Digitalfiend

Does anyone know if you can replace the outer chain guide plate on a DA FD-7900/7970?

I discovered a small chip in the nickel plating on the chain guide's outer plate (near the front...odd place) and it's annoying me more than anything. Looking at the techdocs on Shimano's site, there is no part number for just the outer part of the chain guide, but it does list a "chain guide fixing screw", which suggests the outer plate might come off. Looking at the cage itself, it appears that the inner and outer plates are separate pieces but it's possible that they aren't designed to be field serviceable and won't easily come apart.

I searched but couldn't find any info on this topic. I called the Trek dealer to see what they thought and the tech said that Shimano probably wouldn't warranty it. I don't mind buying a new outer plate, if possible, but I have a sinking feeling that, due to the lack of a part number, this isn't possible. I'll most likely have to live with it but was wondering if someone here might know a bit more.

Thanks!

mechBgon

The chain guide fixing screw is the small aluminum screw that holds the tail of the cage together. As you can see, the cage's pivots aren't removable, so the cage is non-replacable in Shimano's viewpoint, it's part of the derailleur as a whole..

Digitalfiend

Thanks.

That's kind of what I was figuring. You can see the front portion of the outer plate loops over the inner plate and has a little pin that pushes through a hole and holds the front part in place. I was hoping it'd be pressed in and something that could be popped out after removing the fixing screw at the rear. Meh. I wish I wasn't so anal about this stuff lol. From a functional standpoint I guess my concern is that it will eventually get significantly worse though I doubt it will affect shifting performance. I'm not even sure how it got chipped here:

fietsbob

It's just a chip in the chrome plating ..

rccardr 

...and not uncommon on D-A FD's for some reason. You can use a little piece of 1200 grade wet/dry sandpaper followed by some Mother's metal polish to minimize it, but it will always be a little different tone than the chrome and you'll have to keep it polished.

Digitalfiend

The underlying metal is aluminum and therefore it shouldn't rust, right?

jimc101

It's not on the Tech Docs https://techdocs.shimano.com/media/te...9830654470.pdf so unfortunatly not.

For the chrome plating on FD's I had a lot of corrosion on an 7800 series FD, currently using 5700 series with no sign of any corrosion after a few thousand km of all weather riding.

fietsbob

why ask Us? get out a magnet, and test..

Digitalfiend

But I thought this was where we were supposed to ask obvious, easily answered questions?

bobotech

Sometimes I love the anality of roadies. Makes for finding awesome yet cheap parts at my bike coop great. Parts like that which are scoffed at by anal roadies are dumped off once in a while and the vultures like me eat them up.

I would never care much about a chip like that, i would just polish it out and call it a day and enjoy that I had a Dura Ace part on my bike. Meh. its just a little chip that will never hurt the functionality of the derailleur.

Digitalfiend

I know, I know.

I'm more concerned about the chain catching on the rough edge and chipping off even more. I'll likely just do as suggested and sand + polish. I'm anal but certainly not anal enough to go and buy another Di2 FD for $500!

Al1943

Take 2 aspirins and go ride.