Sora mech for a touring bike?

rolf_f
rolf_f Posts: 16,015
edited February 2012 in Road buying advice
Hello all

I need a new rear mech for my 1990 Dawes (7 speed triple). Front is standard 28-38-48 and rear is 13-30.

I'd like something appropriate for the style of the bike and a Sora long cage looks like a tolerable solution but would it have the range? If not, what would do? I don't want to inflict an ugly MTB mech on it so if the Sora is no good I'll have to source an old mech. Customer reviews on Wiggle imply it would work but I'd prefer something more concrete!
Faster than a tent.......

Comments

  • rothers_bikeo
    rothers_bikeo Posts: 225
    What is the old mech ?
  • rolf_f
    rolf_f Posts: 16,015
    The old mech is a Sachs Aris - see below. I've also had a Shimano 200GS of similar vintage on it - I might put that one back on as it's probably better than the Sachs one. TBH though, the springs seem rather weak on them compared to the modern mechs and with the mileage I do, I'd rather go for something new.

    P1030658.jpg
    Faster than a tent.......
  • Crankbrother
    Crankbrother Posts: 1,695
    A rear mech's range is based purely on the indexing as far as I know ...

    I guess the width of the chain is the issue so you'd be lookng for no more than an 8spd mech ...
  • rolf_f
    rolf_f Posts: 16,015
    Crankbrother wrote:
    A rear mech's range is based purely on the indexing as far as I know ...

    I guess the width of the chain is the issue so you'd be lookng for no more than an 8spd mech ...

    There is no indexing - either on any rear mech or on my bike! And I don't think chain width is an issue either - the 9 speed chain on my MTB looks pretty much the same width as the 8 speed chain that the (7 speed) Dawes uses.

    The issues as I see it are:

    1) Is the swing of the cage enough to take up a 20 tooth change at the front and a 17 tooth change at the back?
    2) Is there enough clearance between the upper sprocket and a 30 tooth cassette ring?
    Faster than a tent.......
  • rolf_f
    rolf_f Posts: 16,015
    Bump: anyone?! I'll even accept crap advice :lol:
    Faster than a tent.......
  • graham_g
    graham_g Posts: 652
    Road mech is no good at all for 30t cassette, although the new shimano road mechs (i.e 2011 onwards) would appear to accommodate a 28t sprocket, not sure if that includes sora though. If the aesthetics are that much of an issue then put a wanted ad up for a nice old deore LX/XT mech on the MTB wanted boards (or any other appropriate forum). This way you can use anything up to a 34t cassette in future should the need arise (i.e. fully loaded in the alps!).
  • keef66
    keef66 Posts: 13,123
    According to the Shimano Techdocs the Sora long cage mech will cope with:
    a 37 tooth total capacity; yours is 38, so probably OK
    a 27t largest sprocket; I've read of people getting 28t sprockets to work, but your 30 may be a bit big
    a 22t front chainring difference; yours is a mere 20, so fine there.

    Would you consider a cassette change too?

    What about an Apex rear mech if you're friction shifting??
  • keef66
    keef66 Posts: 13,123
    Forget the Apex suggestion, I've just had a look at one and I think it fails on the "in keeping with the rest of the bike" criterium.
  • keef66
    keef66 Posts: 13,123
    The latest 10 speed Tiagra rear mech will apparently take a 30t rear sprocket, and cope with your other tooth differences. It definitely looks less offensive than that Apex thing.
    What I don't know is whether your fat chain will fit through it.
  • rolf_f
    rolf_f Posts: 16,015
    keef66 wrote:
    The latest 10 speed Tiagra rear mech will apparently take a 30t rear sprocket, and cope with your other tooth differences. It definitely looks less offensive than that Apex thing.
    What I don't know is whether your fat chain will fit through it.

    So why must it be that any mech that takes a 30 tooth sprocket always has to look like it's made out of shrapnel? :lol:

    Interesting suggestion re the Tiagra. My slightly oversize (not fat!) chain does fit in my Camapg 10 speed cage but I'm not sure there is enough clearance for it not to rub a bit.

    I can probably stomach the black cage of this - http://www.ebay.co.uk/itm/Shimano-Deore ... 1e66e9061f

    But a bit of period Suntour has more appeal - http://www.ebay.co.uk/itm/Suntour-XC-90 ... 4cfe4421a0

    But then that would be wasted on my commute!

    I dunno.....!

    PS thanks for the suggestions - feel free to add more!
    Faster than a tent.......
  • keef66
    keef66 Posts: 13,123
    I did look at Spa Cycles since they cater for the tourist fraternity, but nothing stood out. You could try phoning them? Kind of in your neck of the woods too.
  • rolf_f
    rolf_f Posts: 16,015
    keef66 wrote:
    I did look at Spa Cycles since they cater for the tourist fraternity, but nothing stood out. You could try phoning them? Kind of in your neck of the woods too.

    I was over there the other week at the new shop! They don't have anything that ticks the box. I'm tempted to make an offer on an old Suntour mech on ebay as I do like Suntour stuff but those are almost too good to use (NOS).

    I can see myself getting two rear mechs at this rate!
    Faster than a tent.......

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