Fitting modern crank set to a 1975 bb

[Dorsey]

I have a 1975 Hutchins road bike and want to, if possible, fit a modern crank set, say a Campy Centaur Compact, to the bike. Can this be done and would the existing 1975 front Campy derailleur work?
Thanks,
Dorsey

[ReapThaWhirlwind]

What type of bottom bracket shell does it have?

If it's a basic standard american threaded 68mm, then absolutely. If it's a one piece ashtabula 68mm, you can get a BSA conversion kit that's a thread-together in order to use a BSA bottom bracket and crankset.

[Jesper]

(05-23-2022, 12:27 PM)Dorsey Wrote:  I have a 1975 Hutchins road bike and want to, if possible, fit a modern crank set, say a Campy Centaur Compact, to the bike. Can this be done and would the existing 1975 front Campy derailleur work?
Thanks,
Dorsey

The front derailleur can be used unless you are drastically changing the chainrings' sizes. Probably good for between 40T to 55T rings. I use Campy Record derailleurs for many applications and I think I have used them down to a 38T small ring without any issue. You can always try it first and if it's not shifting well try a different/more modern FD unit. Make sure the cage barely clears the large ring (2mm, 1/16") for optimal shifting.
Are you just changing the cranks and keeping the actual bottom bracket assembly or changing out the whole crankset (BB and cranks)? If you are changing the BB make sure that your spindle length will provide the desired chainline in relation to the rear cluster.
Your chain might need to be changed if you are using a modern crankarm/spider set-up due to spacing between the rings. It may depend more on what your freewheel or cassette is due to the gear spacing in the rear. The front is more forgiving than the rear if the front spacing is narrower than the rear. Newer chainrings are designed for non-protruding pins on the chain and have "ramps" and pins designed into them to help move the chain between gears. Older chains had pins which protruded enough to catch the teeth during gear changes.

I use modern Campy cartridge BBs on many older bikes; generally 111mm to 115.5mm spindle lengths. I am using them on 70mm BB shell widths (standard Italian BB shell with Italian threads).

I would like to see an image of the bike if possible; you can upload to this site or link us to wherever you have a photo.