Headset/Crown Race help
05-19-18, 01:18 PM
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Headset/Crown Race help
Hello all,
In a break with my tradition, I am asking for some assistance before jumping into a build and ordering the wrong parts. I've recently acquired what the previous owner believed (and what does seem to match) a late '70s Panasonic Touring Deluxe frame and fork. Someone had already stripped most of the paint off, and I am in the process of rust removal/cleaning/polishing. I've picked up a little experience along the way with a couple of previous builds, but I've not worked on anything of this vintage before. I am not sure what to make of the crimping (I guess it could be called that) on the steerer tube, or how to manage installing a crown race over it. I believe the original headset was a Dura-Ace model, but my searches have not unearthed any specific model. Any info/suggestions?
https://
https://
https://
The calipers are pressed against the fork crown, below the ridges.
In a break with my tradition, I am asking for some assistance before jumping into a build and ordering the wrong parts. I've recently acquired what the previous owner believed (and what does seem to match) a late '70s Panasonic Touring Deluxe frame and fork. Someone had already stripped most of the paint off, and I am in the process of rust removal/cleaning/polishing. I've picked up a little experience along the way with a couple of previous builds, but I've not worked on anything of this vintage before. I am not sure what to make of the crimping (I guess it could be called that) on the steerer tube, or how to manage installing a crown race over it. I believe the original headset was a Dura-Ace model, but my searches have not unearthed any specific model. Any info/suggestions?
https://
https://
https://
The calipers are pressed against the fork crown, below the ridges.
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05-19-18, 01:34 PM
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The crown race will actually seat in the ridged area. Measure that, got to be either 26.4 or 27.0, more or less.
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05-19-18, 03:16 PM
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And edit: I went back to double check measurements and I guess I didn't have the calipers pressed against the crown like I thought I did in the last picture. I'm getting 26.1-26.3 at various points around the ridged area. So, considering the tool I'm using is pretty cheap, 26.4 sounds reasonable.
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05-19-18, 03:32 PM
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@Jadesfire
27.0 is JIS
26.4 is ISO
If you are measuring 26.4 mm then you need an ISO 26.4 crown race.
27.0 is JIS
26.4 is ISO
If you are measuring 26.4 mm then you need an ISO 26.4 crown race.
05-19-18, 04:32 PM
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Crown race seats are knurled to increase the effective diameter. If it was cut undersize for some reason, you can knurl the seat to make an acceptable fit. Stein makes a tool for this purpose:
Stein Tools forFork and Frame
Stein Tools forFork and Frame
05-19-18, 05:42 PM
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@Jadesfire
27.0 is JIS
26.4 is ISO
If you are measuring 26.4 mm then you need an ISO 26.4 crown race.
27.0 is JIS
26.4 is ISO
If you are measuring 26.4 mm then you need an ISO 26.4 crown race.
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05-19-18, 05:44 PM
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Crown race seats are knurled to increase the effective diameter. If it was cut undersize for some reason, you can knurl the seat to make an acceptable fit. Stein makes a tool for this purpose:
Stein Tools forFork and Frame
Stein Tools forFork and Frame
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05-19-18, 06:58 PM
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The fact that the crown race seat measures 26.1 to 26.3 is a concern.
The crown race is an interference fit and the crown race seat on the fork is supposed to be slightly larger than the crown race itself.
IIRC a 26.4 mm crown race requires a 26.5 mm crown race seat. Please confirm this.
This may explain why it is knurled. Someone may have tried to increase the size.
The crown race is an interference fit and the crown race seat on the fork is supposed to be slightly larger than the crown race itself.
IIRC a 26.4 mm crown race requires a 26.5 mm crown race seat. Please confirm this.
This may explain why it is knurled. Someone may have tried to increase the size.
05-20-18, 08:32 AM
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In a pinch you can "knurl" the crown race seat with a center punch
05-23-18, 04:33 PM
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Well, I can't say now that I would recommend Harbor Freight calipers. New ones from Home Depot gave me measurements of 26.4 multiple times in several areas of the fork crown.
Thanks for the pointers, gentlemen. It wouldn't be a project of mine without asking a silly question or two.
Thanks for the pointers, gentlemen. It wouldn't be a project of mine without asking a silly question or two.
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