Single Chainring throwing chain
 

Where's the best place to look for SS or track chainrings? I've got a 50T truvativ up front that is ramped for shifting and I keep tossing the chain to the outside. Figure a ring with bigger teeth, no ramps, and probably a chainkeeper are in order.

Have you checked to see if mis-alignment of the wheel and sprocket is causing the chain to derail?

Yes, it's an older bike with horizontal dropouts. I have both eyeballed the wheel to center and also measured from the center of the axle to center of crankarm bolts. Brand new wheel and straight as an arrow. I installed a 108 BB in it, if a straight teeth chainring doesn't work then I think I may need to go to a wider BB as well.

Not having shift gates will help. The teeth won't be bigger, but the gate (cut down one or to teeth) allow a chain to move sideways a bit where it might snag the next upcoming tooth.

There are a number of sources plain or SS chainrings. I have a bunch from a variety brnds, but the dirst step is knowing the BCD required.

As I said, eliminating the gates will help, but if the chain is running straight, as it should be, then there's no reason for the chain to deflect sideways at a gate and come off. Double check that the chainline is correct by measuring both the hub and cranks offset as follows.

Hub-- measure from sprocket to the inside face of the dropout, subtract that from 1/2 the hub's axle width to find the center to sprocket distance.

Chainring -- measure from the teeth to a frame tube, add 1/2 the frame tubes diameter for the chainline offset. This number should be within 2mm from that of the rear.

I have run a double chainring in an SS setup for years without an issue. I recently changed the rear hub to an IGH 2sp and so went with a 1/8" chain, but still no issue. I'd say that you either have an alignment issue or something is worn.

-G

New chain, chainring, and 8-speed cassette. Do you run a chain keeper on your setup? I do believe I need a wider BB, maybe I'll throw the old spindle and loose bearings back in it and try that.

QBP,[thru most bike shops] stainless steel. Surly branded.

110 [34t+] & 130 BCD [38t+] up to 50t. for single chainring

I have one on my IGH bike, another single chainring bike I use a chainguard disc outside
and a chainminder, inside..

By any chance, when converting to a 1x8 setup, did you move the chainring to the inner (or middle) position. If so that's likely a big part of the problem. Move it back to the original outer position, which is about 8mm farther out and it'll be much better in not perfect.

By any chance, when converting to a 1x8 setup, did you move the chainring to the inner (or middle) position. If so that's likely a big part of the problem. Move it back to the original outer position, which is about 8mm farther out and it'll be much better if not perfect.

It still sits on the outside, but I did put a much skinnier BB in which had the same effect as you describe. So I guess first thing is to get a wider BB in it and see how that acts :)

chainring needs to line up with the middle of the rear cassette, for 8 thats between #4 and 5.

I think you can have a good chain line and an unramped track style chain ring and still run into dropped chains pretty easily on a 1x8 with no chain watcher or guide.

While improving the chain line will help, I think you should get a chain watcher or use a cable-less front derailleur with its limit screws clamped down as a chain guide. 1x8 1x9 and 1x10 systems all seem to rely on some safety guard to avoid dropping the chain off the front.

Took a look at it yesterday, and forgot it's a 7 speed cluster and not an 8. A moot point anyway. I ordered a chain watcher type thing last night I will put on and solve my issues. I knew I needed one, but I will probably also get a SS type chainring later as well. Thanks for all the replies folks, was interested in others opinions/ideas and you all came through :)

I have a similar problem with my chainring. I have an old 5 spd and replaced the crank and corresponding chainring. I did my best to have a straight line to gear 3, but still lose the chain from time to time. I'll will implement some of the ideas I read here to see what works. I can easily mount a fixed front derailluer cage to keep the chain, or look for some sort of chain keeper for my BCD. Where would one find a chain guard disc to attach to the crank spider? Robert