Rusting frame

[ají]

hey there!
just flipped my bike upside down and saw this rust. Just wondering, how would you treat this?
not sure what this support is called, but its located on the down tube and the fork tube.
cheers!
Andrew

[ají]

or does anyone know what that part is called?

[martinf]

I'd call it a reinforcing gusset.

On my bikes I don't worry much about surface rust that I can see. Every few years I do an overhaul and sand or file rusty spots down to bare metal, then repaint the affected area. Hidden rust inside the tubes would worry me more, so far I have been lucky not to have this.

If the paint is getting very tatty I lightly sand the complete frame and forks (and racks if applicable) and repaint completely.

It's also possible to use a phosphoric acid based rust inhibitor, there was a thread about this on the forum recently.

[Danneaux]

or does anyone know what that part is called?

Yes, Andrew, it is called the "downtube frame gusset". It adds a bit of extra bracing for strength on Thorn frames capable of using a suspension fork (i.e. the Nomad Mk2).

I would treat the rust with a little phosphoric acid to convert it to an oxide, then treat it with paint, wax or oil as desired. It is open at the bottom so should drain rather than trap water in the future.

My Nomad has this gusset, as does another bike. My Nomad is still unrusted, but another bike came to look a bit like yours (I purchased the frame used and it had been pressure washed, causing water to blow up into this area). I treated it as mentioned and it has given no further problems.

Best,

Dan.

[Danneaux]

Sorry Martin! Our posts crossed and I figured I'd go ahead and leave mine up as a second data point.

All the best,

Dan.

[ají]

thanks Martin, the phosphoric acid could help as this gusset is pretty inaccessible.
do you internally treat your frames?

[ají]

or does anyone know what that part is called?

Yes, Andrew, it is called the "downtube frame gusset". It adds a bit of extra bracing for strength on Thorn frames capable of using a suspension fork (i.e. the Nomad Mk2).

I would treat the rust with a little phosphoric acid to convert it to an oxide, then treat it with paint, wax or oil as desired. It is open at the bottom so should drain rather than trap water in the future.

My Nomad has this gusset, as does another bike. My Nomad is still unrusted, but another bike came to look a bit like yours (I purchased the frame used and it had been pressure washed, causing water to blow up into this area). I treated it as mentioned and it has given no further problems.

Best,

Dan.

cheers Dan. looks like i'll put some P on it, then maybe spray in some cavity wax or frame saver

[mickeg]

...
do you internally treat your frames?

Yes.  I use Framesaver.  I do not know if it is available outside of USA.  I suspect that there are similar products available elsewhere.
https://www.amazon.com/J-P-Weigles-Bicycle-Frame-Inhibitor/dp/B0012GO58Y/ref=sr_1_2

I treated my Nomad Mk II frame before I built it up.  I think I shot a bit of it into that void where you had the rust on yours.  I have seen no sign of rust there. 

[martinf]

thanks Martin, the phosphoric acid could help as this gusset is pretty inaccessible.
do you internally treat your frames?

Sometimes. But it isn't usually possible to treat everything, for example the insides of fork blades are usually inaccessible.

I did the family Brompton folding bikes as soon as I bought them, as Bromptons used to be notorious for the rear triangles rusting out. So I poured some LPS3 (a sticky and slightly waxy liquid lubricant/corrosion inhibitor from the 1970's that dries into a coating) into all the accessible tubes except the seat tube (on Bromptons this must be free of lubricant or else the seat post will slip when riding), then sealed the open ends of the rear triangle tubes with window sealant to prevent water/road grit from entering.

I've also done the insides of the tubing on some of the other family bikes with LPS3.

But not yet my Thorns