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If I ream a headtube for 30.2mm cups, is the headtube reamed slightly undersize for the press fit or are the cups slightly oversize?
The nominal size is 30mm, which is your target for the bore. The cups are 30.2mm to provide the necessary interference. 30.000mm bore will be very tight and might end up shaving material off one or other component depending on the materials and gauges. It will be OK for steel cups in a thin walled steel head tube, but if the cups are at the upper end of their tolerance, expect to see chips of the softer material if you're combining steel and aluminium🙂
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gbj_tester
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Uuuugh, the headtube is dead on 30.00 but 0.2mm difference is making me nervous. Where is that list from?
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Knew you’d be the one to ask but didn’t want to @ you at that unsociable an hour.
In my experience, .05-.1mm tolerance for cups is a level of precision that many headset manufacturers fail to hold.
Jonny69
M_V
Apologies if this has been covered before. If I ream a headtube for 30.2mm cups, is the headtube reamed slightly undersize for the press fit or are the cups slightly oversize?