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Single gear bike

darrell1967darrell1967 Posts: 470
edited April 2021 in Workshop
Hi,
I’ve got an old Dolan frame and some odd parts including a Tiagra 4600 chainset, brakes and 10 speed cassette.

Can I run this without a derailleur with the chain on the 6th cog for example?

I’m thinking of building a simple bike to go up the gym on.

Cheers

Posts

  • shirley_bassoshirley_basso Posts: 6,194
    The tricky part is getting the chain the right length and tension so it doesn't bounce out the sprockets.

    The simple solution is to use a chain tensioner - like a rear mech but doesn't move up and down, just the spring bit.
  • darrell1967darrell1967 Posts: 470
    I’ve just nosed at tensioners on eBay. Only £20.

    Why is it hard to get the chain length correct? It was straightforward on my old BMX or is it because of the drop-outs??
  • elbowlohelbowloh Posts: 7,078
    darrell1967 said:

    I’ve just nosed at tensioners on eBay. Only £20.

    Why is it hard to get the chain length correct? It was straightforward on my old BMX or is it because of the drop-outs??

    If you have a tensioner it shouldn't be hard to get the chain length right.
    Felt F1 2014
    Felt Z6 2012
    Red Arthur Caygill steel frame
    Tall....
    www.seewildlife.co.uk
  • darrell1967darrell1967 Posts: 470
    edited April 2021
    elbowloh said:

    darrell1967 said:

    I’ve just nosed at tensioners on eBay. Only £20.

    Why is it hard to get the chain length correct? It was straightforward on my old BMX or is it because of the drop-outs??

    If you have a tensioner it shouldn't be hard to get the chain length right.
    Will it work ok to go from the 4th or 5th sprocket to the chain wheel??
  • imposter2.0imposter2.0 Posts: 12,015
    You haven't said what the frame is, or whether it has vertical or horizontal dropouts. Unless you are running a straight chain line, it is likely to be at best unreliable, or at worst, unworkable.
  • darrell1967darrell1967 Posts: 470
    Its got vertical drop-outs.
  • elbowlohelbowloh Posts: 7,078
    Yeah your BMX would have had horizontal drop outs, which you use for getting the chain tension
    Felt F1 2014
    Felt Z6 2012
    Red Arthur Caygill steel frame
    Tall....
    www.seewildlife.co.uk
  • darrell1967darrell1967 Posts: 470
    elbowloh said:

    Yeah your BMX would have had horizontal drop outs, which you use for getting the chain tension

    So vertical drop-outs can’t do that then? Hence the chain tensioner.
  • imposter2.0imposter2.0 Posts: 12,015
    Chain line and chain tension (or slack) are going to be the biggest issues. All very well saying 'put the chain on the 6th sprocket' - but unless the chain line is straight, it's not going to want to stay there. You can get single speed freehub spacer kits which will help you achieve a straight line, by replacing the cassette with a single sprocket and spacers.
  • MattFalleMattFalle Posts: 11,644
    You can use a single sprocket and lots of those plastic spacers from cassettes if you can't get hold of one of those those kits as above.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • darrell1967darrell1967 Posts: 470
    Thanks guys. I think I understand it all now.
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