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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 07-17-10, 03:35 PM   #1
shreddedmeat
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Advice on transforming a mountain bike

Hi all,

Please forgive my absolute ignorance in advance...


I've got a Diamondback M:05 mountain bike which I bought some years ago (yes, it was a Halfords special) which I chose because it was a Diamondback, looked pretty nice, and had what I assumed was a decent spec (front disc, front shocks, aluminium frame, chunky tires). With hindsight, these parts aren't the greatest, but they do the job for cheap since I don't actually ride offroad!

With that in mind, I quite fancied transforming it into a fixie, since I like them a lot and it would probably be more practical on city streets. I've done my best to read up on the process, but I've just succeeded in making myself thoroughly confused.

Do you think this is this a good idea? What sort of parts should I be looking at? Or should I just save up and get a decent bike (don't have a lot of cash to spare for this)

Any advice would be greatly appreciated!

Last edited by shreddedmeat; 07-17-10 at 03:38 PM.
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Old 07-17-10, 03:41 PM   #2
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without slotted dropouts the best you could do is singlespeed
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Old 07-17-10, 03:50 PM   #3
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Guess that's answered it for me then...
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Old 07-17-10, 03:56 PM   #4
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If you have vertical dropouts, then you can do single speed with a chain tensioner. Just buy one of the single speed kits. In the rare event you have horizontal dropouts, then you have a lot more work in store, you'll need to build up a 26 inch rim to a 135mm fixed hub.
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Old 07-17-10, 04:07 PM   #5
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Thanks fuzz, I might consider that. I should say that I've got absolutely no idea what "build up a 26 inch rim to a 135mm fixed hub" means . Steep learnign curve.

Thinking hunting down a good ready-to-go fixie looks like the best idea now!
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Old 07-17-10, 04:31 PM   #6
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Not all advice has been too accurate. Obviously single speed with a tensioner makes the most sense, but making it fixed is possible with some work. My bike (early 90s GT Outpost) has a vertical dropout, but I managed to get the "magical ratio" on my first try. 46-16 seems to be perfect for my particular frame. My chain tension worked out perfect. I was even able to fit a 700c wheelset to it for a complete "road" fixie conversion. Not to say that it's possible with every mountain frame, but maybe with some trial and error you can do it. Of course, a proper fixed gear would be much easier... Either way, good luck.
Here's how mine looks now.
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Old 07-17-10, 04:32 PM   #7
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Also - 26" rim is the mountain bike standard, and 135mm is the typical mountain bike rear axle spacing.
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Old 07-17-10, 05:38 PM   #8
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Quote:
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Also - 26" rim is the mountain bike standard, and 135mm is the typical mountain bike rear axle spacing.
I should of specified, but it only matters if you have horizontal dropouts.

Magic Ratios are a bad idea (in my mind) as there is no way to adjust chain tension. A little bit of chain wear, and the chain is liable to jump off. They are doubly a bad idea when used on a 26 to 700c bike, where getting brakes to work can be challenge enough. Not all bikes were made to be fixed gears, and there are some kludges that just aren't worth it to me. Single speed can be done simply and elegantly on most any bike, and I would suggest it over kludging your way to a mechanically questionably fixed gear.
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Old 07-17-10, 07:29 PM   #9
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Don't get me wrong, I don't think that my setup is the best, and I'm also not saying that anyone else should do it. I'm simply saying that it is possible. My brake is fine, and my chainline is perfect. Plus I have seen many bikes on this forum with much more slack than I would have before replacing it (since I can't adjust!). I'm not too worried about my chain jumping off.
Again, I don't want to say that anyone should do this or that. And I agree, SS would be much easier and an all around better idea. But it is possible...
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Old 07-17-10, 07:45 PM   #10
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Quote:
Originally Posted by shreddedmeat View Post
Thanks fuzz, I might consider that. I should say that I've got absolutely no idea what "build up a 26 inch rim to a 135mm fixed hub" means . Steep learnign curve.

Thinking hunting down a good ready-to-go fixie looks like the best idea now!
If you do go the fixed gear method, an easier and cheaper method to building a wheel is to get a surly fixxer. It may seem pricy at $80+, but compared to a 135mm hub, rim, spokes, labour cost etc, it is alot cheaper. My fixed mtb wheel cost over $200. And it needs to be a 135mm hub, not a hub spaced to 135mm.

There are several ways to get some adjustment with vertical dropouts. Google Sheldon Brown and seach for fixed gear. I have filed my droupoutd and used the cut down axle method with workable results. But not methods I would recommend for someone with basic fixedgear/bike knowledge.
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Old 07-17-10, 09:04 PM   #11
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To make the Fuji MX-200 atb I have into urban commuter transportation the most I'd want to do with it is change out tire width. It has 26 x 2.10 tire on 1.5 width rims. I'd keep mine at a 21 speed with anything between a 26 x 1.5 to 26 x 2.10 for a street tire. The 2.10's I have seem to be a hybrid knobby for street and trail.

Anyway there seems to be a wide selection:

http://www.performancebike.com/bikes..._400013_400013
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Old 07-18-10, 07:26 AM   #12
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Thanks for all the replies

I've come across this which I guess is an option (a complicated one at that)
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Old 07-18-10, 02:03 PM   #13
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Forgot about eno eccentric hub. Pricey, but will work no problem.
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Old 07-18-10, 04:08 PM   #14
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Forgot about eno eccentric hub. Pricey, but will work no problem.
Pricey as hell, I could probably track down a half decent used bike for close to that...
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Old 07-18-10, 08:06 PM   #15
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I have a cheap former 18 speed MTB with horizontal dropouts. I removed the cassette and replaced it with an 18T freewheel. I threw away the chainrings, cranks (nasty, heavy, solid chrome) and the BB, and replaced that with an SRAM S100 crankset and Powerspline BB. It's a Frankenbike setup on the rear, as I removed the 1/2" spacer from the right side of the hub and put it on the left side in order to move the wheel to the right for a better chainline.

Very odd setup but it works. I didn't want to build it as an FG with that hub, as I don't trust a lockring to keep the cog from spinning off, but lots of riders have simply spun a cog onto the hub and added a lockring.
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Old 07-19-10, 05:31 PM   #16
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You know, everything else mtb/atb just isn't the same after you get a glimpse of one of these ?

http://www.flickr.com/photos/4001066...ol-560618@N20/
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Old 07-20-10, 02:49 AM   #17
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Quote:
Originally Posted by coma061 View Post
Not all advice has been too accurate. Obviously single speed with a tensioner makes the most sense, but making it fixed is possible with some work. My bike (early 90s GT Outpost) has a vertical dropout, but I managed to get the "magical ratio" on my first try. 46-16 seems to be perfect for my particular frame. My chain tension worked out perfect. I was even able to fit a 700c wheelset to it for a complete "road" fixie conversion. Not to say that it's possible with every mountain frame, but maybe with some trial and error you can do it. Of course, a proper fixed gear would be much easier... Either way, good luck.
Here's how mine looks now.
YAY you added the 700s, how do you like it?

Quote:
Originally Posted by fuji86 View Post
You know, everything else mtb/atb just isn't the same after you get a glimpse of one of these ?

http://www.flickr.com/photos/4001066...ol-560618@N20/
OMFG I want a Pugsley SO bad!!
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Old 07-21-10, 09:59 AM   #18
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bleedingapple, I saw one here in Miami, the guy was riding it anywhere in the soft sand on the beach, It was ridiculous where he was going with it. That picture I posted, looks like the front wheel is a SS/FG hub & the rear is the cassette multi-speed. I didn't realize it until I started to look beyond the 3.7 wide tires. I figured you would need 21 speeds to get that thing going as it's a human powered dirt bike.

http://vimeo.com/11056499

Last edited by fuji86; 07-21-10 at 02:46 PM. Reason: Added Video linky
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