making a single speed

[gonzo]

anyone got any tips on making a single speed? I have a M2 stumpjumper from 1995ish that i am going to retire - figure i'll hop on the single speed train. frame is great (ass ugly paintjob) and has a non-replaceable derailer hanger, which is funny - nearly snapped it a few times...

anyways, any tips would be schweet. i have limited bike tech experience - always done my own tunes, etc. but all major stuff (headsets etc) i let tha shop handle it.

seem to be a good number of serious bikers here who might have some experience. and phunk, i know I should check ww.mtb.com or something, but i don't wanna!

[Innominatus]

Well... the SS forum at mtbr.com IS slightly more topic appropriate...

Anyway, Golden Rule: It's all about getting the chainline lined up straight.

I've only done road bike conversions, and usually fixies at that, but for a freewheel mtn. bike it shouldn't be too bad.

Couple things come to mind.

First, without going so far as to rebraze on a set of horizontal rear dropouts, you'll need some way to adjust tension on the chain. A Singleator might be just your ticket - its basically a little spring arm with a sprocket. You can get one for $40 at Excel in Boulder -->
here.

Second, you will either need to rebuild your rear wheel on a BMX or road hub (make sure the dropout spacing matches). You can opt to redish the spokes with minimal dishing while you're at it, but mainly the point is to get a hub that takes a thread-on BMX freewheel.

Finally, Keith Bontrager wrote the perfect article for you already:

http://www.bontrager.com/keith/rants.asp?id=8

Failing all that, head on down to the local velo shop and befriend one of the techs. For good bartered beer, they'll spew advice until your ears hurt.

Good luck...

[gonzo]

that article is awesome - thanks man.

i think i may go for the "manual shift" option - seems pretty cool...

[mntlion]

Originally posted by Innominatus


Second, you will either need to rebuild your rear wheel on a BMX or road hub (make sure the dropout spacing matches). You can opt to redish the spokes with minimal dishing while you're at it, but mainly the point is to get a hub that takes a thread-on BMX freewheel.

Just a thought, but why can't you just use a freewheel spacers and a single ring, most 7-9 spped cassettes the smallest 2 rings are removeable and also have removeable spacers inbetween, can;t you just add a bunch of spacers and a single ring?

Great info and links

[Innominatus]

Originally posted by mntlion
Just a thought, but why can't you just use a freewheel spacers and a single ring, most 7-9 spped cassettes the smallest 2 rings are removeable and also have removeable spacers inbetween, can;t you just add a bunch of spacers and a single ring?

Good call -- yep, you can do this, too.

Kind of the Ghetto Way (and offensive to the purists), but might actually be the superior first-timer approach as it would let you play around with different rear cog sizes and spacer combos to arrive at a gear ratio you like.

Then, once you nail down your preferred rear cog size, and you decide the whole singlespeed aesthetic is your cup of antiestablishmentarian tea, you can plunk down the $ on a dedicated SS setup.

BTW - regarding gear ratio: most folk seem to like 2:1 front/rear for MTB-based setups (30 ring up front and a 15 in back), but you might want to go taller for those flat Chicago concrete canyons.

[laseranimal]

and I thought ski tech was complicated

[bagtagley]

If you can get your hands on 10-12 casette spacers, then you can run it BMX style. Basically, you pick a gear, place the spacers on either side of it on the hub so that the chain line is straight. If you're lucky, you'll have picked the right gear combo and the chain will be the right tightness (after removing links). I did this on my trials bike, and it works great. However, don't know how it would hold up to the rigors of single speed riding.

Edit: Yeah, what mtnlion said. The hardest part is getting the chain to a desired tension. The size of the rear cog is more dependent on this than personal preference. I was lucky enough to be at a bike shop where I had a box of loose rear casette gears to choose from. The difference between way too tight and way too loose was one tooth. The solution to this problem would be a cheap chain tensioner like this: