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Building a fixed-couple of quick (& maybe stupid!) quest

KirkyKirky Posts: 459
edited October 2007 in Road general
Hi all, I've got an old bike that I'm thinking of turning into a fixed - from what I've read it should be pretty straight forward. It's an old bike with pretty long forward facing drop-outs, and a screw on rear block. Can someone confirm the following....

1) The older framesets have narrower rear spacing of the dropouts and are therefore OK if I decide to use a proper fixed rear hub. And what is the track spacing anyway?
2) If I remove the screw on block, a fixed sprocket will screw straight into it's place - which can then be locked in place with a lockring from an old style bottom bracket?
3) What's the deal with what appears to be different 'sizing' on the fixed sprockets you can buy? I've seem them advertised as 3/32" or 1/8" - does this relate to the chain width to be used? Or have I missed something completely!!
4) Will it be OK to run it on the 42 tooth inner ring of the original chainset that's on the bike (170m crank length), that I can then set-up with an appropriate rear sprocket?
5) Do people continue to use a quick release rear? Or is it too difficult to get it tight enough to stop the wheel from pulling over?

Hopefully that's it!! I'm hoping that this should be a VERY cheap way to turn an old bike that never see's the light of day into a fixed - by my reckoning it should cost me about £10, i.e. the price of a fixed sprocket!!

Thanks in advance, the above all makes sense to me - but to be honest it also sounds far too easy!! I'm sure this has been covered a number of times before on these forums, but I thought this would be the quickest way to answer these fairly simple questions!!

Many thanks

KIRKY
Las Vegas Institute of Sport

Posts

  • 1 - Older road spacing can be 120mm (same as modern track), 126mm or a couple of others, check out sheldon brown for a definitive list of OLN (over lock-nut?) measurements. Track is 120mm and I've had no problems using a 120mm hub in a 126 spaced frame. Get out your ruler and check - 6mm either way will be OK

    2, 3 - You are entirely right!

    4 - 42x16 is a common ratio for around town. Get a 15t on the back later if you want..
    You may have to swap the chainring to the outside and/or use spacing washers to get better chainline. This is USUALLY in addition to re-dishing & re-spacing the rear wheel (take off the tyre, tube, and rim-tape and check that the spokes do not stick up too much) and perhaps using a cog spacer between the new cog and the hub flange to ensure that the cog lines up better.. there are lots of instructions on the intarweb. Sheldon, bikeforums.net, 63xc.com, google 'conversion chainline'...
    Hopefully you will be alright with minimal work, but be aware that chainline fettling is the main source of pain in a conversion! Are you confident wielding a spoke-key? Bad chainline = dangerous. but a 3/32 chain should handle up to 2mm difference fine..

    5 - I used QR for a while - after 2 months on a singlespeed I snapped the hollow axle. a new axle + nuts + cones can usually be had cheaply from your local bike shop.

    Good luck! it will be entirely worth it to get the beast back on the road where it belongs..
  • peejay78peejay78 Posts: 3,378
    that's good advice that is.

    living in london a 48:16 or 18 is a much more common ratio.
  • BronzieBronzie Posts: 4,927
    Kirky wrote:
    3) What's the deal with what appears to be different 'sizing' on the fixed sprockets you can buy? I've seem them advertised as 3/32" or 1/8" - does this relate to the chain width to be used? Or have I missed something completely!!
    1/8" chain & sprockets are designed for track where the force through the chain (in sprint events at least) is higher and where the consequence of a snapped chain (on a bike without brakes) will probably cause a pile-up.

    You can use 3/32" chain on a fixie sucessfully, although 1/8" is a bit tougher.

    If you do fit 1/8" chain and rear sprocket, you can still use a 3/32" front chainring with it quite safely.

    Good luck and don't forget - KEEP PEDALLING (you'll only forget once)!!
  • rendorendo Posts: 194
    only thing i'd add, is if you are using a hub designed for a screw-on cassette. it probably won't have the lockring thread, typically these are for use on freewheels (be they single or multiple sprockets). the risk with fixed is if you try and slow down using your legs you risk the sprocket coming loose.
  • andrew_sandrew_s Posts: 2,511
    2) The BB lockring isn't a completely solid lock like a proper LH thread lockring. Given enough provocation the cog and lockring will just unscrew as a single unit. You may as well leave off the lockring, leave the rear brake on, and not get into the habit of trying to stop using your legs.

    3) 1/8 vs 3/32 chain. Most 3/32 chain is derailleur chain and designed to be side-to-side flexible. It will come off more easily if you let your chain become slack. If you don't, there isn't much difference in strength.
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