chainring guides

[scotto]

my 11yr olds race bike is now age legal (5.5m rollout), and with a 34 tooth single front chainring i was wondering about a chain guide.
The chains only dropped off once, and since then i have shortened the chain appropriatlely. Seems OK now but trying not to invoke murphy's law.
1. is a guide advisable / necessary for road use for an U13 rider ?
2. Is it worth trying to just use the derailliuer ? i have held off as i reckon there could be some rubbing issues..

thanks

[rustychisel]

if in doubt probably best to instal one, though the issue of dropoff from the small chainring is usually dependent on angle of incidence (chain crossover) which is a function of chainstay length), the less the chainstay length the greater the chain angle = the greater chance of chain dropping off the inside of the ring. Adjust front derailleur carefully and add a dog fang or similar. The little tacker would be miffed if he miossed a podium because his chain derailled under a pressure shift.

[singlespeedscott]

Use a single speed specific chainring with longer teeth and no shift ramps. A cheap mtb single ring chain guide should also help keep it in place on rough roads.

[pjt]

I think the conventional solution to this is to use a derailleur, just don't run any cable to it and use the L/H screws so it's fixed in the correct position. It's a very good idea to do this as (assuming a multispeed rear) the chain will jump around and could come off. Among other times it happened in a semi-recent Tour prologue IIRC.

If you decide to go the chainguard route, I got one recently for my folding bike (though this uses a hub gear with chain tensioner, not a multispeed derailleur rear) from a place in the USA called BBG Chainguards. http://bbgbashguard.com/" onclick="window.open(this.href);return false; Good quality and arrived in the post relatively quickly. Price was reasonable compared to getting a name-brand ring ordered in from c r c/Wiggle or the like.

[scotto]

Thanks. FD and correct chain length and its rock solid now.