Presta Valve Stem Lengths
Standard - 32mm
Medium - 42mm
Long - 60mm+
Medium - 42mm
Long - 60mm+
Quill Stems
1. Stem diameter - that's 22.2mm to fit the inside diameter of 1" (25.4mm) threaded forks. There is such a thing as a 25.4mm quill stem made to fit the inside of 1 1/8" threaded forks, but those are rare.
2. Clamp diameter - that's either 25.4mm, 26.0mm, 26.4mm or 31.8mm (rare for quill stems). That's the diameter of the handlebar clamp area. Most MTB handlebars have a 25.4mm clamp area, most road handlebars have a 26.0mm clamp area. 26.4mm is for older Cinelli handlebars.
1. Stem diameter - that's 22.2mm to fit the inside diameter of 1" (25.4mm) threaded forks. There is such a thing as a 25.4mm quill stem made to fit the inside of 1 1/8" threaded forks, but those are rare.
2. Clamp diameter - that's either 25.4mm, 26.0mm, 26.4mm or 31.8mm (rare for quill stems). That's the diameter of the handlebar clamp area. Most MTB handlebars have a 25.4mm clamp area, most road handlebars have a 26.0mm clamp area. 26.4mm is for older Cinelli handlebars.
Freewheel Threading
Italian-thread freewheels use 24 TPI and a 35mm = 1.378" diameter, which is virtually the same as the ISO standard of 24 TPI and 1.375" diameter. However, because the threads are cut at a different angle, 55degs vs 60 (think of them as sharper "teeth" in profile), swapping back and forth between Italian and ISO will presumably erode the aluminum threads on the hub shell, leading to potential failure on an out-of-saddle climb or sprint (ouch!). In my experience, mismatched freewheel/hub sets put up a bit more resistance than normal during assembly and disassembly.
Yes, French-threaded freewheels are completely incompatible with Italian and ISO, and blessedly rare in the U.S. (I had one on a circa 1980 Carbolite 103 Peugeot, which also had Swiss BB threading.) - 1.366" x 25.4 tpi.
Regarding the Italian/English freewheels compatibility issue, our rule of thumb was that you could place an English threaded freewheel on an Italian theaded hub (or vica-versa), so long as you did not later revert to a freewheel with threading that matched the hub.
Campagnolo hubs may be marked with the thread size, but some older ones do not. Older ones with a single groove cut between the freewheel threads and flange are English thread. If there is no marking or groove they could be either French or Italian.
On English threaded Atom and Normandy hubs, there will be a single groove between the freewheel threads and flange. If there is no groove it is French threading (unless Pierre had a little too much wine during lunch and forgot to cut the groove).
Yes, French-threaded freewheels are completely incompatible with Italian and ISO, and blessedly rare in the U.S. (I had one on a circa 1980 Carbolite 103 Peugeot, which also had Swiss BB threading.) - 1.366" x 25.4 tpi.
Regarding the Italian/English freewheels compatibility issue, our rule of thumb was that you could place an English threaded freewheel on an Italian theaded hub (or vica-versa), so long as you did not later revert to a freewheel with threading that matched the hub.
Campagnolo hubs may be marked with the thread size, but some older ones do not. Older ones with a single groove cut between the freewheel threads and flange are English thread. If there is no marking or groove they could be either French or Italian.
On English threaded Atom and Normandy hubs, there will be a single groove between the freewheel threads and flange. If there is no groove it is French threading (unless Pierre had a little too much wine during lunch and forgot to cut the groove).