Advice needed!
I am quite new to cx, and not great at it but I enjoy it.
Anyway I never shift out of the small ring 36T in the front, I think I might go faster if I switch to a single set-up at the front.
Various sources (websites, books, forums etc) point to a 42T but I think this will be too big (plus I do not want to change the rear sprockets). I run a 10 speed 105, 12/25 on the rear.
If I put on a 38T or a 39T single on the front would it work without making any other changes?
Also would I need to add a chain catcher or chain guide
All advice gratefully accepted

I'm riding 39t with 11-25 and it works great. Using the old front derailleur as steerer as I haven't found any good for braze-on yet.

Bash and Deda dog fang is my favorite solution otherwise. You need something.

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/jonas l
http://cerrol.wordpress.com (my cyclingblog)

My setup is a 42t chainring (with a superlight BBG chainguard on the outside and an N-Gear jump stop on the inside) with a 11-28 cassette.
I never use the 11t sprocket in races and I sometimes struggle on steep climbs with the 28t sprockets - but that makes me go faster than the other guys spinning a 36t chainring .

I don't think a dog fang would keep the chain from dropping off the chainring - I have a dog fang, but I still went with the n-gear jump stop which is 20g heavier.

Another way of setting up a single chainring is to sandwich it between two chain guards: chain guard mounted on the inside, chainring on the outside, some spacers and then another chain guard, but you must have enough room between the chainring and the crank arm for the spacers and the chain guard. I would have gone with that setup, but there is not enough room on the Sram Red 2012 crankset due to the hidden bolt.

I've been running a 39T up front for years, with an 11-28 out back. I've used both a Salsa Crossing Guard / Jump Stop combo, and a Paul's Chaincatcher. Both systems have worked well for me. I spin out that combo at about 27 mph - a speed I rarely reach on a cross course. There's only one race a year I do with a long enough straight (slightly downhill) gravel road stretch where I run out of gears. Other than that one course, I never feel like I miss more gears.

I've run a single front ring for a few years. Started with a BBG outer guard and a Dog Fang inside. That worked OK, but occasionally (usually after accidentally kicking the pedals backwards) the chain could go under the Dog Fang. That was difficult and time consuming during a race to get back on. Now I have BBG Superlites on both sides of the chainring and that works great. I've used chainrings in the 39-42 range, and 11-21 or 11-25 cassettes depending on the course.

This year I'm eliminating the whole decision making process by matching my single front ring with a single cog -

42 x 12-25 here and works 99% of the time. I have chain guards on both sides and run short chain that is difficult to wiggle over the chain guards even if I try.

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Rather than putting on a chain guide, once you've determined you are happy with the single ring, make sure you get a new ring that is single chain ring specific. Without shifting ramps, chain is less likely to come off. Ring will also last longer (and pick the right one and you can flip it so that you have fresh tooth faces).

Running a 38t and 11-28 on the back. Worked great this weekend on very steep stuff with enough gear to leg out a guy at the downhill finish.

I'm running the BBG Bash on the outside (next time I'll go with the extra light) and a K-Edge watcher on the inside.

I'm also running the new SRAM Red Medium cage RD in the back in case I really need to go big with a 32 cog in the back.