I need to replace my bike's forks. So this morning I removed the headset & stem, dropped the forks out and put vernier calipers around the tube, at the threads. I measured outside, inside and the tube length. It's an italian bike (Olmo) so I assume measurements are in mm. I get 30mm for outside, 26mm for inside and 190mm for length.
So I'm feeling confident when I phone the bike shop to place the order. The guy asks me what diameter and tube length and there's a pause when I tell him "30mm"
"With respect" he says, "I think sir might be mistaken. Its most likeley to be 1 inch - 25.4 mm" I confirm that my headset is Campagnolo Mirage, so it definitley is 1 inch.
How could I be out by nearly 5mm on my measuring? I must have been looking at the wrong marker on the calipers or something. I can't wait to get home and check it again.
Like I say, it's a good thing I'm not a toolmaker or working for NASA! Nothing would ever fit together!
FWIW I bought clerance LOOK forks, a new Campag headset, the shop are going to press on the lower bearing for me.