OP may have to actually purchase a HS for this project (he posted links to ebay adds so I assume he is shopping) Personally I would go for something shorter.
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Old 01-11-13, 08:27 AM   #6
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Quote:
Originally Posted by 100bikes View Post
Done correctly, the mill will remove the same amount of material from both the top and bottom of the headtube.
If you are just facing the headtube to assure parallelism and not removing any significant amount of metal, this is fine. If you are intentionally shortening the headtube to allow a headset to match an existing steerer length, you want to remove material only from the top. Removing any significant amount of metal from the bottom will change the bike's geometry by lowering the front end.
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Old 01-11-13, 08:31 AM   #7
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Thanks for the great advice. I'm working with my lbs to try to build a similar headset from spare parts they have (they have the levin njs top race). If this doesn't pan out, I may risk it. As its a winter project, I'm not in any rush.

thanks! - Jeff
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