Terrapin Ben

But before we get to that, Hello from the MTB board! I was droping in to ask a question i am sure you have had asked a thousand times and i just got off work and i just got my bike in the mail and i need to go ride it so i dont have time to scour the archives and find my answer myself so i appologize for my laziness but here it goes! I have a mountain bike i want to single speed. it has verticle dropouts. Question A.) Do my verticle dropouts pose a problem to single speeding my bicycle? and B.) What is the easiest way to ss my bike? and finally C.) What is the cheapest way to do it? Thank you so much in advance for your input and advice. Keep those wheels rolling!

onetwentyeight 

White Industries Eno Eccentric Hub will help you with chain tension problems, or you can use a magic gearing. Search the forum for both should get you what you need. THe magic gear is cheaper.

Terrapin Ben

good vibes and much thanks to you onetwentyeight! i cannot wait to strip my bike down to the nitty gritty and get rid of that annoying cog set...

onetwentyeight 

Welcome. Have fun.

humancongereel

just for ss, you can use the rear derailleur, a ghost chainring, or use a chain tensioner and be fine.

Toolshed

If you want to single speed it, you can also use a chain tensioner like https://www.dmrbikes.com/?Section=pro...s&itemid=CDSTS or simply rig the old derailer as a chain tensioner. If it's a freewheel mountain wheel, you can pull off the multi-gear freewheel and add a BMX freewheel, something you should cheaply find at a lbs.

megatherium

what about a half link?

the pope

See, now THIS is the way to enter as a newb as get respectful replies from the rum-soaked inhabitants. Welcome aboard.

evanyc

magic gearing is cheaper if you already have various chainrings and freewheels to work with or are able to test the set up out at a show before buying.

baxtefer

just get a chain tensioner. like a surly singulator or a paul melvin or an old derailleur.
use your old freehub-based wheel and use a BMX cog with cassette spacers (or PVC pipe) to get proper chainline.

LóFarkas

+1

No need to **** around with half-links, magic ratios and all that jazz. Slap on an old der. or a tensioner and be done with it.

Aeroplane

I would never plan on finding the magic ratio unless you are confident with a file. A tensioner like the DMR or the Rennen one will do you well, and will accomodate chain stretch. Plus, it's just much, much less headache.

eddiebrannan

once you've determined your ideal gear ratio, remove the casette and replace with a bmx cog and cassette spacers. cassette spacers can be had from your lbs. the cog can be set at the ideal position for good chainline.

here's how that will look as you'e putting it together. there are spacers inside of the cog and none outside at this point:


don't use an old derailleur. the derailleur's spring mechanism causes it to default to either the innermost or outermost position (depending on make/model) so you'd have to retain all the cabling/shifting mechanism to maintain it in a central position, which you'd need for chainline. if you're going to keep all the crap you might as well have gears. if you don't want gears, you don't want the crap. use a surly singleator or similar to tension the chain.

use a bmx chain. the stock chain on your bike is designed to flex to permit shifting. as you'll not be shifting you don't want flex, especially as the cassette cog wil be ramped, causing the chain to "want" to shift.

this is the easiest and cheapest way to do it properly and enjoyably. the only additional stuff you'll be buying is the singleator and the chain. jenson usa has the singleator for $37 here. a chain is dirt cheap.

crackerjack

+1 for this as well. Mtbr has a nice rundown as well. Good luck.

dutret

You've never done this before have you? Most derailers can be set to the right postition by adjusting thier limits. They are not as ideal as a real chain tensioner but work on alot of bikes. Try with the derailer and if it fails then you can buy a singulator or somthing but there is no reason not to try it first.

lunacycle

My recommendation: Rennen Rollenlager + Surly bmx cog + singlespeed chainring of your choice + new chain. I've gotten very good performance out of this system.

Also, don't throw away your old lockring and smallest cog from your cassette, as you will need both to lock down the spacers and cog.

The chainrings on your bike are probably pinned and ramped to assist in shifting -- which is why you will want to replace them with a chainring that is not. It's important to keep in mind that with a single speed, you'll be exerting much more force on the teeth of the cogs and chainring than you would by churning away in the granny gear. Therefore, you want a more robust drivetrain. This is why I recommend the singlespeed chainring and Surly cog. The surly cog is 4mm thick at the splines. A typical bmx cog is just a thin, stamped piece of steel. The splined teeth can dig into the freehub body. The Surly cog allows the force to spread out over a larger surface area, which reduces the localized stress on the freehub body.

One other note: If you know what gear ratio you want to use (2:1 is a good start for 26" wheels), then use a larger cog / chainring combination. This will distribute the pedaling force to more teeth, and reduce wear. For instance, I use 36x18 gearing for a 2:1 gear ratio, instead of the standard 32x16.

Of course, as others have mentioned, you could just reuse your old derailleur. But you really should replace your chainring and chain, and buy yourself a bmx cog if you go that route. It may not be as robust, but It will certainly save you some bucks over the system I recommended.

eddiebrannan

no i've never done it using a derailleur as a tensioner. whenever i singlespeeded a geared bike it had either horizontal dropouts in the case of my bridgestone mb3 or a sliding vertical set-up in the case of my .243, so i never needed any kind of tensioner.

i didn't imagine that limit adjusters would permit you to restrict movement up and down entirely, especially to a setting right in the middle. if so, well there it is. far from ideal, IMO, and $37 is hardly a lot of money to have something that's designed for the job.

Grand Bois

I suggest that you experiment with some cassette cogs before you spend the money for a chain tensioner. You may get lucky and find a "magic gear" combination that works for you. That's what I did. A half link increases your chances, but I didn't need one. If you find a cog that works, then you can get a Surly cog the same size.

My geared bikes are being neglected since I built the single speed, and I just built another SS for my wife.

https://community.webshots.com/photo/...68014369jHohCP

https://community.webshots.com/photo/...68014369yGtTZp

dutret

those aren't mtbs though. magic gears need a much tighter tolerance off road due to the constant bouncing and sudden application of force.

Also I reccomend starting a bit lower then 2:1 34x18 is probably the most popular gear but you may want to start even lower with 32x18 until you(and your knees) are a bit more used to climbing is a high gear.

Grand Bois

The Trek 930 used to be a mountain bike. The chain is as tight as it can be without binding. There's no way it's going to come off as long as it's replaced before it wears too much. The one in the picture has been replaced with a cheap nickel plated Wipperman. I just think it's a much nicer setup if you can avoid using a chain tensioner.

dutret

used to be a mtb. It may work I'm just saying that to get a magic gear on an mtb you have alot less room to play with and usually that means experimenting with a range of chainrings not just cogs. given how much gearing matters I think it's just easier to not bother with it.

Are those scott MTB aero bars you cut off?

max-a-mill

i don't recommend these two pieces of advice.

an old rear-d works just tfine you just use a little piece of shifter cable to adjust it to where the chainline is.

also i find a 3/32nds chain works much better with 3/32nd components (all non-track SS stuff) then a 1/8" chain. a 1/8th will work but a 3/32nd's will work better. all that crap about not being desgined to shift is hooey IMHO....

powers2b

Just cut all the shift cables.
Instant SS

Grand Bois

Like I said, I got lucky. The second combination I tried worked. If I had spent an hour trying different combinations, it still would have been worth it to me. I never have to worry about chain tension because my rear axel is locked in by the vertical dropouts. The downside is that I can't change gear ratios unless I find another magic gear, which isn't likely.

Those are uncut Scott AT-2 bars. Somebody was dumping them for $7 on eBay. I wish they were narrower.

dutret

The problem in my mind isn;t the time but noone I know has a set of 32-40t chainrings and at that point you might as well just buy an eno.