HI, i have run into trouble here .
i have a frame set that has the original fork and i have a headset ( Campagnolo Chorus ) this is from 1990 both the frame set and the headset .
i the fork is about ( exactly ) 1.5cm to long for this headset i am trying to use . i have a carbon spacer & another spacer from one of my modern headsets on there now so i could caculate how much space is in there , and as i state 1.5 cm to long .
problems , new headset . how do you caculate the stack height ?
here is a picture of the madness



any help would be great
Cheers
T

are there any super star mechanics .that can help ?

Buy a single 15 mm spacer and be done with it.

Timo, the photo makes the extra length look quite severe, but I'm guessing that your Corsa Extra was designed to take a Mavic headset like this one, though it still looks shorter then what you have available:



Correct me if I am wrong, but didn't Mavic make one particular, other headset with a whopping big locknut (1.5" tall or so) on it?

You might want to look through the Merckx catalogs online to see what the usual headsets used on the TT frames were - it might indicate which bizarre headset was used on this machine.

-Kurt

If I'm seeing this correctly, you have a threaded steering tube that is longer than needed. There are two solutions. Normally, threaded steerers are cut to the proper length, so the lock nut screws on with no spacers. Sometimes, a thin spacer(s) in the .5-2mm range might be used to adjust the length, instead of cutting the steerer very precisely.

It was never common in the days of threaded steerers, to use a large amount of spacer under the lock nut. If someone wanted the bars up high, a quill stem will extra quill length was usually purchased to raise the bars.

Correct, and that technique caused a lot of forks to be replaced when you couldn't get a replacement headset with a short enough stack height.

Trek did exactly that to my '92 1420. They cut the fork steerer to exactly fit the Tange OEM headset with a 30.5 mm stack height. A few years later nearly all good threaded headsets had gone to 36 - 37 mm stack heights and the fork was obsolete.

There is nothing wrong with using spacers between the top race and lock nut of a threaded steerer, but as you said, it isn't done often. In my case, not often enough.