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replacing old transmission parts

stefanostefano Posts: 254
edited July 2018 in Workshop
Hi, I recently bought an old Koga road bike from the late 70s with 5 speed cassette and friction shifters. What are the options for replacing old parts, in particular the cassette and rear derailleur.
Can I just change the cassette and the rear derailleur with a new indexed derailleur and use the old friction shifter?
Or else, can I reset the 126mm rear spacing to 130mm and get a modern rear wheel and a new rear derailleur and use the old friction shifter?
thanks!

Posts

  • keef66keef66 Posts: 13,123
    edited July 2018
    If it's from the 70s and rear spacing is 126mm the 'cassette' will likely be a screw-on freewheel. You can still get replacements; I stuck a new 7 speed on an 80s Peugeot that still had the original 5 speed freewheel and paired it with some NOS downtube friction shifters because the originals were buggered.

    You could probably do either of your suggestions, or indeed fit a new wheel in the frame just by springing the dropouts apart each time rather than cold-setting it permanently. You'll need a freewheel remover to er remove the freewheel. A new one just threads straight on and is then tightened by pedalling. Which often makes them quite hard to remove. Often easier to engage the tool and grip it in a bench vice, then unscrew the wheel from the now stationary freewheel. Leaving the inflated tyre on the rim helps with grip.

    What's wrong with the derailleur? A modern one would work with friction shifters, but might look a bit odd on an otherwise retro frame unless you go the whole hog and fit all new components.
  • keef66keef66 Posts: 13,123
    Just a thought; all this talk of screw-on freewheels assumes it's a Shimano pattern hub / standard threading. If it's something weird and wonderful like a Maillard you might be stuck
  • stefanostefano Posts: 254
    It is a Koga Miyata bike made in Japan with Shimano shifters. I am planning to do a lot of miles commuting with the bike so I need to have ready solutions for replacing the old parts as they ware out...
    The cheaper one should be to change the cassette and service the derailleur...until the wheel is gone...
  • keef66keef66 Posts: 13,123
    You should be OK with your cheapest option then; new 6 or 7 speed freewheel, new chain and you're good to go
  • Nick PayneNick Payne Posts: 288
    If the bike is from the late 70s with original components then it's very probably a five speed freewheel rather than a five speed cassette. Sunrace and IRD are two manufacturers who still make five speed freewheels; the IRD are much more expensive than the Sunrace.

    If you're going to re-space the rear end and get a new rear wheel and derailleur, you might as well also get indexed DT shifters to go with them. If you re-space it to 130 then you can use 8/9/10/11 speed components. Sheldon Brown has a web page on re-spacing steel frames at https://www.sheldonbrown.com/frame-spacing.html. I re-spaced one of my old steel road frames from 126mm to 130mm some years back using that method, and it worked fine.
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