So chain guards are, as my handy neighborhood mechanic tells me, badly out of fashion (this being the reason he offered for why the shop doesn't carry them). But I'm a commuter, and try as I might, I can't completely avoid some schmutz on my pants from the chain. Hence my desire for a chain guard. My chain ring is 42t, and I found this chain guard for a 44t. Would it fit, do you think?

Yep, it will just be a little more friendly with space.

Velo Orange also makes one in several sizes. I bought one for a bike I am building for my wife:

VO Alloy Chainguard

But it only comes in 38t, 44t, and 48t. Should I go up a size (buy the 44t) or down a size (buy the 38t)?

Go up one size, or it may be too tight, space wise

Have to pull the BB out, the bracket is held on by the Fixed Cup flange. Back one clamps on the Chainstay.

I think 44t would be the right size. You don't want the chain rubbing on the chain guard if you can even fit a 38t chain guard over a 42t chainring. You could send an email to or call Velo Orange and ask them.

Been thinking about this myself for a few years. I've looked at the Civia and VO. Any opinions on quality, ease of fit, tendency to rattle, etc.?

For the OP: Definitely go to the larger size. The difference in radius between 42t and 44t chain ring can't be much more than 1/4 inch, if that.

Lets say you have a 33" waist but the pants only come in 32" or 34". Which do you buy?

Definitely the 44. VO chainguards fit snugly. And the quality is top notch. If mounted securely and ridden onroad, no curb jumping, there won't be any rattles or squeaks. It wouldn't surprise me if the linked model VO chainguard and the Civia Bryant guard were made by the same company. Very similar, and both are beautiful, if you are a fan of highly polished aluminum

I like highly polished aluminum, but I am actually going to have it powder coated along with the frame I am putting it on. The frame is at a frame builder who is putting a brazed on bracket for the chainguard on it among other things.

Touché!

Adding 2T increases the radius by about 1/6 inch. The difference might not even be noticeable.