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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 10-07-10, 02:58 PM   #1
daven1986
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converting my bike to fixed gear - questions

Hi,

So I want a fixed gear bike for winter, however can't justify shelling out for a new bike. I have a geared bike which is a perfect candidate. But I also want it to be able to be used as a geared bike still - so no changing out chainrings! I will build a new rear wheel with a fixed hub to use.

Questions:

1) with 3 chainrings I assume I can use all 3 chainrings to find a magic gear if I use spacers for the chainline - is this correct?
2) do I just need some cassette rings, spacers, a lockring and a 135mm fixed hub?

Any tips appreciated

Thanks

Daven
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Old 10-07-10, 03:14 PM   #2
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1. One of the chainrings will create the best chainline with your hub. My guess is most likely it will be the middle ring, use that one.

2. If youre buying a new fixed hub(Id recomend the surly one if you have 135 spacing) the only other things you would need are a cog and lockring.

Im going to debate your assertion that your frame is ideal for a fixed gear. It sounds like its a newer mountain bike with vertical drop outs, that would actually be a poor choice for converting. The "magic gearing" doesnt really work all that well, and mountain geometry does not lend itself well to urban fixed gears.
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Old 10-07-10, 03:22 PM   #3
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Quote:
Originally Posted by Kayce View Post
1. One of the chainrings will create the best chainline with your hub. My guess is most likely it will be the middle ring, use that one.

2. If youre buying a new fixed hub(Id recomend the surly one if you have 135 spacing) the only other things you would need are a cog and lockring.

Im going to debate your assertion that your frame is ideal for a fixed gear. It sounds like its a newer mountain bike with vertical drop outs, that would actually be a poor choice for converting. The "magic gearing" doesnt really work all that well, and mountain geometry does not lend itself well to urban fixed gears.
Well the frame is a 2 year old hybrid which I have converted to drop bars. It gives me a really nice ride, has disc brakes, has my dynamo lights on it and can fit nice fat tyres. So it works for me. Also might have a bash at my road bike, depending on how this works out!

Thanks for the answers, if I used spacers with the cogs can I not make the other chainrings give a good chain line?

Thanks again

Daven
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Old 10-07-10, 03:45 PM   #4
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There is no way to put any sort of spacer on a fixed hub to push the cog in or out.Its fixed in place. The only type of respacing you can do is to take a narrower shell hub and fit in in wider spaced drop outs.
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Old 10-07-10, 03:46 PM   #5
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Quote:
Originally Posted by daven1986 View Post
1) with 3 chainrings I assume I can use all 3 chainrings to find a magic gear if I use spacers for the chainline - is this correct?
2) do I just need some cassette rings, spacers, a lockring and a 135mm fixed hub?
I think you're confusing some terms here. A cassette goes on a Freehub, which does not lend itself well to fixed gear purposes. You don't need cassette rings or spacers at all. You just need the fixed hub, cog, and lockring.

I'm with Kayce on this one. It sounds like you have a bike with vertical dropouts, which makes it pretty difficult to convert to fixed gear. It is possible though.
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Old 10-07-10, 03:49 PM   #6
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I don't want to rain on your parade but if your hybrid has disc brakes front and rear, chance are that you have vertical dropouts.

For fixed gear, you'll need a magic-gear, perfect gear where you will have no slack in the chain since your dropouts don't allow you to adjust chain tension. Once the chain begins to wear out and 'stretch' you will run into problems.

Another option is to go single-speed and use a tensioner.
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Old 10-07-10, 04:26 PM   #7
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Quote:
Originally Posted by Kayce View Post
There is no way to put any sort of spacer on a fixed hub to push the cog in or out.Its fixed in place. The only type of respacing you can do is to take a narrower shell hub and fit in in wider spaced drop outs.
Thanks, I was misunderstanding

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Originally Posted by FastJake View Post
I think you're confusing some terms here. A cassette goes on a Freehub, which does not lend itself well to fixed gear purposes. You don't need cassette rings or spacers at all. You just need the fixed hub, cog, and lockring.

I'm with Kayce on this one. It sounds like you have a bike with vertical dropouts, which makes it pretty difficult to convert to fixed gear. It is possible though.
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Originally Posted by WeirdOddity View Post
I don't want to rain on your parade but if your hybrid has disc brakes front and rear, chance are that you have vertical dropouts.

For fixed gear, you'll need a magic-gear, perfect gear where you will have no slack in the chain since your dropouts don't allow you to adjust chain tension. Once the chain begins to wear out and 'stretch' you will run into problems.

Another option is to go single-speed and use a tensioner.
Yep I have vertical drop outs, I will be using the "magic gear" or an ENO eccentric hub (although not sure how much difference 15mm will make...) not a fan of single speed though so that is out!

Thanks
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Old 10-07-10, 08:52 PM   #8
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The ENO hub will give you enough room to play with. If it doesn't, you may use a half-link or a half-link chain.

Using an eccentric hub might cause problems with your disc brakes though, since they will not hit the rotor properly. You'll have weaker brakes and your pads will wear not wear evenly, so I'd suggest switching to a good V-brake.
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Old 10-08-10, 11:55 AM   #9
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Yeah good point r.e. the brake. I can always use it with just a front brake though. Hopefully I can find a good magic gear though!
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Old 10-11-10, 02:11 PM   #10
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Ok here is the new plan.

Use my existing spare front wheel with disc brake mount, get a 6 bolt cog, some washers, a chain and an axle bolt. I can use the washers to get the chainline correct and make the wheel snug in the rear dropouts. The axle can be filed down using sheldon brown's method to give some wiggle room.

How does this sound?

Thanks

Daven
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Old 10-11-10, 03:32 PM   #11
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Originally Posted by daven1986 View Post
Use my existing spare front wheel with disc brake mount, get a 6 bolt cog, some washers, a chain and an axle bolt. I can use the washers to get the chainline correct and make the wheel snug in the rear dropouts. The axle can be filed down using sheldon brown's method to give some wiggle room.
I think I understand what you want to do. You'll need a longer axle, but why use a front wheel in the back? You'll have to space it out quite a bit. Just put the cog on your rear wheel.

Again, it's pretty hard to make a FG with vertical dropouts, but you seem pretty set on doing it.
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Old 10-12-10, 12:32 PM   #12
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Thanks for the advice. The only reason for wanting to use a front hub is that I have a front wheel lying around which I could use

All I'm worried about is the chainline once I space it...

I'm set on doing it as I fancy a fixed gear but don't want to spend money on another bike, and I am due a little project!

Daven
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