$0 single speed "conversion"?

This topic has 63 replies, 15 voices, and was last updated 12 years, 2 months ago by vvill.

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November 20, 2012 at 3:32 pm #955896

DSalovesh
Participant

Using a derailer to keep chain tension is dicey if the chain is still the original length. With the limit screws locked you can’t recover if the chain hops a gear and doesn’t settle back. Probably won’t be a big problem, but to fix it you’ll need to hop off and fiddle around.

If you shorten the chain (or buy a new one and trim it) you should be fine for playing around while you figure out if it’s worth the <$100 to commit.

November 20, 2012 at 3:38 pm #955901

Dirt
Participant

Yup. You gotta shorten the chain so that the derailleur is stretched pretty tightly. Most derailleurs don’t let you completely lock the limit screws so that the derailleur is incapable of moving. The one governing how far to the small end of the cogs is the most important.

The problem with the $10 kits is that they also tend to use a cheap stamped cog that is very narrow at the base (where it goes over the freehub body splines). That makes it very easy to damage the freehub body. If you have an idea of what size cog you’d like, I probably have a spare you can try for free. It will be worn a bit, but will still have life in it.

Let me know.

Pete

November 20, 2012 at 3:50 pm #955905

vvill
Participant

Thanks for the replies. So sounds like I need to shorten the chain – I guess otherwise the chain would be too slack? It’s an 8 speed chain, probably Shimano – safe enough to just relink it anywhere?

But what’s the difference between what I have now and a normal geared setup in terms of the rear derailleur/chain tension?
I haven’t removed the rear cassette or anything. I’m just “locking” the chain onto the 15T cog of the existing cassette using the H limit screw. If the chain jumps couldn’t it just land on the 12T, 13T, 17T, etc?

All I’m after at this point is one step up from having a geared bike that I’m not shifting on. I could spend $ on this but I’m being stubborn and don’t want to because it’s an old bike that’s a bit too big… if I decide I like SS enough I would just get a whole different bike and something with horizontal dropouts. This one will probably go back to toddler pulling duty come springtime.

November 20, 2012 at 4:00 pm #955908

DSalovesh
Participant

Yeah, the chain would engage another gear, mostly, unless it falls between. And it could be close enough to “in” gear that it wouldn’t seem wrong except it would not be as solidly engaged so it’s more likely to slip when you put extra pressure on it. With the chain shortened it’ll stay bottomed out on the cog teeth.

It would be fine to relink it anywhere that works, yes. I really like using tool-free links (have a couple in my porta-tool bag), but they’re not necessary.

The biggest difference between what you have and what you’re describing is that now you can shift if you want/need to, but you’re disabling that system. Most likely nothing much will happen because of it, but shortening the chain and/or replacing the derailer with a tensioner drops the bad outcome chances below any concern at all.

November 20, 2012 at 4:15 pm #955911

Dirt
Participant

@vvill 36233 wrote:

But what’s the difference between what I have now and a normal geared setup in terms of the rear derailleur/chain tension?
I haven’t removed the rear cassette or anything. I’m just “locking” the chain onto the 15T cog of the existing cassette using the H limit screw. If the chain jumps couldn’t it just land on the 12T, 13T, 17T, etc?

It might not be a big deal…. nothing different than your chain slipping or skipping on a normal geared bike. Honestly, you could just leave the bike as-is and not shift. You sort of get the idea of single speeding, but not really.

I used to get that question all the time with single speeding. “Can’t I just not shift and my bike is a single speed?” True. I’m pretty sure that I couldn’t do that. There’s a mental side to not being able to shift that makes a difference in how you ride. I’m not exactly a model of mental discipline. If I have shifters I use them.

Does that help?

November 20, 2012 at 4:18 pm #955912

baiskeli
Participant

Why not just not shift gears? Leave it in the speed you want and don’t touch the shifters for the whole ride.

That way you can always change your mind, even mid-ride.

November 20, 2012 at 4:22 pm #955913

Dirt
Participant

My original answer was made while doing about 3 too many tasks and isn’t 100% relevant to what you’re thinking of doing.

November 20, 2012 at 4:24 pm #955914

dcv
Participant

I say take the plunge and go fixed, you’re almost there. My offer stands if you want to try my FG CX (i will flip to the fixed side just for you).
56cm frame with 90mm stem, both brakes. Offer is good for anyone else who wants to try too, just let me know.

November 20, 2012 at 4:29 pm #955915

jrenaut
Participant

@dcv 36242 wrote:

I say take the plunge and go fixed, you’re almost there. My offer stands if you want to try my FG CX (i will flip to the fixed side just for you).
56cm frame with 90mm stem, both brakes. Offer is good for anyone else who wants to try too, just let me know.

That’s very tempting – I’ve been wanting to try fixed for a while, and I could ride a 56 . . .

November 20, 2012 at 4:33 pm #955916

ShawnoftheDread
Participant

@jrenaut 36243 wrote:

That’s very tempting – I’ve been wanting to try fixed for a while, and I could ride a 56 . . .

So the line goes vvill, jrenaut, and then me. Who’s next?

November 20, 2012 at 4:43 pm #955918

Tim Kelley
Participant

I’ve got an old Bottecchia frame from the early 70s that is set up as a single speed. I’m just waiting for the freehub to seize up and then I’ll have a fixed gear.

November 20, 2012 at 4:48 pm #955919

vvill
Participant

Just Loctite it!

@DSalovesh 36236 wrote:

Most likely nothing much will happen because of it, but shortening the chain and/or replacing the derailer with a tensioner drops the bad outcome chances below any concern at all.

So basically: unhooking the derailleur cable makes it more likely for the chain to slip because the derailleur can move laterally on it’s own? Not trying to be difficult, I’m just trying to understand the mechanics that could lead to the bad outcome.

@Dirt 36239 wrote:

you could just leave the bike as-is and not shift. You sort of get the idea of single speeding, but not really.

@baiskeli 36240 wrote:

Why not just not shift gears? Leave it in the speed you want and don’t touch the shifters for the whole ride.

Yep, similar to what Dirt said, I don’t have the ability/discipline to ride SS the whole way. I’ve tried to do this for rides and kept it like that for 90% of the time, but I’m too used to having the shifters there and I forget. With just brake levers on the handlebars I think the ride will be quite different mentally.

@dcv 36242 wrote:

I say take the plunge and go fixed, you’re almost there. My offer stands if you want to try my FG CX (i will flip to the fixed side just for you).
56cm frame with 90mm stem, both brakes. Offer is good for anyone else who wants to try too, just let me know.

Thanks! Honestly, I’m too scared to try fixed for any decent length rides right now for a number of reasons, including a history of bad knees, my local hills and the impending winter season. That doesn’t mean I won’t try in the future – but not right now. I’ve heard people say you should just go straight to fixed instead of SS => FG but I want to figure out if I can even stay in one gear (with coasting available) on my commute.

@ShawnoftheDread 36244 wrote:

So the line goes vvill, jrenaut, and then me. Who’s next?

jabberwocky has also offered his FG bikes for trial runs in the past. His are smaller frames than 56cm and are in the Bike Pics thread, if I recall correctly.

November 20, 2012 at 7:03 pm #955924

DSalovesh
Participant

@vvill 36247 wrote:

So basically: unhooking the derailleur cable makes it more likely for the chain to slip because the derailleur can move laterally on it’s own? Not trying to be difficult, I’m just trying to understand the mechanics that could lead to the bad outcome.

(No worries – you’re nowhere near difficult…)

The mechanics are that while the derailer is hooked to a shifter and operating normally it isn’t as steady as you may think. It moves a lot, and in all three axes. But it’s balanced, so when it moves away it also moves back pretty quickly, and it’s meant to be adjusted if it doesn’t snap right back in place. If the derailer hangs there with no particular connections it will still want to move as it can but it has no balance and no adjustment.

But the bad outcome isn’t all that bad either. It won’t jam, it’s very unlikely to leave you unable to pedal on, and even in the worst cases it won’t break any parts that are expensive or critical.

I’d have no comment at all if you hadn’t asked, and since you did I’m tossing in my opinion that the $20 version (trim chain and add a tensioner) is the reasonable step up from just avoiding the shifter.

November 20, 2012 at 7:09 pm #955925

DismalScientist
Participant

Can you just trim the chain and not use a tensioner? (Don’t feed the chain through the derailleur.) If you have horizontal dropouts, you can potentially adjust the chain tension somewhat by wheel position.

November 20, 2012 at 8:22 pm #955929

krazygl00
Participant

Check out Saint Sheldon’s page on singlespeed and his page on fixed gears for some background info. He also has a page on fixed conversions. While you’re not talking about going fixed with your current setup, the info is still good to know.

I think a conversion using a derailleur is possible, but I think you’ll be happier using dedicated singlespeed parts. It may be worth your while to visit benscycle.net. While no longer a $0 proposition, single/fixed parts are still very cheap, and you’ll enjoy it more if you do it right.

Here is a 15T single speed cassette cog (surly)

Here is a variety of SS spacer kits.

Here is a variety of chain tensioners.
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