fixing gears on subway carrera - how to?

Discussion in 'Bicycle Mechanics and Repairs' started by murrawo, 24 Jul 2012.

  1. murrawo

    murrawo Regular

    hello folks,
    got great advice last time from you lovely folk on cyclechat!
    can anybody tell me how to fix the back shifter on my carrera?
    and how do i discern if the chain has too many links?
    i think that's a prob too.
    when in lowest gear at the back shifter, I can't shift to a higher gear, unless i put it in a much higher gear and back pedal before pedalling forward again.
    I don't know how to fix the back shifter - the cable is static against a lead tube into the shifter itself.
    many thanks if you have the nous to do this!
  2. MrJamie

    MrJamie Oaf on a Bike

    By lowest gear do you mean the biggest sprocket at the back and it wont change to the smaller ones?

    Search for park tools rear derailleur video on google/youtube, they explain things very well :smile:
  3. wiggydiggy

    wiggydiggy Über Member

    Honestly? I'd get the bike checked over either back at Halfords or at your local LBS - on my Carerra Subway 2 I had problems similar to yours after around 2000 miles and had the chain and front/back cogs replaced as they'd simply been worn out.
  4. Pauluk

    Pauluk Senior Member

    Usually gear shift problems like this can be down to cable tension or a sticking cable. Try adjusting the barrel adjuster on the back derailleur if its equipped with one.

    To test the chain length you can do one of two things:

    1. Split the chain and remove it from the rear derailleur. Then pass it over the large front cog and the large back cog, don't pass it through the rear derailleur. When you hold the chain taught there should be a 1" (two links) over lap in the chain. IE it should be 1" longer than the travel over the large large cog combination.

    2. If you don't want to remove the chain you will have to count your large front and large back sprocket teeth. Then:
    Chain Length = 2C+0.25(F+R)+1 in inches.
    Where C is the chain stay length (centre to centre of sprockets).
    F is the number of teeth on the largest front cog.
    R is the number of teeth on the largest rear cog.

    Hope this all makes sense.
  5. Pauluk

    Pauluk Senior Member

    As wiggydiggy said, check your chain wear first as that may be a more obvious problem.
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