Workshop question...Gear modifications on an old bike...

Iain C
Iain C Posts: 464
edited February 2009 in Workshop
I'm rebuilding an old Raleigh Quasar for my mate so he can get out road riding with us. Frame's quite cool actually (especially after some paint!), has an ovalised tube profile, and it will make quite a nice semi-retro ride. I've picked up some new components and wheels at some knockdown prices making it viable.

It came as a bitsa...it had a traditional non-sealed square taper BB, 105 front mech, 400ex rear mech, 7 speed downube shifters, and hideous 6 speed freewheel that was on a STEEL back wheel (now binned!) and no chain. It's got a Sugino 170mm doble chainset with the non-driveside crank knackered...taper's gone.

I've got some bargain new wheels for it and a 7 speed cassette, and I've got 2 spacers between bottom cog and the hub to convert the hub spacing from 8 to 7 speed. I've got a new Shimano 7/8 speed chain I've been given an old Tiagra double chainset (9 speed).

Questions...

1-Is the "offset" and therefore chainline between the Sugino and the Shimano chainsets likely to be the same, meaning I can use the old BB? (I know I can test this when the paint's dry if no-one knows off the top of their head)

2-Will a 7/8 speed chain be happy on the 9 speed Shimano chainset, or do I need to just use the Sugino and replace the duff non-driveside crank with the Shimano item? I guess the rings/teeth are thinner on a 9 speed...I guess you'd never get a 9 speed chain to run on a 7 speed ring but is it OK vice versa?

3-I've got no "old" chain to measure, so is it standard big ring/big cog and add 3 complete links (where 1 link is one thin link and one thick link, so in effect it's 3 thin, 3 thick, 6 in total)?

Many thanks!

Comments

  • alfablue
    alfablue Posts: 8,497
    2) I was running a 9 speed Ultegra chainset with a 7 speed rear setup and chain, works fine.

    3) As for chain length the formula is put the chain on large chain ring and large sprocket (but not threaded through the rear mech) and add ONE link.

    Alternatively, when threaded through the rear mech, when on big chain ring and little sprocket, the jockey wheels should be in vertical alignment (this is my preferred method).
  • whyamihere
    whyamihere Posts: 7,708
    1. Probably, if they're both doubles. Can't be absolutely sure though, obviously.

    2. No problem.

    3. I prefer to fit the rear mech, put the chain through, then it's big-big exactly. If the mech can cope with what you're doing, it won't break.
  • For a roadbike, the chainline of a double chainset is 43.5mm. However, different cranksets use different length bottom bracket axles to get that chainline. Each crankset will have a recommended axle length.