safety heads-up; frame integrity

Discussion in 'Bicycle Repair' started by bluegoatwoods, Aug 25, 2009.

  1. bluegoatwoods

    bluegoatwoods Well-Known Member

    I'm sorry I haven't thought to post this before. I guess I assumed it was something that anyone would keep in mind. But it's easy to forget, so here's a reminder.

    Spring of 2008 I built an MB using an old Columbia ten-speed. It was really a great bike and I was happy with it.

    This summer I pulled off the motor and all components to sand and re-paint the frame.

    I discovered matching rust holes on the underside of the rear chain-stays. They were just about even with the front of the rear wheel. Their edges looked clean, so I wondered for a moment if they were supposed to be there. Maybe drain holes? But they were about two inches long and snake-like. They wobbled back and forth. I doubt if anyone would design a shape like that. They must have been caused by rust, or perhaps fatigue.

    This was a "mechanical failure" just waiting to happen.

    So, especially on older bikes, inspect the frame regularly. Often, I suppose. Often enough to be kind of a pain. But it's better than having your bike collapse at speed.

  2. srdavo

    srdavo Active Member

    Great post!!

    I am glad you found this, this way.... rather than after the crash!!

    Ya know... we put a lot more stress on bicycles, than what they were meant for.
    Frames, wheels, all bearings, etc.

    Look 'em over....often!
  3. fetor56

    fetor56 Guest

    Good idea too if your in the market for a 2nd hand steel bike is also check everywhere for rust.Most bad rust comes from the inside out so what's visible to the naked eye is perhaps the tip of the iceburg.
    Very underrated subject this rust biz.
  4. GearNut

    GearNut Active Member

    If at all possible, coat the inside of every tube possible with boiled linseed oil. It will cure to a waterproof coating and inhibit rust from forming in the first place.
    It will in no way stop existing rust or prevent it from getting worse though.

    It was a technique used in the aviation industry, specifically during the heydays of bi-planes, and I have been told in the home built aircraft of today.
  5. Happy Valley

    Happy Valley Active Member

    Yes, good post. Complete maintenance includes thorough inspections like that. BTW, the holes in steel frame tubes are not drain holes like many may think but put there for the necessary venting when the closed tubes are joined with the heat of the welding process.

    As suggested, the linseed oil coating is an old idea and it works if little rust in the steel is present. There are commercial rust inhibitors available and one I know of made especially for bikes:

    A cheaper homebrew I've also used is automobile ATF thinned 3:1 with mineral spirits and put into a spray bottle, the mineral spirits aids in spreading and then evaporates leaving a coating.
    Last edited: Aug 26, 2009