Threadless headset compression

What is the range of the threadless headset compression, between being completely loose and so tight that it won't spin? I mean, how much does the top part move between this two settings, in mm's or inch fractions? I really need this info.
 

the_SD_local

I own SR.
Pete Pachota said:
eric magray said:
about one inch is the length of the threads on the bolt
I don't think that this is how much the headset can actually squeeze. Any more accurate measurements?
1/4-1/2 turn which probably translates to about 1-2mm... no different than a threaded headset.

It doesn't take much to compress a headset especially since steel balls and even more so ceramic don't really give under pressure.
 
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