Obeast

I have a few of these lying around from older steel mountain bikes I took off. They are very heavy and I ride in slippery icy condition in the winter. I do wonder if they offer any real world protection to the rear derailleur though as they are kind of heavy.

madpogue 

Things to ask yourself:
- How likely are you to fall on that side, in just such a way that the bash guard makes contact before the RD does? And in such a fall, is your RD your main concern? My WAG is that your right leg will make contact before the RD does.
- How badly do you want to protect the RD? Is it a cheap enough one that you could afford to replace it readily? I'd be more interested in installing one of these over a Deore LX than an Altus C10.

davester

I think that these are great for kids who are the type to park heir bike by jumping off and letting it crash to the ground on the derailleur side. Otherwise, you don't need one.

non-fixie 

At least get a Campagnolo one.

NothEndReCycle

I've only ever seen these installed on children's bicycles; interesting idea to do it on an adult bicycle don't see why not

tiger1964 

Wow.

Of course, if the Campy RD is a Grand Turismo, I think it would take a "shaped charge" to destroy one, so this is not needed.

non-fixie 

Paint the faceplate black, and it will fit right in with your Super Record.

T-Mar

Some boom era, entry level derailleurs had integral bash guards. I'm thinking of models like the Huret Allvit and Shimano Eagle. Personally, I think they make even more sense on a modern bicycle, as indexing is very sensitive to hanger misalignment, which is easily affected by a fall. Also, for ATBs, they defect a lot a lot of branches that could get in the derailleur. IMO, they're cheap insurance and while they don't work in all cases, they probably prevent a lot more incidents than you'll ever realize. When I had my shop, misaligned hangers were probably my most frequent repair outside of flat tyres, and rarely a week went by without someone bringing in a bicycle with a snapped off derailleur or hanger, often with a tacoed rear wheel. Derailleur guards would have prevented many of these repairs. However, most owners are far more concerned with the inconvenience they cause installing and removing the wheel, at least until they have to replace their Shimano XTR rear derailleur and/or walk home from a ride deep in the forest, while getting eaten by mosquitoes and black flies.

John E

In the 1960s lots of kids installed rigid steel derailleur guards over their Huret Alvitt derailleurs, often on the recommendation of the local Schwinn dealer.

Road Fan

When a bash guard gets bashed real good, it keeps the derailleur from working, so no, I don't think they work.

Last ride 76 

Glad there's one on my 11 year old daughter's bike. 24 in wheels, and she doesn't always notice how close the RD is to objects when she's walking it.
Riding, I,m not sure it would do much good. I don't think that's primarily what it was designed for.

JaccoW

Only if you get one of these:

Obeast

most of the take offs came from adult steel mountain bikes of 1990s

Obeast

I also have one of these but it is severely rusted but it looks so cool. I actually find vintage bikes much cooler on the accessories side than most new bikes now. Some of the older steel and aluminum fenders are just so much cooler than the ubiquitous plastic ones sold everywhere these days.

SurferRosa

The only times I wish I had one of these are when I'm walking the bike through the big grocery, and I cut the corner a little too close and hit the big wood bin of produce. It's happened a few times. I always look down and check the nuovo record derailleur, and it seems no worse for wear. But the sound it makes against the wood! Clunk! <Cringe>

Still, way better than locking up the bike.

T-Mar

In such cases, without the bash guard, you would probably have needed to replace the rear derailleur, possibly some spokes, maybe the rim...

T-Mar

N+1 means not having to take your good bicycle to the grocery.

SurferRosa

All my bikes fall in that category.

The nice thing is I get compliments all the time on my french grocery getter. Recently, a guy asked about it while I was standing in the grocery line and wanted to take a pic to share with his buddies. About a week later, I bump into him again at the post office, which was kinda neat. The lady at the post office loves it too.