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Bike Tech Tips

Tech Tip: Deraileur Fine Tuning

Quite often during a ride the rear deraileur will lose it's crisp shifting ability and start lagging between shifts, or worse, start missing shifts completely and/or shift unexpectedly. Contrary to what one might expect, this occurence can most often be found when the bike is brand new or after installing brand new cables, due to the new cables' natural tendency to stretch out during break-in.
Assuming the problem is not a bent deraileur, gummed up cables or worn out shifters, the problem is usually cable tension. Luckily, there is an easy way to fine tune cable tension on the trail, or in between tune-ups. Again, assuming the deraileur, cables and shifters are in good shape, the fine tuning goes as follows:

  • Have a friend (one reason why it is always better to ride with a friend) stand on the non-drivetrain (left) side of the bike and lift up the rear wheel using the rear of the saddle. It only needs to be high enough so that the wheel can spin freely. The friend can be substituted by a bicycle workstand where applicable.
  • Crouch down on the drivetrain (right) side of the bike and turn the cranks (pedals) by hand as if you were riding, warning your friend in the process so the pedals do not strike their shins.
  • Reaching up to the handlebars with one hand and cranking with the other, shift the front deraileur to the middle ring.
  • Continue to pedal and shift the rear deraileur from the lowest gear to the highest and back again, noting any time that the shifting is not crisp and immediate.
  • If the chain is having trouble moving from a smaller cog to a larger cog (ie. from a harder gear to an easier gear), turn the deraileur adjusting barrel, found where the deraileur cable housing enters the rear deraileur, counter-clockwise a quarter turn. This tightens the cable tension so that the deraileur can push the chain up the cogs easier.
  • If the chain is having trouble moving from a larger cog to a smaller cog (ie. from an easier gear to a harder gear), turn the deraileur adjusting barrel clockwise a quarter turn.
  • Pedal and shift the rear deraileur from the lowest gear to the highest and back again once more and repeat the tensioning steps as required.
  • Usually, quarter turn increments are all that are needed. It is easy to turn the adjuster too far, so that the deraileur shifts in one direction well, but can not shift back the other direction.
  • The barrel adjuster is only a fine tuning tool. If the shifting is way out of whack, or if the barrel adjuster is adjusted to it's limits, the deraileur should be tuned by a bike mechanic.

Tech Tip: Bike Washing

Never hose your bike down, especially with those high pressure car wash hoses, but even a garden hose with a nozzle can be too much. Hosing your bike down can force dirt and water into cable housings and past bearing seals, causing those parts to corrode and deteriorate.

Instead, use the water from the bare end of the hose, and a bucket of water with lots of dish or similar soap. Use a sponge or brush, with mostly suds. For the chain or chainrings/cogs, you can use degreaser, but try and avoid getting the degreaser into the bearing areas of the rear hub/freehub and bottom bracket. Rinse, dry with a cloth, and lube your chain and cable housings to prevent rust.

Tech Tip: Helmet Replacement

The design of modern micro-shell bicycle helmets is such that when impacted, the styrofoam-like middle liner gets crushed, but the outer shell tends to bounce back. It is the crushing of the middle liner that absorbs the impact energy, and thus protects your head.

Unfortunately, the crushed liner is now unable to protect against further impacts. Because the outer liner tends to bounce back into shape, the impacted middle liner is now not visible as damaged, and the helmet can look good as new.

It is for this reason that any impacted helmet must be replaced immediately, even if it looks undamaged. Check with your local independent bike dealer or the manufacturer of the helmet, as many manufacturers sell crash replacements at a discount off of regular retail price (the crashed helmet must be sent back to the manufacturer for inspection).

Park Tools Tech Tip: Drivetrain Maintenance

Until the bicycle industry comes out of the dark ages and develops a low or no maintenance long life drivetrain, we are stuck with an archaic shifting/gearing system that requires periodic maintenance and replacement.

To keep your bicycle's drivetrain working well and lasting long, keep it clean and well lubed. A chain cleaner unit like the ones available from Park (photo at right) and others will help out in this task. A good biodegradeable citrus based degreaser works best for this type of job. In lieu of a chain cleaner unit, a toothbrush and the aforementioned degreaser can work just as well.

Once the chain is cleaned with the degreaser, wipe clean and let the degreaser evaporate for a few minutes, then apply a good chain lube. Currently, I use Shimano's Slippery Spitt, but there are many good products out there from Finish Line, Pedros, Phils, etc. Just remember to use a bicycle specific lube, as your common household lube or automotive lube will tend to attract dust and dirt.

Lube your chain after every wet ride, and clean and lube after muddy rides.

As a drivetrain wears out, the three main components of the drivetrain wear out toghther (chain, rear cogs, chainrings). It is for this reason that when a drivetrain wears out, all three components should be replaced for best results. Putting a brand new chain on old cogs and chainrings will result in worse shifting than with the old chain.

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