Keeping the chain on without a front derailleur

[Cornholio]

On my "new" 'cross bike, dubbed "The Tank" by some and "The Frankenbike" by 'Nater, I have a single 46 up front. With no derailleur up there, the chain has a nasty habit of leaping from the ring at inopportune moments.

How can I keep this from happening? Right now, I've got an old front derailleur on there, just bolted on and adjusted to keep the chain in place, but there must be a better solution.

Any thoughts?

Any thoughts I can implement before my race tonight at 6?

[bagtagley]

You could rig some sort of chain tensioning device. One possibility is to clamp some sort of roller to the chain stay that basically pulls the chain up.

[mildbill.]

just leave the derailleur on there, waste zero more time and money. don't be a bike nerd. why fuck with your bike if nothing's broken?

[Cornholio]

Well, first, I like fucking with my bikes. Heh.

Also, the derailleur fix doesn't work that well. There's still a lot of play. The advantage is that when the chain hops now, the derailleur holds it and I can sometimes get it back on the ring without getting out of the saddle.

[mildbill.]

Well, first, I like fucking with my bikes. Heh.

ugh. that's all you dude.

not sure what kind of spider you're running, but you could maybe put a bigger ring on the inside and a bigger one on the outside to just hold the chain in-between on the 'drive' ring? i've seen that work on the back to ghetto-rig a singlespeed (with a hacked derailleur for a chain tensioner).

plus, you'd be nicely adding some weight to make sure you're over your self-imposed 30lbs cross bike weight limit, so you've got that going for you.

[Innominatus]

I've gone the single ring route. I used a Third Eye chain-watcher on the inside ($10) and a chainring guard in place of the big chainring ($25). Works like it's, uh, single-minded in purpose. Should be able to get all that from your local shop, and possibly even in time for your 6 PM race.

But, then, sometimes its just easiest to throw money at a problem to make it go away. Ergo, the best specific application: CX World's single ring kit.


[edit] never mind, those guys are out of stock.

[Viva]

How long are your dropouts? SSs traditionally have long dropouts for this very reason. Loosen the rear wheel, pull it back a little to tension the chain, retighten. Done.

If your dropouts are too short for this, take a couple, or more, links out of your chain.

[Oarhead]

I am assuming that it is not a single speed, just a single ring up front. Are you still running a rear cassette?

First off, does it happen with only a few of the gears? (like only on the 15 or whatever). If it only happens at one end of the cassette, I would start messing with chainline. It may be that it is too much angle for the chain to handle.

Make sure your chain is clean, having a dirty chain really messes with shifting I have found. Dirt makes the cahin 'stiffer' and can't flex properly.

Another suggestion is to take a few links out of the chain to give it a bit more tension.

Lastly, I don't know what combos are best for cross since I ride road/track and mtn, but the 46 in combo with whatever cassette you're using may not be the best for tension and shifting. A different bigring may be neccessary.

[Viva]

Good point Oarhead, I totally assumed it was a SS. If there is a rear derailleur, maybe it's old and the spring's getting worn?

[Cornholio]

Good point Oarhead, I totally assumed it was a SS. If there is a rear derailleur, maybe it's old and the spring's getting worn?

It's not a SS, its just single front ring. The rear derailleur is pretty good. I'm going to make sure the chain is the right length, and if I still have problems look in to a solution like He Who Has No Name mentioned.

I also thought about this ghetto rig- a 2" long piece of 3/4" pvc clamped to the seat tube and positioned so that the chain runs through it and right on to the ring. I was thinking if I cut one end on a diagonal and maybe made a little notch, it could get pretty close to the ring. It would be like the derailleur but exert a little more control. Ghet-o. But it might work. Nah. Actually writing it down made it sound a lot worse than I thought.