Please excuse this noob question, but could anyone tell me what exactly this part is called?



The translucent blue thing.

Chain guard?

Does it go by a different name? 'Cause I've only ever known this kind of chain guard:

Chainring guard seems to be used for that.

Pants saver??

chainring guard?

Yeah, chainring guard must be what it's called. Is there anywhere I could purchase the plastic/translucent ones like in the first photo?

nope, work at an lbs and get asked this occasionally

problem is, there isnt a standard mounting hole pattern for the plastic ones; basically they are integrated with the crank they come with; no aftermarket product available

A similar device used in mountain biking is a bashguard -made of steel not plastic, bolts using chainring bolts in standard chanring patterns, so sacrifice your big ring for a guard.....

I see. Very helpful, thanks mate.

can you get one of these to protect the outer ring, not replace it?
or is OP wanting something to keep trouser legs out of the chain?

https://www.ebay.com/itm/Rock-ring-bi...-/320918992342

The trouser leg function is performed by the "Kool-Stop Chain Disc". They come in a couple of sizes depending on the tooth count of your chainring and they mount with a center screw which goes into the crank arm hole so that they are agnostic of the chainring bolt pattern. I Have two and spent a few minutes with WD-40 and my fingernail taking off the dorky logos but they work fine and don't make noise. I had to open up the clearance slot a little for one crank but that was just a few minutes work with my Dremel.

Americans call each other mate now?

Heh.

Only when they're speaking to Aussies.

While plastic chain guards like the one the OP has aren't generally offered in the after-market, there are a number of other options which serve the same purpose.

If the crank has a standard 110mm or other common BCD he might buy a bashguard, or chain keeper ring (like for cyclocross) which will serve the same purpose.

Otherwise there's the universal (two sizes) Chain Disc sold by the folks at KoolStop.

I felt it was a g'day to start.

https://www.universalcycles.com/shopp...hp?category=58

https://store.velo-orange.com/index.p...ing-guard.html