flipchip

Just how bad is it? I pulled the cables out and turning the bike over netted me about 2 tbsp of dark orange, rusty water. The bike definitely wasn't stored outside, as the exterior is pretty much pristine, so I'm not entirely sure how it happened.

Andrew R Stewart 

Water defeats most all attempts at sealing given time and exposure. I've seen a lot of car rack induced (at 65mph) internal water in repairs where the customer had no idea about what they were subjecting their bike to, till... Once in the frame those seals tend to not let the water leave or evaporate quicker than rust can develop. One more reason why internal cable routing is a poor idea. Andy
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trashbiker

Doesn't look awful. Can't give a proper diagnosis without knowing what kind of bike it is and seeing the rest of the bike, but I've ridden some pretty messed up steel bikes as go-to-the-store beaters without issue. If it were my bike, I'd strip it and inspect inside where possibile.Then put some wd40 or framesaver inside and rebuild after everything is dry.

flipchip

Its a 1991 miyata 914, and the rest of the bike is pretty much fine. The only rust on the exterior is a tiny bit on the exposed cables and bolts. Does wd40 dry? It won't damage the frame more?

Andrew R Stewart 

In an ideal world one would flush out the frame's interior best possible, dry it out totally, dip in a rust converter (like Evapo Rust) and follow up with a rust inhibitor (like Framesaver).

WD40 will dry out in time and lacking better solutions is not a wrong choice. It will do no more harm to the frame but to better collect grime at the ports and vent holes. Andy

flipchip

Ok thanks, how do you flush the interior? More water? And can i just shoot some evapo rust in there? Will it dry as well?

awac

Hmm, you could try something I am going to do on a project build. I use Ballistol oil and grease exclusively for a couple of reasons, (mainly because they have told me they do not test on animals and the ingredients are eco, I mean why use anything else?) but the one that will interest you is the oils ability to mix with water. Mix it up pour it in the tube until full, drain off and let the water evaporate and the oil is left covering the complete internal surface.

The USA site is; https://ballistol.com/about-us/

The uk site is; https://ballistol.co.uk

Black powder shooters in the USA call it I believe, “moose milk” which they use to clean powder residue from the barrel and then protect it from rusting. It does smell of aniseed or sweaty socks depending who you ask, I smell aniseed, and love the smell. It is also good for your skin.

I would also fill your frame up with a 30% dilution of phosphoric acid/water mix before if worried about rust (it is very cheap). Phosphoric only eats rust (and you drink it in coke!), and careful, aluminium! Clean it out with that (re-use it, don’t just chuck it out) and then ballistol it.

Ciao.

HillRider

If the top tube is open at both ends into the seat tube and head tube you could remove the fork and pass a 10GA shotgun cleaning brass brush through it by pulling the brush with a strong cord followed by dry patches. Then spray Frame Saver into the tube copiously.

easyupbug 

The only way to know for sure is to know the steel original thickness and do ultrasonic thickness measurements throughout the tubing hoping to find the weak spot. If you take your chances I expect it would be a subtle shift in a tube you could see rather than catastrophic failure. My thoughts after doing NDT inspections on steel air receivers vessels for several years prone to corroding from the inside out. The Andrew R Stewart suggestion I though reasonable for that frame.

3alarmer 

.
...it's not a big deal to pull the fork, plug up any hole at the ends of the top tube into seat post and head tube, as well as one of the internal cable holes, and to then fill the top tube only, with evaporust. The stuff works better and more quickly if it's warm, so I usually find some place out in the sun here, where it will get solar heated, then leave it for a couple of days. Then drain and flush with water, then blow dry with compressed air. If you don't have compressed air, hang it to dry thoroughly in the same place where it got heated by the sun.

Then you can either treat with some sort of corrosion preventive oil, sprayed in and worked around by rocking/rotating the frame. On the one frame with internal routing and top tube internal rust I was a little worried about, instead of oil, I just sprayed in a little of that red primer paint, that is good for rusted surfaces. Then I rocked and rotated the frame to get better coverage. Give it time to dry thoroughly before reassembly.

I agree with the sentiment expressed that internal routing in steel frames was probably a solution in search of a problem. Not a fan here.

Pratt

Let's not let the good advice from the contributing Forum members obscure the possibility of using this as a clear example of the inferiority of steel as a frame material, to every other imaginable substance.

Keefusb

I would second or third the use of Evaporust inside the tubes of rusty steel frame bikes. I have used it a couple of times on my two steelies with good results. It did take a few days in the sun to completely dry them out. Once they were 100% dry I used Boeshield for the inside of the frames. My local framebuilder told me that once Boeshield dries inside the frame I shouldn't need to reapply for many years.

soyabean

This happens all the time when you ride in the rain, or wash the bike.

Remove seatpost, turn it upside down to drip out, let it dry out those days when you aren't riding it.

Just enjoy that Miyata. You'll die of old age before that rust becomes a problem. Remember, in the end it's still a $50 bike.

79pmooney

If you are a big, strong rider and commute (say) in the wet, you well break that frame at the brake cable exit. I worked 1989-92 with a fellow who was 200 pounds, strong, tough on bikes. no car and commuted year 'round, 20 miles each way on a Miyata simi9lar to your except every few years they would break at the exit and he would get a new one under warranty. Happened twice the three years I was there. Now he probably had a lot more rust there simply commuting in Seattle those miles and all year.

For the poster above who says steel sucks as a frame material, my Mooney, built 13 years before the OPs, is still going strong and has done quite a few wet rides including a few epic wets. First year, down Alba Road above Santa Cruz in a winter Pacific storm. Sheets of water running across the road. A few years later in Seattle a rain so hard the frogs were seeking shelter. It has some rust but is riding just fine at 50,000 miles and is probably less than halfway through its life. But ... the Mooney never got internal cabling.