| With modern bike parts, a little technical knowledge can | | | | breaking the soft alloy bolt. At the same time, if you |
| go a long way toward keeping them in good shape | | | | are over-cautious, a loose bolt can cause just as much |
| and getting the most use for your money. One of | | | | damage; just ask anyone who has had bars slip on a |
| those useful concepts you should understand if you | | | | long descent or a seatpost slide into the frame in the |
| plan on installing your new bike parts or giving your ride | | | | middle of a long ride. The key is to tighten using the |
| a tune-up is torque. | | | | maximum allowable torque without damaging the bolt |
| Torque /tork/ n: The measure of the force applied to | | | | or any component that is affected. |
| an object to produce rotational motion, usually | | | | How is torque determined? A quick calculation: |
| measured in inch-pounds. Torque is determined by | | | | Let's say we need to tighten a fastener to 120 in.-lbs. |
| multiplying the applied force by the distance from the | | | | We have a ratchet lever that is 1 foot (12 inches) long. |
| pivot point to the point where the force is applied. | | | | We must apply 10 lbs of pressure to the end of the |
| As bolts and screws are tightened, the resistance | | | | lever to attain the 120 in.-lbs. |
| causes bolts to twist and become distorted (they | | | | 10 lbs x 12 in. = 120 in.-lbs |
| normalize once the force is removed). The | | | | This also demonstrates how a "cheater bar" or |
| measurement of this force is called torque and is | | | | wrench extender aids in tightening or loosening a |
| measured by multiplying the applied force (pound) by | | | | difficult bolt. The longer the lever, the less force |
| the length (inch) of the fulcrum used to turn the object. | | | | needed to achieve the same level of torque. If we |
| Torque in bicycles is becoming more and more | | | | substitute the 1-foot lever with a 10-foot lever, how |
| important. As kids, many of us went by the theory that | | | | much applied force do we need to reach our 120 |
| tighter was better, and we would stand on wrenches | | | | in.-lbs? |
| to make sure that the rear wheel would stay in place | | | | (X) lbs x 120 in. = 120 in.-lbs |
| and keep the chain tight. Today is a different story. | | | | 1 x 120 = 120 |
| You probably don't ride or work on many bikes with | | | | Luckily, torque wrenches make these calculations for |
| solid steel axles and nuts with seemingly infinite torque | | | | us. You adjust the setting or watch the indicator on |
| limits. Today's bikes are carbon fiber and aluminum and | | | | your wrench and it tells you when you have reached |
| titanium--softer composites that have fairly specific | | | | your desired torque. Beam-type and digital torque |
| torque limits. | | | | wrenches can also easily tell you how tight or loose |
| Tighten a clamp around a carbon handlebar too tightly | | | | the bolt was as you are removing it (a good way to |
| and you run the risk of crushing the bar and stripping or | | | | test that last mechanic that worked on the bike). |