Have you ever tightened a bolt on your mountain bike and then all of a sudden SNAP?! Yeah, you just tightened it too much causing the bolt to break and possibly crushed the part it was attached to. I remember putting my first couple of bikes together at the bike shop in upstate NY where I twisted off numerous handlebar bolts. Tighter has to be better right? Not so much….
Why care about the tightness and torque?
More and more parts like stems, handlebars, cranks, and seatposts are being made out of carbon these days. Some carbon is inexpensive but most of it is pricy. Some product manufactures may question a broken part and possibly not honor a warrantee if it’s evident that excessive force was used to tighten down a part that ends up broken. For example, over tightening the stem bolts that keep the handlebar in place can cause serious damage to carbon handlebars. Serious damage to a carbon part can cause serious human bodily harm. So why not protect your investment and protect yourself by properly tightening bolts to specific measurements.
There’s a tool for that.
Back in the day us bike mechanics had a good “feel” on what was the correct tightness for the various bolts on a bike. Today it’s still good to have a rough estimate on what is tight enough not to do damage. But if you own carbon fiber, aluminum, or just high-end expensive parts for that matter your best friend and possibly a huge money saver protecting you from crushing carbon fiber and denting aluminum parts is a good torque wrench.
There are several different types of torque wrenches designed to be used with bicycle components in mind. Some are Clicking type of wrench; some are a Bending-Bar type of wrench , and my favorite the Digital torque wrench.
“Clicker” wrenches have a spring mechanism that gives way when a certain force is reached preventing the bolt from tightening further. These can cost around $90.
A bending-bar type wrench works on a bending beam. Force is applied to the handle causing flex which moves an indicating needle. Simply stop when the needle reaches the desired setting of the bike part. These type of wrenches cost around $40.
My favorite is the digital torque wrench. It’s super accurate, easy to read, easy to set, and gives you an audible tone when the force equals the setting on the wrench. The drawback to this type of wrench is it can cost a little over $300.
So what does all this mean? What is a torque setting? The torque setting is how much force must be applied to the bolt or fastener to be correctly tightened without the chance of it backing out and becoming loose. Of course things can become loose from bouncing down the trail and over time you need to check and recheck bolts for tightness.
o MTorque is measured in Netwon meters (Nm) and inch pounds (in-lbs). One Newton-meter is a force of one Newton on a meter long lever. Inch-pound comes from Pound foot measurement of force or the energy transferred on applying a force of one pound-force (lbf) through a displacement of one foot. Conversion tables can be found on the internet. Some part manufactures print the proper settings on the part itself in either Nm or in-lb making it easy to know how tight you should go on the bolts. The most common in the bicycle industry are the Nm and in-lb.
If you’re not sure about the tightness of your bolts and don’t want to commit to the purchase of a torque wrench get down to your local bike shop and have them do a one over on your bike checking the torque.
Torque Check List: Crankarms, all stem bolts, brake lever pinch bolt, seat binder bolt, and saddle attachment bolts. Depending on your suspension type you may want to have the suspension fork checked also.