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I have a 6ku fixie, 49cm frame. There is not much clearance between the top tube and me. So I wanted to buy the 47cm and change all the parts on that one, instead of purchasing a whole new bike. Is that possible? I'm guessing it is, because it will be the 6ku just a smaller frame. I ride the 49cm okay, but I know it would be more comfortable if it was a 47cm.

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If they are both the same model fixie then should be not problem. You might need to take a links off the chain. –  Blam Jun 12 at 1:21

2 Answers 2

up vote 3 down vote accepted

Just had a quick look at their site, there doesn't appear to be anything too special about these that'd cause problems.

However, it doesn't look like they sell frames on their own.

If you're changing to a frame from another brand then you'll have to make sure the following things are the same.

  • Bottom Bracket

    There are a variety of styles for these, your's is most likely BSA threaded and 73mm wide. You need to make sure a replacement frame matches this to just swap the parts over. You can replace the cartridge in the middle, as this looks like a fairly standard square taper crankset, but finding the right one can take some thought.

  • Seat Tube Diameter

    Seat tubes come in all kinds of sizes. Your's could be anything. To fix a mismatch here all you need is a new seat tube though, and these are pretty cheap.

  • Rear OLD, or spacing.

    The space between the fork ends on the rear could be either 120 (almost certainty on a fixie) or 135mm. This should match, but you can bend a non matching frame or space out your hub to make it match later. This can affect your chainline.

  • Headset

    Often frames come as a set with forks & headset, often not. If the new frame doesn't include a fork & headset the head tube of the frame will either need to match, or you'll need a new headset.

    This bike looks like it has threadless headset, most are these days, be sure to get a matching frame or you'll need to replace forks & stem too.

  • Steerer

    The steerer of your current fork may not be long enough if it's cut to size and the new frame has a longer head tube.

Other than that, most things should be ok. There's no guarantees though.


However, the easiest way to sort this out would be to sell this one to someone taller and buy yourself another in the correct size.

Buying bikes whole is always much better value and you're not going to have to buy a hundred new specialist tools to get the job done.

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Some areas have bike co-ops where you can rent tools. These don't appear to be fancy frames, so i think the resale value on a frame alone will be low. –  Batman Jun 12 at 2:20
    
Very good point, Batman. I would still just flog it and get another though. Unless you want to learn all about stripping and rebuilding a bike, which is a fun way to spend a day, it's just a lot of hassel for a fairly standard OTS fixie. –  alex Jun 12 at 2:24
    
You'd lose too much money trying to sell the bike and buying a new one. Realistically you'll only get 50% back from a bike for a quick sale, $200 for a new fixie and your $300 down. Buy a frame for $75, sell your existing one for $30 and your only $245 into the bike. If you sell the whole bike your losing money on everything not just the frame. –  DWGKNZ Jun 12 at 4:25
    
But you don't have to buy a brand new one. –  alex Jun 12 at 4:26
    
@alex: There also may be a difference in head tube diameter and bearing style if the OP only buys a frame without fork. –  arne Jun 12 at 5:27

You may have issues with toe overlap, especially with a fixed gear.

The smaller frame will mean your cranks are closer to the front wheel, so your toes could touch the tyre when you turn tightly. And with a fixed gear, the pedals are turning all of the time, so more chance of this happening. Its debatable as to whether toe overlap is a problem or not - some people find it annoying or dangerous, others soon get used to it.

It will depend on the frame geometry as to how much difference a smaller frame makes to toe overlap. You can reduce toe overlap by changing to shorter cranks, which may suit you better if you are not very tall. Also narrower tyres would give more clearance.

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