curieux88

I found an okay mtb on facebook marketplace for free. It's one of those kmart/walmart/costco kind of a trail bike. no suspension, but can take large wheels. I plan on using this for winter commuting in montreal. I was told to get a cheap and simple bike, because it may not last all that long due to salt.

well, it is cheap for sure. (free!) I figured I should drop all of the derailleurs to make it a SS. Probably the easiest to clean and maintain, because I don't have to worry about complex geometry of derailleurs. So I was started looking into different spacers and adapters I need to purchase, and that's when I thought I might be able to achieve the samething without spending more money.

I was hoping that you folks could correct my idea and perhaps suggest if there's any better idea.

If all I'm doing is getting rid of derailleurs and unused chainrings and cogs (and replacing with spaces as necessary), why don't I just get rid of the derailleurs and keep the unused chainrings and cogs? Simple pick a chain ring that I want to use, and then use the cogs that's inline with the chainring. The only additional thing I need to get is a chain tensioner. It's still easy to clean and maintain. The only downsides I see are 1. I can't fully customize the gear, but I don't really care that much 2. it's heavy - I also don't care.

Any thoughts?

blamester

You would have to be very lucky for it too work well.
​​​​​​Best just leave it as it is.
The salt isn't going to kill it that quickly.
Spray lube every now and again.

dabac

The easiest way to an SS is to stop shifting.
derailer gear bikes are meant to derail. Removing derailers and keeping it reliable usually means adding other bits and pieces to keep the chain settled.
Your Rear derailer IS a chain tensioner.
if you really want to ”customize” your bike, run a piece of wire through the RD. Button end of wire in the barrel adjuster, then clamp the wire to the RD with the RD in position for the preferred gear. Fine tube with the barrel adjuster.

Thomas15

Leave it as is. 15 minutes of casual study will take all the mystery out of what is termed "complex geometry of derailleurs". If I can figure it out, anyone can.

FastJake

I've used derailer bikes as winter commuters but eventually got sick of maintaining them and now exclusively ride fixed gear in the winter. Single-speed/fixed gear definitely has real merits in the winter.

With that said, you could indeed get pretty much the same thing from simply not shifting. Shortening the chain and running it on the middle ring and one of the cogs might work, or you might end up with bad chainline. People have done it before.

70sSanO

The idea on locking the derailleur in place is a good idea. You can probably just use the shifter cable and the battle adjuster or the cable housing stop before the last loop before the derailleur, might need to add a washer.

You might also be able to bypass the upper jockey (pulley) and just run the chain from the cog to the lower pulley. You are basically creating a chain tensioner without having to serpentine the chain through the derailleur per se. Less chain bend to deal with.

I would ride the bike and figure out what ratio works best. If you set it up right, you can probably select one of two adjacent cogs by just using the barrel adjuster.

John

WizardOfBoz

This quote made me chuckle. See, it's funny because it's true.

squirtdad

if even on a cheapy bike the cassette/freewheel has any sort of modern tooth design, then taking the derailler off will just let it shift by it self to the smallest cog

simple and cheapest and most reliable is to use it as is

Oneder

The front deraileur can be annoying but I would not take the rear off. You have gears for a reason and whatever you choose now you may feel is wrong later and probably will. To really make a single speed you should have different cogs that are not designed to slip anyway. In short don't waste your time. Just adjust the limits on the front derailleur to stay on the same chainring and you are set.

Ironfish653

There’s more to successfully making a single-speed bike than just stripping off the derailleurs. A bike designed for single speed usually has long horizontal dropouts, that let you adjust the chain tension by moving the rear wheel forward and back. Derailleur bikes have vertical dropouts, because the derailleur takes up the slack in the chain. There’s typically not enough movement in a vertical dropout to get correct tension unless you hit the ‘magic ratio’ of gears to get the chain length exactly right.


For bad weather winter beater, provided it’s already in passable mechanical shape, I’d suggest a heavy duty lube job: WD-40 or even light grease on the derailleur linkage, ATF or gear oil on the chain. It’s a little messy, and a little more ‘draggy’ than a typical bike lube, but it’ll last longer in bad conditions.

70sSanO

OP wants a single speed. I say just strip everything you don’t need off the bike and lock the derailleur in one position. Who needs all that other crap on there. It’s not like this bike is worth anything.

Ride it till it rusts and then throw it away. Go find another one.

John

Miele Man

Okay Mr. OP.

Do you have a cassette or a freewheel on your bike?

If it's a cassette you have a few options. #1 and a great thing about a cassette is that you can scrounge some extra spacers from a t rashed cassette. Most bike shops will give you a trashed cassette that you can take apart for those spacers.

With those spacers and cogs you can pick the cog that gives you the best gear for your riding style. Then by moving the spacers and the cog on the freehub body you can get the best chainline. The straighter the chainline the less chance of derailing the chain.

If you use the middle chainring on your bike you can remove the inner chainring and the outer chainring. You'll need to either get single speed bolts and nuts if you do that, or you'll need to cut down the nuts from your existing crankset. that is if you have removable chainrings.

I've done many such conversions and they work well.

If your bike has a freewheel, then you can by an inexpensive single-speed freewheel and new chain to match.

I've done that too.

Road bike converted to single-speed freewheel and ex double crank. MTB works the same way.








Cheers

tyrion

RJ will walk you through it:

70sSanO

I think The question is what type of dropouts. Horizontal is a piece of cake, vertical is a bit tougher.

John

79pmooney

Winter salt; an excellent reason to take the rear derailleur off (and just use the front as a chain guide if needed). 1) Salt quickly makes chains run very poorly through the pulley slalom. 2) In ice and snow, crashes happen; usually simply doing down to the side as the tires slip out. Rarely an issue beyond a bruise or two except rear derailleurs take the right side falls personally, Very often simply up and quit. 10 miles from home, that isn't fun. (I used to do a 12 mile commute into Boston through the the winter. Also several in Ann Arbor. I didn't own a car. It's been a few decades but I know what I am talking about.)

I typed the above and realized you probably have vertical dropouts. (The slots the rear wheel axle slides into. Newer bikes (past 30-40 years) have vertical. Older have horizontal as do all the popular bikes for singe speed and fix gear.) With vertical dropouts, you need the rear derailleur or a chain tensioner, Either is prone to damage in a right-side fall. The tensioner cheaper but harder to find in a parts bin.

So I say try the single-speed this winter with what you've go. Like it? Look for a bike or frame with horizontal drops or track ends. (Horizontal dropouts open to the front, track ends to the rear. Track ends are popular, horizontal dropout work just as well and are a lot easier for what you want. (Much less hassle with fenders, removing the wheel and messing with the chain is easier and faster - much appreciated when you flat in the dark. (Commuting in Montreal - you won't get a lot of flats but they will happen in the dark!) Oh, for bikes with horizontal dropouts, look for almost any Japanese bike of the early to mid '80s. Try bike coops. shops with used bikes. garage sales ... (A lot were made.) Most of the mid-priced Japanese bikes could take fenders and a lot of them came with 27" wheels. Use modern 700c wheels - you might have to mess with the brakes - and with the smaller replacement wheels you will have lots of room for fenders.

Ben

curieux88

hi! Sorry for late response. It took me a while to be allowed to post photos.

it looks like a vertical drop out, but it also looks like horizontal. Not quite vertical, but definitely not 180 degrees horizontal.


edit: damn, idk why it's upside down. sorry for the photo.
edit2: fixed the photo!

FastJake

You have horizontal dropouts which make it easy to convert to single-speed or fixed gear. They're called "horizontal" but that shouldn't be taken too literally.

caloso

You are in good shape with those drop outs. Now the thing to do is see if you have a cassette or freewheel.

Miele Man

If it's a Uniglide cassette, he's really in luck. That's because a bottom bracket lockring is the same threading as most Uniglide screw-on cogs. Here's a Uniglide cassette body with a bottom bracket lockring but without the spacers or cogs.


Cheers

Miele Man

Bike Forums is having problems allowing me to post today. I'll tryu again.

Miele Man

When bicycle co-ops open again, and if there's one in your area, they are a great source for chainrings and used cogsets. I say that because if a certain gear combination you want to use is too short or too long with the chain installed for your dropout then a slightly smaller chainring or a slightly bigger cog might work. Also, there is a neat item called a half-link that can be used with chains to give that wee bit of extra length or shortening of the chain that one might need to work best.

Cheers

FastJake

Come on guys, x-mart bike. It's almost certainly a freewheel. Has a cassette hub ever been installed on one? The bolt-on axle all but confirms it.

Oh, and a Uniglide cassette hub? That was good for a laugh.

curieux88

damn. you are right. I just got to check it, and it's freewheel.

curieux88

freewheel.

caloso

Shrug. I have no idea what comes on an X-mart bike.