Chapter 3: inspection, adjustment, and lubrication
Torque is a measurement of the tightness of a threaded fastener such as a screw or bolt, determined by using a torque wrench. The torque specifications on this page and in this manual are listed to help you determine the correct tightness of parts and their threaded fasteners.
The torque specifications should be used to make sure you do not over-tighten a fastener. Slight differences in a similar part may require a different torque, so in most cases we offer a range of torque. Applying more than the recommended torque to a fastener does not provide extra holding power, and may actually lead to damage or breakage of a part.
However, leaving a part with less than the correct torque also leads to problems. This can lead to fatigue failure. Again, use a torque wrench and use it correctly. Also read the Warning About Mechanical Work.
Always perform the simple function tests listed in this manual to make sure a part is properly tightened, whether or not the part was tightened with a torque wrench. If the part does not pass inspection at the recommended torque, take the bicycle to your dealer.
Many of the parts on Trek bicycles have the torque specification printed on or near the part. The torque printed on the part is always the best, most accurate source. If you cannot find the specification on the part, check the torque specifications page. If you still cannot find the correct specification, consult your dealer.
Some people refer to a bolt by its wrench size. Although this is convenient for the user, it is not as accurate as referring to bolt size (Figure 1) because bolt size is usually the best determiner of correct torque. The bolt-size method requires that you remove the bolt to determine its size. Bolt size is denoted by an upper-case 'M' followed by the diameter in millimeters; a 5mm bolt is referred to as M5.
· M7 bolts: Tighten to 160-180 lb•in (18.0-20.3 Nm)
· M6 bolts: Tighten to 100-120 lb•in (11.3-13.6 Nm)
· M5 bolts: Tighten to 40-60 lb•in (4.5-6.8 Nm)
If you do not know the bolt size, there are several ways to determine it. The most direct is to measure the outer diameter of the bolt's threads (Figure 1). If this is not possible, you can compare the widest point of a metric allen wrench to the outer diameter of the bolt threads (Figure 2):
· 6mm allen wrench ~ M7 bolt
· 5mm allen wrench ~ M6 bolt
· 4mm allen wrench ~ M5 bolt
Figure 1:
Bolt sizes
Figure 2:
Comparing wrench sizes to bolt diameter