Mysterious hole part 2

[PT1029]

In December I posted about using a bike whose suspension forks had a mysterious hole in the RH fork leg. I was quite rightly persuaded not to use them.

The parts went on another (hole free) frame, but the hole in the forks was a mystery - especially when the forks originally looked absolutely fine, the hole only appeared when I wire brushed off what looked like a spot of surface (red/brown) rust.
The bike was about 15 - 20 years old, a sound but lower end Giant hybrid. Some minor rust spots in the chrome on the handlebars, nothing siezed (seat post/stem/pedals/BB cups in an alloy shell), just a dusty bike with virtually no wear on anything - it looked like years of dry storage. I had had the bike upside down, no water came out of anywhere. Even the hole in the fork had no red/brown rust colour on the inside, ditto the suspension spring visible through the hole.
I thought I'd take a closer look and dismantle the forks.
I took the caps off the top of the for legs, turned the forks upside down to remove the bolts at the bottom. Rust coloured water came out this time, but only from the LH leg, no water came out of the RH leg (there was a hole at the bottom). Then I cut off the bottom of the RH for leg just below the mysterious hole.
The LHS spring was wet with brown rust, the RHS was more black with some crud, but the LHS looked more of a mess/rusty than the RHS:

Although there wasn't much red rust visible in the RH leg, cutting off the bottom of the fork leg showed it had all fallen to the bottom :

Looking inside the fork leg showed the pitted surface where the rust had come from. Inside the leg was quite black (ferrous oxide I think), where as the crud at the bottom was red/brown (ferric oxode I think).

I'll be running out of photos on this post, so I'll continue shortly...

[PT1029]

There were places where the wall thickness was visibly reduced (I had filed off the cutting burrs):

and one place where another hole was about to appear:

NB The hole at this point was larger as I had wiggled a screw driver in it.

I have never seen/heard of suspension forks failing by corrosion, but I have seen a few bent at the alloy crown (impact of some sort) and quite a few over the years full of water and/or siezed solid. Having seen what actually lurks inside, the "they are so heavy they could have been built by Brunel" perhaps is not enough!

I might cut off the bottom of the LH fork leg at some point to see what delights are inside.

[Brucey]

all good reasons for not using cheap suspension forks on bikes that get wet.

Or at all, then...…?

cheers

[the dark lord]

I use a bike that lives outside in a bus stop type shelter. It sees a lot of salty water and the forks never serviced. The forks seized after about 3yrs and after about 10 the chrome part of the stanchion cracked all around. I pulled it apart and found significant corrosion resistant inside thinning the be walls.