Monday, February 10, 2014

Straightening the steering tube of my bianchi

Do not try this yourself, ever.  According to everyone I've talked to it is the most dangerous thing you can do, you will die a horrible, burning death if you try this.

My bianci is awesome.  It's a steel frame, red, I bought it from Stos & Alicia for $75 a few years ago.  I think they got it off of Craigslist.  It is a great commuter bike because it is rugged but goes fast - the frame actually fits me.  Unfortunately it is hard to get parts for it.  The rear axle broke awhile back and none of the bike shops had one or could get one.  I finally went to Harris Cyclery, and they had one that was close to the right size, so I bought it and a hack saw, made a rough measurement using the broken pieces of the old axle, and voila!  Back in the saddle.  This was after I partially rebuilt the rear wheel (replacing dead spokes, truing).

Not long after that, while I was riding along the Charles to work one morning, the front brake fell off, lodged in the front wheel, and I went flying over the handle bars.
Shame on me - I had noticed the brake acting funny but hadn't checked it out, it turns out it was loose.  Luckily no concussion, but my shoulder hurt for several months.  But the real tragedy was that the front steering tube had been bent so that the front wheel was pressed against the frame.  Actually, that might have been lucky, because if the wheel hadn't hit and jammed against the frame, the steering tube might have been bent further.

So having just rebuilt the rear wheel and replaced the axle, I was in no mood to to start another repair project.  The bike sat in my basement for about a year and half, until recently, when I lost my smallish commuter to some broken rear spokes, and I started getting sick of riding my way-too-small commuter.

Looking at the bike, I realized the frame itself was fine, and taking the fork off, could clearly see that it was bent.  It wasn't that badly bent - the handle bars / fork could still turn from 45 degrees to the left of straight to 90 degrees right of straight.  The steering tube was bent approximately 10 degrees.

I had always heard that you could bend steel back.  But it was always in the context of my aluminum frame bike, where bike shop mechanics would say "Yeah, we can't bend this back, it's aluminum.  If it were steel we could, but not aluminum".  Surprisingly, when I went to 2 different bike shops and asked them to bend the fork back, or to help me, they refused.  First, liability, totally understandable.  They also said it just could not be done - and that part is not understandable.  We're not talking about a rocket engine or laser eye surgery - let's be realistic about the tolerances on how perfectly straight a bike part - any bike part - has to be.  And of course, the one fork that was for sale that might have fit was out of stock.

I thought of a lot of different ways to try to straighten it, and read a bunch of things online, got a lot of helpful advice from friends on facebook.  I settled on this plan:  put the fork in a vice, get a really long steel tube that fits around the steering tube, and use it to bend the fork straight.

Part zero: buy vice, attach vice to table in basement that is secured to wall.
Part one:  clamp fork into vice

I initially tried to use some wood shims to protect the fork and vice from each other, but they just gave way.  This isn't what I would choose as the most ideal way to secure the fork in the vicec, but the central axle of the vice prevented aligning the middle of the fork with the vice clamps.

Part two:  put long (5 feet) steel tube around steering tube of fork.  I put the end of the steel tube where the bend was:

Part three: pull on the steel tube to bend the steering tube.  Go very slowly, stopping often to check progress.  I ultimately had to pull hard enough on the tube so that it was actually flexing a bit.  I thought that I could feel the steering tube responding, when I did I would stop and check the progress.

As of now, I've put the fork back in the bike.  The wheel is no longer jammed against the frame, and it has the full range of turning motion.  Now to fix that front brake...

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