Do I need a torque wrench for working on my mountain bike?
Unless you’re a master bike mechanic or intuitively know how to apply precise force measurements, you should USE a torque wrench to tighten nuts and bolts to specific bicycle manufacture specifications.
Also, most bicycle manufacturer's warranties can be voided unless a torque wrench was used.
What is torque?
Torque is a measure of the tightness of a screw or bolt. This is the simple answer.
The term torque describes the amount of effort exerted to turn something. A specific unit of weight/force is applied to a lever, and the resulting leverage is called torque.
How does torque work & your mtb
When you apply a wrench to a nut and turn it, the force rotates the bolt. As the bolt is tightened, tension stress actually stretches the bolt. If the bolt is optimally tightened then the bolt becomes spring-like and allows for the correct amount of clamping pressure.
Tightening a handlebar stem with a torque wrench.
Torque wrench = gauge tool
“torque specs are there for a reason ”
Some mechanics and manufacturers describe a torque wrench as a gauge tool and can be compared to any other tools of measure, such as a tape measure, as it allows you to torque fasteners to specification.
Many bike mechanics initially start out using a torque wrench until they can intuitively tighten fasteners to specification. These master bike mechanics have hundreds of hours behind the wrench and can tighten nuts and bolts to spec by feel.
Park Tool in their book, the Big Blue Book of Bicycle Repair, which is basically the Bible for bike mechanics says:
“With experience, a person may learn the amount of force to apply to a wrench when tightening a fastener. It may require both overtightening and then undertightening fasteners in order to learn acceptable torques.” ---(emphasis mine)
Mountain biking in Pucón - Pedal Chile
Carbon fiber & clamping force
Carbon fiber is significantly stronger than steel under certain types of load. However, carbon fiber doesn’t handle clamping force as well as other frame materials. All carbon fiber components should be tightened with a torque wrench to manufacture recommended specifications.
Even many experienced bike mechanics use a torque wrench when working with carbon components since over-tightening is the biggest cause of carbon component failure.
over/under-tightening & mechanical issues
Various problems arise when fasteners are not torqued to specification:
Cause damage to bike components
Component failure can lead to safety issues while riding
More bike damage is caused by over-tightening than under-tightening, however, problems can arise from bolts that are too loose:
Too much torque/over-tighten - Can stretch, deform, and/or break the bolt/component that the bolt attaches to. Stripping threads are common among overly torqued fasteners
Example - Over-tightening the bottom bracket will cause the bearings to drag and wear
Too little torque/under-tighten - Allows the part to move, which can lead to component fatigue, and eventual part failure
More potential safety issues than mechanical failures from under-torqued bolts
why use a torque wrench
My riding buddy and friend from Crested Butte put this brand new Trek together…..without a torque wrench
Mountain bikes are using more carbon fiber and alloy materials to make components lighter:
These parts often become prone to damage/failure when over-tightened.
When you use a torque wrench, you will be assured that the bolt is at the exact manufacture’s specification.
Also…..you need to think about the warranty.
warranty claims & torque wrench
As every bicycle owner’s manual requires the use of a torque wrench, the bicycle manufacture can reject your warranty claim unless you can show that a torque wrench was used.
If you want to tinker on your bike and do your own bike maintenance, then you should get a torque wrench……. and put the receipt someplace safe.
optimally tight nuts & bolts
Bicycle owner’s manual recommenced regular checks of critical fasteners by using a calibrated torque wrench. Nuts and Bolts become loose from riding and should be re-set to their specific torque specification.
What are critical fasteners?
Chilean Lake District
Giant Bicycles says “although all fasteners on a bicycle are important, pay special attention to applying the correct torque to the following critical fasteners”:
Wheels
Pedals
Seat post clamp
Saddle clamp
Steerer clamp
Handlebar clamp
Control level clamps
Keeping the nuts and bolts optimally tight plays a vital role in ensuring the structural integrity of your bike parts and components.
What does Park Tool say?
From the 3rd edition of the Big Blue Book of Bicycle Repair (BBB-3), written by Park Tool Director of Education, Calvin Jones:
“To prevent overtightening and undertightening, many manufacturers provide specific torque values, best achieved by using a torque wrench. Torque wrenches are simply a type of measuring tool, like a tape measure or a ruler. Torque wrenches measure the amount of turning effort applied to the bolt or nut. A torque wrench should be part of the bicycle tool kit, but it is possible to work without one at some risk.” (emphasis mine)
Should I carry a torque wrench on the trail?
No. Just tighten to feel, and once back at the garage, check the bolt to make sure it’s within its specified range.
newton-Meters, Inch-Pounds or foot-pound
Measured torque may be given in Newton-meter, inch-pound, or foot-pound units. These units of measure are referring to the force at the end of a lever.
Since the 1970s, Newton-meter is the metric base unit or SI unit. One Newton-meter is a force of one Newton on a one-meter long lever/wrench.
English units of torque are:
Pound-inches - Equal to the force of one-pound acting at the end of a lever/wrench that is one-inch long
Bicycle manufactures & torque wrenches
Every mountain bike owner’s manual strongly urges you to use a properly calibrated torque wrench for tightening any fastener. Below, I provided torque wrench highlights from the most popular mtb manufactures.
Final Thought
It really depends on the bike. Are we talking about a high-end MTB or a beater commuter you ride to pick up a six-pack of craft? If you want to follow your owner’s manual and keep your warranty valid, you’ll need a torque wrench.
Today, as the materials used in bicycles have gotten more lightweight, advanced, and expensive, securing bolts with the proper amount of torque is essential. Unless you're a professional bike mechanic, I’d recommend using a torque wrench…. excepting our beater commuter.
Jesse is Director of Pedal Chile and lives in Chile’s Patagonia (most of the year). Jesse has a Master of Science in Health and Human Performance and enjoys riding single-track down the active volcano near Pucón. I’m also an avid reader and blogger for Pedal Chile.
Sources & References
Andrews, G., 2013. Complete Road Bike Maintenance. London: Bloomsbury Publishing.
Jones, C., 2013. Big Blue Book Of Bicycle Repair.
Milson, F., 2011. Complete Bike Maintenance For Road, Mountain, & Commuter Bicycles. Minneapolis: MVP Books.
Peter Ballin., 2017. Mountain Bike Maintenance. Crowood.