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Monday, June 18, 2012

When NOT to Repair a Bicycle

By Smokey Dymny from the Quadra Bike School

Some home-based bicycle mechanics like to “repair” an used bicycle for resale. Before you start down this path make sure you are able to assess an used bicycle’s potential.

1.) WHEEL TRUING

The wheels must be able to be trued and YOU have to be able to do it. It costs too much to pay for this repair. Check if the spoke nipples will turn with the proper size of spoke wrench (you need to have the red and black spoke wrenches at least). A spoke gauge would be handy too.

It’s best to UNWIND the nipples rather than tighten them, so you don’t get blamed for wrecking the wheel if a spoke should break from tightening. If most of the spokes will turn, then you can oil all the spoke nipples and maybe true up the wheel at home. I say MAYBE because you also need to check the wheel rims for dents, which may prevent you from making the wheels workable.

Also spin the axles with your fingers to assess how badly worn or pitted the hubs are – you need to have the hubs turn smoothly for proper truing and for riding. Finally, if the rims are alloy, place a small straight edge across the sidewall (braking surface) to see if the brakes have worn the sidewalls down. If there is a 1mm gap between your straight edge and the rim there is too little metal left in the rims for the wheels to last. Braking will soon wear right through the rim and the tube will burst through the weak sidewall.

If all these things check out then you need access to a community bike shop to use their truing stand to straighten and tighten the wheels properly.

(It also possible to purchase a truing stand, but its a tad out of reach unless you have the funds to do so and plan to be truing wheels regularly.)

2.) BRAKES AND SHIFTERS

If the wheels pass inspection check the brakes and shifters to see if they will operate from the controls. If they do – good. If they don’t, disconnect the brake and shifter cables and see if the brakes and shifters move well on their own. The problem could just be rusted cables and housings, which you can replace.

3.) CHAIN STATUS

You need a chain checker to assess if the chain is worn. Most mechanics call this chain “stretch”. Of course if the chain’s rusted, you should just toss it anyway - a rusty drivetrain is a major loss of efficiency on a bicycle.

4.) TIRE WEAR

Check the tires for cracks and wear. If they look like they have tread, let out the air and pinch them till you see into any cracks. If the tire casing (white cloth) is visible at the bottom of a crack, the tire is crap. Also check for wear and cracks on sidewalls. Maladjusted brakes may have destroyed those too.

5.) HANDLE BARS

Finally check the headset (steering) and crank rotation for looseness or rust and corrosion, these symptoms will indicate you have to replace the ball bearings inside it.

6.) FORK STRAIGHTNESS

Check if the front fork has been crashed. A straight-edge held along the steerer tube should continue in a straight line down the fork till it begins to bend forward. You can eyeball the frame for straightness front–to-back or, better yet, tie a string to one rear drop-out, run it around front steerer tube and back to the other rear drop-out. Then check that the distance from this string to the seat tube is the same on each side. This only sounds tricky till you try it in practice.

7.) FINAL ANALYSIS

If you can fix all the problems you have analyzed, then buy the used bike but point out all its problems to the owner to bring down the price. If the bike has ALL the above problems, even getting it for free may not be worth it, unless the frame is really, really good.

Don't waste your time on a bicycle with a crappy frame if it has lots of problems with its parts that need repairing or replacing.

8.) PRICING

Estimate how much you can sell the bicycle for after its been fixed. Your selling price should cover your new parts and a reasonable charge for your labour.

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